TWI425188B - Microscope system and imaging interferometer system - Google Patents

Description

Microscope system and imaging interferometer system

The present invention relates to interference techniques.

Interferometric techniques are often used to obtain information about a test object, such as measuring the surface profile of a test object. In order to measure the surface profile of the object to be tested, an interferometer is generated by mixing measurement light reflected from the surface of the object to be tested with reference light reflected from the reference surface. Interferogram. The fringes in the interference spectrum represent spatial variations between the surface of the object to be tested and the reference surface.

A variety of interference techniques have been used to characterize the object under test. These techniques include low coherence scanning techniques and phase-shifting interferometry (PSI).

With respect to PSI, optical interference patterns representing each of the multiple phase shifts between the reference wavefronts and the test light wavefront are recorded to produce a series of optical interference patterns. For example, a series of optical interference patterns last at least half of the period of optical interference (eg, from constructive interference to destructive interference). Each spatial position of the optical interference pattern defines a series of intensity values, wherein each series of intensity values has a sinusoidal relationship with the phase displacement, and the phase shift has a phase offset equal to the post-mixing test. The phase difference between the optical wavefront and the reference optical wavefront at the spatial position. Using a numerical technique, the phase deviation of each spatial position can be found from the sinusoidal relationship of the intensity values to provide the surface profile of the object to be tested associated with the reference surface. These numerical methods are often referred to as phase shift algorithms.

The phase shift in the phase shift interference technique can be generated by varying the relative optical path length from the surface of the object to be measured to the interferometer and from the reference surface to the interferometer. For example, the reference surface can be moved relative to the surface of the object to be tested. Another method is to generate a phase shift by changing the constant and non-zero optical path difference (OPD) obtained by measuring the wavelength of the light and the reference light. Recently, a wavelength tuning PSI has been invented, please refer to the invention of G. E. Sommargren (U.S. Patent No. 4,594,003).

On the other hand, within a range equal to (i.e., having at least some modulation of the homology wave seal where the interference fringes occur) or greater than the coherence length of the test light and the reference light interfering with each other, low coherence The scanning technique produces a scanning interferometric signal for each camera pixel by scanning the optical path difference between the reference light and the interferometer's measured optical delay, each camera pixel being used to measure the interference spectrum. The optical coherence length used by low coherence scanning techniques is relatively short compared to the range of OPD scans used by PSI for optical coherence length and low homology scanning techniques. For example, a white light source can produce light with a low coherence length, which is also known as white light interferometry (SWLI). A typical SWLI signal is a number of stripes located near the zero path difference. The SWLI signal is characterized by a sinusoidal carrier modulation with bell-shaped fringe-contrast envelop. The use of low coherence interference techniques to measure surface contours is to take advantage of the localization of the fringes.

There are two main methods for processing signals with low coherence interference techniques. The first method is to locate the peak or center position of the envelope, assuming that this position corresponds to the zero path difference position of the two-beam interferometer, one of which is reflected from the surface of the object to be tested. The second method is to convert the signal to the frequency domain and calculate the rate of change of the phase with the wavelength, assuming that a substantially linear slope is proportional to the position of the object to be tested. For example, please refer to the Peter de Groot patent (US Patent No. 5,398,113). The second method is called frequency domain analysis (FDA).

Low coherence scanning interferometry is used to measure surface topologies and/or other properties of the object under test with complex surface structures, such as thin films, individual structures of dissimilar materials, or interference microscopy. Individual structures that cannot be resolved by optical resolution. These measurements relate to the characteristics of flat panel display components, the measurement of semiconductor wafers, and in-situ film or heterogeneous material analysis. For example, please refer to a patent entitled "Profiling Complex Surface Structures Using Scanning Interferometry" by Peter de Groot et al. (US Patent Publication No.: US-2004-0189999-A1; publication date: 2004/09/30). The above-referenced patent references are hereby incorporated by reference in their entirety in their entireties in the entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all all No.: US-2004-0085544-A1; publication date: 2004/05/06), the entire disclosure of each of the above-referenced patents is hereby incorporated by reference.

In general, the present invention relates to methods and systems for reducing uncertainty in interferometric measurements. Specifically, during the measurement, the method and system of the present invention are used when the actual optical path difference increment between two consecutive detector frames deviates from the nominal optical path difference increment. Reduce the error that will increase in low coherence interference measurements. This error comes from vibration and is called scanning error.

One possible way to solve the scanning error problem is to characterize or monitor the true scan history of the instrument and use this information for signal processing to correct this information. One way to collect this information is to use an interferometer and then use a laser displacement measurement interferometer. More generally, the scan history can be obtained using a monitor interfer signal that is obtained using a source having a coherence length greater than the scan range of the optical path difference. Although the scan history information can be obtained from the monitoring interfering signal using the conventional PSI algorithm, the applicant believes that the above method will not be able to obtain the scan error information when the vibration frequency is higher than the interferometer's detector frequency. However, where multiple monitoring signals are acquired and have different phases, the monitoring signal can be used to determine the information of the scanning error caused by the high frequency vibration.

Therefore, during the data acquisition of the low-coherent interference signal, the system of the present invention simultaneously collects interference data at some points in the visible area, and the interference data has a range of phase deviation or interference frequency deviation, using the same low-coherence interference data. The interferometer optics are used, but the interferometer optics have separate detectors or equivalent detection devices that operate at a single wavelength (or a band that has a sufficiently large coherence length). The processor determines the scan movement history based on the monitored interference data, including vibrations outside of the vibration frequency range (including low or high vibration frequencies). This information is then used to correct the interference data for the wideband before any processing is performed.

In general, the method and system of the present invention can be used to image an object to be imaged to an interferometric microscope (conventional imaging) of the detector, or the position in the detector corresponds to a particular angle of incidence of the object to be tested. Interferometric microscope (for example, imaging the pupil plane of the microscope in the detector). This later configuration is called the white plane interference technology (PUPS) of the pupil plane. For example, conventional imaging systems provide three-dimensional data of surface features of the object under test. On the other hand, PUPS provides detailed structural information on the small surface area, including multilayer film thickness, refractive index analysis, and dimensions that cannot be optically resolved in the measurement range. The above two measurement modes usually use multiple detector elements (such as cameras) to collect data in the visible area, and the visible area covers surface images or pupil plane images.

In conventional imaging or PUPS, data is typically acquired in 1/10 second to several seconds, and both of the above measurement modes are sensitive to mechanical vibration during data acquisition, where scanning errors cause system miscellaneous The rise of the news.

In the measurement using PUPS because it cannot be optically resolved, the size resolution of the system is inversely proportional to the noise of the spectral amplitude in the interfering signal, where the interfering signal is a complex function of vibration and scanning error. It is generally believed that if the noise caused by vibration and scanning errors can be reduced, the resolution of the PUPS tool will be greatly improved, which will help the PUPS system (such as semiconductor process measurement) to keep up with the size reduction of the feature components. .

Low coherence interference measurements are widely used in production environments with very poor environmental control, which produces extremely large vibrational noise. Because of the need to use advanced 3D optical metrology in the above environments, solutions that require vibration, such as the methods and systems disclosed herein, are needed.

In another version, the method includes correcting low homology interference data after obtaining scan error data. Other methods are also possible when using the above techniques to obtain scan error information. For example, information on scan errors can be obtained in a variety of ways, such as using accelerometers, contact probes, capacitance meters, barometers, optical encoders, and/or techniques based on low coherence interference signals.

In general, after the scan error information is obtained, the information is further used for processing the data, as much as possible to produce data that is close to the data of the undisturbed system. In general, the scanning error data can be used in a variety of ways to improve the correctness of the scanning interference measurement.

In some embodiments, data processing is associated with a spectral analysis method that uses scanning mobile information and thereby replacing a portion of conventional discrete Fourier (DFT). However, spectral analysis methods are widely used for various non-uniformly sampled materials, and are not limited to some versions of the embodiments of the present invention.

In some embodiments, the algorithm begins by generating a set of basis functions that correspond to the basis functions of purely vibratory signals of different frequencies that are known and unevenly incremented. These basal functions represent distorted sine waves. Similar to the result of a uniformly sampled data set using a general DFT calculation, by solving a linear equation system, the signal can be decomposed into a basis function and the spectral components of the signal are generated.

Solving a linear equation system can be computed by inverting the matrix, where the matrix acts as a basis function. Next, the inverse matrix is multiplied by a vector including the data after spectral analysis.

When analyzing low-homology interfering signals from conventional images, it is important to note that the same inverse matrix should be used for all pixels. Therefore, the spectrum analysis is simplified to the inverse matrix operation of the matrix, and the inverse matrix is multiplied by the P-th power of a vector, where P is the number of pixels. Regarding the speed of the calculation, this method is not faster than performing a general DFT because there is already a highly optimized algorithm for Discrete Fourier Transform (DFT), and in another embodiment, the present invention can be used for When the signals recorded at different locations in the viewable area of the interferometer have different (but known) sample increments. For example, in some cases, the incremental distribution can be represented as a combination of a tilt disturbance and a piston motion disturbance of the interference cavity.

With a few changes, the method is capable of compensating for variations in the intensity of a light source, such as a light source in a microscope. The basal function is a purely vibratory signal that is sampled at a known sampling position, where each value is multiplied by a factor proportional to the intensity of the corresponding source, and the corresponding source intensity is known in a separate measurement.

In some embodiments, the composite reference plane is used to determine information about scan errors. A composite reference is a reference having at least two reference faces. For example, the reference surface is the interface between the surface of the optical element, the interface between the two optical elements, the interface between an optical element and a coating layer, or the interface between the two coating layers of the optical element. The primary reference plane serves as a conventional reference surface that provides reference light in the interference system to view the surface of the object to be tested, such as surface height or other features. In general, the interference fringes produced by the primary reference surface can be detected by a primary camera or other imaging device that is coupled to a computer or other data capture or processing device.

When scanning the optical path difference of the interference microscope, the second reference surface provides information so that the movement of the analyte relative to the interference microscope can be monitored. In general, the first and second reference faces are mechanically secured to each other. In other words, the relative position and deflection of the second reference plane with respect to the primary reference plane remains constant during data capture. The effects of the primary reference plane and the second reference plane provide a complex effective reflectivity with respect to the visible area (FOV), wherein in the FOV of the system, the complex effective reflectivity at least has a phase that varies. In general, determining the effective reflectivity will help determine the phase shift of the overall or low spatial frequency of the interference image.

In some embodiments, the interference result of the second reference surface of the composite reference plane is detectable by the second camera (also referred to as a monitoring camera), but is not detectable by the main camera, and the main camera only Interference between the primary reference plane reflection and the surface reflection of the object can be monitored.

In some embodiments, there is a relative deflection between the primary reference surface and the second reference surface, thereby producing an effective reflectance of phase sudden changes in the direction of deflection.

In general, analysis of the interference results based only on the second reference surface monitored by the monitoring camera provides information that facilitates analysis of the interference effects based only on the primary reference plane monitored by the primary camera.

In order to resolve the interference results of the primary reference plane and the second reference plane, the monitoring camera is capable of operating in the main spectrum, which is different from the spectrum of the main camera operation. For example, a surveillance camera can only detect narrow-band light (such as monochromatic light), while a main camera can detect broadband light. In another embodiment, the monitoring camera is capable of detecting light of different wavelengths incident outside of the main camera.

In another embodiment, the second reference surface can be adjusted such that it has sufficient included angle or other geometrical characteristics relative to the primary reference surface for the separate reflections to be detected by the monitoring camera. For example, light reflected from the second reference surface will propagate along a path blocked by the main camera.

In some embodiments, the information of the scan error is determined using a displacement measurement interferometer (DMI). Fiber optic DMIs include simple and contact sensors formed using commercial components such as communication components. In general, fiber optic sensor systems are operated independently of the interferometric system and can be synchronized by using a common processor that is used to control the system. The separate sensors are multiplexed by a common source and a common reference cavity. Examples of sensors include elements that provide illumination, heterodyne, light distribution, and phase extraction. In some embodiments, the sensors of the sensor system are attached to different portions of the interference system to monitor the various scan movements (degrees of freedom) produced during the measurement process. Fiber-optic DMI can be used for autofocusing of interference systems such as interference microscopes.

A summary of various aspects of the invention follows.

In general, in one form, the present invention provides an apparatus comprising a broadband scanning interferometric system comprising an interferometer optical component for combining test light from a test object and From the reference light of a reference object, an interference pattern is formed in a detector, wherein the test light and the reference light are from a common light source. The interference system further includes a scanning platform for scanning an optical path difference between the test light and the reference light from the common light source to the detector, and a detector system including one of the detectors for recording one The interference pattern for each of the series of optical path difference increments, wherein the frequency of each optical path difference increment defines a frame frequency. The interferometer optical component is further configured to generate at least two monitoring interference signals. When scanning the optical path difference, each of the monitoring interference signals represents a change in the optical path difference, wherein the detecting system is further configured to record the monitoring interference signal. The device also includes an electronic processor electrically coupled to the detection system and the scanning platform for determining the sensitivity of the optical path difference increment to the disturbance sensitivity at a frequency greater than the frame frequency.

Embodiments of the device include one or more of the following features and/or other features. For example, the scanning platform is configured to scan the optical path difference in a range greater than one of the common light sources. The scanning platform scans the optical path difference by changing the focal length of the interferometer optical component relative to the object under test. The scanning platform scans the optical path difference without changing the focal length of the interferometer optical component relative to the object under test. The scanning platform scans the optical path difference by changing the position of the reference associated with the interferometer optical component.

In some embodiments, the interferometer optical component comprises a Mirau objective or a Linnik objective. The interferometer optical component images the object to be detected to the detector.

The interferometer optical component defines a pupil plane and is used to image the pupil plane to the detector. The scanning platform is configured to scan the optical path difference, wherein the optical path difference is changed according to the position in the pupil plane, and the step of determining the information of the optical path difference increment includes considering the positional correlation of the interference pattern. In some embodiments, the scanning platform scans the optical path difference without changing the focal length of the interferometer optical component relative to the object under test.

The interferometer optical assembly includes an optical component for generating monitoring light from the output light, the output light being produced by the interferometer optical component, wherein the output light comprises test light and reference light. The optical component is a beam splitter for directing a portion of the output light to the detector and for directing another portion of the output light to the second detector, the second detector for recording the monitoring interference signal. In another embodiment, the optical component includes a spectral filter for directing a portion of the output light to the detector system, wherein the monitoring interference signal is detected based on a portion of the output light. A portion of the output light is the monochromatic portion of the output light. The monitoring light comes from a shared light source. A spectral component of the light corresponding to the test light and the reference light is monitored. The interference pattern corresponds to the intensity data of the output light. The monitoring light is from a second source that is different from the common source. The coherence length of the monitoring source is greater than the coherence length of the shared source.

In some embodiments, the electronic processor determines the information of the optical path difference increment by fitting each of the at least two monitoring interference signals using a corresponding sinusoidal function. Each of the monitoring interfering signals includes a plurality of sampling data points, and the sampling data points are obtained by using a detector when scanning the optical path difference, and the step of fitting the monitoring interference signals using the sinusoidal function includes sampling the data points. Interpolated to provide an interpolated signal. Fitting the sinusoidal function to the monitoring interfering signal further includes associating a theoretical interferometric phase with each interfering signal based on the interpolated signal. The step of determining information of the optical path difference increment further includes calculating an offset in the measured phase of one of the monitored interference signals based on the corresponding theoretical interference phase.

At least two monitor the interference signals with different phases. At least two monitor the interference signals with different frequencies.

In some embodiments, the second detector is a multi-component detector for each component to record at least two corresponding monitoring interference signals.

The detector system includes a second detector that is separate from the main detector, and the second detector records at least two monitoring interference signals. The second detector is a multi-component detector for each component to record a corresponding monitoring interference signal.

The electronic processor is further configured to determine information of the object to be tested according to a main interference signal corresponding to the interference pattern, and the interference pattern is recorded using the detector. The step of determining the information includes reducing the uncertainty of the information based on the information of the optical path difference increment.

In general, in another embodiment, the method includes providing a low coherent interference signal generated by a scan interferometric system, wherein when scanning a series of optical path difference increments, the test is performed. When the optical path difference between the light and the reference light is different, the scanning interference system uses the interferometer optical component to combine the test light from a test object and the reference light from a reference object to generate a low coherent interference signal. And forming an interference pattern in a detector, the detector is used to record the interference pattern, and the frequency of each optical path difference increment defines a frame frequency. The method further includes providing at least two monitoring interference signals, each of which is generated by the interferometer optical component, and each of the monitoring interference signals represents a change in the optical path difference when the scanning optical path is poor. The invention further includes determining information on the sensitivity of the optical path difference increment to the disturbance sensitivity at a frequency greater than the frame frequency based on the monitoring interference signal.

Embodiments of the method include one or more of the following features and/or other features. For example, the test light and the reference light are generated from a common light source, and the optical path difference is scanned over a range greater than the coherence length of the shared light source. Scanning the optical path difference includes changing the position of the reference object with respect to the interferometer optical component. The step of providing a low homology interference signal includes imaging the object to be detected to the detector.

In some embodiments, the interferometer optical component defines a pupil plane and provides a low homology interference signal, and the step of providing a low homology interference signal includes imaging the pupil plane to the detector. The step of determining the information of the optical path difference increment includes considering the positional correlation of the interference pattern described above.

The step of providing at least two monitoring interference signals includes generating output light provided by the interferometer optical component, wherein the output light comprises test light and reference light. The monitoring light is detected using a detector. The monitoring light is detected using a second detector that is different from the detector used to record the interference pattern. The step of generating the monitor light includes spectrally filtering the output light. In some embodiments, the monitoring light is generated from a light source that is the same as the test light and the reference light. In some embodiments, the monitoring light is generated from a source other than the test light and the reference light. The coherence length of the monitoring light source is greater than the coherence length of the test light and the reference light source.

The step of determining information of the optical path difference increment includes fitting a respective one of the at least two monitored interference signals using a corresponding sinusoidal function. Each of the monitoring interfering signals includes a plurality of sampled data points, and the step of fitting the monitoring interfering signals using the sinusoidal function includes interpolating the sampled data points to provide an interpolated signal. The step of fitting the monitoring interference signal using the sinusoidal function further includes associating the theoretical interference phase with each of the interference signals based on the interpolated signal.

At least two monitoring interference signals have different interference phases. At least two monitor the interference signals with different frequencies.

The method further includes determining information of the object to be tested according to one of the main interference signals corresponding to the interference pattern, and the interference pattern is recorded in the detector. The step in determining the information is to reduce the uncertainty of the information based on the information of the optical path difference increment.

In another form, the present invention provides a program for fabricating a display panel comprising elements for providing a display panel; determining information of the device by a method related to the above-discussed discussion or a device discussed below; A device is used to manufacture the display panel. The device includes a pair of substrates spaced apart from each other by a gap, and the information includes information of the gap. The step of forming the display panel includes adjusting the gap based on the information. The step of forming the display panel includes filling the gap with a liquid crystal material.

The above components include a substrate and a photoresist layer on the substrate. The above information includes information on the thickness of the photoresist layer. The photoresist layer is a patterned layer, and the information includes dimensional errors or overlay errors of one of the features of the patterned layer. The step of forming the display includes etching a layer of material under the photoresist layer.

The above component includes a substrate, and the substrate includes a spacer. The above information includes information on the spacers. The step of forming the display includes correcting the spacer based on the information.

In general, in another embodiment, the method includes providing one or more interfering signals of an object to be tested, wherein the interfering signal corresponds to a series of optical path difference values, and the series of optical path difference values are due to miscellaneous The news is not equally spaced. The method further includes providing information about the unequal spacing of the values of the plurality of optical path differences; decomposing each of the interfering signals into a contribution of the complex basis function, each of the basis functions corresponding to a different frequency and being equally spaced The optical path difference value is sampled; and information on the contribution of each of the multiple base functions is determined using information of each of the interference signals.

Embodiments of the method include one or more of the following features and/or other features. The contribution of decomposing each of the interfering signals into a basis function includes information on the amplitude and phase of each of the basis functions of the interfering signals. Each basal function is a sinusoidal base function sampled by unequal spacing optical path difference values. The above decomposition is a linear decomposition.

The one or more interfering signals include multiple interfering signals corresponding to different locations of the object to be tested. The one or more interfering signals include multiple interfering signals corresponding to different positions of a pupil plane of an objective lens, and the objective lens is used to illuminate the object to be tested to generate an interference signal. Each interfering signal is broken down into contributions from the same basis function.

Each of the interference signals corresponds to the intensity of the interference signal, and the value of the interference intensity is measured when the test light and the reference light from the object to be tested are combined in a detector, wherein the test light and the reference light are from a common one. The light source, and the optical path difference is the optical path difference between the test light and the reference light from the common light source to the detector.

The multiple basis functions include non-orthogonal basis functions. The multiple basis functions include linearly independent basis functions.

The step of decomposing the interfering signal includes forming a matrix, each row of the matrix corresponding to a basis function; finding an inverse matrix of the matrix; and applying the inverse matrix to each of the interfering signals. The number of matrix elements per base function is greater than the number of base functions.

Each of the interference signals corresponds to the intensity of the interference signal, and the value of the interference intensity is measured when the test light and the reference light from the object to be tested are combined in a detector, wherein the test light and the reference light are from a common one. The light source, and each of the base functions represents a variation between the measured interference intensity value and a theoretical value after the measurement, the theoretical value corresponding to an interference signal having no error. The change is caused by a change in the intensity level of one of the light sources. The change is due to the finite integration time of the detector.

The step of providing information on the unequal spacing of the series of optical path difference values includes providing at least one monitoring interference signal indicative of a change in optical path difference, wherein the monitoring interference signal is generated when an interfering signal corresponding to a series of optical path differences is obtained . The monitoring interferometric signal can be generated using the same interferometer optical component that is used to generate an interfering signal corresponding to a series of optical path differences.

The step of using the information includes generating a corrected interference signal according to the information of each of the multiple base functions on each of the interference signals; and determining the information of the object to be tested according to the corrected interference signal.

Information about the unequal spacing of a series of optical path difference values is generated by a sensor, such as a displacement measuring interferometer, an accelerometer, a contact probe, a capacitance meter, a barometer, and An optical encoder.

In another form, the present invention provides a program for fabricating a display panel comprising elements for providing a display panel; determining information of the device by a method related to the above-discussed discussion or a device discussed below; A device is used to form the display panel. The above apparatus includes a pair of substrates spaced apart from each other by a gap and the information includes information of the gap. The step of forming the display panel includes adjusting the gap based on the information. The step of forming the display panel includes filling the gap with a liquid crystal material.

The above component includes a substrate and a photoresist layer on the substrate. The above information includes information on the thickness of the photoresist layer. The photoresist layer is a patterned layer, and the information includes dimensional errors or overlay errors of one of the features of the patterned layer. The step of forming the display includes etching a layer of material under the photoresist layer.

The component includes a substrate, and the substrate includes a spacer, and the information includes information of the spacer. The step of forming the display includes correcting the spacer based on the information.

In general, in another form, the apparatus further includes a sensor for an interference system and an electronic processor. The interference system includes an interferometer optical component for combining test light from a test object and reference light from a reference object to form an interference pattern in a detector, wherein the test light and the reference light are from A common light source. The interference system further includes a scanning platform for scanning an optical path difference between the test light and the reference light from the common light source to the detector, and a detector system including the detector for recording An interference pattern for each of a series of optical path difference increments, thereby providing one or more interfering signals. The electronic processor is coupled to the detection system and the scanning platform, and determines the information of the object to be tested according to the one or more interference signals. A series of optical path difference increments are not equally spaced due to noise, and the electronic processor determines the information of the object to be tested by decomposing each of the interference signals into a contribution of the complex basis function, each of the substrates. The function corresponds to different frequencies and is sampled by unequal spacing optical path difference values.

Embodiments of the device include one or more of the following features and/or other features. For example, the interferometer optical component images the object to be detected to the detector. The interferometer optics define a pupil plane and image the pupil plane to the detector. The interferometer is part of the interference microscope. The scanning platform is configured to scan the optical path difference over a range greater than the coherence length of the shared light source.

In some embodiments, the apparatus further includes a sensor in communication with the electronic processor, the sensor providing information of the unequal spacing optical path difference increments to the electronic processor. The sensor guides the monitoring beam from the object to be tested by the interferometer optical component. The sensor is a displacement measuring interferometer, an accelerometer, a contact probe, a capacitance meter, a barometer or an optical encoder. In some embodiments, the sensor defines a frame frequency and the electronic processor is operative to determine information about the optical path difference increment versus disturbance sensitivity at frequencies greater than the frame frequency. The scanning interferometric system generates at least one monitoring interference signal by the interferometer optical component.

In general, in another form, the apparatus of the present invention includes a scanning interference system and an electronic processor, the scanning interference system including an interferometer optical component for directing test light having different incident angles to a test object, And combining the test light reflected from the object to be tested with reference light from a reference object to form an interference pattern in a multi-element detector, wherein the test light and the reference light are from a common light source, And the interferometer optical component directs at least a portion of the combined light to the detector such that different elements of the detector correspond to different angles of incidence illuminated by the test object to be tested. The interference system further includes a scanning platform for scanning an optical path difference between the test light and the reference light from the common light source to the detector, and a detector system including one of the detectors for recording one The interference pattern of each of the series of optical path difference increments is used to generate at least one monitoring interference signal. When scanning the optical path difference, the monitoring interference signal indicates a change in the optical path difference. The electronic processor is electrically coupled to the detection system and the scanning platform to determine information on the sensitivity of the optical path difference increment to the disturbance.

Embodiments of the apparatus include one or more of the other types of features. For example, the interferometer optical component defines a pupil plane and images the pupil plane to the detector. The scanning interferometric system is a broadband scanning interferometric system. The scanning platform is configured to scan the optical path difference over a range greater than or less than the coherence length of the shared light source. When scanning the optical path difference, the scanning interference system is further configured to generate at least two monitoring interference signals, each of which monitors the interference signal to indicate a change in the optical path difference. The frequency of each optical path difference increment defines a frame frequency, and the electronic processor determines information about the sensitivity of the optical path difference increment to the disturbance sensitivity at a frequency greater than the frame frequency. The scanning interferometric system generates at least one monitoring interference signal by interfering with the optical component.

In general, in another form, the present invention provides an apparatus comprising an interference microscope comprising an objective lens and a platform movable relative to the objective lens. The device also includes a sensor that generates a first wavefront of the input light and a second wavefront and combines the first and second wavefronts to provide output light, the output light comprising first and second The information of the optical path difference between the wavefront paths, the sensor includes a reflective element disposed in the first wavefront path, and the reflective element is disposed on the objective lens or the platform. The device also includes a fiber optic waveguide for generating input light incident to the sensor or outputting light from the sensor to the respective detector from the sensor. The electronic processor monitors the displacement of the platform relative to the objective lens based on information from the sensor.

Embodiments of the device include one or more of the other types of features. For example, an interference microscope is a low coherence interference scanning interference microscope. The interference microscope includes an interferometer optical component and a detector, and the interferometer optical component is used to image the object to be tested disposed on the platform to the detector. The interference microscope includes an interferometer optical component and a detector, wherein the interferometer optical component defines a pupil plane and is used to image the pupil plane to the detector.

The objective lens is a Mirau objective or a Linnik objective.

In another form, the present invention provides an interference system including a detector subsystem, a scanning platform, and an electronic processor. The detector subsystem includes a monitoring detector and an interferometer optical component. The interferometer optical component combines the test light from a test object with the primary reference light and the second reference light from the first and second reference faces. The combination is for forming a first interference pattern in a monitoring detector, wherein the first and second reference surfaces are mechanically fixed to each other. When the detector subsystem records the monitoring interference signal of each of a series of optical path differences, the scanning platform scans the optical path difference between the test light and the primary reference light and the second reference light to the monitoring detector. The electronic processor is electrically coupled to the detector subsystem and the scanning platform, and the electronic processor is configured to determine the information of the optical path difference increment according to the detected monitoring interference pattern.

Embodiments of the present interference system include one or more of the other types of features. For example, the detector subsystem includes a main detector and an interferometer optical component, and the interferometer optical component combines the test light and the first reference light to form a main interference pattern in the main detector, the main interference pattern. Unlike monitoring interference patterns. The electronic processor is configured to determine information of the object to be tested according to the detected main interference pattern. The step of determining the information of the object to be tested includes reducing the data uncertainty of the object to be tested due to the vibration of the object to be tested according to the information of the optical path difference increment.

The interferometer optics are used to prevent the main detector from receiving the second reference light. The interferometer optical component includes a field of view light bar for transmitting test light and primary reference light to the main detector but blocking the second reference light from the main detector. The interferometer optical component includes a wavelength filter for transmitting the test light and the primary reference light to the primary detector but blocking the second reference light from the primary detector.

The monitor detector is a multi-element detector, and the first and second reference planes are arranged to allow a relative phase difference between the primary reference light and the second reference light to be varied in the viewable area of the multi-element detector.

The first and second reference planes are positioned to propagate the primary reference light and the second reference light along a non-parallel path of the monitoring detector. The first and second reference faces are surfaces. The first and second reference faces correspond to opposing surfaces of a common optical component. The shared optical component is a wedge. The first and second reference faces correspond to surfaces of different optical elements.

The second reference surface is a planar interface. For example, the primary reference plane is a plane. In some embodiments, the primary reference plane is a non-planar. The non-planar interface is a spherical surface. The main reference plane is an aspherical surface.

The interferometer optical component defines an optical axis and first and second reference faces that are deflected at different angles relative to the optical axis.

The interference system includes a light source subsystem for generating test light, primary reference light, and second reference light. The light source subsystem includes a common light source for generating test light, primary reference light, and second reference light. In some embodiments, the shared light source is a broadband light source. The light source subsystem includes a primary light source for providing test light and primary reference light, and a monitoring light source for providing a second reference light. The main source is a broadband source. The monitoring source is a narrowband source (eg, a monochromatic source).

The light source subsystem includes a light source for providing at least one test light and a main reference light, and a scanning platform for scanning the optical path difference over a range of coherent lengths of the light source. The light source subsystem includes a light source for providing at least one test light and a main reference light, and a scanning platform for scanning the optical path difference in a range smaller than a coherence length of the light source.

The interferometer optics image the object under test to a multi-element detector in the detector subsystem. The interferometer optics define an aperture and the interferometer optics image the pupil to a multi-element detector in the detector subsystem. The multi-element detector is a monitor detector.

The interferometer optical component is configured as a Fizeau interferometer, a Linnik interferometer or a Mirau interferometer.

In general, in another form, the present invention provides a method comprising combining test light from a test object with primary reference light and second reference light from first and second reference faces, Forming a first monitoring interference pattern in a monitoring detector, wherein the first and second reference surfaces are mechanically fixed to each other; scanning the test light and the main reference light and the second reference light to the monitoring detector The optical path difference; a monitoring interference pattern for each of a series of optical path difference increments; and information for determining the optical path difference increment based on the detected monitoring interference pattern. The apparatus of the method includes other types of features.

In general, in another form, the present invention provides an interference system comprising an interferometer optical component and an electronic processor. The interferometer optical component combines test light from a test object with primary reference light and second reference light from the first and second reference planes to form a first interference pattern in a monitor detector The interferometer optical assembly also combines the test light with the primary reference light to form a second interference pattern in a primary detector, wherein the first and second reference faces are mechanically secured to each other. The electronic processor is coupled to the main detector and the monitoring detector. The electronic processor determines the information of the object to be tested according to the second interference pattern, and the step of determining the information of the object to be tested includes the information according to the first interference pattern. Reduce the uncertainty caused by the scanning error of the object under test. Embodiments of the present interference system include other types of feature devices.

In general, in another form, the present invention provides a method comprising combining test light from a test object with primary reference light and second reference light from first and second reference faces, Forming a first interference pattern in a monitoring detector; combining the test light with the main reference light to form a second interference pattern in a main detector, wherein the first and second reference planes are each other Mechanically fixed; and determining information of the object to be tested according to the second interference pattern, wherein the step of determining information of the object to be tested includes reducing information of the object to be tested due to scanning error according to information of the first interference pattern Certainty. Embodiments of the present interference system include other types of feature devices.

In general, in another form, the present invention provides an apparatus comprising a microscope and a sensor system. The platform is configured to position a test object relative to the one or more optical components, and the platform is movable relative to the one or more optical components, the sensor system includes a sensor light source, an interference sensor, and a A fiber optic waveguide, an adjustable optical cavity, and an electronic controller. The interference sensor receives light from the sensor light source; generates an optical path difference between the first portion and the second portion of the light, each optical path difference having a distance between the objective lens and the platform; The first portion and the second portion of the light combine to provide output light. The detector detects light from the interference sensor. The fiber waveguide transmits the input light to the sensor source, the interference sensor, and the sensor. The adjustable optical cavity is in the optical path from the sensing source to the interference sensor. The electronic controller communicates with the detector to determine the optical path difference information based on the output light detected by each of the interference sensors.

Embodiments of the device include the following features and/or other features. For example, the electronic controller adjusts the focal length of one of the microscopes based on the information. The microscope is an interference microscope. The interference microscope is a scanning white light interference technique (SWLI) microscope. The interference microscope is a pupil plane SWLI microscope. The objective lens can be a Mirau objective, a Linnik objective or a Michelson objective. The interference microscope uses the test light to illuminate a test object to determine the information of the object to be tested disposed on the platform, and combines the test light with reference light from a reference object to form an interference in a detector. A pattern in which the test light and the reference light are from a common light source, and the apparatus reduces the uncertainty of the object to be detected due to the scanning error based on the determined information related to the optical path difference of the sensor.

In some embodiments, the sensor system includes one or more additional interference sensors, each of which receives light from the sensor source. Each of the interferometric sensors produces an optical path difference between the two elements of the corresponding light emitted by it, each optical path difference having a corresponding displacement along the respective axis between the objective lens and the platform. The electronic controller determines information about the deflection angle of the platform relative to the objective lens based on the steps of determining the respective optical path differences of the at least two interference sensors. The sensing system includes one or more additional detectors, each of which receives output light from a respective interference sensor. Each additional interference sensor receives light from the sensor source by a corresponding fiber waveguide and directs the output light to its respective sensor. The adjustable optical cavity is in the optical path from the sensing source to the interference sensor.

The interference sensor includes a lens for receiving light exiting the fiber waveguide and focusing the light to a waist. The lens is a graded index lens. A lens is attached to the objective lens. In another embodiment, the lens is attached to the platform. In some embodiments, the fiber waveguide is an optical fiber having a thermally expanded core.

The microscope includes a microscope light source and an objective lens, the objective lens including one or more optical elements. The microscope produces light from the microscope source that is incident on the object under test, and one or more optical elements collect light from the object under test, and the interference sensor directs light to the platform by one or more optical elements of the objective lens.

The sensor source is a broadband source. The sensor source has maximum intensity at wavelengths between 900 nm and 1,600 nm. The sensor light source has a half width at 50 nm or less. The coherent length of the sensor source is about 100 nm or less.

The adjustable optical cavity includes two paths of light, each path including a fiber extension module. The sensor source and detector are in a housing that is separated from the microscope.

The above information can be information about the displacement of the objective lens and the platform along the axis. The microscope scans the platform parallel to the above axis. The above information can be an absolute displacement between the objective lens and the platform. In another embodiment, the information may be information about a relative displacement between the objective lens and the platform.

The microscope includes a microscope light source that produces light from the microscope source to the object to be tested placed on the platform, wherein the maximum intensity of the microscope source is about 100 nm or greater than the maximum intensity of the detector source. The maximum intensity of the microscope source ranges from 300 nm to 700 nm, and the maximum intensity of the detector source ranges from 900 nm to 1,600 nm.

In general, in another form, the present invention provides an apparatus comprising an imaging interferometer and a sensor system. The imaging interferometer includes one or more optical components and a platform for positioning a test object relative to one or more optical components, the platform being movable relative to the one or more optical components. The sensor system includes a sensor light source, an interference sensor, a fiber waveguide, an adjustable optical cavity, and an electronic controller. The interference sensor receives light from the sensor light source; generates an optical path difference between the first portion and the second portion of the light, each optical path difference having a distance between the objective lens and the platform; The first portion and the second portion of the light combine to provide a corresponding output light. Each detector detects light from a corresponding interference sensor. The adjustable optical cavity is in the optical path from the sensing source to the interference sensor. The electronic controller communicates with the detector to determine the optical path difference information based on the output light detected by each of the interference sensors.

Embodiments of the device include the following features and/or other features. For example, the imaging interferometer is an interference microscope. The imaging interferometer is a SWLI interferometer or a PUPS interferometer.

In general, in another form, the present invention provides an apparatus comprising an imaging interferometer and a sensor system. The imaging interferometer includes one or more optical components and a platform for positioning a test object relative to one or more optical components, the platform being movable relative to the one or more optical components. The sensor system includes a sensor light source, a plurality of interference sensors, a complex detector, an adjustable optical cavity, and an electronic controller. Each of the interference sensors receives light from the sensor light source; generates an optical path difference between the first portion and the second portion of the light, each optical path difference being related to a distance between the objective lens and the platform; And combining the first portion and the second portion of the light to provide corresponding output light. Each detector detects light from a corresponding interference sensor. The adjustable optical cavity is in the optical path from the sensing source to the interference sensor. The electronic controller communicates with the detector to determine the optical path difference information based on the output light detected by each of the interference sensors. Embodiments of the device include one or more feature devices of other types.

In general, in another form, the present invention provides an apparatus comprising a microscope and a sensor system. The microscope includes an objective lens and a platform for positioning a test object relative to the objective lens, and the platform is movable relative to the objective lens. The sensor system includes a sensor light source, a plurality of interference sensors, a complex detector, an adjustable optical cavity, and an electronic controller. Each of the interference sensors receives light from the sensing source; produces an optical path difference between the first portion and a second portion of the light, each optical path difference having a distance between the objective lens and the platform; The first portion and the second portion of the light are combined to provide corresponding output light. Each detector detects light from a corresponding interference sensor. The adjustable optical cavity is in the optical path from the sensing source to the interference sensor. The electronic controller communicates with the detector to determine the optical path difference information based on the output light detected by each of the interference sensors. Embodiments of the device include one or more feature devices of other types.

In another aspect, the present invention provides a system comprising the apparatus as described above, comprising a detector system, one or more microscopes, each microscope comprising a respective objective lens and a corresponding platform, wherein the detector device comprises a Or a plurality of interference detectors, each of which is associated with one of the microscopes, the interference detectors for receiving light emitted by the detector light source.

Each of the above-mentioned interference detectors is configured to generate an optical path difference between a corresponding first portion and a corresponding second portion of the emitted light, the optical path difference being related to the distance between the corresponding objective lens and the corresponding platform And the interference detector combines the corresponding first portion of the emitted light and the corresponding second portion to provide output light. The detector system includes one or more detectors, each detector for detecting output light from a corresponding interference detector. In some embodiments, the detector system includes one or more fiber waveguides for directing light between the detector source, the interference detector, and the detector.

Each microscope is used to detect different strips (eg different LCD panel substrates).

In general, in another aspect, the present invention provides a system comprising a plurality of microscopes, each microscope comprising a corresponding objective lens and a corresponding platform, the corresponding platform for positioning a test object relative to the corresponding objective lens; And a detector subsystem comprising: a detector light source, a complex interference detector, one or more fiber waveguides and a complex interference detector, and the fiber waveguide is used to guide the detector light source to the interference detector Each of the interference detectors corresponds to one of the microscopes; the detector subsystem further includes a complex detector and an electronic controller, each detector for receiving light from the interference detector, and the electronic controller is used for Communicating with the detector; wherein during operation, the detector light source directs light to each of the interference detectors via the fiber waveguide, and each of the interference detectors directs an output light to the corresponding detector, the output light including an interference phase The interference phase has a distance between the corresponding objective lens and the corresponding platform of the microscope, the microscope system is related to the interference detector, and the electronic controller is based on the detected output light. Decision information corresponding distance between the objective lens and the appropriate platform.

Some references are cited as disclosures of this specification. When different from the above references, the present invention will prevail.

The details of one or more of the above-described embodiments are set forth in the accompanying drawings. Other features and advantages of the present invention will be apparent from the description, appended claims and appended claims.

Referring to FIG. 1, the low coherence interference system 100 includes an interference microscope 110 for studying the object to be tested 175. The interference microscope 110 is in communication with a general purpose computer 192 for analyzing the data signals from the interference microscope 110 to provide information about the object 175 to be tested. A Cartesian coordinate system is provided as a reference coordinate.

The interference microscope 110 includes an interference objective lens 167 and a beam splitter 170 that reflects the light beam from the light source subsystem of the interference microscope 110 to the object to be tested 175 via the interference objective lens 167, and transmits the transmitted light beam reflected from the object to be tested 175. Transfer to the detector subsystem for subsequent detection. The interference objective 167 is a Mirau objective and includes an objective lens 177, a beam splitter 179, and a reference surface 181.

The light source subsystem includes a main light source 163, a second light source 197, and a beam combiner 164. After combining the light of the autonomous light source 163 and the second light source 197, the combined light is passed through the optical repeater 169 and 171 is guided to the beam splitter 170. As will be explained in more detail later, primary light source 163 provides low coherence light for low coherence interference measurements, while second source provides light with a longer coherence length to monitor scan history during scanning.

The primary light source 163 is a spatially-extended broadband source for providing an illumination beam having a wide wavelength range (e.g., an emission spectrum with a full width at half maximum (FWHM) of more than 50 nm, or preferably more than 100 nm). For example, the main light source 163 is a white light emitting diode, a filament of a halogen lamp, an arc lamp (such as a xenon arc lamp), or a light source called a supercontinuum source, and the nonlinear effect of the supercontinuum source by optical materials To produce a broadband source spectrum (eg, a spectrum of FWHM at 200 nm (or above)).

The coherence length of the second light source 197 is greater than the coherence length of the main light source 163. In some embodiments, the second source 197 is a high coherence source, such as a single mode laser source. The second light source 197 is a monochromatic light source.

The detector subsystem also includes a light intensity monitor 161 coupled to the primary light source 163. The light intensity monitor 161 provides light intensity information of the primary light source 163 such that the low coherence interference system 100 is capable of estimating the variation in light intensity.

The detector subsystem includes a main detector 191, a second detector 199, and a beam splitter 198 that directs light from the interference objective 167 to the main detector and the second detector. The main detector 191 and the second detector 199 are multi-element detectors (for example, multi-element CCD or CMOS detectors). The detector subsystem selectively includes a band pass filter 101 that filters light incident on the second detector 199 such that only light from the second source 197 can reach the second Detector 199.

During operation of the low coherence interference system 100, the primary light source 163 provides input light 165 via optical repeaters 169/171 and beam splitter 170 to the interference objective 167. Light from the second source 197 is combined with the input light 165 by a beam combiner. The interference objective 167 and the optical repeater 189 guide the light rays 183 and 187 reflected from the object to be tested 175 to the main detector 191, and form a field in the field of view (FOV) of the main detector 191. Image of the object 175. The beam splitter 198 also directs light from portions of the interference objective 167 to the second detector 199. It is to be noted that the edge rays are represented by the symbol 183 and the chief ray is represented by the symbol 187.

The beam splitter 179 guides a portion of the light (indicated by light 185) to the reference surface 181 and re-mixes the light reflected from the reference surface 181 with the light 185 reflected from the object under test. In the detector 191, the mixed light of light reflected from the object to be tested 175 (referred to as test light) and light reflected from the reference surface 181 (referred to as reference light) forms an optical interference pattern in the detector 191. Since the interference microscope 100 is used for general imaging, an optical interference pattern (also referred to as an interference spectrum or an interference image) corresponds to an image of the surface of the object to be tested.

The interference microscope 110 also includes a modulator 193 that controls the position of the interference objective 167 relative to the object under test 175. For example, the modulator 193 is a piezoelectric transducer coupled to the interference objective 167 for adjusting the distance between the object to be tested 175 and the interference objective 167 in the Z direction. Since this type of relative movement scans the focal plane position of the interference objective 167 relative to the object 175, it is also referred to as a focal plane scan.

During operation, the modulator 193 controls the scanning of the interference objective relative to the object under test 175, thereby changing the OPD between the test light and the reference light, and detecting each of the OPD between the test light and the reference light in the detector. The component will generate an interference signal. Modulator 193 is coupled to computer 192 by a connection line 195 that is capable of controlling the scanning speed during data capture. In addition, modulator 193 provides for scanning of mobile information (eg, expected scan increments) to computer 192.

For a single scanning position, Figure 2 shows a typical optical interference pattern in the main detector 191 that shows interference fringes about the height modulation of the surface of the object in the X and Y directions. The intensity values of the optical interference pattern are measured by different detection elements of the main detector 191 and provided to the microelectronic processor of computer 192 for further analysis. Each detecting component of the detector obtains light intensity data (for example, about 30 Hz or more, about 50 Hz or more, about 100 Hz or more) when the sampling frequency is the frame frequency, wherein the frame frequency is usually during scanning. Constant (constant). The value of the light intensity forms a low homology interference signal, the value of the light intensity being measured by the detector and relating to the sequence of OPD values between the test light and the reference light.

For a single detecting component of the detector 191, Figure 3 is a graphical representation of the relationship between the detected intensity (I _j ) and the scanning position. At the zero OPD position of the test and reference light, Figure 3 shows a typical low-coherence interference signal with sinusoidal interference fringes modulated by Gaussian packets. The width of the Gaussian packet is related to the coherence length of the primary light source 163. The range of OPD scan length is greater than the coherence length of the primary source.

When the main detector 191 obtains a low coherence interference signal, the second detector 199 obtains an interference signal according to the same dimming light from the second light source 197. For a single pixel (detector element) of the second detector 199, FIG. 4 is an illustration of a (highly homophonic) interference signal, which is a function of the scanning position Z. The interference signal obtained by using the second detector 199 is called a monitoring signal.

In general, OPD scanning is performed at constant velocity, and data points are acquired in an isochronous manner. In theory, each data point is obtained in the case of an equal displacement increment of the OPD. However, although scanning is usually assumed to be performed at a constant speed, scanning movement often results in linear movement due to mechanical defects or moving interference vibrations. Thus, the interfering signals obtained include errors with respect to non-uniform scanning, where non-uniform scanning causes deviations of the actual scanning position, which causes the actual scanning position to be moved from the theoretical scanning position to the actual value of the measured intensity value. Scan location.

This error is called "scanning error", as shown in Figure 5. Figure 5 shows an illustration of z as a function of time, where z is the relative displacement between the object under test 175 and the interference objective 167. In general, z corresponds to the OPD between the test light and the reference light. Figure 5 shows a straight line representing a constant speed scan. The four sampling times are t ₁ -t ₄ . In the case where no scanning error occurs, the position z of the object to be tested will lie on a straight line. However, the scanning error causes an offset between the theoretical and actual scanning positions of the object to be tested at the sampling time, so that the actual scanning position of the object to be tested deviates from a straight line, such as the data point shown in FIG. At each sampling time, the value of the scanning error is shown as ε _i , where i = 1...4.

In general, the sensitivity of the low coherence interference system 100 for measurement depends on the frequency of the source of the scan error. For example, system sensitivity will vary with the frequency of vibration of the system. For example, as shown in Fig. 6, for a low-coherence interference system, its relative sensitivity to vibration S _v is a function of the vibration frequency f _vib , where the operating parameters of the system are: average wavelength is 570 nm, FWHM is The 200 nm, low numerical aperture interference objective, sampling scan spacing is 71.5 nm, and the main detector frame frequency is 100 Hz. When the vibration frequency of the system is 20-30Hz and 70-80Hz, the sensitivity is very low. When the vibration frequency is between 20-30Hz and 70-80Hz, the sensitivity is relatively high. For SWLI, the typical fringe carrier frequency is about 25 Hz, so the main detector samples 4 times per second for each stripe. It is generally considered that a high-sensitivity region corresponding to a vibration frequency of less than 25 Hz has an error with respect to a scanning speed, and a high-sensitivity region corresponding to a vibration frequency of more than 25 Hz has a distortion caused by vibration in a scanning increment. When capturing data, the distortion quickly changes polarity between adjacent scan positions, such as from the polarity of the recorded camera frame to the polarity of another camera frame. In general, the so-called "low frequency" scanning error source (ie, low frequency vibration) herein refers to a frequency less than or equal to the frame frequency of the detector (ie, the main detector 191), wherein the detector is used to obtain low homology interference signals. . The source of the "high frequency" scan error (i.e., high frequency vibration) represents a frequency higher than the frame frequency of the detector (i.e., main detector 191), wherein the detector is used to obtain low homology interference signals.

When using the low coherence interference system 100 for measurement, in order to reduce the influence of the scanning error, the computer 192 uses the information of the monitoring signal obtained by the second detector 199 to reduce the use of the main detector 193 to achieve low homology. The effect of the scanning error of the interference signal. Because the monitoring signal is from a coherent light source (second light source 197), the fringes extend beyond the scan length and provide a description of the phase information (and a range that exceeds the relative displacement information provided accordingly). As will be explained in more detail later, in general, the analysis of the monitoring signals at many points in the FOV of the second detector 199 can determine the scanning error, which includes the scanning error caused by the vibration, especially in the above. The scanning error of the defined high frequency region.

Assuming that the phase of the monitored signal after scanning has a phase difference in the FOV, phase divergence (eg, different phase offsets of at least some of the monitoring signals) can be used to correct the system error to indicate that the scanning position is different. Varying scan error. Therefore, when the phase divergence is correctly analyzed, the above characteristics enable the high frequency vibration to be correctly measured, and in the case where many measurements of the phase divergence are not provided, the high frequency vibration is erroneously measured. For monitoring signals, the choice of providing image points also includes highly patterned surfaces, such as semiconductor wafers.

Thus, after the computer 192 determines the scan movement history, the true (or at least more accurate) scan movement can be determined based on the monitoring signal to obtain a low coherent interference signal. Further processing of the low coherent interference signals collected by the main detector 191 (e.g., the cubic line internal difference method or other algorithms) reduces the effects of scanning errors in the data. Data analysis of monitoring signal data and low coherent interference signal data is detailed below.

Optical Plane Scanning Interferometry System (PUPS Interferometry Systems)

Although the above discussion relates to the interference objective that images the object to the detector, the scan error correction can be used for other configurations. For example, in some embodiments, the interference objective mirrors the pupil plane of the microscope to the detector. This configuration is called the "Plan Plane Scanning (PUPS)" configuration. This mode of operation is very useful, for example, it can be used to determine the complex reflectivity on the surface of the object under test.

Figure 7 shows a PUPS interferometric system 200, most of which are identical to the low coherence interference system 100 of Figure 1. However, unlike the low coherence interference system 100, the PUPS interference system 200 includes a tubular lens 213 and a polarizer 215 for pupil planar imaging, the polarizer 215 being disposed between the interference objective 167 and the beam splitter 170. In the PUPS interferometric system 200, the pupil plane 217 is imaged to the main detector 191. The field diaphragm 219 limits the sample beam to a small area on the object to be tested 175. The low homology interference system 200 acquires the data in the same manner as the low homology interference system 100 acquires the data, as described above.

For analysis, the computer 192 converts the interference signal of the autonomous detector 191 to the frequency domain, and obtains phase and amplitude information of different wavelength components of the main light source 163. Because the primary source is wideband, many independent spectral components can be calculated. The amplitude and phase data are directly related to the complex reflectivity on the surface of the object to be tested, and the amplitude and phase data can also be used to determine the information of the object to be tested.

Because of the manner in which the PUPS interfering system 200 is configured, each of the detection elements of the main detector 191 is capable of providing a multi-wavelength measurement of a particular angle of incidence and polarization (according to the polarizer 215). Thus, the detector component set can cover a range of angles of incidence, polarization states, and wavelengths.

Figure 8 shows the relationship between the light on the focus plane 229 (e.g., the object under test) and the light on the pupil plane 217. Since each of the light source points irradiated to the pupil plane 217 causes the test light that illuminates the object to be tested to generate a plane wavefront, the radial position of the light source point in the pupil plane 217 defines the relationship between the incident beam and the normal of the object to be tested. Angle of incidence. Therefore, all the light source points at a fixed distance r from the optical axis correspond to a fixed incident angle θ, by which the objective lens focuses the test light onto the object to be tested. For a tubular lens for pupil plane imaging with a numerical aperture of NA and light having a maximum radial distance r _max , on the pupil plane 217, the distance from the optical axis OA is the point of r and the focal plane 229 The relationship of the incident angle θ can be expressed by sin(θ)=(r/ r _max ) NA .

Path-length Scanning

The above embodiments for explaining the relationship between Fig. 1 and Fig. 6 both use a Mirau objective lens for focal plane scanning. In general, other configurations are also possible. For example, an interference system including a Linnik objective lens can also be used. This system is shown in Figure 9. In particular, the optical path length scanning interference system 300 includes an interference microscope 310 that images the object under test 175 to the main detector 191. Most of the components of the optical path length scanning interferometric system 300 are identical to the low coherence interference system 100 of FIG. However, the optical path length scanning interference system 300 includes a Linnik interference objective 325 instead of a Mirau interference objective, wherein the optical path length scanning interference system 300 is characterized in that the beam splitter 379 directs light from the beam splitter 170 along the Linnik interference objective 325. Different optical arms are divided into test light and reference light. The Linnik interference objective 325 includes a test light objective 327 in the test arm and a reference light objective 329 in the reference arm. The reference object 381 is disposed in the reference light arm and reflects the reference light back to the beam splitter 379.

Reference light objective 329 and reference 381 are assembled together and then coupled to other elements of the Linnik interference objective by modulator 331. During operation, with respect to the beam splitter 379, the modulator 331 adjusts the OPD between the test light and the reference light by moving the surface of the reference light objective lens 329 and the reference object 381. During the scanning, the optical path length between the reference light objective lens 329 and the reference object 381 remains unchanged. Therefore, the OPD change between the test light and the reference light is irrelevant. This scanning mode is called the "optical path length scanning" mode. In the optical path length scanning interferometric system 300, the optical path level scanning increases the length of the collimating space in the reference optical arm of the Linnik configuration, while during the scanning, the object under test in the test arm remains at the same position.

Interferometric systems featuring Linnik interference objectives can also be used in PUPS mode of operation. For example, referring to FIG. 10, the interference system 400 includes an interference microscope 410 for imaging a pupil plane to the main detector 191, and the interference microscope 410 includes a Linnik interference objective 325, such as the PUPS interference system 200 described above.

In general, when correcting scan errors, the scan motion analysis should be based on the scan mode of the interferometric system (eg, the scan mode of the focal plane or optical path length) and the imaging mode (eg, the imaging mode of the DUT or PUPS). For example, the carrier fringe frequency in a low coherence signal will vary with the operating mode of the system. For example, for a Linnik interferometric system operating in PUPS mode, the scan mode of the optical path length is such that the fringe carrier frequencies are the same at all locations in the pupil plane image. On the other hand, for the Mirau interferometric system operating in PUPS mode, the scanning mode of the focal plane causes the carrier fringe frequency to increase with the distance of the optical axis (OA) in the pupil plane as cos(θ). The form is reduced, where θ is the angle between the ray and the optical axis on the plane of the object to be tested (refer to Figure 8).

It should be noted that although the Linnik interferometric system operating in the mode of optical path length scanning typically produces a monitoring signal with a constant frequency on the pupil plane, there are still two perturbations from the interfering cavity. The first type of perturbation is a (non-linear) vibration caused by unwanted scanning movements that occur when the reference light objective lens 329 and the reference object 381 (e.g., a reference mirror) move together. In this case, the scanning error causes the monitoring signal to produce an optical path change, and the monitoring signal on the pupil plane is originally independent of the position to be measured. Another type of disturbance is the vibration of the object leg, which causes a change in the distance between the lens 127 and the surface of the object to be tested 175. In this case, the vibration causes the monitoring signal to produce an optical path variation, wherein the optical path variation is a function of the angle of incidence of the light in the object space to be tested (or a function of the radial position on the pupil plane). Therefore, in this configuration, it is necessary to distinguish the two vibrations (moving components) so that subsequent signal correction can be properly considered.

In some embodiments, variations in the fringe carrier frequency can be used in the FOV of the PUPS mode, with multiple monitoring signals having minimal phase divergence at the zero OPD position. The radial positional variation of the fringe carrier frequency produces phase divergence on both sides of the zero OPD position in the FOV of the PUPS mode to provide the necessary information to determine the scan increment in the case of high frequency and low frequency vibrations.

In general, the scanning error correction techniques discussed herein can be used for both scanning methods, as well as general imaging and pupil plane imaging, and can be used for data processing in different modes, particularly PUPS operating modes. If the optical path length is scanned in a Linnik interference microscope (refer to Figure 10) operating in PUPS mode, the fringe carrier frequencies are the same for all pixels of the pupil image. If the focal plane of the object to be tested and the OPD are simultaneously scanned (as in the Mirau interference microscope of Fig. 7), the fringe carrier frequency is cos with the distance from the optical axis (OA) in the pupil plane. The form of θ) is reduced, where θ is the angle between the ray and the optical axis on the plane of the object to be tested. The advantage of the fringe frequency variation is that it can be used in the FOV of the PUPS mode, where there are multiple monitoring signals with minimal phase divergence at the zero OPD position. The radial position variation of the fringe carrier frequency causes phase divergence in both the zero OPD position in the FOV of the PUPS mode to provide the necessary information to determine the scan increment for all vibration frequencies.

Determine the scanning position based on the monitoring data

In general, there are currently a number of methods for determining the scanning position based on monitoring data. For example, if the source of the scan error is limited to a low frequency source, then using a general PSI algorithm is sufficient to determine the phase of the monitor signal at a particular camera frame and pixel. For example, if the theoretical phase shift between camera frames is π/2, then a known phase shift algorithm can be expressed as follows:

Where r is the vector specifying the position of the pixel (the position vector of a pixel), and g _1,2,...5 represents a series of corresponding intensities of the pixel during data acquisition (see Schwider et al., 1983; Encyclopedia of Optics, p. 2101, Table 2). Theoretically, (Formula 1) to provide the intermediate frame Φ ₃ g of phase. In another example, the PSI algorithm proposed by Deck and Olszak and Schmit can be used to determine the scanning position (L. Deck, "Vibration-resistant phase-shifting interferometry", Appl. Opt. 35, 6555-6662 (1996); Olszak and Schmit, US 6,624,894). However, because its proposed PSI algorithm is sensitive to high frequency vibrations (like low homology signals), its proposed PSI algorithm is only suitable for low frequency vibration.

A method of measuring the phase Φ(r) of the (intensity) minimum of two different pixel positions is used to improve the defect of the above PSI algorithm at high frequency vibration (making it suitable for low frequency vibration). For example, when using the PSI algorithm, in a specific case (for example, using (Formula 1) or a similar formula), it is generally considered that the error generated when determining Φ(r) is 2 of the Φ(r) frequency. Repeat for periodic cycles. Therefore, averaging two (or more) phases orthogonal to each other (90° out of phase) can reduce errors with respect to high frequency vibrations.

More generally, the above several methods are based on the PSI algorithm, and then the actual scanning position is determined after the interference data is obtained. In general, if a multi-detection component detector (as described in the above embodiment) can be used to obtain a range of phase Φ(r) and/or frequency, the above method is in a multi-detection component detector. It is the most efficient way to obtain the characteristics of the monitoring signal and the interference spectrum that produce a slight phase divergence (where all monitoring signals have the same frequency) in the FOV.

For example, when the interferometric system is operated in a conventional imaging mode, the height variation of the object to be tested may cause phase divergence. In another example, when the interference system is operated in a conventional imaging mode, phase divergence also occurs when the object or reference is flipped in order to generate interference fringes. In the case of a Mirau interference objective (or similar interference objective) and PUPS mode, this interference system architecture naturally produces a range of interference fringes in the detector's FOV.

The following discussion will provide a specific method for determining the scanning position by a range of phases Φ(r). First consider a PUPS-Linnik interferometric system (for example, Figure 10), which considers the reference mirror (381) and the reference light objective 329 as a rigid object and moves along the optical axis to achieve optical path length scanning. The optical path difference of the specular reflection at different points in the plane is z(t, r), where t represents the time parameter during the scan. The optical path difference is composed of ideal scan and error terms:

z ( t , r )= z ₀ ( t , r )+ ε ( t , r ) (Formula 2)

Where z ₀ represents the ideal scan and ε represents the error term or the noise term. The phase of the interferometer is:

Φ( t , r )=Φ ₀ ( r )+2π z ( t , r )/ λ (Equation 3)

Where Φ ₀ is the phase deviation, which is used to indicate the possible phase difference between different points in the pixel plane. The light source of the second source has a wavelength of λ, and it is assumed that λ is independent of r.

The origin of r is selected as the point corresponding to the optical axis in the pupil plane, and θ(r) represents the angle of incidence on the focal plane of the object to be tested, which means that the reflected ray passes through r in the pupil plane, The Abbe sine condition should be met as follows:

Sin[θ( r )]=κ| r |, κ is a constant (Equation 4)

Like the Linnik interferometric system, when the object under test moves with the reference mirror, the scan of the optical path difference (OPD) will be independent of θ , thereby completing the scan in the collimated space. However, when the focal plane of the object to be tested is scanned by the Mirau interferometric system, the OPD will be related to θ . Therefore, two restrictions can be obtained as follows:

z ₀ ( t , r )= z ₀ ( t ), if it is a scan of the optical path length, z ₀ is independent of θ (Equation 5)

z ₀ ( t , r )=cos(θ( r )) z ₀ ( t ,0), if it is a scan of the focal plane

If the optical path length and the focal plane are scanned simultaneously, z ₀ is equal to the linear sum of the above two movements (optical path difference).

As discussed above, in some embodiments, the scan is theoretically a perfect linear function of t. When starting the scan, all points of the pupil plane have theoretically the same OPD, and during the scan, the object to be tested and The reference is ideally not flipped. In this case, you can get the following formula:

Where c is a constant and varies with the scan itself, and It is also a constant. The relationship between scanning and r depends on the type of scanning.

In general, the error term ε is related to both t and r. However, when the scan is performed, the object to be tested is assumed to be a rigid body and there is no flip, so the error term can be simplified as follows:

ε( t , r )=ε _p ( t )+cos(θ( r ))ε _f ( t ) (Equation 7)

The first term of (Equation 7) represents the vibration or scanning error in the collimated space, and the second term proportional to cos( θ ) represents the vibration or scanning error in the high numerical aperture space of the interferometer, which is the focal plane Caused by errors. Suppose ε is small.

The interference intensity of the monitoring signal detected by the second detector in the pupil plane is related to time, and is also related to the phase difference in the interferometer, and is expressed by (Expression 8) as follows:

I ( t , r )=[ A ( r )+ dA ( t , r )]cOs[Φ( t , r )]+ c ( r )+ dc ( t , r ) (Equation 8)

A (r) represents the average amplitude of the interference spectrum at point r. dA ( t , r) represents the variation in the average amplitude of the interference spectrum at point r. Φ( t , r) represents the phase at point r, which is a function of time t . c (r) represents the average deviation of the interference signal, which is usually the function of r. Dc ( t , r) represents the variation of the average deviation of the interference signal. (Equation 8) is usually a time-varying function.

The intensity I ( t , r) is sampled by a discrete set of time points { t _i } and a discrete set of points { r _i } in the pupil plane. The ideal sampling time point is equidistant, so

t _{i +1} = t _i +δ t , where t _{i is} independent of time (Equation 9)

For a point r, all time point sets { t _i } can be regarded as a one-dimensional array, and then the estimates of the error terms ε _p ( t ) and ε _f ( t ) are made. As described above, in the case of high frequency vibration, a single pixel cannot reliably estimate the error terms. However, by using multiple vectors represented by { r _i } different points, a large number of estimates can be made for each of these error terms. The median of a set of measurements can be used to get a final estimate.

Wherein for point r _i , i represents an estimate made using different points in time. To some extent, the set of points { r _i } used can be arbitrarily chosen. The main consideration is that the starting phase of the above set of points must have sufficient degree of variation, otherwise there will be several kinds of θ when performing focal plane scanning. The value.

The following algorithm is used for a single set of time vector points { t _i }. The first step is to accurately calculate the peak value of the intensity vector I ( t _i ,r). This requires a very small δ t such that in a single sine wave of the interfering signal, the number of (time) sampling points ranges from 8 to 30 sampling points per sine wave. Based on this fine sampling, interpolation can be used on the sampled points, such as a cubic spline.

I _Fine = spline ( z , I , z _fine ) (Equation 11)

According to the vector I _fine , the extreme value of the signal (including the maximum value and the minimum value) can be obtained, where the extreme value occurs at an odd multiple of the phase π/2.

peaks = peakfinder (I _Fine) (Formula 12)

Using these peaks, the following values can be estimated: c ( t ) + dc ( t ), A + dA ( t ), and the ideal phase Φ _ideal , where Φ _ideal is a function of time. By fitting (Fitting 13) to the peak data, you can find Φ _ideal :

Φ _Ideal ( t _i , r )=Φ _Ideal ( t ₀ , r )+(i-1)ΔΦ _Ideal ( r ) (Equation 13)

among them,

When scanning the optical path length (Equation 14)

When scanning the focal plane

The fitting calculation produces an optimum value for the starting phase Φ _ideal ( t ₀ , r) such that the peak of the cosine function is at the found position of the observed peak. If The value is not known accurately, and it can also be part of the data fitting algorithm.

It is also possible to use other methods to fit the monitoring signal. For example, another way to find the peak is to estimate the fast Fourier transform (FFT) of the phase. However, the use of peaks does not require dividing the sampling period by the entire scan length, which is an advantage when scanning the focal plane because, for PUPS analysis, the sampling period varies as the interference loop in the pupil plane changes.

The next calculation is to estimate the error of the phase Φ caused by the incorrect scan. For example, this calculation can be done by the following inverse cosine function (where the inverse cosine function makes the function value reciprocate between 0 and π)

d Φ=Φ-Φ _ideal = sign (sinΦ _Ideal )*(cos ^-1 (( I - c - dc )/( A + dA ))-Φ _Ideal (Equation 15)

This mathematical formula (Equation 15) is used for all sampling points of the vector. After the dΦ estimation, it is easier to calculate the error term ε ( t , r ). θ processing complex numbers for different values provides sufficient information to distinguish between the error terms ε _p ( t ) and ε _f ( t ). For example, if n monitoring signals with different angles of incidence are analyzed, for each sampling time point t , the collected information will produce n equations:

The above equations provide an overdetermined system that can be easily solved to provide estimates of ε _p ( t ) and ε _f ( t ). The above process must be performed in the case where both vibrations (reference light delay and delay of the object to be tested) occur simultaneously, for example in the architecture of the Linnik interferometric system. For Linnik or Mirau interferometers that use focal plane scanning, the above equations can be simplified to:

In this case, the calculation can be simplified to find the median value of the final n estimates of ε _f ( t ).

Correction of low homology signal data

In general, after the scan error is determined, the low-coherence interference data can be corrected based on the scan error. The following is a detailed example to illustrate the correction of low coherent interference signals before further processing of low coherence interference signals. After the scan position is measured, the low-coherence scan data is corrected by cubic interpolation (or other type of interpolation). I _w ( t , r) represents low homology scan data. From the scanning error analysis, it is known that the low-homology scan data is not accurately sampled at the time point { t _i }, but is sampled at the time point when the error term is added at the above time point. Therefore the actual sampling time is

T _i (r)= t _i +Δ _i ( r ) (Equation 16)

among them

among them

When scanning the optical path length (Equation 18)

When scanning the focal plane of the object to be tested

In other words, the value of I _w ( T _i ,r) has been measured, but I _w ( t _i ,r) is the value to be measured, so the cubic spline interpolation is used to calculate I _w ( t _i , r), as follows

I _w ( t _i , r )= I _w ,( T _i -Δ _i ( r ), r ) (Equation 19)

A comparison table [ T _i , I _i ] of the data points is established for the calculation of the cubic square spline interpolation method, where i =0, 1, 2, ..., n and I = I ( t ). The curve of the cubic square spline interpolation is a typical continuous curve of the segment, which passes through each data point (value) of the comparison table. Each spacing has its own cubic polynomial and coefficient, expressed as follows

S _i ( t )= a _i ( t - T _i ) ³ + b _i ( t - T _i ) ³ + c _i ( t - T _i ) ³ + d _i , t [ T _i , T _{i +1} ] (Equation 20)

The cubic polynomials of all the spacings are included together and represent the curve of the cubic square spline with S ( t ).

Since there are n pitches and each of the pitches has 4 coefficients, a total of 4 n parameters need to be determined in order to define the curve of the cubic cube. Therefore, 4 n independent constraints are required to determine them (4 n parameters). For each spacing, since the cubic polynomial curve and the cubic square spline curve (reference table) must have equal values at the two endpoints, two constraints can be obtained:

S _i ( T _i )= I _i S _i ( T _{i +1} )= I _{i +1} (Equation 21)

It should be noted that these constraints (Equation 21) result in a segment continuous function. More than 2 n restrictions are still required. Since it is desirable to make the interpolation curve as smooth as possible, another set of constraints is that the first and second derivatives must be consecutive:

These restrictions (Equation 22) apply to i = 1, 2, ..., n -1, resulting in 2 n -1 constraints. Therefore, more than two constraints are required to determine the cubic square spline curve. There are some standard options available to users: , called the "normal" restriction (Equation 23) , called the "clamped" restriction (Equation 24)

If the function is periodic, other options are also possible. Which is better for the application.

After obtaining 4n coefficients and 4n linear constraints, it is easy to solve them (equation equations), for example using a general algorithm.

The low-coherence interference signals corrected in this way are then further processed according to their application, such as PUPS analysis of surface structures or general surface topography measurements.

J-matrix Approach

In some embodiments, an approximation method called "J matrix approximation" can be used to correct the interference data using scan error information from the monitoring signal. This approximation is detailed below.

In a measurement without a scan error (which provides a strictly equal sampling point for a signal), the last unsampled signal is represented by a vector a with M elements and then by discrete Fourier transform (DFT) Perform a spectrum analysis on it. DFT is mathematically equivalent to solving a linear equation system in the form of a matrix, as shown below

Where M×M matrix The lines represent the base functions of purely vibrating signals and the signal u is treated as a linear combination of such basis functions. Matrix The elements are represented by the plural symbols as follows:

In order to get the vector The spectral coefficient is solved by (Equation 25) as follows:

become

So vector The mth element becomes

(Formula 29) has the general definition of DFT (except for subscript changes, the subscript of DFT originally started with 1 instead of 0). vector m elements represent unsampled signals The frequency components of the 0th, 1st, ..., ( m -1)th harmonic. It is noted that the first (m - h) and the second harmonics (- h) harmonics are equivalent. This means that in the spectrum, the spectral components of the high frequencies are actually negative spectral components.

Consider now a signal taken from a non-uniform sampling increment, such as a scanning error (caused by the vibration of the measurement system) or a theoretically uniform sampling increment of missing data points. Spectral analysis of discrete signals using a general DFT necessarily produces discrete spectra.

If the sampling increment is known, the Lomb-Scargle method is one of the methods for performing spectrum analysis on data that is unevenly sampled. The power spectrum estimates for each frequency are calculated independently. The fact that the fitting functions are not orthogonal to each other causes a loss of information between different frequency components. Therefore, the Lomb-Scargle method is not a formal method, but it is still a good method with a lot of noise.

In some embodiments, an approximation similar to DFT can be used for spectral analysis of data that is not uniformly sampled. A modified set of basis functions is used to form a new M×M matrix . Each of the base functions (rows of the matrix) includes the value of the purely vibratory signal sampled at a known scan position. Like DFT, the goal is to represent the measured signal as a linear combination of (corrected) basis functions, a new matrix The element is

The function X _m retains information about the scan position of the uneven sampling. For example, in the OPD scan of the interferometer, X _m represents the M scan positions of the acquired data (eg Where z _m is the actual scan position, where z _m takes into account the angular relationship of (Equation 7). In general, there are many ways to obtain the value of X _m , such as the techniques discussed above. Another technique will be discussed below.

The function Y _n defines the frequency to be studied. For example, for applications that replace DFT with frequency analysis, the function Y _n becomes

It can be seen from (Expression 30) that Y _{n is} expressed in the scan, and the range is from 0 to equivalent. The positive and negative frequencies of the frequency of the cycle. The upper limit of the frequency is commonly referred to as the Nyquist frequency, which is a general limitation of the DFT, and in special cases, the J matrix approximation can be used to analyze frequencies above the Nyquist frequency, as discussed in the numerical examples below. If you need a definition similar to DFT, the constant c is an option of 1 or Factor.

The new linear equations are represented in matrix form as follows:

In order to get the vector The spectral component is solved by (Equation 31) as follows:

If all the data points of the vector d are independent of each other (ie, the M values of X _m are unique), the J matrix approximation method obtains a positive solution.

It should be noted that, in general, the matrix The basis functions are not orthogonal. However, the base functions of positive solutions must be linearly independent of each other.

In applications similar to low coherence interference techniques, there is usually a large collection of data (each pixel represents a data set) that requires spectral analysis. Since the uneven OPD samples are the same for all pixels, the same J matrix inverse matrix can be used for all data sets. . Because vector The calculation is simplified to the P-th power and vector of an inverse matrix The product, so the result can be quickly found, where P is the number of camera pixels.

As discussed above, the actual measurement system is affected by the scanning error caused by the vibration, and is also affected by the measurement of noise (such as pulse noise or digital error in the camera of the interferometer), where the measurement The error adds an undetermined value to one or more of the recorded data points.

In general, the correctness of spectrum analysis using J matrices can be affected by many factors. For example, the correctness of spectrum analysis using J matrix is affected by the signal-to-noise ratio, the constraints of the J matrix, and the inverse matrix of the J matrix.

Generally, in the case where there is noise, for different values of m, almost the same value of _m X-electrode scanning pitch will result in unevenness hardly functions with linearly independent conditions are very poor substrate matrix, And thus the calculated spectrum has an unsteady solution.

It is generally believed that if the stability problem arises from noise, an extremely high degree of stability can be achieved by limiting the spectrum analysis to a frequency band with a spectral amplitude greater than zero. The J matrix then becomes a rectangular matrix (the number of rows is less than the number of columns). Therefore, the linear equation system is overdetermined. The best solution based on the least squares is calculated. Since the rectangular matrix does not have an inverse matrix, the virtual inverse matrix can only be obtained by singular value decomposition (SVD) or Moore-Penrose method. The inverse matrix obtained by the Moore-Penrose method is expressed by the following formula:

J ^-1 =( J ^T J ) ^-1 J ^T (Equation 33)

The superscript T represents the transposition operation of the matrix J. In addition to making the calculated spectrum more stable, the approximation method using a rectangular J matrix has the advantage of quickly obtaining calculation results, especially when the inverse matrix has to be multiplied by many data vectors. Time.

This calculation method can perform spectrum analysis on the data obtained by the uneven sampling position, and can also be extended for signal distortion compensation. These additional distortions are functions of the camera frame m (eg, a flicker source in an interferometric system), a function of frequency components (eg, spectral filtering effects of measurement settings), or a combination of the two. These effects are combined to represent the function I _mn . The monitoring function I _mn requires independent measurements. Compared to the disturbed signal (Materials that must be analyzed for spectrum analysis) The functions X _m and I _mn containing information on the sampling position are highly likely to have a high sampling rate. The elements of the J matrix become the weighted average of the items on the right side of the equation (Eq. 29). S is the number of values I and X in the integration time of the detector (for example, in the frame integration time of the camera), where the detector is used to measure Elements. A new set of basal functions is used to form a general form of J matrix.

The general form of the J matrix can be further simplified for the distortion of various monitoring schemes, and the following summary illustrates two simplified methods.

In some embodiments, the intensity and scanner position are monitored once for each camera frame, the intensity variation is small in one camera frame (eg, giving a very short camera shutter time) and the variation in light source intensity is equally Affects all frequencies. The average calculation of (Equation 34) is simplified to an summed (summand). I is only a function of the frame m . (Expression 34) is simplified to a J matrix indicating the variation in the intensity of the light source.

In some embodiments, the intensity and scanner position are monitored once for each camera frame. In a camera frame, the intensity variation caused by the scan is large and the intensity variation is frequency dependent. Although only one scanner position is measured in each camera frame, the scanner movement during frame integration and the final result of the measurement can still be estimated. Assuming that the linear movement of the scanner is between the frames m -1 and m +1, during the camera frame m, the value of X will be from X _m - T ‧ FR ‧ ( X _{m +1} - X _{m - 1} ) / 4 becomes X _m + T ‧ FR ‧ ( X _{m +1} - X _{m -1} ) / 4, where T is the integration time of the camera frame and FR is the frame frequency of the camera (unit: Hz (1/ s)). After the solution, the addition is replaced by the integral (Expression 34).

Where sinc(x)=sin πx/πx and during the integration of the camera frame, it is assumed that the intensity of the light source remains unchanged. Since the integration time of the camera is limited, (Equation 36) shows that the reduction of the fringe contrast is related to the frequency (frame frequency). For the first and last frames, the scores in the sinc function are replaced by X _{m + 1} - X _m and X _m - X _{m -1} , respectively.

In some interference applications, the function I of (Equation 34) or the function X of (Equation 29) or (Equation 34) is not applicable to all camera pixels. In this case, the J matrix must be calculated for individual pixels or a set of pixels. Possible causes of function changes related to pixels include tilt and tip-tilt (rotation of the axis of symmetry in the vertical or horizontal direction). For example, the vibration of the interference cavity disturbs the movement of the piston scan and vignetting. The edge of the FOV significantly affects the pixel, and the normal angle of the surface changes as the scanning moves (as when using a Fizeau-type interferometer and a reference sphere to measure a spherical surface).

The advantage of using the J-matrix approximation for signal analysis is that there is no need to perform a spectrum analysis of the signal after each scan. Since the process of the J matrix approximation can be considered as a substitute for DFT, the inverse of the calculated spectrum for DFT will produce a signal equivalent to the original signal sampled by the uniform increment, and the signal removes the J matrix calculation. Any other effects considered (changes in light source intensity, reduced fringe contrast due to limited integration time, etc.).

The flowcharts of Figures 11, 12A and 12B summarize three variants of the J-matrix approximation. Specifically, the flowchart of FIG. 11 is for explaining spectrum analysis using the J matrix, and the flowchart of FIG. 12A is for explaining the extended J-matrix for compensating for signal distortion. The flowchart of FIG. 12B is used to illustrate the use of the J matrix to reconstruct the corrected interference signal.

Referring to Fig. 11, the J matrix approximation includes a data generation phase (1151) and a spectrum analysis phase (1133), and is used to generate N spectra (1159). For example, the data generation stage 1151 includes a step of data capture and scan motion analysis (1153), wherein the data capture and scan motion analysis step (1153) generates N scan positions (1155) and N interference data sets ( 1157) to the spectrum analysis phase (1133). The N scanning positions are not necessarily equidistant, but the offset can be known from the determined scanning movement history. The N interfering data sets 1157 correspond to low homology interfering signals obtained using the main source and detector of the interferometric system.

The spectrum analysis 1133 phase is related to the spectral decomposition of the N interference data sets 1157 and provides N spectra 1159 as outputs for further analysis. Specifically, the spectrum analysis stage 1133 includes a step (1161) of constructing the J matrix, a step 1163 of finding the inverse matrix of the J matrix, and a step 1165 of multiplying the inverse matrix of the J matrix by the N sets of interference data sets 1157.

In order to form the J matrix, the basis function (1161A) corresponding to the different frequencies is first calculated, and then the base function is used as the column to form the J matrix (1161B). In general, the basis function corresponds to the value of a purely vibratory signal known to be disturbed by the scanning position.

The N spectra 1159 are suitable for the evaluation of the scan; they can also be used to reconstruct the corrected interference signal according to the (uncorrected) basis function of the DFT.

Referring to Fig. 12A, for the augmented J matrix approximation, in addition to step 1273, which additionally measures the influence of signal distortion, the portion of the other data generation (1271) is similar to the portion of the data generation (1151) of the J matrix approximation method. The influence of signal distortion will be considered when constructing the J matrix. Specifically, the base function of the augmented J matrix corresponds to the value of a purely vibratory signal known to be disturbed by the scanning position, wherein the value is corrected based on the effects of signal distortion. Spectral analysis 1233 includes steps similar to the J matrix approximation, and the calculations that make up the J matrix include the calculation of the basis function, whereas the basis functions correspond to different frequencies that are modified according to the record of step 1273 affected by the signal distortion.

The flowchart of the 12B illustrates the application of the augmented J-matrix, in which the N spectra 1159 are calculated in the same manner as in the 12A diagram. Next, the corrected spectrum is used to reconstruct N corrected interference data sets 1211, wherein the N corrected interference data sets 1212 are derived from the discrete Fourier inverse conversion corrected interference data set 1212.

The results of J matrix approximation and general DFT for different low-coherence interference signals are illustrated by numerical experiments from Fig. 13A to Fig. 15C.

Figures 13A through 13E illustrate vibration data and signals without camera noise (ie, signals without scan errors). Figure 13A shows the signal itself, which is the cosine fluctuation produced with the Gaussian packet. The solid line is the unsampled continuous signal, while the point indicates the actual data point. These signal diagrams only show a quarter of the entire SWLI signal. Figures 13B through 13E show the spectral amplitude and spectral error values using the DFT and J matrix approximations. Specifically, Figures 13B and 13D are spectral and spectral errors using DFT, while Figures 13C and 13E are spectral and spectral errors using the J-matrix approximation. In the absence of scan errors, the spectral Gaussian distribution of the DFT and J matrices is the same and both have a spectral error of zero.

Figures 14A to 14E have vibration data similar to those of Figs. 13A to 13E. Although the data points are still on the ideal curve at this time, they are sampled at the scanning position of the uneven sampling. As shown in Fig. 14B, when the DFT method is used, the scanning error shifts the spectrum by an ideal Gaussian curve. When the DFT method is used, the information of the correct scanning position is missed, and thus the spectral error is caused, as shown in Fig. 14D. However, Figures 14C and 14E show that the J-matrix approximation can still achieve spectra without spectral errors.

Fig. 15A to Fig. 15E show patterns similar to those of Figs. 13A to 13E, except for the scanning position of uneven sampling and the influence of floor noise on the signal. As shown in Fig. 15A, it shows the result of the data points sampled by the uneven scan increment on the ideal Gaussian curve. Referring to Figures 15B to 15E, the baseline noise makes the spectrum calculated by the DFT and J matrix no longer a slow-change function and produces spectral errors. However, in general, the spectral error value of the DFT method is larger than the spectral error value of the J matrix approximation.

In the above discussion about the 13A-15E picture, the sampling position is set to be offset from a strictly equal interval sampling position by about 0.16 times the square root mean square value, and in the 15A to 15E pictures, the camera is miscellaneous. The level of the signal is the 1% rms value of the entire signal range.

In fact, the benefit of using a J matrix is when the source of the scan error. For example, when vibration is the primary source of scanning error and the vibration can be monitored, the J matrix has a significant improvement in measurement correctness. When the main source of error cannot be monitored, the effect of the J-matrix approximation may be poor.

Although the above only discusses the J matrix approximation associated with the improved accuracy of the measurement using a low coherence interferometer (such as a SWLI interferometer), the J matrix can also be applied to other types of interference data. For example, the J-matrix approximation can be used to analyze signals obtained using long coherence length interferometers (ie, interferometers that include sinusoidal fringes, but whose interference fringes are not modulated by Gaussian envelopes as is the SWLI signal). The theoretical analysis will be omitted, and the results of numerical experiments will be used to illustrate the results of the analysis of the above signals using the J matrix. For example, referring to Figures 16A through 16B, a signal consisting of 80 pure sine waves is sampled at only 100 sample locations, 100 of which are completely randomly sampled within a known interval. of. Figure 16A shows a pattern of the signal, where the points on the sinusoid represent the sampled data points. In the case of Nyquist, the signal is undersampled. Specifically, referring to FIG. 16B, 100 data points are analyzed by a 100×100 J matrix, wherein a 100×100 J matrix is composed of a basis function corresponding to 50-99 cycles, and 50- 99 cycles are in the negative counterparts with which the known spacing is associated. Suppose there is some information about the frequency components. The selectable frequency band is used to define the basis function. The information is free of noise. The J-matrix spectrum has a distinct peak at 80 cycles per pitch, which means that the J-matrix approximation can be reliably performed.

Referring to Figures 17A through 17C, the data identical to Figure 16 is used to perform a second number of value experiments, and additional noise corresponding to the 2% signal range is added to the signal. Two J matrix analyses were performed on this data. Specifically, referring to Fig. 17B, when the first analysis is performed, a spectrum having a large spectral error is generated because a badly-conditioned 100 × 100 J matrix is used. Referring to Figure 17C, in the local secondary analysis, because a 100×80 J matrix is used to analyze the data, significant peaks are obtained at the correct frequency.

Referring to Fig. 18, Fig. 18 shows the results of a numerical experiment in which an augmented J matrix is used to correct the interfering interference signal compared to the corrected spectrum of only the calculated signal. This example shows six possible signals for low homology interferometers (marked by (a)-(f)). From signal (b) to signal (f), more and more signal distortion effects are added. This series of signals begins with a signal (a) that displays an undistorted interference signal. Signal (b) corresponds to a scan with a non-uniform scan increment. Some of the light source flashes are added to the signal (c), and the effect of the limited frame integration time is added to the signal (d). In the 128 frames, the impact of the limited frame integration time is most obvious. The last source of noise added was camera noise and produced a distorted interference signal (e). In addition to camera noise, the base function of the augmented J-matrix includes the effects of all signal distortion, but the effects of signal distortion cannot be individually monitored. After the spectrum calculation, the discrete Fourier inverse transform produces a corrected interference signal (f). The original undistorted signal (dashed line) is overlapped with the signal (f) and compared. In this experiment, a rectangular augmented J matrix of 256 x 181 after removal of the high frequency range was used.

As described above, there are several sources of information generated about the scanning position X _m of non-uniform sampling. Of course, in some embodiments (e.g., embodiments related to Figures 1, 7, 9, and 10), measurements of the monitoring system also produce such information. However, in general, this information comes from other sources. For example, this information can come from accelerometers, contact probes, capacitance meters, barometers, optical encoders (such as optical linear encoders), or the technology itself using low coherence interference data.

Compound Reference Surface (Compound Reference)

In some embodiments, the composite reference plane is used to determine information about scan errors. The composite reference is a reference having at least two reference faces (a primary reference face and a second reference face).

The main reference surface serves as a general reference surface. When the interferometric microscope scans the OPD, the second reference surface is used to provide information so that the displacement of the object to be measured relative to the interference microscope can be monitored. In general, the second reference surface is fixed relative to the primary reference plane.

The effects of the primary reference plane and the second reference plane provide a complex effective reflectivity with respect to the FOV, wherein in the FOV of the system, the effective reflectivity described above varies at least in phase. In general, determining the effective reflectivity will help determine the phase shift of the overall or low spatial frequency of the interference image.

Figure 19 to Figure 31 illustrate the principle of operation of the composite reference plane.

Figure 19 shows a simplified diagram of an embodiment of a laser Fizeau interference system 2000 comprising a light source 2163, a beam splitter 2198, an interference cavity formed by the object under test 2175 and a composite reference plane 2100, wherein the composite reference plane 2100 has a reflectivity r ₁ The primary reference surface 2181A and the second reference surface 2181B having a reflectivity of r ₂ . The composite reference 2100 can be moved in the Z direction relative to the modulator 2193 (also referred to as a phase adjuster) for interference scanning. The laser Fizeau interference system 2000 further includes a main camera 2191, an aperture 2106, and a second camera 2199 (also referred to as a monitoring camera). Figure 19 does not show additional optical components, such as lenses or other features of the imaging interference system, some of which will be described in Figure 28.

The second reference surface 2181B is deflected such that light reflected back from the second reference surface 2181B cannot enter the main camera 2191, but can be incident on the second camera 2199. The monitoring camera 2199 and the composite reference surface 2100 are used together to determine the characteristics of the interference cavity, such as the instantaneous average optical path length change (also referred to as piston motion) relative to the beginning of the scanning movement, at the beginning of the scanning movement. The position is initialized by the modulator 2193.

The monitoring camera 2199 detects the interference pattern formed by the main reference surface 2181A, the second reference surface, and the object to be tested 2175; and the main camera detects only the double-sided interference formed by the main reference surface 2181A and the object to be tested 2175. . Even if there is vibration or atmospheric disturbance, by providing relevant information to the entire optical path of the object to be tested 175, monitoring the information about the interference cavity collected by the camera 2199 will contribute to the three-dimensional surface height of the object to be tested. .

The theoretical analysis will be omitted and the interference signals generated using the laser Fizeau Interference System 2000 are as follows. It is assumed that in Fig. 19, the surface of the object to be tested 2175 has a complex reflectance r . The main reference plane 2181A has a reflectivity r ₁ and the second reference plane 2181B has a reflectivity r ₂ . The above reflectances are all related to the lateral coordinates x, y. Light from the light source 2163 is partially reflected back from the surface of the object to be tested 2175 in addition to being partially reflected back from the main reference surface 2181A and the second reference surface 2181B. However, since the second reference surface 2181B is deflected in such a manner that its reflected light is blocked by the aperture 2106, the main detector 2191 detects only the light reflected from the main reference surface 2181A and the object to be tested 2175. On the other hand, since the monitoring camera 2199 does not have an aperture, it can detect three kinds of reflected light.

The interference (signal strength) detected by the main detector 2191 can be expressed as follows:

The reflectance of the intensity

R ₀ =| r ₀ | ² (Expression 38)

R ₁ =| r ₁ | ² (Equation 39)

And θ is proportional to the surface height h of the object to be tested,

θ=arg( r ₀ ) (Equation 41)

And the phase profile offset relative to the (main) reference plane is

φ=arg( r ₁ ) (Equation 42)

For the surveillance camera 2199, the detected interference (signal strength) can be expressed as:

among them

P=| ρ ₁ | ² (Equation 44)

=arg( ρ ) (Equation 45)

Effective reflectivity of a given composite reference plane

ρ = r ₁ + r ₂ (Equation 46)

Taking FIG. 20 as an example, a composite intensity reflectivity profile P calculated by simulating 100×100 pixels is illustrated, in which the object to be tested 2175 is not set and accumulated to two wavelengths of the OPD. and between the main reference plane 2181A 2181B relative deflection between the second reference plane, the whole FOV, the main reflectance R ₁ is 4% and the second reflectivity R ₂ of 0.4%.

Fig. 21A is a cross-sectional view showing the image of Fig. 20 in the x (i.e., horizontal direction) direction, showing the intensity profile P (Expression 44) produced by the combination of the two reference faces in actual numbers. Figure 21B shows the complex phase of the composite reference plane 2100 The same cross-sectional variation of the intensity profile along the 21A map.

The object to be tested 2175 is introduced, and the 22nd image shows the monitoring interference pattern I monitored by the monitoring camera 2199, wherein the reflectance of the object to be tested 2175 is 2%, and the object to be tested 2175 is along the pair with respect to the main reference surface 2181A. The angle is slightly deflected from the upper left to the lower right of the monitoring interference pattern I. The intensity change is primarily related to the composite reference plane 2100 and cannot be detected by the main camera 2191.

The analog interference image detected by the main camera 2191 is as shown in Fig. 23. In Figs. 24A, 24B, 25A, and 25B, the difference between the interference detected by the main camera 2191 and the interference detected by the monitoring camera 2199 is apparent. Specifically, for the composite reference plane as in FIG. 19 and the object to be tested having a 2% reflectance and slightly deflected, FIG. 24A shows the interference variation in the monitoring camera 2199, and FIG. 24B shows the monitoring camera 2199. Corresponding phase changes.

According to the same parameters, for the composite reference plane and the slightly deflected object to be tested 2175, FIG. 25A shows the interference variation in the main camera 2191, and FIG. 24B shows the corresponding phase variation in the main camera 2191.

During operation, the phase adjuster 2193 mechanically moves the composite reference plane 2100 relative to the object under test 2175. For the signals detected by the surveillance camera 2199 and the main camera 2191, this will result in a series of phase shifts. Even if the interfering signals are very different, the phase shifts of the two cameras are the same, as shown. Therefore, determining the phase shift detected by the monitoring camera will help to correctly determine the phase shift from the data acquired by the main camera 2191.

Several specific data processing techniques for determining the phase shift of single-frequency interference data acquired over time have been described above, and the above data processing techniques show that for all vibration frequencies, the initial phase value of a range can be improved. Judgment of the instantaneous total optical path length of the interference cavity.

Comparing Figs. 24B and 25B shows that the composite reference plane 2100 has a phase variation irrespective of the structure of the object to be tested 2175 throughout the FOV because the monitoring camera 2199 and the composite reference plane 2100 are used at the same time.

Referring to the flowchart of Fig. 26, an interference system (e.g., interference system 2000) is operated according to the composite reference plane 2100, including data acquisition steps of the monitoring data and interference data of the sample 2175, data processing of the monitoring data, and use. Data processing of interference data for the results of data processing of monitoring data.

Specifically, in step 2010, the monitoring signal of the monitoring camera and the interference signal of the main camera are obtained in a range in which the phase shift is generated. The monitoring camera detects the interference pattern contributed by the primary reference interference interface and the second reference surface, while the primary camera only detects the interference pattern contributed by the primary reference surface.

Next, at step 2020, the interference signal of the monitoring camera is analyzed to determine the phase shift generated during the data capture.

In step 2030, the information about the phase shift is determined from the interference signal of the monitoring camera, and then the interference signal detected by the main camera is analyzed, and the three-dimensional surface height of the surface of the object to be tested is determined.

The data processing, which is summarized in Figure 26, illustrates the method of using the data obtained by introducing a composite reference plane into the interferometer. However, other types of data processing can also use a composite reference plane to determine the surface characteristics of the object under test. For example, the apparent intensity pattern (including dense interference fringes) in Figure 20 can be analyzed using a spatial method that interprets the position of the interference fringes. For the following additional examples, for example, the spatial phase measurement method proposed by M. Kujawinska; on pages 145-166 of the book "Interference Spectrum Analysis" edited by DW Robinson and GT Reid et al. (Bristol and Philadelphia, Inst. of Physics Publishing, 1993), the entire disclosures of the above-referenced patents are hereby incorporated by reference.

In Fig. 19, although only a single optical element is used to provide the first and second reference faces, other configurations are possible. For example, in some embodiments, the first and second reference faces, each of which are different optical elements, are mechanically secured to each other at their individual locations.

For example, Figure 27 shows an interference system 2001 that includes many of the elements of Figure 19. However, composite reference surface assembly 2200 is used in place of composite reference surface 2100, where the primary reference surface and the second reference surface are part of a discrete optical component. In particular, the composite reference surface assembly 2200 includes a first optical element 2202A and a second optical element 2202B, each of which is mechanically secured to each other by a shared mounting flange 2204.

Referring to FIG. 28, in some embodiments, the interference system 2001 includes a light source detection unit 3210, wherein the light source detection unit 3210 includes a plurality of light beam guiding elements. For example, optical repeaters 2169 and 2171 direct light from source 2163 to beam splitter 2164, and then light from source 2163 passes through aperture 2106 and is aimed by optical collimator 2177. The light is then reflected back to the interference cavity and imaged by imaging lens 2189 to main detector 2199. Light is also directed by beam splitter 2198 to monitoring camera 2199, where light is imaged by lens 2190 to monitoring camera 2199.

Although the interference system 2001 is used to study the planar object to be tested, other configurations are possible.

For example, FIG. 29 shows an interference system 2002 including a light source detection system 3215 and a composite reference surface 2250. The light source and detection system 3215 is similar to the light source detection unit 3210. However, the composite reference plane 2250 differs from the composite reference plane 2200 in that the composite reference plane 2250 is used to form a spherical wavefront (rather than a plane wavefront) to illuminate the curved object to be tested 3175. In particular, the composite reference surface 2250 includes a first optical element 2252A, a lens 2258, and a second optical element 2252B. The lens 2258 and the second optical element 2252B are combined to form a single unit, wherein the lens 2258 is mechanically secured to the second optical element 2252B by a mounting flange 2204. The first optical element 2252A provides a curved first reference surface 2181A, and the second optical element provides a planar second reference surface 2181B, thereby providing a complex effective reflectivity of the interference cavity with respect to the light field, wherein the plurality of effective reflectances The phase of the FOV in the interference system 2002 will change.

In some embodiments (eg, Figures 20 and 27), although the image is monitored by means of an optical path (eg, blocking light from the second reference surface, light from the second reference surface is from the main camera) ) is separated from the main image, but other configurations are also possible. For example, in some embodiments, different wavelengths of monitored images can be separated from the main image.

Taking Figure 30 as an example, Figure 30 shows an interference system 2003 that uses a monitoring image to monitor the displacement of the analyte relative to the interference microscope when performing an OPD scan of the interference microscope.

In particular, the interference system 2003 includes an interference platform 3310, a monitor assembly 3300, and an interference objective 3167. The interference platform 3310 includes a broadband light source 3163, a beam splitter 3170, and an imaging lens 3189 that images the interference pattern to the white light camera 3191. In addition, the interference platform 3310 includes a pickoff mirror 3308, a monitor image lens 3190, and a monitor camera 3199.

The interference platform 3310 is attached to the monitor assembly 3300 and the interference objective 3167 by a mechanical scanner 3193 that moves the subsystems of the monitor assembly 3300 and the interference objective 3167 in a manner relative to the object under test 2175.

The monitor assembly 3300 includes a second source 3197 (eg, a narrow band, such as a monochromatic source), a partial mirror 3304 (eg, a 50/50 mirror) that monitors the wavelength to be transflective. ), a reference lens 3306, and a second reference 3302B having a second reference surface 2181B.

The interference objective lens 3167 includes an objective lens, an interferometer beam splitter 3179, and a main reference mirror 3302A that provides a main reference plane 2181A.

According to the separate second light source 3197, monitoring the displacement of the object to be tested 2175 is accomplished by monitoring the image. The monitoring image is used to determine the phase shift correction. The monitoring image is formed by 3-surface interference, wherein for the effective reference planes of the primary reference surface 2181A and the second reference surface 2181B, the three-sided interference has a fixed complex reflectivity. In some embodiments, the quality of the monitored image is worse than the quality of the SWLI interfering image.

In general, the phase modulation history can be independently estimated on each pixel of the monitored image, for example, using cosine inverse conversion. In order to correct SWLI data acquisition, knowledge of phase shift can then be used to correctly interpret white SWLI images. The benefit of this monitoring method is the ability to use a general interference objective without modification (or only minor modifications). Therefore, the configuration of this monitoring mechanism can be compatible with standard objective design.

Although the interference system of Figures 19 to 30 is for SWLI, another mode of operation is also possible. For example, referring to Figure 31, the interference system 2004 is used for PUPS imaging. Here, the monitoring image can be separated from the PUPS image by a wavelength similar to that of the interference system 2003. Light of a wide band and a narrow band is generated by a common light source unit, and the common light source unit couples light to the interference objective lens 5167 having the lens 5177 by a common beam splitter 5170. The light source unit includes a broadband light source 5163, lenses 5169 and 5171, a monitoring light source 5197, and a beam splitter 5164. The beam is focused to a point 5400 on the object to be tested 5175. The interference objective lens 5167 is scanned by moving the platform 5193.

The optical elements of the interference system 2004 (e.g., the tubular lens 5198 and the beam splitter 5189) are arranged such that the main camera 5191 and the monitoring camera 5199 are both positioned on a surface conjugate with the pupil of the object to be tested 5167. A second reference having a second reference surface 2181B is disposed such that the second reference surface 2181B is deflected relative to the primary reference surface 2181A. The second reference plane 2181B is partially reflective with respect to the (plural) monitoring wavelength, thus producing a range of phase deviations in the final three-sided interference.

The image information in the main camera 5191 and the monitoring camera 5199 is supplied to a control computer 5192 having a processor. Control computer 5192 also interacts with mobile platform 5193.

While several embodiments including composite reference planes have been disclosed above, in general, other types of architectures are also possible. For example, while the above embodiments featuring a composite reference plane include a second camera for recording information, in some embodiments, it is also possible to use a single camera. For example, the second camera and the main camera are combined into a single camera, and the single camera has a FOV of the main image and the monitoring image, respectively.

Furthermore, time-multiplexed data capture can be used, or only a single image can be used, and then the single image can be processed to simultaneously determine all interferences in individual or instantaneous data processing steps. Phase deviation and surface characteristics of the object to be tested.

The composite reference surface can be composed of two (or more) reference reflective surfaces having any desired shape, such as a planar, spherical, aspheric or other shaped reflective surface. Furthermore, the composite reference plane will work in the entire FOV or in some of the FOVs.

Displacement Measuring Interferometers (DMI)

In some embodiments, information about the scan error is determined using a Displacement Interferometer (DMI), which is separate from the interference microscope (eg, without the use of a common optical component), and when the interference microscope performs OPD When scanning, the DMI is used to monitor the displacement of the analyte relative to the interference microscope. An example of such a system is shown in Figure 32, which shows a modified interference microscope 110 that does not include a second source 197 and a second detector 199. The displacement measurement interferometer 1801 uses a laser source instead of the second source 197, wherein the laser source is placed in a Mirau interference objective 167, which is used to direct the beam so that the beam can be reflected back from the surface of the object to be tested. DMI 1801 is coupled to computer 192 and transmits an interfering signal to computer 192 during operation. The computer 192 monitors the relative displacement between the Mirau interference objective 167 and the object under test 175 based on the interferometric signal and provides information regarding the scan error in conjunction with the operation of the interferometric microscope 110, wherein the scan error is related to the measurements made using the interference system 110.

In general, there are a variety of DMIs that can be used. For example, commercial DMIs include the ZMI series of displacement measurement interferometers manufactured by Zygo Corporation (Middlefield, Connecticut). A U.S. Patent entitled "Interferometer System for Monitoring an Object" (U.S. Patent Application Serial No.: U.S. Patent Application Serial No.: U.S. Patent Application Serial No. Reveal the content.

In some embodiments, the light source used by the DMI 1801 is included within the assembly that is mounted to the Mirau interference objective 167. In some embodiments, the light source is shielded and spaced apart from the interference objective, and the light source of the DMI can be directed to the DMI by the fiber waveguide. For example, such a system has been disclosed in a U.S. Patent (U.S. Patent Application Serial No. 11/656,597). The advantage of this arrangement is that although the processed electronics and light source are both disposed outside of the interference objective, the components actually mounted to the interference objective are small and unobtrusive.

In some embodiments, a multiple DMI system can be used to monitor the displacement of the object under test during the scan. For example, a U.S. Patent Application Serial No. 11/656,597 discloses a system including multiple detection channels, each of which uses DMI to measure displacement at different locations.

Fiber-based Systems

Figures 33A through 48B and 53 illustrate various configurations of fiber optic DMI systems (also known as detector systems) for monitoring scanning errors.

In some embodiments, positioning the detector system into the interference system can further be used to determine the position of the monitoring surface, such as the surface of the analyte or reference. For example, this can be used to determine the relative distance between the object under test and the internal reference plane of the autofocus function of the interference system.

Figure 33A shows an example of a detector system 4000 that includes a subsystem 4010, and detectors 4099A and 4099B attached to the Mirau interference objective of the interference system 4110.

The subsystem 4010 includes a broadband light source 4020, a lumen 4030 that is illuminated by light from the light source 4020 (which has a large OPD adjustment range) (because the lumen 4030 is remote from the detectors 4099A and 4099B, it is also referred to as a remote cavity) (remote cavity)), a light source distribution module 4040 (which receives light from the inner cavity 4030 and distributes light through a plurality of channels 4050-4053), and a detection and phase meter electronic module 4060 (for each One channel 4050-4053 has its own detection module 4070-4073).

In particular, the broadband light source 4020 is a surface-emitting LED that emits light having a center wavelength away from the wavelength used by the interference system 4110. For example, the source 4020 has a power of about 9 mW, a center wavelength of 1550 nm, a FWHM of 30 nm, and a coherence length of about 50 nm.

The fiber 4012 is used to direct the light emitted by the light source 4020, and the isolators 4014 and 4016 are used to avoid the return of light from the inner cavity 4030 to the light source 4020 and from the light source distribution module 4040 to the inner cavity 4030. System distortion. For example, isolators 4014 and 4016 provide 30 dB of rejection of feedback light.

In the detector system, 50/50 fiber couplers are placed at different locations to separate, distribute, and/or combine incoming light and/or outgoing light. For example, the inner cavity 4030 includes a 50/50 fiber coupler 4095, and the 50/50 fiber coupler 4095 is coupled to one side of the light source 4020 and the light source distribution module 4040. On the other side, a 50/50 fiber coupler 4095 is connected to the two branching legs of the inner cavity 4030 where the OPD can be adjusted. Each branch optical path includes a 10m fiber fiber stretching module (FSM) 4032A and 4032B, and each FSM is set to a push-pull mode to generate an adjustable OPD. Each branch optical path further includes Faraday mirrors 4034B and 4034B, respectively, to reduce the contrast attenuation caused by the polarization in the optical path.

For light propagating along two lumen optical paths along the lumen, the OPD can be controlled, for example, by using FSM to extend or shorten the optical path. In some implementations, for example, the OPD can be varied in a range of at least 3 mm or 10 mm. When leaving the inner cavity, light from the two branched optical paths is recombined in the fiber coupler 4095.

In another example, a 50/50 fiber coupler is used to separate incident and reflected light from multiple channels 4050-4053 so that light returning from the detector is directed to the detection and phase measurement after passing through the fiber coupler. Electronic module 4060. Specifically, the fiber coupler 4090 provides light from the channel 4050 of the light source distribution module 4040 to the reference signal cavity 4080 and directs light from the reference signal cavity 4080 to the detection module 4070. Similarly, the 50/50 fiber coupler 4091 provides light from the channel 4051 of the light source distribution module 4040 to the detector 4099A and directs light from the detector 4099B to the detection module 4071. In the same manner, fiber couplers 4092 and 4093 interact with light from their associated channels and detectors.

With respect to motion measurements, the detectors are typically measured separately or attached to a physical component for measurement using a suitable (plural) degree of freedom (eg, relative to a reference position). For example, as shown in FIG. 33A, channels 4051 and 4052 are connected to detectors 4099A and 4099B, respectively, wherein channels 4051 and 4052 are used to measure the distance between the object under test 4175 and the detectors 4099A and 4099B, and Thereby, the distance between the test object 4175 and the Mirau interference objective lens 4167 is measured. Each detector has its own detector cavity, and the distance measurement is based on the change in the OPD of the detector cavity. Channels 4051 and 4052 are also referred to as measurement channels. Figure 34 illustrates an example of a detector configuration (refer to the description below).

To provide a reference signal, reference signal cavity 4080 is coupled to channel 4050. As explained in Figure 35 (refer to the description below), the reference signal cavity has a configuration similar to detectors 4099A and 4099B, except that the OPD of the reference signal cavity is fixed. Channel 4050 is also referred to as a reference signal channel.

Each of the detectors 4099A and 4099B is used to view the detector cavity, wherein the detector cavity forms a separate coupled-cavity interferometer with the inner cavity 4030. For example, the detector cavity is formed between the reflective surface of the detector and the reflective surface of the observed portion. In this configuration, the OPD change of the detector cavity is proportional to the scanning movement along the mirror axis of the Mirau interference objective.

Figure 34 shows a configuration embodiment of the detector 4100. A thermally expanded core (TEC) fiber 4102 is attached to a graded index (GRIN) lens 4104. The detector 4100 provides a beam of a particular width at the beam waist position 4106. An adjustable gap between the GRIN lens 4104 and the TEC fiber can be added during the manufacturing process to set the beam waist position 4106 relative to the last surface 4108 of the detector 4100 for use in the detector The beam waist position is set during the manufacturing process. During operation, the detector 4100 forms a detector cavity with the target surface 4112 of the target 4114. For example, the target 4114 is the object to be tested 4175, an optical component, or a part of one of the above components.

In the configuration of the detector 4000, the second side 4108 of the GRIN lens 4104 can be used as a reference surface if desired. Next, the second side 4108 and the target side 4112 form a detector cavity. In another configuration, the second side 4108 is anti-reflection (AR) coated to reduce surface reflection. Depending on the application, the detector 4100 does not necessarily use the second side as a reference surface. The detector 4100 is a simple configuration that reduces size and cost.

Because the limited coherence length of the incident beam eliminates unwanted surface interference, the desired surface used to form the detector cavity can be selected by adjusting the architecture of the cavity coupled interferometer.

Figure 35 shows a configuration embodiment of the reference signal cavity 4200. The reference signal cavity 4200 includes a fiber optic cable 4202 for receiving light from the dispenser 4040. The GRIN lens 4204 aligns the beam with a Fabry-Perot (FP) cavity with a fixed OPD. In some embodiments, the OPD of the reference signal is adjusted to be twice the balance distance D (as shown in FIG. 34), wherein the equilibrium distance D is equal to the second face 4108 when the object to be tested is in the best focus condition. The distance to the surface of the object to be tested.

Referring again to Figure 33A, during operation of the detector system 4000, light having suitable uniformity and intensity is provided to the inner cavity 4030 which provides an adjustable OPD between the two branched optical paths. After the light passes through the inner cavity 4030, the light source distribution module 4040 separates the light between the plurality of measurement channels 4051-4052 and the reference signal channel 4050. Isolators 4014 and 4016 are used to ensure that the illumination performance is not reduced by optical feedback. The measurement channels 4051-5042 direct light to or from the detectors 4099A and 4099B, wherein the detectors 4099A and 4099B are attached to the interference system 4110 such that the detector cavity has The OPD associated with the degree of freedom detected by the individual detectors. The light is returned along the measurement channel 4051-4052 along the optical fiber 4012 having the same illumination beam and directed to the electronic module 4060, wherein the electronic module 4060 detects and processes the signal of one or more channels for obtaining the monitored ( Plural) information about the degree of freedom.

Adjusting the OPD of the inner cavity 4030 changes the phase modulation, wherein the OPD of the inner cavity 4030 is adjusted to determine the interference phase and OPD of the detector cavity in the measurement channel. The detector system 4000 can use phase modulation for the following measurement modes: coherent scan mode and mobile (or phase) monitoring mode. Depending on the mode desired, the detector system 4000 is used to quickly switch between the modes described above.

In the coherent scan mode, by finding the point to be adjusted in the inner cavity, the OPD of the detector can be determined within the adjustment range of the inner cavity, wherein the adjustment of the homology signal in the individual channel becomes the maximum value. For example, the coherent scan mode can be used for the auto focus function, as shown in Figures 38 and 39 below.

In the coherent scan mode, when the phase meter electronic module 4060 finds the coherent peak of the measurement channel 4051-4053 (maximum interference modulation), the OPD of the inner cavity 4030 will simultaneously vary greatly. When the channel is coherent to a maximum value, the OPD of the inner cavity 4030 determines the OPD of the detector cavity of the channel. Specifically, at a preferred setting of the reference signal cavity OPD, the distance between the interference peak position of the reference signal channel 4050 and the interference peak position of the measurement channel 4051 or 4052 shows the object to be tested 4175 deviating from the optimal focus position. relative position.

The mobile monitoring mode is suitable for vibration monitoring. In the mobile monitoring mode, the interference phase of the measurement channels 4051-4053 is quickly measured (eg, approximately 50 KHz or above). Therefore, if the measurement channels 4051-4053 are in the coherent peak of the illumination light, the OPD variation of one channel relative to any other channel can be monitored.

In the mobile monitoring mode, the OPD of the inner cavity 4030 is fluctuated at a high frequency with a small amplitude, so that the interference phase of the detector cavity can be calculated by the phase extraction algorithm at a very high update speed. come out. It is assumed that the rate of change of the detector cavity is sufficiently small that the phase change of the interference between adjacent samples is less than π, so continuous phase interpolation of the standard phase connection method can be used.

In the mobile monitoring mode, the reference signal channel 4050 is capable of removing the optical path variation in the inner cavity 4030 from the measured phase, wherein the measured phase corresponds to the observed movement of the surface of the object under test. For example, the reference signal channel can tolerate drift of the lumen as long as the drift is below the updated frequency of the measured phase.

In some embodiments, the beam emitted from the detector propagates substantially parallel to the monitoring axis of the microscope platform to reduce misalignment, wherein misalignment can cause errors in the measured movement, and The error is proportional to the cosine of the misalignment angle. The return loss of the detector is also related to the incident angle of the incident beam that is incident on the surface of the object to be tested. Specifically, the angle of incidence increases with the deflection of the target surface. In general, the detector's sensitivity to deflection is related to the details of the detector design. For example, it can be related to the GRIN lens and the spacing of the beam waist position. This is called the detector working pitch. In general, vertically aligning the detector beam with the theoretical surface of the observed portion will amplify the available deflection phase space.

In the embodiment shown in Fig. 33A, when the FSM is not energized, the OPD of the inner cavity 4030 is defined as "theoretical OPD". If the detector is used for autofocus, the OPD of the detector cavity should be close to the theoretical OPD when the interference objective is optimally focused. In this way, the contrast position of the interference peak can be used to determine whether the best focus is achieved.

The FSM used to control the lumen OPD is temperature sensitive. For example, the FSM has an OPD temperature coefficient of about 10 ppm/C. Tightening the two FSMs in thermal contact will reduce OPD variations due to temperature differences. In addition, the FSM is affected by the creeping PZT. The cause of creep is the realignment of PZT material caused by electrostatic stress in the presence of thermal perturbations, where creep has a logarithmic relationship with time. Therefore, in the manufacture of FSM, it is difficult to make the lengths of the optical fibers of the two branch optical paths of the inner cavity equal to each other.

In view of the variation of OPD, a channel can be used as a fixed reference signal cavity for the compensation mechanism. In some embodiments, the OPD of the reference signal cavity is set equal to the theoretical OPD of the lumen. An example of a fixed reference signal cavity is shown in Figure 35.

The reference signal channel can be prepared simultaneously and simultaneously with the remaining measurement channels. When analyzing the signal of the monitoring channel, the reference phase can be removed from the phase measurement result. Therefore, if the OPD of the reference signal cavity is fixed, the OPD change of the inner cavity can be removed as long as the OPD of the inner cavity is less than the coherence length and the reference signal is not missed.

The reference signal cavity is further used to define a theoretical OPD position, wherein the theoretical OPD position corresponds to the best focus position of the autofocus interference objective lens.

Taking the operation of the microscope with the detector system as an example in Figs. 36 to 38. For example, the detector system is the treasurer system described in Figure 33A. The above operations include the auto focus function and the motion (or phase) monitoring function of the detector system.

As shown in the flow chart 4300 of Fig. 36, the head of the microscope (e.g., the objective lens of the interference microscope) is a measurement position disposed above the object to be tested (step 4310). The object to be tested has a surface to be tested which is examined by a microscope.

After the auto focus mode of the detector system is activated (step 4320), an OPD scan is then performed.

Figure 37 shows the modulated peak 4410 of the test signal of the monitoring signal cavity, and the modulated peak 4420 of the reference signal of the reference signal cavity measured during the OPD scan of the autofocus. For example, the measured signal is analyzed using an electronic processor that is used to distinguish the position of the modulated peak and the position of the surface of the object to be measured relative to the best focus position (step 4330). In this example, the position of the modulated peak 4420 of the reference signal represents the best focus position.

Based on the determined relative position, the microscope then moves the surface of the object to be measured toward the optimal surface position for the measured distance (step 4340). As shown in Fig. 38, the final position of the surface of the object to be tested is verifiable (step 4350), wherein the modulated peak 4410' of the monitoring signal cavity and the modulated peak 4420 of the reference signal cavity are identical in the OPD scan. The location of the OPD. To ensure that the microscope head can be properly positioned or accurately positioned, after steps 4330 and 4340, a loop step 4355 can be performed.

After the microscope is focused (when the homology functions of the test signal cavity and the reference signal cavity overlap), the DC voltage of the autofocus of the OPD scan is set to the maximum modulation (step 4360). Figure 38 shows a fast sinusoidal scan of this OPD in the detector system. In some embodiments, the FSM DC voltage having the point of maximum interference fringe contrast is capable of being clamped.

Next, the vibration mode is initiated (step 4370), wherein the movement of the surface of the object to be tested is monitored, and then the SWLI (or PUPS) scan measurement of the object to be tested is started using a microscope. The synchronized sync measurement is used to calculate and output the actual mobile data, where the actual mobile data and SWLI (or PUPS) data are synchronized.

Based on the actual movement, the measured phase change can be used along with SWLI (or PUPS) analysis to remove the effects of the scan error (step 4395). The above removal process can be performed on-the-fly or when post-processing of SWLI (or PUPS) data is performed.

Although in the above embodiment, the functions of autofocus and motion monitoring are performed sequentially, each of the above functions can be used individually and/or individually.

In some embodiments using an autofocus mode, the OPD scan and parameters of the detector system are selected to provide: for example, a working range greater than 1 mm; a working distance of 5 mm; a position resolution of 100 nm; The portion having the structure) has a position repeatability of about 250 nm; a spot size of about 0.5 mm in diameter; and a speed of more than 10 Hz.

When the autofocus function is used in a detector system with FSM (such as the FSMs 4032A and 4032B shown in the interference system of Figure 33), the FSM will be relatively slow (eg, about 10 Hz) and have a large amplitude sinusoidal voltage. It is activated and the position of the surface with the test object can be determined based on the relative delay between the homology peaks of the test signal and the reference signal. The total range of variation of the OPD is related to the length of the fiber in the spools of the FSM 4032A and 4032B and the maximum extension of the PZT of the FSM 4032A and 4032B, so the optimum amount of fiber is usually the length variation of the fiber and the acceptable sensitivity. The result after weighing each other. For example, an 18 m fiber can provide an OPD scan of 6.6 mm, a conversion factor of 9.5 μm/V, and a temperature sensitivity of 254 μm/C.

In some embodiments using a motion monitoring mode, the OPD scan and parameters of the detector system are selected to provide: a resolution of less than 0.2 nm, and a reproduction of less than 1 nm (on a structured portion) Saturation, sampling rate of approximately 200 kHz, and update frequency greater than 5 kHz.

In addition, when the autofocus function is used in a detector system with FSM (such as the FSM 4032A and 4032B shown in the interferometric system of Figure 33A), the FSM is subjected to a high frequency (eg, 10 kHz) waveform (providing optimal interference). The DC clamp voltage), as well as the amplitude of the calculated high frequency phase, is initiated. In some embodiments, if a standard linear phase shift algorithm is used, this can be done by sawtooth or triangular modulation data. In other embodiments, sinusoidal modulation and SinPSI algorithms are used. For example, please refer to PJ De Groot, a US patent on the sinusoidal phase shift algorithm (invention name: "Sinusoidal Phase Shifting Interferometry"; US Patent Publication No.: US-2008/0180679-A1), and/or a U.S. Patent Application Serial No.: 12/408,121, filed on Jan. No. 2009. The channels can be simultaneously sampled with the appropriate frequency and phase (relative to modulation) so that the new phase can be taken once per cycle. By multiplying the phase variation by λ/4π, the phase variation can be converted into a change in the length of the entity. At the above sampling rate, the computational burden is small and a standard microprocessor can be used for simultaneous simultaneous processing of all channels.

During interferometric measurements (such as SWLI or PUPS), the movement of the chamber can be read by the microprocessor controlling the interferometric system. By means of a feedback mechanism or time stamped to the interferometric data, the moving data can instantly correct the scanning movement of the interference system, and the moving data can also be used for post processing of the interference data for correction. Scanning movements that are not expected, such as using the J matrix approximation described herein.

As described above with respect to the detector system of the embodiment of the invention in Fig. 33A, although the FSM is used to change the OPD of the cavity of the detector system, other configurations may be used. For example, in some embodiments, the detector system can utilize an optical modulator (eg, an electro-optic modulator or an Acousto-Optic Modulator). One or two optical paths (or optical paths) in the lumen to produce a phase shift directed to the light component of the interference detector.

For example, the detector system uses a light modulator as described in Figure 33B. In this embodiment, the detector system 5400 includes five modular subsystems: an illumination module 5420, a heterodyne module 5440, and a distribution module 5460. The detector 5480 and the detection and calculation module 5499. The illumination module 5420, the heterodyne module 5440 and the distribution module 5460 are configured to generate, condition and transmit light to each detector through an optical fiber connection, and also receive the light through the optical fiber. Light to the distribution module 5460. The distribution module will return the light to the detection and calculation module 5499, wherein the detection and calculation module 5499 detects the interference signal corresponding to the light and the processing, and determines the information of the microscope (or other system) to arrange the detector. monitor. In general, although the reference detector provides additional information about other systems to improve the accuracy of the detector measurement, each detector provides an independent axis of measurement.

The illumination module 5420 includes a light source 5422 (eg, amplified spontaneous emission source (ASE)), 1:4 optical switches 5424 and 5434, and three different bandpass filters. 5426, 5428, and 5430, wherein the center wavelengths of the band pass filters 5426, 5428, and 5430 are different (λ 1, λ 2, and λ 3 , respectively). Additionally, the illumination module 5420 can include an amplitude modulator 5432. Bandpass filters 5426, 5428 and 5430 and amplitude modulator 5432 are interconnected between the 1:4 optical switches 5424 and 5434 in separate parallel channels, wherein 1:4 optical switches 5424 and 5434 can It is a micro-electrical-mechanical (MEMS) switcher. When the band pass filters 5426, 5428, and 5430 are used in the illumination module 5420, the illumination mode is used. Group 5420 can provide an output light that exceeds the three narrow eavelength ranges of the emission spectrum of source 5422, and amplitude modulator 5432 (if any) provides an internal correction function.

In general, the transmission profiles of bandpass filters 5426, 5428, and 5430 are selected to provide light having a desired coherence length for introduction into the detector. In the present embodiment, the band pass filters 5426, 5428, and 5430 have a full width at half maximum of 1 nm or more (for example, 2 nm or more, 3 nm or more, 5 nm or more, 10 nm or more). FWHM). The band pass filters 5426, 5428, and 5430 may have a full width at half maximum of 30 nm or less (for example, 20 nm or less, 15 nm or less, 10 nm or less). In certain embodiments, band pass filters 5426, 5428, and 5430 provide light having a coherent length, wherein light having a coherence length provides more than 1 mm or less (eg, about 800 μm or less, about 600 μm or less, about 400 μm or The following is a comparison of the signals.

In some embodiments, λ 1, λ 2, and λ 3 are selected to aid in absolute length measurements (as opposed to simply detecting relative displacement), as described in more detail below.

The heterodyne module 5440 includes 50/50 fiber couplers 5442 and 5448, optical modulators 5444 and 5446, and an optional optical delay line 5450. These two optical paths form a remote cavity. The 50/50 fiber coupler 5442 receives light from the illumination module and separates the light along two parallel optical paths. At least one optical path includes a light modulator (light modulator 5444 or light modulator 5446), wherein the light modulator can be an electro-optic modulator or an acousto-optic modulator. One of the two optical paths may include an optical delay line 5450, wherein the optical delay line 5450 is generated The extra path length, the theoretical OPD generated by the offset detector cavity. Optionally, each optical path may include a modulator (optical modulator 5444 or optical modulator 5446), for example, to match the thermal sensitivity of the two branched optical paths.

In general, a light modulator (optical modulator 5444 or light modulator 5446) is used to generate a controlled phase shift between two branches of light, wherein the light branches are along two different optical paths of the internal cavity. For example, in some embodiments, the modulator is driven according to a sawtooth signal such that the amplitude of the phase modulator is an integer multiple of 2π (eg, a phased forward modulator). When the other cavity is coupled in series (for example, from the detector), and the light is broad-band, if the OPD difference of the two coupled cavity is within the coherence length, the phase-modulated forwarding OPD modulator generates Interference of the modulator frequency N times.

The second modulator, in addition to providing a positive thermal sensitivity matching, can also be tuned to a low frequency and used to perform cyclic phase error compensation as described in U.S. Patent No. US7576868, entitled Demarest. (All of the above-referenced patent references are incorporated by reference in its entirety herein).

The distribution module 5460 is configured to perform the distribution of light from the heterodyne module 5440 to each of the detectors and the reference cavity. The distribution module 5460 is composed of a plurality of 50/50 fiber couplers for connecting separate light. The separated light system is from the heterodyne module 5440 to a plurality of channels so that light can be supplied to each of the detectors and the reference cavity. As shown in Figure 33B, an initial 50/50 coupler 5462 receives light from the heterodyne module and separates the light along two parallel channels. 50/50 couplers 5464 and 5466, in which the incident light is separately separated into two channels in sequence. Once separated into sufficient channels, each channel passes directly through a 50/50 coupler (eg, couplers 5468, 5470, 5472, and 5474 as shown in Figure 33B) to the detector. These couplers direct light to the detector and direct the light back from the detector to the detection and calculation module 5499.

As previously described, the detector 5480 includes a plurality of individual measurement detectors (eg, detectors 5482 and 5484) and reference detectors 5486, 5488, and 5490, for example, each measurement type detector. The detector is combined with one or more microscopes. In general, the reference detector is used to monitor various parameters related to the detector system, and the information obtained by the reference detector is used to improve the accuracy of the detector system. For example, the reference type detector includes a refractometer (for measuring the atmospheric refractive index near the detector and other locations near the system) and a wavelength meter. For example, the refractometer can be constructed by a detector combined with an air-spaced etalon such that the phase change measured by the detector is due to changes in the air refractive index within the etalon cavity. Other reference type detectors can be used to use fixed length optical cavities (eg etalon). For example, a reference type detector using a sealed etalon is used to provide a reference phase to the system, and a second reference type detector can utilize a fixed length cavity having a different cavity length to provide a relevant wavelength change of the light used. Message.

In general, reference detectors can be placed close to each other or can be placed with modules of other detector systems.

The detection and calculation module 5499 includes a plurality of detectors 5453, each of which is coupled to a 50/50 coupler of the distribution module 5460 for receiving from a corresponding measurement type detector or reference type detector. The light output. A detector 5453 is coupled to a detection and amplification sub-module 5492, wherein the detection and amplification sub-module 5492 receives a signal from the detector and amplifies the received signal (eg, a component of the signal, The AC component of the signal) directs the amplified signal to an analysis sub-module 5494 (application-specific integration circuit). In general, the detection and computing module can be a stand alone module, a module that incorporates other modules within the system 5400, or a module that combines processing electronics (such as a portion of a computer).

For example, system 5400 tracks the incremental changes in the OPD of the detector cavity based on the phase change of the interferometric signal monitored by the detector relative to the refractometer and the wavelength meter (corresponding to the objective lens of the microscope) The movement between the analytes, which is the case at a single wavelength (for example one of λ1, λ2 and λ3).

A wide variety of operating modes can also be used to reduce significant errors in various system measurements. For example, taking the information of the data age and applying the information to the subsequent measurements can be done by measuring the relative phase deviation between each channel, and is equivalent to measuring each The fiber length of the channel. For example, by adjusting the amplitude of the light source by the amplitude modulator 5432, the frequency of the amplitude modulator is varied to exceed the operating range, and a relative phase deviation between each channel is measured to determine the frequency function correlation. Data time.

System 5400 can also be used to measure the absolute wavelength of the illumination source, for example, thermal variations of each fiber wavelength (i.e., λ1, λ2, and λ3) can affect spectral characteristics. This is done, for example, by measuring the relative phase difference between fixed reference cavities of two different known paths. The absolute wavelength output by each fiber can be derived from the phase difference measured by two known fixed reference cavities, the different cavity length values, and the refractive index of the intracavity medium.

System 5400 can also be used to measure the OPD of the absolute cavity of each detector. For example, for each fiber output wavelength, the phase of the light output by each detector is measured against a fixed reference cavity. This provides three corresponding phases φλ1, φλ2, and φλ3 to each detector. The system uses phase differences (φλ1-λ2, φλ2-λ3, and φλ3-λ1) to calculate the wavelength order and the absolute wavelength of each fiber output signal (as previously described). As is known in the art of multi-wavelength interferometry, the system then uses the aforementioned wavelength magnitude and the single phase of each cavity (eg, phase φλ1) to calculate the absolute OPD of each detector cavity.

In general, the OPD generated by the inner cavity of the heterodyne module 5440 and the OPD generated by the detector cavity need to be within the coherence length of the light source to provide an interference signal. A shorter coherent length source is also used to eliminate coherence noise (eg, the effects of the optical interface, and the photo interface detector's test surface or reference surface). In general, optical delay line 5450 is used to bias the OPD of the nominal detector such that at least a particular component of the detected light in the detector has a nominal zero OPD. However, if the OPD of the detector is only slightly deviated from the OPD of the nominal detector (for example, less than 1 mm), the device provides an interference signal.

In some embodiments, the FSM and the optical modulator are used to provide an appropriate cavity OPD range and appropriate phase shift characteristics of accurate motion monitoring. For example, in the present embodiment, the optical modulator 5446 can be replaced by an FSM. The FSM can be used in larger OPD scans (eg, at the millimeter level, about 1-10 mm). For example, autofocus targets require this type of scanning, in which case a smaller phase shift is required (eg, the OPD of the heterodyne module and the OPD of the detector are nominally offset from each other), phase shift It can still be executed when the light modulator is replaced. For example, when using a light modulator, the object to be tested remains in the same position under the objective lens of the microscope, and the detector is used for vibration monitoring.

In general, a variety of forms of interference objective can be used with a detector system having a detector to form a monitoring signal cavity with the monitoring surface during operation. Some examples will be described below in which the detector is disposed on the interference objective to allow the monitoring signal cavity using the object to be inspected by the interference objective to be formed.

As shown in Fig. 33, Fig. 39 is an enlarged view of the interference objective unit 4540 including a Mirau interference objective lens 4167 and a detector ring 4545. The Mirau interference objective 4167 includes a lens 4550 and a mirror 4560 for providing an optical path of the object to be measured and an optical path of the reference. The detector ring 4545 includes detectors 4099A and 4099B, wherein the detectors 4099A and 4099B are coupled to the subsystem 4010 by an optical fiber 4012, as shown in FIG. The detectors 4099A and 4099B emit incident light and are vertically irradiated on the object to be tested 4175, thereby forming a monitoring signal cavity on the surface of the object to be tested in addition to the FOV of the Mirau interference objective lens 4167.

The combination of the 40th detector 4570 and the Michelson interference objective 4580. With the beam splitter 4585, the illumination of the detector 4570 is substantially within the FOV of the Michelson interference objective 4580.

Figure 41 shows the arrangement of the two detectors 4590A and 4590B in the Linnik Interference Objective 4592. The Linnik Interferometric Objective 4592 includes Schwarzschild optical components 4594A and 4594B. The polarizer P in each of the analyte branch 4596A and the reference branch 4596B is polarized Linnik and lacks a non-polarized pattern. Detectors 4590A and 4590B are disposed intermediate the Linnik interference objective 4592. The detector 4590A (eg, within the FOV of the Linnik interference objective 4592) illuminates the object under test 4175, thereby forming a first monitor signal cavity with the surface of the object under test 4175. Similarly, the detector 4590B illuminates the object to be tested 4181, thereby forming a second monitoring signal cavity with the surface of the reference 4181. As described above, the purpose of setting the reference 4181 is to provide a phase shift of the SWLI measurement of the interference.

As mentioned above, the detector system can be configured in a variety of ways depending on the interference objective used. In addition, the detector system can also be configured in a variety of ways depending on the scanning mode used for the interferometry. For example, when held in the scanning position, we can decide whether the scan is a focal plane scan and an optical path length scan depending on whether the focal plane or the optical path length is scanned.

In the focal plane scanning, since the focal plane position of the interference objective lens is varied with respect to the surface of the object to be tested, the interference objective lens is generally moved integrally. The focal plane scan can be used with an interference objective having an inaccessible reference plane, such as a Mirau-like interference objective.

In optical path length scanning, the reference plane is moved (eg, its position is sinusoidally modulated) and the focal plane is fixed. The optical path length scan can be used with a Linnik or Michelson interference objective, where the reference surface can be accessed and the interference measurement of SWLI and PUPS can be performed.

As for the example of focal plane scanning, the 42A to 42C have a detector configuration of the general-purpose interference objective 4600. Although only one detector is shown in Figures 42A through 42C, in the remaining illustrations, most of the detectors used are more than one for redundant or angular motion information.

In FIG. 42A, the detector 4610 is buried in the pedestal 4620 for carrying the object under test, and the detector 4610 monitors the movement of the universal interference objective 4600 relative to the pedestal 4620. In FIG. 42B, the detector 4630 is attached to the universal interference objective lens 4600, and the detector 4630 monitors the movement of the universal interference objective lens 4600 relative to the base 4620 (if the surface portion of the base forms a monitoring signal cavity), Or directly monitoring the movement of the universal interference objective lens 4600 relative to the object to be tested (if the surface portion of the object to be tested forms a monitoring signal cavity). In FIG. 42C, the detector 4640 is disposed on one side of the universal interference objective lens 4600, such that the detector 4640 emits the detection beam 4650, and the detection beam 4650 is obliquely reflected off the pedestal 4620 or the object to be tested. The surface is then reflected back from the mirror 4600 disposed on the other side of the universal interference objective 4600 back to the detector 4640. When the detection beam 4650 is reflected back from the measurement point 4670 of the universal interference objective lens 4600 (as shown in Fig. 42C), the configuration of Fig. 42C can reduce Abb. Error, but it will reduce the sensitivity of vertical movement.

Michelson and Linnik Interferometric Objectives enable focal plane scanning with a particularly simple detector configuration, with Michelson and Linnik Interferometric Objectives defining the optical path of the detected beam by the optical components of the Michelson and Linnik Interferometric Objectives to reduce Abb The error does not affect the sensitivity of vertical movement.

For example, a Michelson interference objective combination having a detector 4570 as shown in FIG. 43A corresponds to the configuration of FIG. 41, wherein the detection beam 4680 of the detector 4570 is vertically reflected by the beam splitter 4585 to be tested. On object 4175. The detector 4570 can provide a built-in reference plane (as shown in Figure 34) to provide an interference cavity.

Compared to the configuration of Figure 34A, since the reference branch 4686 of the Michelson Interferometric Objective also provides a reference 4688 for use as a reference for the detector 4570A, the configuration shown in Figure 43B can only be one. The detector 4570A, which provides a built-in reference plane, is operated. In particular, the interaction of the beam splitter 4585 and the detection beam 4680 is such that the reference beam 4690 is transmitted to the reference 4688 and reflected back by the reference 4688. For example, the beam splitter 4585 performs splitting according to a polarization state or a separation wavelength.

In another example, Figure 34C shows a combination of a Linnik interference objective with a lens-based object interference objective 4715 and a lens-based reference interference objective 4718. As shown in FIG. 34A, the detecting beam 4710 of the detector 4700 is vertically reflected by the beam splitter 4720 to the object to be tested 4175. The detector 4700 can provide a built-in reference plane (as shown in Figure 34) to provide an interference cavity.

Compared to the configuration of Fig. 34C, since the reference branch 4686 of the Linnik interference objective also provides a reference 4740 for use as a reference for the detector 4700A, the configuration shown in Fig. 43D can only be one. A detector 4700A with a built-in reference plane is provided to operate. In particular, the interaction of the beam splitter 4720 and the detection beam 4710 is such that the reference beam 4750 is transmitted to the reference 4740 and reflected back by the reference 4740. For example, the beam splitter 4720 performs splitting according to a polarization state or a separation wavelength.

Although Figures 43A through 43D are illustrated in a focal plane scanning mode, in some embodiments, the detector system can also be combined with an interference system operating in an optical path length scanning mode. In the optical path length scan, the interference objective scans the reference surface instead of the surface of the object to be tested to change the OPD during the interference measurement.

Taking Figure 44A as an example, the Michelson interference objective combines with the detector 4800 to form a monitoring signal cavity with the backside surface of the reference 4810. The detection beam 4820 of the detector 4800 reflected back by the reference 4810 is sensitive to the movement of the reference 4810, and the detection beam 4820 of the detector 4800 can be used to correct the movement error, but cannot be used to correct the auto focus. . The detector 4800 can provide a built-in reference plane (as shown in Figure 34) to provide an interference cavity.

In another example, Figure 44B shows a combination of Linnik interference objectives with detector 4830. As shown in FIG. 44A, the detection beam 4840 of the detector 4830 is reflected back by the reference object 4686. The detector 4830 can provide a built-in reference plane (as shown in Figure 34) to provide an interference cavity.

For example, using a detector that does not have a built-in reference plane, the configurations shown in Figures 43B and 43D can be used for optical path length scanning. Then, what is performed is not to scan the object to be tested 4175 or the Linnik object to be tested in the branch of the object to be tested, but to maintain the focal plane position in the branch of the object to be tested and change the position of the reference object 4688 (Fig. 43B) and the reference. The position of the object 4740, the Linnik reference objective 4740 (Fig. 43D), or both.

In some applications, the reference and target faces are scanned simultaneously. Next, the detector system is used to monitor both movements simultaneously. In addition, additional degrees of freedom can be monitored, such as deflection of the reference plane, where the deflection of the reference plane is very useful for PUPS applications.

Two (or more) discrete detectors can be used to simultaneously monitor two (or more) movements, for example, as shown in Figure 33, the detectors are connected to individual channels of subsystem 4010. Figures 45A through 45C show how two (or more) detectors can be placed in a Michelson or Linnik interferometer.

Figure 45A is a combination of Figure 42B and Figure 44A, wherein the first detector 4630A disposed in the Michelson interference objective is used to monitor the movement of the object under test 4175 relative to the Michelson interference objective, and the second detector The 4800A is used to monitor the movement of the reference 4686.

Figure 45B is a combination of the 42B and 44B, wherein the first detector 4630B disposed in the Linnik interference objective monitors the movement of the object 4175 relative to the Linnik interference objective, and the second detector 4830B detects the reference. The movement of the object is 4740.

The configuration of Figure 45C is similar to the configuration of Figure 45B, in which the deflection of the reference surface of reference 4740 and the piston motion are monitored by two detectors 4830C and 4830D in addition to the movement of reference 4740. Figure 46 shows an embodiment in which the detector 4800 directly detects the movement of the scanner 4810 rather than detecting the interference cavity. If the scanner 4810 is the largest source of motion uncertainty, then monitoring of the scanner 4810 enables a relatively coarse and inexpensive scanning mechanism to be used.

Figure 47 shows an embodiment in which the surface 4820 of the object to be tested 4175 is too small to be directly detected by an off-axis detector, or the surface 4820 of the object to be tested 4175 has A surface slope that does not provide a reliable echo signal to detector 4830, the embodiment shown in Figure 47 enables the interferometric signal cavity to be monitored. In the present configuration, the object to be tested 4175 is disposed at a special position of the base 4840, wherein the base 4840 has a mirror 4850 detected by the detector 4830. The height of the mirror surface corresponds to the height of the extended surface of the object to be tested 4175. For example, this configuration can be used to assemble a production line where the objects to be tested are very similar. 48A and 48B show an embodiment in which an objective turret 4900 is incorporated, wherein the objective turret 4900 has a rotatable portion 4940 and a non-rotatable portion 4930. For example, an objective turret can be used with a microscope to provide different types of objective lenses 4910A and 4910B (eg, having different measurement magnifications). In Fig. 48A, each of the objective lenses 4910A and 4910B has detectors 4920A and 4920B attached thereto, and in Fig. 48B, only one detector 4910C is attached to the non-rotatable portion of the objective lens turntable 4900. The configuration (comparison) of Fig. 48A is not affected by the unpredictable movement of the mechanical linkage, which is between the rotatable portion 4940 of the objective turret 4900 and the non-rotatable portion 4930 because of the mechanical linkage The movement is monitored by detectors 4920A and 4920B. However, the configuration of Figure 48B requires fewer detectors and does not require consideration of the winding of the return fiber when the objective turret 4900 is rotated.

In some embodiments, a single detector system can be used to monitor a complex microscope. For example, with respect to Figure 53, system 5300 includes three microscopes 5310, 5320, and 5330, with each microscope having an interferometric sensor associated with each. In detail, the detector 5312 is associated with the microscope 5310, the detector 5322 is associated with the microscope 5320, and the detector 5332 is associated with the microscope 5330.

The microscope 5310 is for observing the object to be tested 5311 supported by the stage 5314. Similarly, the microscope 5320 is used to observe the object to be tested 5321 supported by the platform 5324, and the microscope 5330 is used to observe the object 5331 supported by the platform 5334.

The various components of the detector system are disposed in module 5340, wherein module 5340 is disposed at the distal ends of detectors 5312, 5322, and 5332. For example, the detector system light source, the light distribution module, the remote cavity, and the phase meter electronic module can be disposed in the module 5340. For example, the connection between the general module 5340 and the detector may be an optical fiber for transmitting light from the distribution module to the detector and returning from the detector to the phase measuring meter electronic module, and the phase The gauge electronic module is disposed within the module 5340.

In general, detectors 5312, 5322, and 5332 can be associated with the corresponding microscope in a variety of ways. In general, this association means that the detector is used to provide information about at least one degree of freedom between the object under test and the microscope. For example, the detector is disposed on or near the objective lens of the microscope, and the relevant optical component is disposed on the corresponding object to be tested or in the vicinity of the object to be tested (for example, fixed on the corresponding platform). Examples of such devices have been previously discussed.

In addition, although the detector described in FIG. 53 is disposed on the corresponding microscope (relative to the platform), other configurations may be used. For example, in some embodiments, the detector can be physically coupled to the platform and the detector includes an optical component that is coupled to the microscope.

In general, the system 5300 can be used to view various types of analytes. For example, in some embodiments, the object to be tested is a flat panel display (eg, a display substrate or other integrated circuit component that supports thin film transistors (TFTs)). In this embodiment, the object to be tested is a semiconductor wafer.

In some embodiments, one or more microscopes 5310, 5320, and 5330 can be used to view the same analyte. For example, two or more microscopes can be used to view different portions of a substrate (eg, a display substrate).

In general, when the system 5300 includes only three microscopes, a single detector system is used to monitor any number of microscopes (eg, 4 or more, 5 or more, 6 or more, 8 or more, 10 or the above). Further, when each microscope is associated with only one detector, a single microscope can be connected to more than one detector. For example, in some embodiments, the microscope can include a plurality of objective lenses, each of which includes an associated detector (e.g., as shown in Figure 33).

Other embodiments (Alternative embodiments)

While the light source subsystem in some of the above embodiments includes the primary light source 163 and the second light source 197, other configurations are possible. In general, the wavelength of light emitted by the second source 197 can be varied to provide the desired wavelength that can be detected by the second detector. The selected wavelength may fall within the bandwidth of the primary source 163 or be a completely different wavelength. For example, primary light source 163 is selected to provide a white light source, a visible light source; and a second light source provides a source of UV or IR portions of the spectrum. Additionally, the second source 197 provides a source of light having a series of discrete wavelengths simultaneously (or sequentially).

Moreover, in some embodiments, the light source subsystem includes a single light source rather than a primary light source and a second light source that are separate from each other. A single light source generates a light source that is incident light of the main detector 191, and also generates a light source that is incident light of the second detector 199. For example, the filter 101 used in conjunction with the second detector 199 can be selected to produce a single wavelength source that is provided from the source to the second detector 199.

In general, the second source 197 is a (space) extended source or point source, and the illumination of the second source is Koehler or a critical illumination. In general, when a point source is used in the PUPS mode, a neutral illumination is used to illuminate the pupil plane; for SWLI, Koehler illumination is typically used to illuminate a large area.

The primary source is an LED, an arc, an incandescent, a white laser, or other source suitable for broadband interference.

In some embodiments, the field of view light bar is used to control the degree of spatial expansion of the light source. It is also possible to use intermediate-plane illumination.

Multiple configurations using the detector subsystem are also possible. For example, the second detector 199 is typically a detector with two minimum detection points or pixels. Therefore, the second detector 199 can be a single detector with an integrated detection element (as illustrated in the illustrated embodiment) or a plurality of discrete and single detection elements.

In some embodiments, a single detector can be replaced by a primary detector 191 or a second detector 199. For example, the main detector 191 includes a plurality of detector components for obtaining a monitoring signal. For example, the main detector further includes a discrete narrowband filter disposed in front of the corresponding detector component, or an optical component, for selectively receiving light to the main detector for obtaining a monitoring signal. A specific detecting component of the detector 191.

A variety of methods for generating phase divergence between monitoring signals have been discussed above. Other methods of generating phase divergence are also possible. For example, in addition to introducing relative deflection between the reference light and the measured light, and creating streaks in the FOV of the main detector 199, additional optical components can be used to achieve the same effect. For example, in some embodiments, the polarizing element is used to change the phase of the main detector 199 light. For example, in the case where only a single measurement point is considered, the relative phase shift between the measurement beam and the reference beam is produced by the polarization element.

In the above embodiment, the detector and the light source subsystem respectively include a main detector/second detector and a main light source/second light source. However, other embodiments are also possible. For example, in some embodiments, the second source and the second detector are bundled together into a separate subsystem, wherein the discrete subsystem shares some optical components with the host system. For example, the second light source and the second detector are assembled into a module, wherein the module is suitable for the main detector or other components of the (main) system, or for the interference objective or its system Other components.

Furthermore, although the above discussion assumes that the scanned data is theoretically linear in time, the scanning error correction technique can also be applied to other scanned data.

While the features of the above embodiments are interference microscopes with Linnik or Mirau interference objectives, the scanning error correction technique can also be applied to other types of interference microscopes (eg, microscopes using Michelson interferometers). More generally, the scanning error correction technique can be used not only for an interference microscope but also for a non-microscope type interferometer.

Computer Program

Any of the above analysis methods of the computer or a combination thereof can be provided in the hardware. In accordance with the method and diagram of the present invention, the computer analysis method described above can be written in a computer program by standard programming techniques. The code is applied to the input data to perform the functions described in the present invention, and the code generates output information. The output data is output to one or more output devices, such as a display or monitor. Each program can be written as a high-level processing program or an object oriented programming language to communicate with a computer system. However, the program can also be written as a combined language or machine language if needed. All programming languages are programming languages that can be compiled or interpreted. In addition, the program can be executed in an integrated circuit that is pre-programmed as needed.

Each of the above computer programs is preferably stored in a storage medium or device (such as a ROM or a magnetic disk), and the storage medium or device can be read by a general-purpose or special-purpose programmable computer. The computer program is used to configure or operate the computer when the storage medium or device is read by the inventive program. The computer program can also be stored in the cache or main memory when the program is executed. The analytical method can also be stored in the form of a computer readable storage medium and configured in the form of a computer program configured to cause the computer to perform the functions described herein in a particular and intended manner.

Embodiments of the present invention relate to an interference system for determining information related to an object to be tested. Further information on suitable low coherence interference systems, electronic processing systems, software, and related processing algorithms is disclosed in the following patent: "Method and System for Interferometric Analysis of Surfaces and Related Applications" (US Patent Publication No.: US-2005-0078318-A1); "Profiling Complex Surface Structures Using Scanning Interferometry" (U.S. Patent Publication No.: US-2004-0189999-A1); and "Interferometry Method for Ellipsometry, Reflectometry, and Scatterometry Measurements, including Characterization of Thin Film Structures (U.S. Patent Publication No.: US-2004-0085544-A1), the entire disclosure of which is hereby incorporated by reference in its entirety in its entirety in its entirety in

application

The low coherence interference method introduced by the scanning error correction technique can be used for the following various surface analysis problems: a simple film, a multilayer film, sharp edge and surface features that cause diffraction or complex interference effects, and cannot Analyzed surface roughness, surface features that cannot be resolved (eg, sub-wavelength trenches (gratings) on other smooth surfaces), heterogeneous materials, polarization-dependent surface properties, and surfaces (or deformable surfaces) Deflection, vibration or movement, wherein the deformable surface is characterized by an angle of incidence that is related to the disturbance of the interference phenomenon. Taking the film as an example, the parameters that can be adjusted are film thickness, refractive index of the film, refractive index of the substrate, or a combination of the above parameters. Specific applications including objects or devices that exhibit the above characteristics will be discussed below.

Semiconductor Process (Semiconductor Processing)

The systems and methods discussed above can be used in semiconductor processes, such as specific monitoring of process tools, or in controlling manufacturing processes. In process monitoring applications, a single/multilayer film is grown, deposited, polished, or etched on an unpatterned germanium wafer (monitoring wafer) by a corresponding process tool, and then used in accordance with the present invention. The interference system of the scanning error correction technique measures thickness and/or optical characteristics. The above-mentioned thickness (and/or optical characteristics) of the wafer is averaged and the uniformity of the wafer is used to determine whether the relevant process tool is operated at the target specification, or whether it should be re-targeted, adjusted, or no longer used.

In process control applications, the single/multilayer film is then grown, deposited, polished, or etched on an unpatterned germanium wafer (monitoring wafer) by a corresponding process tool, and then used in accordance with the present invention. The interferometric system of the scanning error correction technique measures thickness and/or optical characteristics. Production measurements for process control typically include a small measurement location and the measurement equipment can be aligned to the sampling area. This measurement site consists of a stack of multilayer films (which may have been patterned) and therefore requires complex mathematical models to obtain the relevant physical parameters. The measurement of the process control determines the stability of the integrated circuit manufacturing process, and also determines whether the integrated circuit manufacturing process should continue, be retargeted, redirected to other production equipment, or shut down for inspection.

For example, the interference system of the present invention can be used to monitor devices such as diffusion, rapid thermal annealing, chemical vapor deposition (high or low voltage), dielectric layer etching, chemical mechanical polishing, plasma assisted deposition, Plasma assisted etching, lithography, and lithography exposure. Furthermore, the interference system of the present invention can be used to control processes such as trenches and isolation, transistor formation, and interlayer dielectric formation (eg, dual damascene structures).

Copper wire connection structure and chemical mechanical polishing (Copper Interconnect Structures and Chemical Mechanical Polishing)

Currently, wafer manufacturers typically use a process called "dual damascene structure and copper wire bonding" (hereinafter referred to as "dual damascene process") to fabricate electrical connections in different areas of the wafer. The above process is a good example of a process that requires inspection using a suitable surface topography measurement system. The dual damascene process typically involves six process steps: (1) interlayer dielectric (ILD) deposition in which a layer of dielectric material (eg, polymer or glass) is deposited on the wafer (including a plurality of individual wafers). (2) chemical mechanical polishing (CMP), in which the dielectric layer is polished to produce a smooth surface for precise optical lithography; (3) lithography patterning and reactive ion etching processes a step in which a complex wire connection network is formed, including shallow trenches parallel to the surface of the wafer, and small vias from the surface of the trench to a lower conductive layer (as previously defined); (4) metal deposition a processing step in which deposition of copper metal trenches and via holes is generated; (5) a dielectric deposition process step in which a dielectric is deposited over the copper metal trenches and via holes; and (6) a final CMP A step in which excess copper metal is removed, leaving a wire connection network (possibly including via holes) formed by a trench filled with copper metal, the wire connection network being surrounded by a dielectric material.

Referring to Figure 20A, device 500 is a specific example of a structured film in which copper features 502 are deposited over substrate 501 and deposition of dielectric 504 covers copper features 502. Dielectric 504 has a non-uniform outer surface with a height variation along the outer surface. The interference signal of device 500 includes an interference pattern of upper surface 506, an interference pattern of interface 508 (between copper feature 502 and dielectric 504), and an interference pattern of interface 510 (between copper feature 502 and substrate 501). between). Device 500 also includes a plurality of other feature elements that create an interference pattern.

Referring to Figure 20B, device 500' is the state after device 500 has undergone the final CMP process step. Upper surface 506 has been planarized to upper surface 506' and interface 508 may be exposed. The interface 510 on the substrate 501 remains as it is. The effectiveness and uniformity of the components depends on the surface flattening monitoring of the dielectric 504. It should be noted that the polishing rate and the thickness of the copper metal (dielectric) remaining after polishing may be related to (or have a complex relationship with the polishing conditions (for example, the pressure applied to the abrasive paper pad and the composition of the slurry). ); also related to the local placement of copper metal and its surrounding dielectric regions (eg, contact window tilt, component density, and profile). Thus, once the interface 508 of the copper metal 502 component is exposed, the dielectric and copper metal components will have different etch rates.

It is well known that this "position-dependent polishing rate" causes a change in surface topography in many lateral directions. For example, this usually means that the polishing rate of the wafer near the edge of the wafer will be higher than the polishing rate of the wafer near the center of the wafer, thus making the copper (wire) area of the edge thinner than the desired thickness, while the center The copper metal (wire) area is thicker than the desired thickness. This is an example of a "wafer scale" process non-uniformity, a non-uniformity in length dimension compared to the wafer diameter. Further, it is well known that the polishing rate of the region where the copper metal trench density is higher is lower than the polishing rate of the region where the copper metal trench density is lower. This usually leads to a phenomenon called "CMP induced erosion" in areas where the copper metal density is high. This is an example of a "wafer scale" process non-uniformity, a non-uniformity of length dimension compared to a dimension of a single wafer (the value of this non-uniformity is typically less than the one-dimensional length of a single wafer) ). Another wafer-scale non-uniformity called "dishing" occurs in a single trench region filled with copper metal (where the etch rate in this region is higher than the surrounding dielectric region) Etching rate). As long as the width of the trench is increased by several μm, the effect of the dishing is very serious, because the resistance of the copper metal (wire) is increased, thereby causing the wafer to fail.

The wafer- and wafer-scale process non-uniformity caused by CMP is inherently difficult to predict because the conditions of the CMP process system change over time, so the process non-uniformity caused by the above causes also changes over time. In order to effectively monitor and properly adjust process conditions (to ensure that the unevenness remains within acceptable limits), for process engineers, the amount of non-contact surface topography is performed multiple times at multiple locations on the wafer. Testing is very important. Embodiments of the above described interference methods and systems enable this to be achieved.

In some embodiments, during (and/or before) CMP, one (or more) spatial characteristics (eg, the appearance of upper surface 506 and/or dielectric 504) are obtained by taking a low homology interference signal of the structure. The thickness) will be able to be monitored. Depending on the spatial characteristics, the polishing conditions can be adjusted to produce the desired flat upper surface 506'. For example, the pressure applied to the abrasive paper pad, the distribution of the above pressure, the characteristics of the polishing agent (grinding slurry), the composition and flow rate of the solvent, and other conditions can be adjusted according to the spatial characteristics. After several polishing processes, the spatial characteristics can be determined again, and the polishing conditions can be changed as needed. The topography and/or thickness is also an indicator of the end of the CMP process, such as stopping CMP when the thickness of surface 504' is reached. Therefore, low homology interference signals can be used to avoid depressions caused by excessive polishing of different regions of the object to be tested. An advantage of low coherence interference signals and systems is that even if the object under test has many interfaces, the spatial characteristics of the device (eg, (a) the relative thickness of the dielectric between the copper features 502 and (b) above the interface 510) Can be decided.

Photolithography

In many microelectronic applications, the lithography process is used to pattern a photoresist layer on a substrate, such as a photoresist layer on a germanium wafer. Referring to Figures 50A and 50B, object 30 includes a substrate (e.g., wafer 32) and a cover layer (e.g., photoresist layer 34). Object 30 includes a plurality of interfaces, such as interfaces between materials of different refractive indices. For example, interface 38 around the object represents the outer surface 39 of the photoresist layer 34 of the object in contact with the surrounding environment (eg, liquid, air, other gases, or vacuum). The substrate interface 36 is interposed between the surface 35 of the wafer 32 and the lower surface 37 of the photoresist layer 34. The surface 35 of the wafer includes a plurality of patterned features 29 . Some of the feature elements described above have the same height as the adjacent portions of the substrate, but have different indices of refraction. Other features may extend upward or downward beyond the same height as the adjacent portion of the substrate. Thus, interface 36 exhibits a complex and distinct topography beneath the outer surface of the photoresist layer.

A lithography process device is used to image the pattern onto the object. For example, the pattern corresponds to an element of an electronic circuit (or a complementary element of a circuit). After patterning, a portion of the photoresist layer is removed and exposed to the substrate below the removed photoresist layer. The exposed substrate can be etched, covered with deposited material, or otherwise modified. The residual photoresist protects the other parts of the substrate from the correction process.

In order to increase process efficiency, sometimes more than one component is fabricated on a single wafer. These components may be the same or different. Each component requires a wafer to be imaged onto the wafer. In some cases, the patterns are sequentially patterned on different wafers. Sequential patterning is performed for a number of reasons. Optical distortion can result in a lack of proper pattern focus quality over a wide area of the wafer. Even without optical distortion, the spatial characteristics of the wafer and photoresist can result in a lack of proper pattern focus quality over a wide area of the wafer. The relationship between the spatial characteristics of the wafer/resistance and the quality of focus will be discussed in the following types.

Referring to Fig. 20B, object 30 displays N wafers _40i , each of which is smaller than the total area 41 in which the object is to be patterned. In the wafer 40 _i, change (e.g., a wafer or photoresist height and slope change) is typically less than the spatial properties of the spatial variation of properties of the total area 41. Nonetheless, the wafers or photoresists of the different sub-regions 40 _i typically have different heights and slopes. For example, the photoresist layers 34 have thicknesses Δt ₁ and Δt ₂ , respectively, wherein the thicknesses Δt ₁ and Δt ₂ change the height and slope of the outer surface 39. Therefore, each wafer of the object has a different spatial relationship with the photolithography imager. The quality of the focus is related to the spatial relationship, such as the distance between the object and the lithography process imager. Having a suitable focal length for different sets of objects requires repositioning the object and the lithography process imager. Because of the variation in object height and slope, it is not possible to achieve proper object focus by simply determining the position and orientation of the object, where the object has a portion of the object (e.g., the edge 43 of the object) that is far from the patterned wafer.

Appropriate focusing can be achieved by determining the spatial characteristics of the wafer to be patterned (or otherwise processed). After the position of the wafer is determined, the object (and/or lithography process imager) can be moved (eg, moved, rotated, and/or flipped) to correct relative to the reference (eg, a portion of the lithography process imager) Wafer location. (If needed), each of the wafers to be patterned can repeat the above decisions and moves.

The determination of the spatial characteristics of the wafer includes determining the position and height of a point (or multiple points) of the outer surface of the film layer of the object, wherein the one (or more) points are within the range of the wafer to be patterned. For example, the position and orientation of the outer surface 39 of the wafer 40 ₂ (Fig. 20A) can be determined based on the location of the points 42 _{1 -} 42 ₃ within the wafer. The decision to pattern the spatial characteristics of the wafer includes illuminating the wafer using light emitted by the interferometer and detecting the interfering signal, including light reflected from the illuminated wafer. In some embodiments, the plurality of wafers are simultaneously patterned to obtain a complex interference signal. Each interfering signal represents one (or more) spatial characteristics of a wafer. Thus, the interfering signal can be used to form an image that represents the topography of the object on the plurality of wafers. During the lithography process of the wafer, the wafer is positioned according to the topography of the individual wafers formed by the complex interfering signals. Thus, each wafer can be positioned with the best focus of the lithography device.

The interfering signal for detecting each of the wafers to be patterned includes being within an OPD range to detect light reflected from the wafer and the reference light, wherein the OPD is at least equal to the coherence length of the detected light. For example, light is detected at least within the range of its coherence length. In some embodiments, the interferometer causes light reflected from the illuminated wafer to be reflected back by the outer interface (e.g., outer surface 39) or by light reflected from the inner interface (e.g., inner surface 36). leading. In some embodiments, the spatial characteristics of the object are determined based only on a portion of the interfering signal. For example, if the interference signal includes two (or more) overlapping interference patterns, the spatial characteristics of the object can be determined according to a part of one of the interference signals, wherein a part of the interference signal is by the object The contribution of a single interfering signal is dominated.

Solder Bump Processing

Referring to Figures 51A and 51B, structure 1050 is an example of a structure fabricated during a solder bump process. Structure 1050 includes a substrate 1051, a non-wettable region 1002, and a region 1003 that is wetted by solder. Region 1002 has an outer surface 1007. Region 1003 has an outer surface 1009. Therefore, the interface 1005 is formed between the region 1002 and the substrate 1001.

When the solder 1004 is placed in and in contact with the region 1003, the solder forms a secure contact with the wetted region 1003. The adjacent unwetted region 1002 acts like a dam to block solder that is not expected to flow in the structure. It is desirable to be able to know the spatial characteristics of the structure, including the height of the surfaces 1007 and 1009, and the size of the solder 1004 relative to the surface 1002. As with the embodiments determined in accordance with other discussions of the present invention, interface 1050 includes a plurality of interfaces, each of which forms interference fringes. The overlapping interference patterns are such that the spatial characteristics cannot be correctly determined using known interference techniques. The application of the systems and methods discussed herein enables spatial characteristics to be determined.

The spatial characteristics determined by structure 1050 can be used to vary process conditions, such as the deposition time of regions 1002 and 1003, and the amount of solder per unit area of region 1003. In addition, the heating conditions used to flow the solder can also be varied depending on the spatial characteristics to achieve adequate flow and/or to prevent solder from flowing into other areas.

Flat Panel Display

The interference systems and methods disclosed herein can be used in the manufacture of flat panel displays, such as liquid crystal displays (LCDs).

In general, different product applications use many different types of LCDs, such as LCD TVs, monitors for desktop computers, notebook computers, mobile phones, car GPS navigation systems, or entertainment systems for cars and airplanes ( Just to name a few). Although the specific structure of the LCD may vary, most LCDs use a similar panel structure. Referring to Figure 52A, for example, in some embodiments, LCD panel 450 is comprised of a plurality of layers, including two sheets of glass sheets 452 and 453 joined by edge seal 454. The glass sheets 452 and 453 are spaced apart from each other by a gap 464 in which a liquid crystal material is filled. The polarizers 456 and 474 are adhered to the outer surfaces of the glass substrates 453 and 452, respectively. When the LCD is assembled, one of the polarizers is used to polarize light from a display source (such as a backlight, not shown), and the other polarizer acts as an analyzer, allowing only polarization to be transmitted parallel to the filter. The light component of the shaft passes.

An array of color filters 476 is formed over glass plate 453, and patterned electrode layer 458 is formed on color filter 476, which is typically a transparent conductor, such as Indium Tin Oxide (ITO). Passivation layer 460 (sometimes referred to as a hard coat layer) is typically SiOx plated with electrode layer 458 for electrical isolation from the surface. An alignment layer 462 (e.g., a polyimide layer) is deposited over the passivation layer 460 for alignment with the liquid crystal material in the gap 464.

The LCD panel 450 also includes a second electrode layer 472 formed on the glass plate 452. An additional hard coat layer 470 is formed on the second electrode layer 472, and another alignment layer 468 is deposited on the hard coat layer 470. In an active matrix LCD, one of the electrode layers typically includes an array of thin film transistors (TFTs) (eg, one or more TFTs of subpixels) or other integrated circuitry.

The liquid crystal material is birefringent to change the direction of polarization of light passing through the LCD panel. Liquid crystal materials also have dielectric anisotropy, so liquid crystal materials are sensitive to the electric field applied to the gap. Therefore, when an electric field is applied, the liquid crystal molecules change the deflection angle, thus changing the optical characteristics of the panel. By controlling the birefringence of the liquid crystal material, the amount of light passing through the panel can be controlled.

The cell gap Δg (i.e., the thickness of the liquid crystal material) is determined by a spacer 466 that maintains the two glass sheets 452 and 453 at a fixed distance. In general, the spacer can be a cylinder or a sphere having a diameter equal to the desired cell gap, and the spacer can be formed on the substrate in a patterning technique, such as general lithography. The cell gap affects the amount of optical retardation (phase) when the light passes through the panel and the viscosity when aligning the molecules of the liquid crystal material. Therefore, the cell gap is an important parameter that must be precisely controlled during LCD manufacturing.

In general, the manufacture of LCD panels is associated with a multi-process step that is used to form multiple types of layers. For example, referring to Figure 52B, process 499 includes simultaneously forming a plurality of layers on each of the glass sheets and gluing the glass sheets to form a unit. As described in Fig. 52B, first, the TFT electrode is formed on the first glass plate (step 499A1). A passivation layer is formed on the TFT electrode (step 499A2), and then an alignment layer is formed on the passivation layer (step 499A3). Next, spacers are deposited on the alignment layer (step 499A4). The process of the second glass sheet is generally directed to forming a color filter (step 499B1) and a passivation layer formed on the color filter (step 499C1). Next, an electrode (for example, a common electrode) is formed on the passivation layer (step 499B3), and an alignment layer is formed on the electrode (step 499B4).

Next, the first and second glass sheet cells are bonded to form a cell (step 499C1), and then the liquid crystal material is filled into the cell and packaged (step 499C2). After encapsulation, the polarizer is adhered to the outer side surface of each of the glass sheets (step 499C3) to form a complete LCD panel. The order and combination of steps shown in the flowcharts are merely illustrative, and in general, other steps and their corresponding order can be varied.

In addition, each of the steps shown in Fig. 23B includes a number of steps. For example, forming a TFT electrode (generally referred to as a pixel electrode) on a first glass sheet includes several different steps. Similarly, forming a color filter on a second glass sheet involves several different steps. For example, forming a pixel electrode typically includes several steps to form a TFT, an ITO electrode, and a bus bar coupled to the TFT. In fact, the formation of a TFT electrode essentially forms a large integrated circuit and is related to the majority of deposition and lithography patterning processes used in the fabrication of conventional integrated circuits. For example, first, a TFT electrode layer is formed by depositing a layer of material (for example, a semiconductor, a conductor, or a dielectric) to form a plurality of portions of the TFT electrode layer, forming a photoresist layer on the material layer, and exposing the photoresist to patterning. In the light. A photoresist layer is then formed in which a patterned photoresist layer is produced. The material layer under the patterned photoresist layer is then removed during the etching process, thereby transferring the pattern in the photoresist to the material layer. Finally, the residual photoresist layer is removed from the substrate leaving a patterned layer of material. These steps can be repeated several times to form different elements of the TFT electrode layer, and similar deposition and patterning steps are typically used to form the color filter.

In general, the interference techniques disclosed herein can be used for monitoring LCD panels at different stages of production. For example, during LCD manufacturing, interference techniques are used to monitor the thickness and/or uniformity of the photoresist layer. As previously explained, the photoresist layer is typically used for lithographic patterning of TFT elements and color filters. For some process steps, the photoresist layer can be viewed with a low coherence interference system before exposing the photoresist layer to patterned light.

In some embodiments, an interference technique is used to monitor the patterned photoresist layer properties. For example, the critical dimensions (eg, line width) of the patterned features can be viewed using interference techniques. In addition, the interference technique can also be used to determine the overlay error between the patterned photoresist layer and the features below the photoresist layer. Also, where critical dimensions and/or overlay errors are measured, outside of the process, the patterned photoresist can be removed from the substrate and a patterned new photoresist layer is formed.

In some embodiments, the interference technique can be used with gray-tone photolithography. More and more grayscale negative lithography techniques are currently in use when it is desired to produce specific thickness variations in the patterned features of the patterned photoresist layer. The low coherence interference technique disclosed in the present invention is used to monitor the thickness data of the photoresist pattern in the gray scale region. In addition, low coherence interference techniques can also be used to monitor the coverage and critical dimensions of these feature elements.

In some embodiments, the interference technique is used to detect contaminants (eg, particles from the outside) that remain on the glass sheet during different steps of the process. These contaminants can leave visible defects (such as Mura defects) in the display panel and affect the manufacturer's yield. Such defects are usually visually inspected after panel assembly. The interference technique disclosed in the present invention enables automated inspection at one or more points of the glass substrate during the manufacturing process. Where the contaminant is located, the contaminated surface of the glass sheet can be cleaned prior to the next processing step. Therefore, the use of the present technology can reduce the probability of occurrence of Mura defects in the panel, improve panel quality, and reduce manufacturing costs.

Regarding other factors, electro-optic characteristics (such as contrast and brightness) are also related to the cell gap Δg. Control of cell gaps during manufacturing is often critical to achieving a uniform and good quality display. In some embodiments, the interference techniques disclosed herein can be used to confirm that the cell gap has the desired uniformity. For example, the present technology can be used to monitor the height and/or position of spacers on a glass sheet. Monitoring and controlling the height of the compartments can reduce variations in cell gaps on the panel.

In some cases, the actual cell gap will vary with the size of the spacer because during assembly, pressure and vacuum are used to fill the liquid crystal material, the edge seal may change size, and two sheets of glass The liquid crystal between them will produce capillary force. Before and after the filling of the liquid crystal, the surface of the exposed layer on the glass plate reflects light and generates interference fringes indicating the cell gap Δg. Even in the case where there is an interface between the liquid crystal layer and the other layers of the cell, the interfering signal with low coherence characteristics or combined with the expected interferometric signal processing technique can be used to monitor the cell during manufacturing, including the cell gap Δg.

A specific method is to obtain a low-coherence interference signal, including obtaining an interference signal indicating a cell gap Δg before the liquid crystal is filled. The cell gap Δg (or spatial characteristics of other cells) can be determined based on the interference pattern and can also be compared to a specific value. If there is a difference between the specific value and the determined cell gap Δg that is greater than the tolerances, the process conditions (e.g., the pressure applied between the two sheets of glass and the degree of vacuum) can be changed to correct the cell gap Δg. This process can be repeated over and over until the desired cell gap is reached. Next, the liquid crystal material is filled into the cell. The amount of liquid crystal filled can be determined according to the spatial measurement measured by the unit. The filling process can also be monitored by observing the interference signal on the surface of the exposed layer on the glass plate. After the cell fill is complete, the resulting additional low coherence interference pattern can be used to monitor the cell gap Δg (or other spatial characteristics). In addition, process conditions can be changed again such that the cell gap remains within tolerance.

In some LCDs, the alignment layer includes a raised structure to provide the desired alignment features of the liquid crystal material. For example, in some LCDs, each pixel has more than one alignment domain, wherein the structures of the protrusions are used for different alignment regions. The low coherence interference signal is used to measure various characteristics of the protrusion, such as shape, line width, height, and/or coverage error with respect to the characteristic elements of the underlying LCD panel. Where the protruding structure is not as expected, the protruding structure can be repaired or removed and remanufactured as needed.

In general, low coherence interference systems can be configured as needed to monitor different stages of LCD panel production. In some embodiments, the inspection station includes an interference system, wherein the interference system can be placed in the production line. For example, the inspection station can be placed in a clean manufacturing environment where the lithography steps are performed. Transferring the glass sheet to the inspection station or retrieving it from the inspection station can be done by automated machinery. In addition, checkpoints can be placed outside the production line. For example, if only one sample of the display needs to be tested, the sample can be taken from the production line and tested outside the production line.

Referring to Figure 52C, a particular checkpoint 4000 includes a table 4030, wherein the table 4030 includes a stand 4020 that is located where the detector 4010 (e.g., the interference microscope described above) is disposed. A table 4030 (including a vibration isolating bearing) is used to support the LCD panel 4001 (or glass panel) or to position the LCD panel 4001 relative to the detector 4010. The detector 4010 is disposed on the bracket 4020 by a slide rail so that the detector can advance or retreat in the direction of the arrow 4014. In this manner, the inspection station 4000 can move the detector 4010 to check any position on the display panel 4001.

The checkpoint 4000 also includes an electronic control unit 4050 for controlling the positioning system of the detector 4010 and obtaining signals from the detector 4010 regarding the information of the panel 4001. In this way, the electronic control unit 4050 can coordinate the positioning of the detector and the capture of the data.

Laser Scribing and Cutting

Lasers can be used to cut objects for making structures that are distinct from each other and that are fabricated at the same time, such as microelectronic structures. The quality of each other is related to the conditions of the cutting, such as the focus quality of the laser, the laser power, the translation rate of the object, and the depth of cut. Because of the high structural density of the feature elements, the cutting line will abut the film or film layer in the structure. When interfering techniques are used to determine the depth of cut, the interface between the film and the film layer creates an interference pattern. Even if the cutting line is very close to the film or film layer, the depth of cut can be determined by the method and system disclosed herein.

A specific example includes cutting one or more electronic structures and separating the electronic structures along the cutting lines. The low coherence interference signal can be used to determine the depth of cut before and/or after separation. Other cutting conditions are known, such as laser focus point size, laser power, and transfer rate. The depth of cut can be determined based on the interference signal. By estimating the discrete structure, the quality (e.g., depth of cut) with respect to the interval of the cutting conditions can be determined. According to the above decision, the cutting conditions that must be achieved at the required interval quality can be determined. During subsequent manufacturing, low coherent interference signals can be taken from the area being cut to monitor the cutting process. The cutting conditions can be varied such that the cutting characteristics are maintained within tolerances.

Several embodiments of the invention have been disclosed above. Other embodiments are in the claims in the scope of the patent application.

29. . . Characteristic component

30. . . object

32. . . Wafer

34. . . Photoresist layer

35. . . surface

36. . . Substrate interface

37. . . lower surface

38. . . interface

39. . . The outer surface

Δt ₁ , Δt ₂ . . . thickness

40. . . Total area

40 ₁ -40 _N . . . Wafer

42 ₁ -42 ₃ . . . point

100. . . Low coherence interference system

200. . . PUPS interference system

300. . . Optical path length scanning interference system

400, 2001, 2002, 2003, 2004, 4110. . . Interference system

2000. . . Laser Fizeau Interference System

4000. . . Detector system

450, 4001. . . LCD panel

456, 474. . . Polarizer

452, 453. . . glass plate

454. . . Edge sealant

458. . . Electrode layer

460. . . Passivation layer

462, 468. . . Alignment layer

464. . . gap

Δg. . . Cell gap

466. . . Spacer

470. . . Hard coating

472. . . Second electrode layer

476. . . Color filter

4010. . . Subsystem

4012. . . Optical cable

4014, 4016. . . Isolator

4030. . . Inner cavity

4032A, 4032B. . . Fiber extension module

4050-4053. . . aisle

4060. . . Detection and phase measuring meter electronic module

4070-4073. . . Detection module

4080. . . Reference signal cavity

4095. . . Fiber coupler

4099A, 4099B, 4100, 4570, 4570A, 4590A, 4590B, 4610, 4630, 4640, 4660, 4700A, 4800, 4800A, 4830, 4920A, 4920B. . . Detector

4102, 4202. . . optical fiber

4104, 4204. . . GRIN lens

4106. . . Beam waist position

4114. . . Target

4108. . . Second side

4112. . . Target surface

4167. . . Mirau interference objective

4200. . . Reference signal cavity

4410, 4410', 4420. . . Modulated peak

4540. . . Interference objective unit

4545. . . Detector ring

4580. . . Michelson Interference Objective

4600. . . Universal interference objective

4594A, 4594B. . . Schwarzschild optical components

4596A. . . Branch of the object to be tested

4596B, 4686. . . Reference branch

4620. . . Pedestal

4650, 4680, 4710, 4820. . . Detection beam

4670. . . Measuring point

4690, 4750. . . Reference beam

4840. . . Detection beam

4715. . . Object to be measured

4718. . . Reference interference objective

4900. . . Objective turntable

4940. . . Rotatable part

4930. . . Non-rotatable part

110. . . Interference microscope

161. . . Light intensity monitor

163. . . Main light source

197, 3197. . . Second light source

164. . . Beam combiner

165. . . Input light

169, 171, 189, 2169, 2171. . . Optical repeater

191. . . Main detector

4630A, 4630B. . . First detector

199, 4830B, 4830C, 4830D. . . Second detector

170, 179, 198, 2198, 2164, 3170, 5164, 5170, 5189, 4585, 4720. . . Beam splitter

101. . . Band pass filter

183, 187. . . Light

193, 331, 2193. . . Modulator

177, 4910A, 4910B. . . Objective lens

175, 2175, 3175, 4175. . . Analyte

181. . . Reference surface

185. . . Light

192, 5192. . . computer

195. . . Cable

213. . . Tubular lens

215. . . Polarizer

217. . . Optical plane

229. . . Focal plane

310. . . Interference microscope

325, 4592. . . Linnik interference objective

327. . . Test light objective

329. . . Reference light objective

381, 4181, 4740, 4810. . . Reference

410. . . Interference microscope

1801. . . Displacement measuring interferometer

2191, 5191. . . Main camera

2199. . . Second camera

2106. . . Aperture

2163, 4020. . . light source

2181A. . . Main reference plane

2181B. . . Second reference surface

2100. . . Composite reference plane

2202A, 2252A‧‧‧ first optical component

2202B, 2252B‧‧‧ second optical component

2200, 2250‧‧‧Composite reference surface components

2189‧‧‧ imaging lens

2190, 2258, 4550, 5169, 5171, 5177‧‧ lens

4560, 4850‧‧ ‧ mirror

2204‧‧‧ Fixed disk

2177‧‧‧Optical collimator

3163, 5163‧‧‧Broadband light source

5197‧‧‧Monitor light source

3210‧‧‧Light source and detection unit

3310‧‧Interference platform

3191‧‧‧White light camera

3199, 5199‧‧‧Monitor camera

3189‧‧‧ imaging lens

3190‧‧‧Monitoring image lens

3300‧‧‧Monitor components

3302A‧‧‧Main Reference Mirror

3302B‧‧‧Second reference

3304‧‧‧Half-mirror

3306‧‧‧Reference lens

3308‧‧‧Sampling mirror

3179‧‧‧Interferometer beamsplitter

167, 3167, 5167‧‧‧ Interference objective

3193‧‧‧Mechanical scanner

500, 500’‧‧‧ devices

501‧‧‧Substrate

502, 502'‧‧‧ copper feature

504, 504'‧‧‧ dielectric

506, 506'‧‧‧ upper surface

508, 508’, 510‧‧ interface

5193‧‧‧Mobile platform

5400‧‧ points

1050‧‧‧ structure

1051‧‧‧Substrate

1002, 1003‧‧‧ areas

1004‧‧‧ solder

1005‧‧" interface

1007, 1009‧‧‧ outer surface

5422‧‧‧Light source

5424, 5434‧‧1:4 optical switcher

5442, 5448‧‧‧Optocoupler

5426, 5428, 5430‧‧‧ bandpass filters

5444, 5446‧‧‧Light modulator

5450‧‧‧Optical delay line

5420‧‧‧ illumination module

5440‧‧‧heterodyne module

5460‧‧‧Distribution module

5480‧‧‧Detector

5499‧‧‧Detection and calculation module

5453‧‧‧Detector

5462, 5464, 5466‧‧5050/50 couplers

5468, 5470, 5472, 5474‧‧‧ couplers

5482, 5484, 5486, 5488, 5490‧‧ ‧ detectors

5492‧‧‧Detection and amplification sub-module

5494‧‧‧Analysis sub-module

5400, 5300‧‧‧ system

5340‧‧‧Module

5310, 5320, 5330‧‧ ‧ microscope

5312, 5322, 5332‧‧ ‧ detector

5311, 5321, 5331‧‧‧ test objects

5314, 5324, 5334‧‧‧ platform

5432‧‧‧Amplitude Modulator

Figure 1 is a schematic illustration of one embodiment of a low coherence interference system including an interference microscope.

Figure 2 is an illustration of the interference pattern in the viewable area of the detector.

Figure 3 is a graphical representation showing the relationship between intensity and optical path difference of low coherent interference signals.

Figure 4 is a graphical representation showing the relationship between the intensity of the monitoring signal and the optical path difference of the low coherent interference signal.

Figure 5 is a graphical representation of the relationship between relative displacement of the analyte and time during a scan to show the effect of the scan error.

Figure 6 is a graphical representation showing the relationship between the sensitivity of the system to the scanning error and the vibration frequency.

Figure 7 is a schematic illustration of one embodiment of a low coherence interference system including an interference microscope.

Figure 8 is a schematic diagram depicting the relationship between light in the image plane and the pupil plane.

Figure 9 includes a schematic of one embodiment of a low coherence interference system of an interference microscope.

Figure 10 is a schematic illustration of one embodiment of a low coherence interference system including an interference microscope.

Figure 11 is a flow chart of the J matrix approximation.

Fig. 12A and Fig. 12B are flowcharts of the J matrix approximation.

Figures 13A through 13E are diagrams of numerical experiments comparing J matrix approximations with DFT approximations.

Figures 14A through 14E are diagrams of numerical experiments comparing J matrix approximations with DFT approximations.

15A to 15E are diagrams of numerical experiments comparing the J matrix approximation method with the DFT approximation method.

Figures 16A and 16B are graphical representations of numerical experiments illustrating the J-matrix approximation.

17A to 17C are diagrams illustrating numerical experiments of the J matrix approximation.

Figure 18 is a graphical representation of the interference signal for a numerical experiment.

Figure 19 is a schematic illustration of one embodiment of an interference system having a composite reference.

Figure 20 is a simulated image of the intensity reflectance based only on the composite reference.

Fig. 21A is a cross-sectional view showing the intensity reflectance of Fig. 20.

Fig. 21B is a view showing the phase change of the image in Fig. 20.

Figure 22 is a simulated intensity reflectance image of the object to be tested detected by the composite reference plane and the main detector.

Figure 23 is a simulated intensity reflectance image of the object to be tested detected by the composite reference plane and the main detector.

Fig. 24A is a view showing the intensity reflectance of the image in Fig. 22.

Fig. 24B is a view showing the phase change of the image in Fig. 22.

Fig. 25A is a view showing the phase change of the image in Fig. 20.

Fig. 25B is a view showing the phase change of the image in Fig. 23.

Figure 26 is a flow diagram of data processing for an interference system with a composite surface.

Figure 27 is a schematic illustration of an embodiment of an interference system having a composite reference plane.

Figure 28 is a schematic illustration of an embodiment of the interference system of Figure 8, including a beam steering system.

Figure 29 is a schematic illustration of an embodiment with a composite reference plane interference system.

Figure 30 is a schematic illustration of an embodiment with a composite reference plane interference system.

Figure 31 is a schematic illustration of an embodiment with a composite reference plane interference system.

Figure 32 is a schematic illustration of an embodiment of a low coherence interference system including an interference microscope and a laser displacement interferometer.

Figure 33A is a schematic illustration of an embodiment of a combined device including a sensor system and an interference system.

Figure 33B is a schematic illustration of an embodiment of a detector system.

Figure 34 is a schematic illustration of an embodiment of a sensor.

Figure 35 is a graphical representation of the reference cavity.

Figure 36 is a flow diagram of the operation of the combined device, including a sensor system and an interference system.

Figure 37 is a schematic illustration of the autofocus mode of the combined device, including a sensor system and an interference system.

Figure 38 is a schematic illustration of the mobile monitoring mode of the combined device, including a sensor system and an interference system.

Figure 39 is a schematic diagram showing the combination of a Mirau objective and two sensors.

Figure 40 is a schematic diagram showing the combination of a Mirau objective and a sensor.

Figure 41 is a schematic diagram showing the combination of a Linnik objective and two sensors.

Figure 42A is a schematic diagram showing the configuration of a Linnik objective lens and a sensor.

Figure 42B is a schematic diagram showing the configuration of an objective lens and a sensor.

Figure 42C is a schematic diagram showing the configuration of an objective lens and a sensor.

Figure 43A is a schematic diagram showing the combination of a Michelson objective and two sensors.

Figure 43B is a schematic diagram showing the combination of a Michelson objective and two sensors.

Figure 43C is a schematic diagram showing the combination of a Linnik objective lens and a sensor.

Figure 43D is a schematic diagram showing the combination of a Linnik objective lens and a sensor.

Figure 44A is a schematic diagram showing the combination of a Michelson objective and a sensor.

Figure 44B is a schematic diagram showing the combination of a Linnik objective lens and a sensor.

Figure 45A is a schematic diagram showing the combination of a Michelson objective and two sensors.

Figure 45B is a schematic diagram showing the combination of a Linnik objective and two sensors.

Figure 45C is a schematic diagram showing the combination of a Linnik objective and three sensors.

Figure 46 is a schematic diagram showing the combination of an objective lens and a scanner having a sensor.

Figure 47 is a schematic diagram showing the combination of an objective lens having a sensor and a separate reference mirror.

Figure 48A is a schematic diagram showing the configuration of a turntable objective lens with two sensors and two objective lenses.

Figure 48B is a schematic diagram showing the configuration of a turntable objective lens having one sensor and two objective lenses.

Figure 49A is a detailed schematic view of a device for a film structure formed by dielectric deposition of deposited copper features on a substrate.

Figure 49B is a schematic illustration of the apparatus of Figure 49A after the aforementioned chemical mechanical (polishing) procedure.

Figure 50A is a top view of an object including a substrate (e.g., a wafer, or a cover layer, such as a photoresist layer).

Figure 50B is a side view of the object.

Figure 51A is a schematic illustration of a structure suitable for use in a solder bump process.

Figure 51B is a schematic view of the structure of Figure 51A after the solder bump process.

Figure 52A is a schematic view of an LCD panel composed of several layers.

Figure 52B is a flow chart of several steps in the manufacture of an LCD panel.

Figure 52C is a schematic illustration of an embodiment of an inspection station for an LCD panel, the inspection station including an interference sensor.

Figure 53 is a schematic illustration of a system with a complex microscope and a single detector system.

Similar element symbols in the various figures represent similar elements.

100. . . Low coherence interference system

101. . . Band pass filter

110. . . Interference microscope

161. . . Light intensity monitor

163. . . Main light source

164. . . Beam combiner

165. . . Input light

167. . . Interference objective

169, 171, 189. . . Optical repeater

170, 179, 198. . . Beam splitter

175. . . Analyte

177. . . Objective lens

181. . . Reference surface

183, 187. . . Light

185. . . Light

191. . . Main detector

192. . . computer

193. . . Modulator

195. . . Cable

197. . . Second light source

199. . . Second detector

Claims (31)

A microscope system having a fiber-based interferometer system for monitoring a microscope, and comprising: one or more microscopes, each microscope comprising a corresponding objective lens and a corresponding platform for using a corresponding object to be tested Positioning relative to the corresponding objective lens, wherein each corresponding platform is movable relative to the corresponding objective lens, and each microscope images the corresponding object to be tested by the corresponding objective lens; and a detector system, For monitoring the relative position between each corresponding objective lens and the corresponding platform, the detector system includes: a detector light source; one or more interference detectors, each of the interference detectors and the above In one aspect of the microscope, the interference detector is configured to receive light emitted by the detector light source to generate an optical path between the corresponding first portion and a corresponding second portion of the emitted light. Poor, the optical path difference is related to a relative position between the corresponding objective lens and the corresponding platform, and the interference detector emits the light emitted The corresponding first portion and the corresponding second portion are combined to provide a corresponding output light; one or more detectors, each detector for detecting the output light from the corresponding interference detector; a plurality of fiber waveguides for guiding light between the detector light source, the interference detector and the detector; and an adjustable optical cavity for detecting the light source to the interference detection An optical path of the detector; and an electronic controller for communicating with the detector, wherein the electronic controller is configured to determine each corresponding objective lens and the corresponding image according to the output light detected by the interference detector Information about the relative position between the platforms. The microscope system of claim 1, wherein each of the above-mentioned microscopes examines the different analytes. The microscope system of claim 1, wherein the electronic controller determines a focal length of the microscope corresponding to the object to be tested based on the information. The microscope system of claim 1, wherein, in operation, the system uses the microscope to determine information of the object to be tested, wherein determining information of the object to be tested includes using the above information to reduce vibration of the system The above information is determined by the above electronic controller. The microscope system of claim 1, wherein the microscope is a complex interference microscope. The microscope system of claim 5, wherein the interference microscope is a scanning white light interference technique type microscope. The microscope system of claim 5, wherein the interference microscope is a pupil-plane scanning white light interference technique type microscope. The microscope system of claim 5, wherein the corresponding objective lens is a Mirau objective, a Linnik objective or a Michelson objective. The microscope system of claim 5, wherein the interference microscope is configured to determine information of the corresponding object to be tested according to a test light to illuminate the object to be tested, and the object to be tested is positioned in the corresponding a platform, and the interference microscope combines the test light with a reference light to form an interference pattern in the detector, wherein the test light and the reference light are from a common source, and the system is used to reduce complex scanning The uncertainty of the information of the above-mentioned object to be tested caused by the error, wherein the scanning error is based on the above information determined by the electronic controller. The microscope system of claim 1, wherein the adjustable optical cavity is an optical path from the detector light source to the interference detector. The microscope system of claim 1, wherein each of the interference detectors comprises a lens for receiving light output from the fiber waveguide, and focusing the light output by the fiber waveguide to a waist . The microscope system of claim 11, wherein each of the above lenses is a graded index lens. The microscope system of claim 11, wherein each of the above lenses is attached to a corresponding objective lens. The microscope system of claim 11, wherein the lens is attached to a corresponding platform. The microscope system of claim 1, wherein the fiber waveguide comprises an optical fiber having a thermally expanded core. The microscope system of claim 1, wherein each of the microscopes comprises a microscope light source, and the corresponding objective lens comprises one or more optical elements, each of the microscopes for splitting light from the microscope light source to the Measuring, and the optical component is configured to collect light from the object to be tested, and the corresponding interference detector is configured to guide light to the corresponding platform through the optical component of the corresponding objective lens. The microscope system of claim 1, wherein the detector light source is a broadband light source. The microscope system of claim 1, wherein the detector source has a wavelength ranging from 900 nm to 1800 nm. The microscope system of claim 1, wherein the detector source has a full width at half maximum of 50 nm or less. The microscope system of claim 1, wherein the detector light source has a coherence length of about 100 mm or less. The microscope system of claim 1, wherein the adjustable optical cavity comprises two optical paths, each optical path comprising an optical fiber extension module. The microscope system of claim 1, wherein the detector light source and the detector are in a housing, the housing being separated from the microscope. The microscope system of claim 1, wherein the information is related to displacement of the respective objective lens and the corresponding platform along a corresponding axis. The microscope system of claim 23, wherein The microscope is used to scan the respective platforms parallel to the respective axes described above. The microscope system of claim 23, wherein the information is related to an absolute displacement between the corresponding objective lens and the corresponding platform. The microscope system of claim 23, wherein the information is related to the relative position between the corresponding objective lens and the corresponding platform. The microscope system of claim 1, wherein each of the microscopes includes a microscope light source for splitting light from the microscope light source to one of the objects to be tested disposed on the corresponding platform, wherein the maximum intensity of the microscope light source The wavelength is about 100 nm or greater than the maximum intensity of the detector source. The microscope system of claim 27, wherein the maximum intensity of the microscope source ranges from 300 nm to 700 nm, and the maximum intensity of the detector light source ranges from 900 nm to 1600 nm. An imaging interferometer system having a fiber-based interferometer system for monitoring an imaging interferometer and comprising: one or more imaging interferometers, each imaging interferometer comprising one or more optical components and a corresponding platform, a corresponding platform is moved relative to the optical element of the corresponding imaging interferometer, and the imaging interferometer respectively images a plurality of corresponding objects to be tested by the one or more optical elements; a detector system for monitoring a relative position between the one or more optical components and the corresponding platform, the detector system comprising: a detector light source; and one or more interference detectors, Each of the interference detectors is configured to receive the detector light source to generate an optical path difference between the corresponding first portion and a corresponding second portion, wherein the optical path difference is related to the optical component and the corresponding a distance of the platform, and combining the corresponding first portion and the corresponding second portion to provide a corresponding output light; one or more detectors, each detector for detecting a corresponding one of the interference detectors The output light of the interference detector; one or more fiber waveguides for guiding light between the detector light source, the interference detector and the detector; and an adjustable optical cavity for detecting a light source to the optical path of the interference detector; and an electronic controller for communicating with the detector, wherein the electronic controller is configured to detect the input according to the interference detector Light to determine the relative position information between the above-mentioned one or more optical imaging elements of each interferometer and corresponding platforms above. The imaging interferometer system of claim 29, wherein the imaging interferometer is an interference microscope. A microscope system having a fiber-based interferometer system for monitoring a microscope, and comprising: a plurality of microscopes, each microscope comprising a corresponding objective lens and a corresponding platform for opposing a test object relative to said corresponding The objective lens is positioned, wherein each corresponding platform is movable relative to the corresponding objective lens, and each microscope images the corresponding object to be tested by the corresponding objective lens; and a detector subsystem, including: a detector light source, a plurality of interference detectors, one or more fiber waveguides, and a plurality of interference detectors for guiding the detector light source to the interference detector, each of the interference detectors Corresponding to one of the above microscopes; the detector subsystem further includes a complex detector and an electronic controller, each detector for receiving light from the interference detector, and the electronic controller is used for detecting Detector communication; wherein during operation, the detector light source directs light to each of the interference detectors via the fiber waveguide, and each of the interference detectors directs an output light to the corresponding detector, the output light Including an interference phase, the interference phase is related to the distance between the corresponding objective lens and the corresponding platform of the microscope, the microscope system For the interference detector, and the electronic controller determines the information distance between the objective lens and corresponding to the above said corresponding platform based on the output of the detected light.