JP2002350117A - Apparatus and method for measuring shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for measuring a shape in which the shape of an observation object can be correctly measured by a simple configuration of apparatus without reversing bumps and dents of the observation object or the like manner even when the object includes both high step parts and minute shape change parts and without a complicate operation. SOLUTION: There are set a light source device 1 which can select a plurality of wavelengths, a differential interference microscope, a phase change device 2 for changing a relative phase amount of two lights which form interference images, an imaging device 29, and a computing unit 30 for forming a phase distribution image of the observation object by at least two wavelengths and comparing values of points of the formed phase distribution image with each other between selected wavelengths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring device and a shape measuring method for quantitatively measuring an uneven shape and a step amount of an IC pattern or a metal surface.

[0002]

2. Description of the Related Art An interference microscope has both the characteristics of high-precision height measurement of an interferometer and the characteristics of high-resolution observation of a microscope. By utilizing these characteristics, an interference microscope is formed on a silicon wafer. It is widely used for measuring the height of IC patterns and measuring minute steps formed on metal surfaces such as magnetic disks. And among the interference microscopes, the differential interference microscope, in particular, has a characteristic that the measurement is hardly affected by disturbances such as vibrations since it constitutes a common optical path type interferometer using polarization interference. .

By the way, this type of differential interference microscope has a fringe scanning method (phase shift method) which is a high-precision measurement method for interference measurement.
Is disclosed in Japanese Patent Application Laid-Open No. 5-232384. An example in which the resolution is increased by combining a differential interference microscope and a laser scanning microscope is disclosed in JP-A-9-14928. Thus, by combining the interference measurement method with the differential interference microscope, both high-accuracy height measurement and high-resolution observation can be realized.

[0004]

However, the conventional interference measurement method assumes that the incident light is specularly reflected on the surface of the observation object, and performs the measurement on the assumption that the step on the observation object surface is extremely small. I have. For this reason, when the shape change such as a step formed on the observation object surface becomes large, it becomes difficult to perform advanced measurement by the conventional interference measurement method.

[0005] Regarding this problem, see Japanese Patent Application Laid-Open No. 9-149.
No. 28 is also disclosed. When observing an object having a large step with a differential interference microscope, the contrast of the edge portion may be inverted depending on the amount of the step. Therefore, when an object having a large step is measured using the differential interference microscope, a result in which the unevenness is reversed is obtained. JP-A-9-14
No. 928 improves the point that it becomes difficult to distinguish a change in reflected light due to a step and a change in reflectance on the surface of an observation object when the amount of the step becomes large. However, there is no description about a method for improving the inversion of the unevenness when an object having a large step amount is measured. In the case of measuring a step or the like of an object using reflected light in interference measurement, if the amount of the step exceeds λ / 2, an optical path length difference exceeds λ in a round trip, and accurate measurement cannot be performed. In the case of the differential interference microscope, when the step amount exceeds λ / 2, accurate measurement cannot be performed similarly. When the step amount exceeds λ / 4, the contrast of the image is inverted, and it becomes difficult to determine the unevenness.
Accurate measurement cannot be performed.

[0006] These problems which occur when the step height is increased are described in detail in Japanese Patent Application Laid-Open No. 9-236404, and a method for improving the problem is also disclosed. By using the method disclosed in JP-A-9-236404, it is possible to measure a step of λ / 2 or more. However, in the method disclosed in Japanese Patent Application Laid-Open No. 9-236404, the step difference is measured from the interference color on the assumption that the light is specularly reflected on the surface of the observation object, as in the conventional interference measurement. Since the diffraction of light on the surface of the observation object is not considered, if there is a minute shape change on the surface of the observation object, the change of the interference color becomes dull and it becomes difficult to perform accurate measurement. . Furthermore, in this method, it is necessary to obtain the relationship between the interference color and the amount of the step in advance, and the measurement is performed using a spectroscope. become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. Even when both a high step portion and a minute shape change portion are present in an observation object, it is possible to reverse the unevenness of the observation object. It is an object of the present invention to provide a shape measuring device and a shape measuring method capable of measuring a shape accurately without accompanying the same, and capable of measuring with a simple device configuration without complicated operations.

[0008]

In order to achieve the above object, a shape measuring apparatus according to the first aspect of the present invention forms a light source device capable of selecting a plurality of wavelengths, a differential interference microscope, and an interference image. A phase change device that changes a relative phase amount of the two lights, an imaging device, and a phase distribution image of the observation object at at least two wavelengths, and a value of each point of the formed phase distribution image is selected. And an arithmetic unit for comparing between the wavelengths.

The shape measuring apparatus according to the second aspect of the present invention includes a light source device capable of selecting a plurality of wavelengths, a differential interference microscope, and a phase changing means for changing a relative phase amount between two lights forming an interference image. A change device, an imaging device, and at least two
Two differential interference images having different signs with substantially the same phase change amount by the phase changing device at two wavelengths are formed, a difference image is formed from the two obtained differential interference images, and the value of each point of the formed difference image is obtained. And an arithmetic unit for comparing the selected wavelengths with each other.

The shape measuring apparatus according to the third aspect of the present invention includes a light source device capable of selecting a plurality of wavelengths, a differential interference microscope, and a phase changing means for changing a relative phase amount of two lights forming an interference image. A change device, an imaging device, and at least two
Two differential interference images having the same amount of phase change by the phase change device at different wavelengths and having different signs are formed, a difference image and a sum image are formed from the two captured differential interference images, and the sum of the formed difference image and the sum image is obtained. An arithmetic unit for comparing the value of each point in one or both of the images between the selected wavelengths.

Further, in the shape measuring method according to the fourth aspect of the present invention, the step of selecting at least two wavelengths, the step of acquiring an interference image, and the step of changing the relative phase amount of light forming the interference image And a step of converting the interference image into a phase distribution image for each selected wavelength, and a step of comparing and calculating the value of each point of the converted phase distribution image between the selected wavelengths. .

Further, in the shape measuring method according to the fifth invention, the step of selecting at least two wavelengths, the step of acquiring an interference image, and the step of changing the relative phase amount of light forming the interference image A step of forming a difference image from two interference images having substantially the same phase change and different signs, a step of comparing the values of respective points in the formed difference image between selected wavelengths, The method is characterized in that the method includes a step of converting the observation object into a phase distribution image.

Further, in the shape measuring method according to the sixth aspect of the present invention, the step of selecting at least two wavelengths, the step of acquiring an interference image, and the step of changing the relative phase amount of light forming the interference image Forming a difference image and a sum image from two interference images having substantially the same phase change and different signs, and selecting the value of each point in one or both of the formed difference image and the sum image And a step of forming a phase distribution image of the observation object from the difference image and the sum image.

The intensity distribution proportional to the phase distribution of the observation object observed by the differential interference microscope and the phase contrast microscope is such that light transmitted or reflected without being diffracted by the observation object and light diffracted by the observation object are different from each other. It was interference. The relationship among incident light, transmitted light or reflected light, and diffracted light when light enters the observation object surface can be represented by three vectors as shown in FIG. Here, Φ represents the phase amount of the observation object.

Since the differential interference image and the phase difference image can be expressed by the product of transmitted light or reflected light and diffracted light, when Φ approaches π, the product of transmitted light or reflected light and diffracted light is obtained. Is 0
, And the differential interference image and the phase contrast image disappear. Further, when Φ exceeds π, the product of the transmitted light or the reflected light and the diffracted light becomes a negative value, and the intensity distribution of the image is inverted.

When the observed object has a step, the value of the phase amount corresponding to the step changes depending on the wavelength to be observed. Therefore, by measuring the phase amount of the observation object using a plurality of wavelengths and comparing the obtained phase amount Φ, whether Φ is less than π, a value near π, or exceeds π (Hereinafter, referred to as the determination of the phase amount π). When the phase is measured, the value of the phase amount Φ can be accurately measured by performing a fringe scanning method using a phase changing device as disclosed in Japanese Patent Application Laid-Open No. Hei 5-232384. The determination of π can be performed more accurately. Furthermore, by using this determination result, it is possible to accurately determine the unevenness of the step, so that even when the phase amount of the observation object is large, an accurate phase distribution can be obtained.

The present inventor analyzed the imaging characteristics of the differential interference microscope and the phase contrast microscope, and analyzed the results. Etc.

In a normal fringe scanning method, 0,
The measurement is performed by adding four phase shift amounts of π / 2, π, and 3π / 2. As a result of analysis performed by the inventor, the phase shift amounts given through the phase change device are equal in value and different in sign.
Even when the two values of Θ are used, the value obtained by shifting the phase thereof ± ２
By calculating the difference between the two interference images, the phase component can be separated and extracted in the same manner as in the conventional fringe scanning method. Therefore, the phase amount π can be determined by forming a difference image of the observation object at a plurality of wavelengths and comparing the values of the wavelengths at each point in the difference image.

Further, by performing a sum operation of two interference images of ± Θ having the same phase shift amount given by the phase changing device and different signs, it is possible to separate and extract the intensity component from the interference image. When the phase amount of the step is a value close to π, the intensity of the edge portion of the step in the intensity image sharply decreases to a level that can be regarded as substantially zero. Therefore, the phase amount π can also be determined by comparing the intensity component, that is, the sum image for each wavelength.

Further, by forming the sum image, it is possible to obtain the reflectance information of a place other than the edge portion of the step. By obtaining the reflectance information other than the edge portion and complementing the edge portion using the reflectance information, it is possible to accurately determine the phase amount π even when the observed object has a change in reflectance.

The phase amount π can be determined by using either the difference image or the sum image. Furthermore, by using both the difference image and the sum image, the phase amount π can be determined more accurately, and accurate unevenness determination can be performed.

In order to accurately measure the surface shape of an observation object, it is necessary to accurately determine the unevenness even when the shape changes greatly. Therefore, as shown in the first invention, first, a phase change device is added to a differential interference microscope equipped with an imaging device so that an accurate shape can be measured by a technique such as a fringe scanning method. Further, by using a light source device capable of selecting a plurality of wavelengths from a light source, shape measurement can be performed at a plurality of wavelengths. By adding a device that compares the phase distribution image corresponding to the shape of the observation object measured at a plurality of wavelengths between wavelengths, it is possible to determine whether the phase amount exceeds π. , Accurate unevenness determination can be performed, and accurate shape measurement can be performed.

Further, as in the second aspect of the present invention, if a device for comparing a difference image formed from two images shifted by ± Θ phase amount by a phase changing device at a plurality of wavelengths is used, accurate unevenness determination can be performed. And accurate shape measurement can be performed. Further, in this case, since only two states of ± Θ in the phase shift amount by the phase change device are sufficient, there is an effect that the measurement time can be reduced.

Further, as in the third aspect of the present invention, it is possible to determine the unevenness by forming a sum image from two differential interference images. Furthermore, by using both the difference image and the sum image formed from the two differential interference images, it becomes possible to correct the change in the reflectance and the transmittance of the observed object, thereby enabling more accurate shape measurement. Become. In addition,
The shape measuring apparatus of the present invention is not a technique unique to a differential interference microscope, but can be applied to all microscopes of a type that visualizes a phase distribution using an interference effect such as a phase contrast microscope.

In addition, by using the shape measuring method having the steps as shown in the fourth to sixth aspects of the present invention, the shape of the observed object can be accurately determined from the image of the interference microscope which visualizes the phase distribution by the interference effect. It becomes possible to measure.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, a specific device configuration and effects of an epi-illumination type differential interference microscope applicable to the present invention will be described. FIG. 2 is a schematic configuration diagram of an epi-illumination type differential interference microscope. In the microscope of FIG. 2, light emitted from the light source 21 becomes linearly polarized light having a polarization angle of 45 ° via a polarizer 22 disposed in the optical path of the illumination optical system, and further reflected by the half mirror 23. Enter the Nomarski prism 24. The light transmitted through the Nomarski prism 24 is split into two linearly polarized light beams that are orthogonal to each other, and further condensed as two points separated on the observation object plane 26 via the objective lens 25. The two separated light beams are reflected by the observation object surface 26, then pass through the objective lens 25 and the Nomarski prism 24 again, where the two linearly polarized light components are combined, and further pass through the half mirror 23. The transmitted light passes through the analyzer 27 arranged in the optical path of the imaging optical system, and the two polarized light components interfere with each other to form a differential interference image on the image plane of the imaging optical system. The formed differential interference image is an eyepiece (not shown)
, The image is visually observed, or an image is captured by an image sensor such as the CCD camera 29 and analyzed by the computer 30 or the like. In the figure, 28 is an imaging lens, 31 is a lens, and 32 is a field stop such as a brightness stop.

Next, an embodiment of a shape measuring apparatus in which this type of differential interference microscope is applied to the present invention will be described. FIG.
FIG. 3 is a schematic configuration diagram showing an embodiment of a shape measuring device using the present invention for the epi-illumination type differential interference microscope of FIG. In the shape measuring apparatus of the present embodiment, instead of the light source 21 in FIG.
A wavelength selection light source device 1 capable of selecting and emitting light at a plurality of wavelengths is used, and light of specific first and second wavelengths is selected from a plurality of wavelengths that can be emitted from the wavelength selection light source device 1. It can be selected and used for observation. Further, a phase change device 2 is arranged in place of the polarizer 22 arranged in the optical path of the illumination optical system in FIG. 2 so that an arbitrary amount of retardation can be given to polarized light incident on the Nomarski prism 24. Has become. CC on the image plane of the imaging optical system or its conjugate plane
A D camera 29 is provided, and a video signal from the CCD camera 29 can be taken into the computer 30.

In such a configuration, first, light of the first wavelength is selected by the wavelength selection light source device 1, and the phase change device 2
Is adjusted so that the retardation amount of the polarized light incident on the Nomarski prism 24 becomes 、, the differential interference image is captured by the CCD camera 29, and the image is transferred to the computer 30 and stored in the storage area inside the computer 30. Let it be. Next, the phase change device 2 is adjusted so that the retardation amount of the polarized light incident on the Nomarski prism 24 becomes -Θ, and the differential interference image is converted to the CCD camera 2.
9, the image is transferred to the computer 30 and stored in a storage area inside the computer 30. Next, subtraction is performed in units of pixels corresponding to the coordinates on the image plane using two image data held in the data storage unit via an arithmetic processing unit inside the computer 30 to form a difference image. Further, a sum operation is performed for each pixel to form a sum image. The formed difference image is subjected to a deconvolution process or an integration process using a response characteristic OTF of a differential interference microscope to form a phase distribution image of the observation object at the first wavelength, and is displayed on a display of the computer 30. I do.

Next, the light of the second wavelength longer than the first wavelength is selected by the wavelength selecting light source device 1 and adjusted so that the intensity is substantially the same as the first wavelength. Similarly, a differential interference image having a retardation amount of ±
9, the image is stored in a storage area inside the computer 30, a difference image and a sum image are formed through an arithmetic processing unit, and a phase distribution image of the observation object at the second wavelength is formed from the difference image. Display on the display.

FIG. 4 shows how the relative intensity changes depending on the wavelength with the change in the step amount (phase distribution).
Shown in As can be seen from FIG. 4, the relative intensity of each wavelength is the same in that it changes sinusoidally with the change in the amount of step, but the position where the relative intensity is maximized is different. The amount of the step at the position where the relative intensity becomes the maximum value corresponds to the case where the phase change is 波長 wavelength. For example, when the relative intensity is 0.2 at a short wavelength (solid line), the steps are about 18 and about 120. Therefore, with this alone, the phase change is 1 /
It is not possible to determine whether the step amount is two wavelengths or less 18 or the step amount 120 is half wavelength or more. However, at a long wavelength (broken line), when the step amount is 18, the relative intensity is small as compared with the short wavelength (solid line), and when the step amount is 120, the relative intensity is large as compared with the short wavelength. As described above, if the same step amount is compared at different wavelengths, it is determined from the magnitude relationship of the relative intensities whether the step amount, that is, the phase change amount is a step amount of 波長 wavelength or less,
Alternatively, it can be determined whether the amount of the step is equal to or more than １ ／ wavelength.

In consideration of the above points, a phase determination image A is formed by subtracting the phase distribution image of the observation object at the second wavelength from the phase distribution image of the observation object at the first wavelength. The subtraction is performed in pixel units corresponding to the coordinates on the image plane as in the case of forming the difference image.
Then, in the formed phase determination image A, it is classified into three parts: a part where the value is positive, a part where the value is substantially 0, and a part where the value is negative.

Here, the portion where the value is negative in the phase determination image A is a quarter wavelength or more and a half of the first wavelength.
This is a portion that has a phase change equal to or less than the wavelength, and does not involve inversion of the unevenness between the phase distribution information and the shape of the observation object. On the other hand, the portion where the value is positive in the phase determination image A is a portion that has a phase change of 波長 wavelength or more at the first wavelength and is accompanied by inversion of the concavities and convexities in the phase distribution information and the observed object shape. Therefore, this part needs correction accompanying inversion of the unevenness. In addition, the portion where the value is substantially 0 in the phase determination image A is a portion where the phase (shape) does not originally change. However, in the first wavelength, the low step portion of 1/4 wavelength or less has a small phase change due to the wavelength difference, and thus the phase determination image A
Can be considered to be approximately zero. Therefore, this portion can also be included in a portion of the phase distribution information and the shape of the observation object that does not involve inversion of the unevenness.

From the image of the phase determination image A, information on the presence / absence of correction by inversion of concavities and convexities is added to each point of the phase distribution image of the first wavelength via an arithmetic processing unit inside the computer 30 to obtain a sum image. The shape of the observation object is reproduced using the data and the wavelength data of the first wavelength, and the formed image is displayed on the display of the computer 30.

Then, as described above, the wavelength selection in the wavelength selection light source device 1, the control of the retardation amount by the phase change device 2, the capture of the image and the formation of each difference image,
The computer 30 performs the conversion from the difference image to the phase distribution image and the formation of the phase determination image, and the conversion from the unevenness determination information and the phase component image to the shape of the observation object, thereby performing shape measurement using a differential interference microscope. The device can be configured.

The phase judgment image can be formed from the phase distribution image of the observation object at the first wavelength and the phase distribution image of the observation object at the second wavelength, as in the above-mentioned phase judgment image A. In addition, the first wavelength and the second
Can also be formed from the difference images of the wavelengths.

As in the case of forming the phase determination image A,
An image formed by subtracting the difference image of the second wavelength from the difference image of the first wavelength is defined as a phase determination image B. Similarly to the phase determination image A, the phase determination image B is classified into three parts: a part where the value is positive, a part where the value is substantially 0, and a part where the value is negative.

Here, the portion where the value is positive in the phase judgment image B has a phase change of １ ／ wavelength or more at the first wavelength, and the phase distribution information and the shape of the observation object are accompanied by the inversion of the unevenness. It is. Therefore, this part needs correction accompanying inversion of the unevenness. On the other hand, the portion where the value is negative in the phase determination image B has a phase change of not less than ４ wavelength and not more than 波長 wavelength at the first wavelength, and the phase distribution information and the shape of the observed object are not accompanied by the inversion of the unevenness. Part. Also,
The portion where the value is substantially 0 in the phase determination image B is a portion where the phase (shape) does not originally change. However, the value of the phase difference image B can be regarded as substantially zero in the low throwing portion of the first wavelength that is equal to or less than 1/4 wavelength because the phase change due to the difference in wavelength is small. Therefore, this portion can also be included in a portion of the phase distribution information and the shape of the observation object that does not involve inversion of the unevenness.

From the image of the phase determination image B, information on the presence / absence of correction by inversion of concavities and convexities is added to each point of the phase distribution image of the first wavelength via an arithmetic processing unit in the computer 30 to obtain a sum image. The shape of the observation object is reproduced using the data and the wavelength data of the first wavelength, and the formed image is displayed on the display of the computer 30.

In the above, the example in which the phase determination image is formed by subtracting the phase distribution image or the difference image of each of the first wavelength and the second wavelength has been described. Alternatively, it can be formed by calculating the ratio of the phase distribution images of the first wavelength and the second wavelength. In that case, it is possible to determine the unevenness depending on whether the ratio of each phase distribution image is 1 or more and 1 or less. Also, a phase determination image can be formed in the same manner by using the ratio of each difference image between the first wavelength and the second wavelength.

Next, FIGS. 5A to 5D show examples of the configuration of the phase change device used in this embodiment. In FIGS. 5A to 5D,
As shown in FIG. 3, an example of a configuration in which the phase changing device 2 is disposed in the optical path of the illumination optical system will be described.
The arrangement of the phase changing device 2 may be interchanged with that of the analyzer 27 in the optical path of the imaging optical system, and in this case, the same effect as in the case of being arranged in the optical path of the illumination optical system can be obtained.

The phase change device 2 shown in FIG.
The plate 3 is fixed, and a driving device such as a motor 5 is attached to a polarizer 4 rotatable about the optical axis so that the rotation can be controlled. The retardation corresponds to the rotation angle of the polarizer 4. The amount can be changed. In the configuration example of FIG. 5A, the λ / 4 plate 3 is fixed and the polarizer 4 is rotated. However, the rotation is controlled by attaching a motor to the λ / 4 plate 3 so that the polarization can be controlled. Child 4
The same effect can be obtained even if the structure is fixed.

The phase change device 2 shown in FIG.
By fixing the plate 3 and the polarizer 4, disposing the liquid crystal element 6 between the λ / 4 plate 3 and the polarizer 4, and changing the voltage applied to the liquid crystal element 6 via the liquid crystal control device 7 The rotation direction of the polarized light transmitted through the liquid crystal element 6 is rotated to change the retardation amount.

The phase changing device 2 shown in FIG.
The λ / 4 plate 3 is eliminated from the configuration example shown in FIG.
The function of the plate 3 is given to the Nomarski prism. In the phase change device 2 shown in FIG. 5D, an electro-optical element 8 is arranged instead of the liquid crystal element 6 in the configuration example shown in FIG. It is configured such that the retardation amount can be changed by changing the characteristics.

Next, an example of the configuration of the wavelength selection light source used in this embodiment is shown in FIGS. The wavelength selection light source device 1 shown in FIG. 6A is configured by combining a white light source 10 and an interference filter 11, and changing the wavelength of the light source by replacing the interference filter 11 corresponding to the selected wavelength. , A desired wavelength can be selected. In addition to replacing the interference filter 11,
By changing the angle formed between the interference filter 11 and the optical axis by tilting the interference filter, the wavelength transmitted through the interference filter 11 may be shifted to change the wavelength of the light source.

The wavelength selection light source device 1 shown in FIG. 6B combines a white light source 10 and a liquid crystal element 6 to form a liquid crystal control device 7.
The desired wavelength can be selected by changing the voltage applied to the liquid crystal element 6 through the interface, thereby changing the wavelength transmitted through the liquid crystal element 6.

The wavelength selection light source device 1 shown in FIG. 6C has a plurality of monochromatic light sources (lasers, LEDs, etc.) 12, 12 '.
And a dichroic mirror 13 disposed at a position where the optical axes of the plurality of monochromatic light sources 12 and 12 ′ intersect with each other to switch the monochromatic light sources 12 and 12 ′ via the control device 15, or , 12 'are arranged in front of the shutters 14 and 14', and a desired wavelength can be selected by controlling the opening and closing timing of the shutters 14 and 14 'via the control device 15.

The wavelength selection light source device 1 shown in FIG. 6D uses a semiconductor laser 16 as a light source and controls the drive current of the semiconductor laser 16 via a control device 17 so as to reduce the oscillation wavelength of the semiconductor laser. By changing the wavelength, a desired wavelength can be selected. Alternatively, a desired wavelength may be selected by selecting an element to emit light using an LED 16 ′ having a plurality of light emitting elements as a light source.

When the wavelength-selective light source 1 having the configuration as shown in FIG. 6C or 6D is used, it is desirable to employ the configuration of a laser scanning microscope as shown in FIG.
In that case, a beam scanning device is arranged in the optical path of the illumination optical system in the configuration of FIG. 3 so that the laser beam can scan on the observation object plane. Further, a polarizing beam splitter (PBS) 33 is used instead of the analyzer 27 shown in FIG. 3, and two detectors 34 and 35 are arranged in the optical path divided by the PBS 33, and the signals from the respective detectors 34 and 35 are arranged. The difference signal and the sum signal are detected. Further, the polarization state incident on the Nomarski prism 24 is controlled so that both the difference signal and the sum signal are maximized via the phase changing device 2.

In addition, the method for selecting a wavelength in the shape measuring apparatus of the present invention is not limited to the configuration using the wavelength selection light source as shown in FIG. 6, but as shown in FIG. By arranging a dichroic mirror (DM) 38 in front of 36 and 37 and capturing differential interference images with the plurality of CCD cameras 36 and 37, the same effect as selecting a desired wavelength can be obtained. It is. In this case, instead of the wavelength selection light source 1 shown in FIG. 3, a light source 21 ′ having a broadband wavelength close to white is used.

Further, instead of disposing the dichroic mirror 38 and using a plurality of CCD cameras, one CCD camera, which can independently capture three colors of RGB, is used as the CCD camera. The same effect as the configuration shown in FIG. 8 can be obtained by separating the signals. Therefore, 3
Use of a CCD type camera can further simplify the device configuration.

As described above, the shape measuring apparatus and the shape measuring method of the present invention have the following features in addition to the invention described in the claims.

(1) A light source device capable of selecting a plurality of wavelengths, a differential interference microscope, a phase change device that changes a relative phase amount of two lights forming an interference image, an imaging device, and at least two Imaging two differential interference images having substantially the same phase change amount by the phase changing device at two wavelengths and different signs, forming a difference image from the two captured differential interference images,
An arithmetic unit for comparing values of respective points of the formed difference image between selected wavelengths.

(2) A light source device capable of selecting a plurality of wavelengths, a differential interference microscope, a phase change device for changing a relative phase amount of two lights forming an interference image, and an image pickup device Two differential interference images having the same amount of phase change by the phase change device at different wavelengths and having different signs are formed, a difference image and a sum image are formed from the two captured differential interference images, and the sum of the formed difference image and the sum image is obtained. An arithmetic unit for comparing the value of each point in one or both of the images between selected wavelengths.

(3) The step of selecting at least two wavelengths, the step of obtaining an interference image, and the step of changing the relative phase amount of light forming the interference image are substantially the same in phase change amount. Forming a difference image from two interference images different from each other, comparing the value of each point in the formed difference image between selected wavelengths, and converting the interference image into a phase distribution image of the observation object A shape measuring method having:

(4) The step of selecting at least two wavelengths, the step of acquiring an interference image, and the step of changing the relative phase amount of light forming the interference image have substantially the same phase change amount. A step of forming a difference image and a sum image from two different interference images, a step of comparing the value of each point in one or both images of the formed difference image and the sum image between selected wavelengths, A shape measurement method including a step of forming a phase distribution image of an observation object from a difference image and a sum image.

[0056]

According to the present invention, at least two wavelengths are selected, a phase distribution is formed from an image of an interference microscope, and the phase distribution is compared between wavelengths, so that the phase change is λ /
2 is determined.
/ 2 can be detected, and even if there are both large steps and small shape change parts in the observed object, it can be accurately detected without reversing the irregularities. It becomes possible to measure the shape.

[Brief description of the drawings]

FIG. 1 shows incident light when light enters an observation object surface,
It is explanatory drawing which shows the relationship between transmitted light or reflected light, and diffracted light.

FIG. 2 is a schematic configuration diagram of an epi-illumination type differential interference microscope.

FIG. 3 is a schematic configuration diagram showing an embodiment of a shape measuring device using the present invention for the epi-illumination type differential interference microscope of FIG. 2;

FIG. 4 is a graph showing a change characteristic of a relative intensity with respect to a change in a step amount (phase distribution) when each wavelength is selected in the shape measuring apparatus of the present embodiment.

FIG. 5 is a schematic configuration diagram of a phase change device used in the present embodiment.

FIG. 6 is a schematic configuration diagram of a wavelength selection light source used in the present embodiment.

FIG. 7 is a schematic configuration diagram of a shape measuring apparatus according to another embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a shape measuring apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source 2 phase change device 3 λ / 4 plate 4 polarizer 5 motor 6 liquid crystal element 7 liquid crystal control device 8 electro-optical element 9 control device 10 white light source 11 interference filter 12, 12 ′ laser or LED 13 dichroic mirror 14, 14 ′ Shutter 15 Control device 16 Semiconductor laser 16 'Multi-emitting LED 17 Control device 21, 21' Light source 22 Polarizer 23 Half mirror 24 Nomarski prism 25 Objective lens 26 Sample 27 Analyzer 28 Imaging lens 29 CCD camera 30 Computer 31 Lens 32 Aperture 33 polarization beam splitter (PBS) 34 first detector 35 second detector 36 first CCD camera 37 second CCD camera 38 dichroic mirror

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Claims (2)

[Claims] 1. A light source device capable of selecting a plurality of wavelengths, a differential interference microscope, a phase change device that changes a relative phase amount of two lights forming an interference image, an imaging device, and at least two A shape measuring apparatus, comprising: an arithmetic unit that forms a phase distribution image of an observation object at a wavelength and compares values of respective points of the formed phase distribution image between selected wavelengths. 2. A process for selecting at least two wavelengths, a process for acquiring an interference image, a process for changing a relative phase amount of light forming an interference image, and a process for generating an interference image for each of the selected wavelengths. A shape measurement method comprising: converting a phase distribution image to a phase distribution image; and comparing and calculating values of respective points of the converted phase distribution image between selected wavelengths.