JP2014001965A - Shape measuring apparatus and shape measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measuring apparatus and a shape measuring method capable of precisely measuring the height shape of a surface of an object to be measured.SOLUTION: Overlapping received light intensity distributions are obtained in a Z direction for a plurality of portions of an object S to be measured. A received light intensity distribution component of an interference system and a received light intensity distribution component of a confocal system are respectively extracted from the obtained overlapping received light intensity distributions. Interference height data indicating positions in the Z direction are calculated respectively for the plurality of portions on the basis of the extracted received light intensity distribution component of the interference system. Further, based on the extracted received light intensity distribution component of the confocal system, confocal height data indicating positions in the Z direction are respectively calculated for the plurality of portions. Shape data indicating a surface shape of the object S to be measured are generated using the interference height data and the confocal height data for the plurality of portions.

Description

  The present invention relates to a shape measuring apparatus and a shape measuring method.

  In a confocal microscope, light is condensed on a measurement object by an objective lens. The reflected light from the measurement object is collected by the light receiving lens and enters the light receiving element through the pinhole (see, for example, Patent Document 1). The light is scanned two-dimensionally on the surface of the measurement object. Further, the distribution of the amount of light received by the light receiving element is changed by changing the relative distance between the measurement object and the objective lens. A peak in the amount of received light appears when the surface of the measurement object is focused. The height shape of the surface of the measurement object can be measured based on the peak position of the received light amount distribution.

  In the fine structure measuring apparatus of Patent Document 2, a thin film that transmits part of the light irradiated to the measurement object and reflects the remaining light is disposed between the objective lens of the confocal microscope and the measurement object. Is done. In addition, a mirror that reflects light reflected by the thin film toward the thin film is disposed at a position that is substantially symmetric with respect to the focal point of the objective lens with respect to the thin film.

  As described above, when the measurement object is at the focal position of the objective lens, the peak (maximum peak) of the received light amount distribution is detected. In addition to this, when the measurement object is at a position shifted by 1/4 × (2n + 1) wavelengths (n is an integer) from the focal position of the objective lens, the amount of received light is minimized. When the object to be measured is at a position shifted by 1/4 × 2n wavelength from the focal position of the objective lens, the peak of the received light amount smaller than the maximum peak is detected. By comparing these peaks with the maximum peak, the resolution in measuring the height shape of the surface of the measurement object can be improved.

JP 2008-83601A JP-A-7-19827

  However, in the fine structure measuring apparatus of Patent Document 2, it is difficult to accurately detect the maximum peak when the difference in the amount of received light between the maximum peak and the adjacent peak is small. In this case, an error of an integral multiple of ½ × wavelength occurs in the height of the surface of the measurement object to be measured. For this reason, the fine structure measuring device of Patent Document 2 may not be able to accurately measure the height shape of the surface of the measurement object.

  An object of the present invention is to provide a shape measuring device and a shape measuring method capable of accurately measuring the height shape of the surface of a measurement object.

  (1) A shape measuring apparatus according to a first invention is a shape measuring apparatus for measuring the shape of the surface of a measurement object, and irradiates a plurality of portions on the surface of the measurement object with a plurality of portions. By receiving the reflected light, the received light intensity for obtaining a superimposed received light intensity distribution having a superimposed waveform of the interference received light intensity distribution component and the confocal received light intensity distribution component in the light irradiation direction for a plurality of portions Interference-type received light intensity distribution component and confocal-type received light intensity distribution component are extracted from the distribution acquisition unit and the superimposed received light intensity distribution acquired by the received light intensity distribution acquisition unit, respectively, and the extracted interference-type received light intensity distribution component The first data indicating the positions in the light irradiation direction for the plurality of portions can be calculated based on each of the plurality of portions, and the plurality of portions are connected based on the extracted confocal received light intensity distribution components. And a calculation unit configured to be able to calculate second data indicating the position in the light irradiation direction, and shape data indicating the shape of the surface of the measurement object using the first and second data for a plurality of portions. And a processing unit for generating.

  In this shape measuring apparatus, the superimposed received light intensity distribution in the light irradiation direction is acquired for a plurality of portions. The interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are respectively extracted from the acquired superimposed received light intensity distribution. Based on the extracted interference-type received light intensity distribution component, first data indicating positions in the light irradiation direction is calculated for each of the plurality of portions. Further, second data indicating positions in the light irradiation direction is calculated for a plurality of portions based on the extracted confocal light intensity distribution components. Shape data indicating the shape of the surface of the measurement object is generated using the first and second data for a plurality of portions.

  According to the above configuration, the interference received light intensity distribution component and the confocal received light intensity distribution component are respectively extracted from the superimposed received light intensity distribution. According to the second data calculated based on the confocal received light intensity distribution component, there is no inconvenience that a plurality of positions having a specific distance difference cannot be identified. Further, according to the first data calculated based on the received light intensity distribution component of the interference method, higher resolution than the second data can be obtained within a specific distance difference range.

  Therefore, by generating shape data using the first and second data for a plurality of portions, it is possible to detect a position with higher resolution while identifying a plurality of positions having a specific distance difference. In this case, since the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are separated from the superimposed received light intensity distribution, the first and second data can be accurately calculated. As a result, the height shape of the surface of the measurement object can be accurately measured.

  (2) The calculation unit may calculate the first data by the phase shift interference method from the extracted received light intensity distribution component of the interference method.

  In this case, the position can be detected with higher resolution than the second data within the range of (1/2 × wavelength of light) by the first data.

  (3) The calculation unit may calculate a position corresponding to the peak of the extracted confocal received light intensity distribution component as the second data. In this case, a difference in position that is an integral multiple of (1/2 × wavelength of light) can be identified by the second data.

  (4) The calculation unit may extract a confocal received light intensity distribution component from the superimposed received light intensity distribution by applying a frequency filter to the superimposed received light intensity distribution acquired by the received light intensity distribution acquiring unit. In this case, a confocal light intensity distribution component can be reliably extracted from the superimposed light intensity distribution.

  (5) The frequency filter may include a low-pass filter. In this case, it is possible to reliably and easily extract the confocal light intensity distribution component from the superimposed light intensity distribution.

  (6) The calculation unit may extract a confocal received light intensity distribution component from the superimposed received light intensity distribution by applying a morphological filter to the superimposed received light intensity distribution acquired by the received light intensity distribution acquiring unit. In this case, it is possible to reliably and easily extract the confocal light intensity distribution component from the superimposed light intensity distribution.

  (7) The calculation unit may extract the interference-type received light intensity distribution component from the superimposed received light intensity distribution by making the amplitude of the extracted received light intensity distribution component uniform. In this case, in this case, the interference-type received light intensity distribution component can be reliably extracted from the superimposed received light intensity distribution.

  (8) The processing unit may generate shape data by adding the first data to the second data for a plurality of portions. In this case, shape data can be easily generated.

  (9) The processing unit may perform the unwrapping process on the first data so that each of the plurality of parts is continuously connected to the adjacent part.

  Since the first data is calculated based on the received light intensity distribution component of the interference method, the first data may have an arbitrary multiple of (½ × wavelength of light). Even in such a case, by performing the unwrapping process on the first data, it is possible to prevent the shapes of the plurality of portions from being connected discontinuously.

  (10) The received light intensity distribution acquisition unit includes a light source that generates light, a light receiving element, and an optical path through which light irradiated to the measurement target and reflected light from the measurement target pass, and is disposed in the optical path. Including a possible interference type objective lens, the light generated by the light source is irradiated to the measurement object through the interference type objective lens, and the reflected light from the measurement object is guided to the light receiving element, and the received light intensity overlapped by the light receiving element May be obtained.

  In this case, the superimposed received light intensity distribution can be obtained with a simple configuration. Thereby, a shape measuring apparatus can be reduced in size. Moreover, the manufacturing cost of the shape measuring apparatus can be reduced.

  (11) The shape measuring method according to the second invention is a shape measuring method for measuring the shape of the surface of the measuring object, and irradiates a plurality of parts of the surface of the measuring object with a plurality of parts. Obtaining a superimposed received light intensity distribution having a superimposed waveform of an interference received light intensity distribution component and a confocal received light intensity distribution component in a light irradiation direction by receiving reflected light; and Extracting the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component from the acquired superimposed received light intensity distribution, and light for a plurality of portions based on the extracted interference-type received light intensity distribution component Calculating each of the first data indicating the position in the irradiation direction of light, and how to irradiate a plurality of portions based on the extracted confocal received light intensity distribution component Respectively, calculating the second data indicating the position of the measurement object, and generating shape data indicating the shape of the surface of the measurement object using the first and second data for a plurality of portions. .

  In this shape measuring method, the superimposed received light intensity distribution in the light irradiation direction is acquired for a plurality of portions. The interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are respectively extracted from the acquired superimposed received light intensity distribution. Based on the extracted interference-type received light intensity distribution component, first data indicating positions in the light irradiation direction is calculated for each of the plurality of portions. Further, second data indicating positions in the light irradiation direction is calculated for a plurality of portions based on the extracted confocal light intensity distribution components. Shape data indicating the shape of the surface of the measurement object is generated using the first and second data for a plurality of portions.

  According to the above method, the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are respectively extracted from the superimposed received light intensity distribution. According to the second data calculated based on the confocal received light intensity distribution component, there is no inconvenience that a plurality of positions having a specific distance difference cannot be identified. Further, according to the first data calculated based on the received light intensity distribution component of the interference method, higher resolution than the second data can be obtained within a specific distance difference range.

  Therefore, by generating shape data using the first and second data for a plurality of portions, it is possible to detect a position with higher resolution while identifying a plurality of positions having a specific distance difference. In this case, since the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are separated from the superimposed received light intensity distribution, the first and second data can be accurately calculated. As a result, the height shape of the surface of the measurement object can be accurately measured.

  According to the present invention, it is possible to accurately measure the height shape of the surface of the measurement object.

It is a block diagram which shows the structure of the shape measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the definition of X direction, Y direction, and Z direction. It is a figure which shows the structure of an objective lens. It is a figure which shows the other structure of an objective lens. It is a figure which shows an example of the light reception intensity distribution about one pixel. It is a figure which shows the light reception intensity distribution component of the confocal system extracted from the superimposition light reception intensity distribution. It is a figure which shows the light reception intensity distribution component of the interference system extracted from the superimposition light reception intensity distribution. It is a flowchart which shows a height shape measurement process.

  Hereinafter, a shape measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(1) Basic Configuration of Shape Measuring Device FIG. 1 is a block diagram showing the configuration of the shape measuring device according to the embodiment of the present invention. As shown in FIG. 1, the shape measuring apparatus 500 includes a measuring unit 100, a PC (personal computer) 200, a control unit 300, and a display unit 400. The measurement unit 100 includes a laser light source 10, an XY scan optical system 20, a light receiving element 30, and a stage 60. On the stage 60, the measuring object S is placed.

  The laser light source 10 is a semiconductor laser, for example. The laser light emitted from the laser light source 10 is converted into parallel light by the lens 1, passes through the half mirror 4, and enters the XY scan optical system 20. Instead of the laser light source 10, another light source such as a mercury lamp and a band pass filter may be used. In this case, a band pass filter is disposed between the light source such as a mercury lamp and the XY scan optical system 20. Light emitted from a light source such as a mercury lamp passes through a band-pass filter, becomes monochromatic light, and enters the XY scan optical system 20.

  The XY scan optical system 20 is, for example, a galvanometer mirror. The XY scan optical system 20 has a function of scanning the laser light in the X direction and the Y direction on the surface of the measurement object S on the stage 60. The definitions of the X direction, the Y direction, and the Z direction will be described later. The laser beam scanned by the XY scan optical system 20 is reflected by the mirror 5 and then focused on the measurement object S on the stage 60 by the objective lens 3. The objective lens 3 is disposed in an optical path through which light irradiated on the measurement object S and reflected light from the measurement object S pass.

  In this example, the objective lens 3 is an interference type objective lens of, for example, a Michelson interference method, a Mirau interference method, or a linic interference method. Instead of the interference type objective lens, a non-interference type objective lens combined so as to realize the interference type objective lens and an optical system of, for example, a Michelson interference type, a Mirau interference type, or a linic interference type may be used. . Further, a polarization beam splitter may be used instead of the half mirror 4.

  The laser light reflected by the measuring object S passes through the objective lens 3, is reflected by the mirror 5, and passes through the XY scan optical system 20. The laser beam that has passed through the XY scan optical system 20 is reflected by the half mirror 4, collected by the lens 2, passes through the pinhole of the pinhole member 7, and enters the light receiving element 30. The pinhole of the pinhole member 7 is disposed at the focal position of the lens 2. As described above, in the present embodiment, the reflection type shape measuring apparatus 500 is used. However, when the measuring object S is a transparent body such as a cell, a transmission type shape measuring apparatus may be used. .

  In the present embodiment, the light receiving element 30 is a photomultiplier tube. A photodiode and an amplifier may be used as the light receiving element 30. The light receiving element 30 outputs an analog electric signal (hereinafter referred to as a light receiving signal) corresponding to the amount of received light. The controller 300 includes an A / D converter (analog / digital converter), a FIFO (First In First Out) memory, and a CPU (Central Processing Unit). The received light signal output from the light receiving element 30 is sampled at a constant sampling period by the A / D converter of the control unit 300 and converted into a digital signal. Digital signals output from the A / D converter are sequentially stored in the FIFO memory. The digital signals stored in the FIFO memory are sequentially transferred to the PC 200 as pixel data.

  The control unit 300 gives pixel data to the PC 200 and controls the light receiving sensitivity (gain) of the light receiving element 30 based on a command from the PC 200. Further, the control unit 300 controls the XY scan optical system 20 based on a command from the PC 200 to scan the laser beam on the measurement object S in the X direction and the Y direction.

  The objective lens 3 is provided so as to be movable in the Z direction by the lens driving unit 63. The control unit 300 can move the objective lens 3 in the Z direction by controlling the lens driving unit 63 based on a command from the PC 200. Thereby, the position of the measurement object S relative to the objective lens 3 in the Z direction can be changed.

  The PC 200 includes a CPU 210, a ROM (read only memory) 220, a work memory 230, and a storage device 240. The ROM 220 stores a system program. The working memory 230 includes a RAM (Random Access Memory), and is used for processing various data. The storage device 240 is composed of a hard disk or the like. The storage device 240 stores an image processing program. The storage device 240 is used for storing various data such as pixel data given from the control unit 300.

  The CPU 210 generates image data based on the pixel data given from the control unit 300. The CPU 210 performs various processes on the generated image data using the work memory 230 and causes the display unit 400 to display an image based on the image data. Further, the CPU 210 gives a driving pulse to the stage driving unit 62 described later. The display unit 400 is configured by, for example, a liquid crystal display panel or an organic EL (electroluminescence) panel.

  The stage 60 has an X direction moving mechanism, a Y direction moving mechanism, and a Z direction moving mechanism. Stepping motors are used for the X direction moving mechanism, the Y direction moving mechanism, and the Z direction moving mechanism. The X direction moving mechanism, the Y direction moving mechanism, and the Z direction moving mechanism of the stage 60 are driven by a stage operation unit 61 and a stage driving unit 62.

  The user can move the stage 60 in the X direction, the Y direction, and the Z direction relative to the objective lens 3 by manually operating the stage operation unit 61. The stage drive unit 62 moves the stage 60 relative to the objective lens 3 in the X direction, the Y direction, or the Z direction by supplying a current to the stepping motor of the stage 60 based on the drive pulse given from the PC 200. be able to.

  According to the shape measuring apparatus 500 described above, a superimposed received light intensity distribution described later can be obtained with a simple configuration. Thereby, the shape measuring apparatus 500 can be reduced in size. Moreover, the manufacturing cost of the shape measuring apparatus 500 can be reduced.

(2) Definition of X direction, Y direction, and Z direction FIG. 2 is a diagram illustrating the definition of the X direction, the Y direction, and the Z direction. As shown in FIG. 2, the measuring object S is irradiated with the laser light condensed by the objective lens 3. In the present embodiment, the direction of the optical axis of the objective lens 3 is defined as the Z direction. Further, two directions orthogonal to each other in a plane orthogonal to the Z direction are defined as an X direction and a Y direction, respectively. The X, Y, and Z directions are indicated by arrows X, Y, and Z, respectively.

  The relative position of the surface of the measuring object S with respect to the objective lens 3 in the Z direction is referred to as the position of the measuring object S in the Z direction. Image data is generated for each unit area. The unit area is determined by the magnification of the objective lens 3.

  While the position of the measuring object S in the Z direction is constant, the XY scanning optical system 20 scans the laser light in the X direction at the end in the Y direction in the unit region. When scanning in the X direction is completed, the laser light is shifted by the XY scanning optical system 20 in the Y direction by a constant interval. In this state, the laser beam is scanned in the X direction. By repeating the scanning of the laser beam in the X direction and the shifting in the Y direction within the unit region, the scanning of the unit region in the X direction and the Y direction is completed. Next, the objective lens 3 is moved in the Z direction. Thereby, the scanning in the X direction and the Y direction of the unit area is performed in a constant state where the position of the objective lens 3 in the Z direction is different from the previous time. The unit region is scanned in the X and Y directions at a plurality of positions in the Z direction of the measurement object S.

  Image data is generated by scanning in the X direction and the Y direction for each position of the measuring object S in the Z direction. Thereby, a plurality of pieces of image data having different positions in the Z direction within the unit area are generated.

  Here, the number of pixels in the X direction of the image data is determined by the scanning speed of the laser beam in the X direction by the XY scanning optical system 20 and the sampling period of the control unit 300. The number of samples in one X-direction scan (one scan line) is the number of pixels in the X direction. Further, the number of pixels in the Y direction of the image data of the unit area is determined by the amount of shift in the Y direction of the laser light by the XY scan optical system 20 at the end of scanning in the X direction. The number of scanning lines in the Y direction is the number of pixels in the Y direction. Further, the number of image data in the unit area is determined by the number of movements of the measuring object S in the Z direction.

  In the example of FIG. 2, first, a plurality of pieces of image data of the measuring object S in one unit region are generated at the initial position of the stage 60. Subsequently, a plurality of pieces of image data of the measuring object S in other unit regions are generated by the stage 60 moving sequentially. In this case, the unit areas may be set so that some of the adjacent unit areas overlap each other.

(3) Light Received Intensity Distribution FIG. 3 is a diagram showing the configuration of the objective lens 3. In the example of FIG. 3, the objective lens 3 is a Mirau interference type interference objective lens. As shown in FIG. 3, the objective lens 3 includes a lens 31, a beam splitter 32, and a reference mirror 33.

  The laser light emitted from the laser light source 10 in FIG. 1 passes through the lens 31 in FIG. 3 and is then separated into two laser lights by the beam splitter 32. A reference mirror 33 is disposed at the focal position of the lens 31 for one laser beam. The measuring object S is arranged near the focal position of the lens 31 for the other laser beam.

  One laser beam is reflected by the reference mirror 33, reflected by the beam splitter 32, passes through the lens 31, is reflected by the mirror 5 and the half mirror 4 in FIG. 1, and enters the light receiving element 30. The other laser beam is reflected by the measuring object S, passes through the beam splitter 32 and the lens 31, is reflected by the mirror 5 and the half mirror 4 in FIG. 1, and enters the light receiving element 30.

  In this way, the lens 31, the beam splitter 32, and the reference mirror 33 of the objective lens 3 constitute an interference optical system. In this example, the objective lens 3 is a Mirau interference type interference objective lens, but is not limited thereto. FIG. 4 is a diagram showing another configuration of the objective lens 3. In the example of FIG. 4A, the objective lens 3 is a Michelson interference type interference objective lens. In the example of FIG. 4B, the objective lens 3 is a linic interference type interference objective lens.

  As shown in FIG. 4A, the Michelson interference type objective lens 3 includes a lens 31, a beam splitter 32, and a reference mirror 33 in the same manner as the Mirau interference type objective lens 3 shown in FIG. On the other hand, as shown in FIG. 4B, the objective lens 3 of the linic interference system is configured by a lens 31, a beam splitter 32, a reference mirror 33, and a lens 34. In the objective lens 3 of the linic interference method, the laser light emitted from the laser light source 10 in FIG. 1 is separated into two laser lights by the beam splitter 32 before passing through the lens 31. Therefore, the lens 31 is disposed between the beam splitter 32 and the measuring object S, and the lens 34 is disposed between the beam splitter 32 and the reference mirror 33.

  FIG. 5 is a diagram showing an example of the received light intensity distribution for one pixel. 5A to 5C, the horizontal axis represents the position of the measuring object S in the Z direction, and the vertical axis represents the received light intensity of the light receiving element 30. Hereinafter, the difference between the optical path length until one laser beam enters the light receiving element 30 and the optical path length until the optical path length of the other laser beam enters the light receiving element 30 is referred to as an optical path difference. In this example, the reference mirror 33 is disposed at the focal position of the lens 31. In this case, the optical path difference is equal to twice the deviation between the measuring object S and the focal position of the lens 31.

  First, consider the laser beam reflected by the measuring object S. As shown in FIG. 1, the pinhole of the pinhole member 7 is disposed at the focal position of the lens 2. When the surface of the measuring object S is at the focal position of the objective lens 3, the laser light reflected by the measuring object S is condensed at the pinhole position of the pinhole member 7. Thereby, most of the laser light reflected by the measuring object S passes through the pinhole of the pinhole member 7 and enters the light receiving element 30. In this case, as shown in FIG. 5A, the received light intensity of the laser light incident on the light receiving element 30 is maximized.

  On the other hand, when the measuring object S is at a position deviating from the focal position of the objective lens 3, the laser light reflected by the measuring object S is condensed at a position before or after the pinhole of the pinhole member 7. . In this case, as shown in FIG. 5A, the light receiving intensity of the laser light incident on the light receiving element 30 decreases. Thus, a peak appears in the light reception intensity distribution of the light receiving element 30 in a state where the surface of the measuring object S is at the focal position of the objective lens 3. Hereinafter, the received light intensity distribution of FIG. 5A based on the confocal optical system is referred to as a confocal received light intensity distribution.

  Next, consider the laser beam obtained by the interference between the laser beam reflected by the reference mirror 33 and the laser beam reflected by the measuring object S. Here, it is assumed that the pinhole member 7 does not exist. When the optical path difference is 1/2 × (2n) × λ (n: integer, λ: wavelength), that is, the measurement object S is 1/4 × (2n) × λ from the focal position of the lens 31 of the objective lens 3. When in the shifted position, the two laser beams incident on the light receiving element 30 strengthen each other.

  On the other hand, when the optical path difference is ½ × (2n + 1) × λ, that is, when the measurement object S is at a position shifted by ¼ × (2n + 1) × λ from the focal position of the lens 31, the light receiving element 30 The two incident laser beams are weakened. In this case, as shown in FIG. 5B, the intensities of the two laser beams incident on the light receiving element 30 with respect to the position of the measuring object S in the Z direction change in a sine wave shape. Hereinafter, the received light intensity distribution in FIG. 5B based on the interference optical system is referred to as an interference received light intensity distribution.

  FIG. 5C shows the received light intensity distribution obtained by the light receiving element 30. The received light intensity obtained by the light receiving element 30 is a superposition of the confocal light reception intensity distribution of FIG. 5A and the interference light reception intensity distribution of FIG. 5B. Thereby, the light reception intensity obtained by the light receiving element 30 includes a plurality of peaks. When the surface of the measuring object S is at the focal position of the objective lens 3, the two laser beams strengthen each other because the optical path lengths of the two laser beams are equal. In this case, as shown in FIG. 5C, the received light intensity obtained by the light receiving element 30 is maximized.

  On the other hand, when the measurement object S is at a position deviating from the focal position of the interference objective lens 3 </ b> B, a part of the laser light toward the light receiving element 30 is blocked by the pinhole of the pinhole member 7. In this case, as shown in FIG. 5C, even when the two laser beams are intensified, the light reception intensity obtained by the light receiving element 30 is obtained when the measurement object S is at the focal position of the objective lens 3. Lower than the received light intensity. Hereinafter, the received light intensity distribution of FIG. 5C obtained by the light receiving element 30 is referred to as a superimposed received light intensity distribution.

(4) Confocal height data The superimposed received light intensity distribution in FIG. 5C in the Z direction is obtained for each pixel from a plurality of image data of each unit area. By performing arithmetic processing on the obtained superimposed light reception intensity distribution, the confocal light reception intensity distribution of FIG. 5A and the interference light reception intensity distribution of FIG. 5B are extracted. The confocal light intensity distribution extracted from the superimposed light intensity distribution is referred to as a confocal light intensity distribution component. The interference-type received light intensity distribution extracted from the superimposed received-light intensity distribution is referred to as an interference-type received light intensity distribution component.

  By fitting, for example, a Gaussian curve or spline curve to the extracted confocal light intensity distribution component, the peak position and peak intensity of the confocal light intensity distribution component in the Z direction for each pixel (peak light intensity) And are calculated. Based on the peak position in the Z direction, the height shape of the surface of the measuring object S can be measured.

  The resolution of the measurement of the height shape depends on the full width at half maximum Γ of the curve in FIG. The full width at half maximum Γ becomes smaller as the numerical aperture of the objective lens 3 is larger and the wavelength of the laser beam is shorter. For example, when the numerical aperture of the objective lens 3 is 0.95 and the wavelength of the laser light is 408 nm, the full width at half maximum Γ is 500 nm. In this case, the resolution is 0.5 to 1 nm.

  Data representing the peak position in the Z direction for each pixel in each unit area is referred to as confocal height data. The PC 200 generates a plurality of image data of the unit area based on the plurality of pixel data of the unit area given from the control unit 300, and generates confocal height data for each pixel of the unit area based on the plurality of image data. Generate. In this case, a difference in position that is an integral multiple of λ / 2 can be identified from the confocal height data.

(5) Interference Height Data In the present embodiment, the height shape of the surface of the measuring object S is measured by the following phase shift interference method. First, the optical path length is changed by λ / 4, that is, the position of the measuring object S in the Z direction is changed four times by λ / 8. Further, the four light receiving intensities corresponding to the positions in the Z direction of the measuring object S are measured by the light receiving element 30.

  Specifically, first, the light receiving element 30 measures the received light intensity when the measuring object S is at an arbitrary initial position in the Z direction. Next, the light receiving intensity when the measuring object S is at a position λ / 8 from the initial position is measured by the light receiving element 30. Thereafter, the light receiving element 30 measures the light receiving intensity when the measuring object S is at a position of λ / 4 from the initial position. Finally, the light receiving intensity when the measuring object S is at a position 3λ / 8 from the initial position is measured by the light receiving element 30. By performing a calculation process on the received light intensity distribution including the four received light intensity obtained by the measurement, the received light intensity distribution component of the interference method in FIG. 5B is extracted.

  The intensity of the received light intensity distribution component of the interference method corresponding to the received light intensity when the measurement object S is at the initial position in the Z direction is referred to as a first received light intensity I1. The intensity of the received light intensity distribution component of the interference method corresponding to the received light intensity when the measurement object S is at a position λ / 8 from the initial position is referred to as a second received light intensity I2. The intensity of the received light intensity distribution component of the interference method corresponding to the received light intensity when the measurement object S is at a position λ / 4 from the initial position is referred to as a third received light intensity I3. The intensity of the received light intensity distribution component of the interference method corresponding to the received light intensity when the measurement object S is at a position 3λ / 8 from the initial position is referred to as a fourth received light intensity I4.

At this time, the phase difference φ between the two lights is given by φ = tan ⁻¹ [(I1−I3) / (I2−I4)]. Further, the height h from the focal position of the objective lens 3, that is, the peak position of the light receiving intensity distribution component of the confocal type in FIG. 5A, is given by h = φλ / (4π). Since the phase difference φ has an arbitrary multiple of 2π, based on the assumption that the height h changes continuously, an operation such as the neighborhood phase connection method or the MST (Minimum Spanning Tree) method is performed. Processing is performed.

  By calculating the height h for the entire surface of the measuring object S, the height shape of the surface of the measuring object S can be measured. The resolution of height shape measurement by the phase shift interference method is 0.1 nm or less.

  Data representing the height h for each pixel in each unit area is referred to as interference height data. The PC 200 generates a plurality of image data of the unit area based on the plurality of pixel data of the unit area given from the control unit 300, and generates interference height data for each pixel of the unit area based on the plurality of image data. To do. In this case, the position can be detected with higher resolution than the confocal height data within the range of λ / 2 by the interference height data.

(6) Extraction of Confocal Light Receiving Intensity Distribution Component A procedure for extracting the confocal light receiving intensity distribution component from the light receiving intensity distribution obtained by the light receiving element 30 will be described. FIG. 6 is a diagram illustrating a confocal light intensity distribution component extracted from the superimposed light intensity distribution.

  In the example of FIG. 6A, the low-pass filter is applied to the superimposed received light intensity distribution indicated by the dotted line, so that a component having a wavelength longer than a predetermined cutoff wavelength (low frequency component) is superimposed received light intensity. Extracted from the distribution. A curve indicated by the extracted solid line is referred to as an average line La. The average line La extracted from the superimposed received light intensity distribution becomes a confocal received light intensity distribution component.

  The low-pass filter includes, for example, a linear filter such as a Gaussian filter according to ISO (International Organization for Standardization) standard number 16610-21 or a spline filter according to ISO standard number standard number 16610-22. The cutoff wavelength is set to a value sufficiently larger than the wavelength of the laser light. The cutoff wavelength is preferably set to 10 to 20 times the wavelength of the laser beam. In the example of FIG. 6A, the cutoff wavelength is 13 μm.

  In this way, by applying the low-pass filter to the superimposed received light intensity distribution, it is possible to easily and stably extract the confocal received light intensity distribution component from the superimposed received light intensity distribution. On the other hand, depending on the relationship between the intensity of the laser beam reflected by the reference mirror 33 in FIG. 3 and the intensity of the laser beam reflected by the measurement object S, the peak intensity of the average line La may not be sufficiently large. . In this case, the accuracy of calculation of the peak position and peak intensity of the confocal received light intensity distribution component is lowered.

  In such a case, the confocal received light intensity distribution component may be extracted from the superimposed received light intensity distribution using another filter instead of the low-pass filter. In the example of FIG. 6B, a circular Closing filter of a morphological filter according to ISO standard number standard number 16610-41 is applied to the superimposed received light intensity distribution indicated by a dotted line. Thereby, the envelope Le of the superimposed received light intensity distribution indicated by the solid line is extracted from the superimposed received light intensity distribution. The envelope Le extracted from the superimposed received light intensity distribution is a confocal received light intensity distribution component.

  The radius of the circle of the circle closing filter is set to a value sufficiently larger than the wavelength of the laser beam. The radius of the circle of the circle closing filter is preferably set to 5 to 10 times the wavelength of the laser beam. In the example of FIG. 6B, the radius of the circle of the circle Closing filter is 3.2 μm.

  A high frequency component may remain in the envelope Le. For this reason, the envelope Le is subjected to correction processing for removing high-frequency components. Specifically, the above low-pass filter is applied to the envelope Le. Thereby, the high frequency component is removed from the envelope Le.

  In order to extract the confocal light intensity distribution component from the superimposed light intensity distribution, both a low-pass filter and a morphological filter may be applied. In this case, the average value of the peak position based on the average line La and the peak position based on the envelope Le is the peak position of the confocal received light intensity distribution component.

(7) Extraction of Interference-Based Light Intensity Distribution Component A procedure for extracting the interference-type received light intensity distribution component from the superimposed received light intensity distribution obtained by the light receiving element 30 will be described. FIG. 7 is a diagram showing the received light intensity distribution component of the interference method extracted from the superimposed received light intensity distribution.

  In the example of FIG. 7A, a process of subtracting the average line La of FIG. 6A or the envelope Le of FIG. 6B subjected to correction processing from the superimposed received light intensity distribution indicated by the dotted line is performed. . As a result, the curve Lc of the high frequency component indicated by the solid line is extracted from the superimposed received light intensity distribution. The curve Lc includes a plurality of peaks. A curve Lc extracted from the superimposed received light intensity distribution is a light intensity distribution component of the interference method.

  In this state, the amplitudes of the plurality of peaks of the extracted curve Lc vary according to the position of the measuring object S in the Z direction due to the influence of the confocal received light intensity distribution component. Therefore, a correction process is performed to make the amplitudes of the plurality of peaks of the curve Lc substantially uniform. Specifically, the above morphological filter is applied to the curve Lc. In this case, as indicated by a one-dot chain line in FIG. 7A, an upper envelope Le1 in contact with the upper portion of the curve Lc and a lower envelope Le2 in contact with the lower portion of the curve Lc are extracted from the curve Lc. Based on the difference between the upper envelope Le1 and the lower envelope Le2, a calculation process is performed on the curve Lc so that the amplitude of each peak of the curve Lc is substantially uniform. Thereby, as shown in FIG.7 (b), the amplitude of each peak of the curve Lc is substantially equalized.

(8) Generation of Height Data In the present embodiment, the measurement object S is disposed sufficiently below the focal position of the objective lens 3, for example. In this state, the laser beam is scanned in the X direction and the Y direction within each unit region.

  After the scanning in each unit area is completed, the objective lens 3 is moved downward by λ / 8. Thereby, the measuring object S moves upward so as to approach the focal position of the objective lens 3. In this state, the laser beam is scanned in the X direction and the Y direction within each unit region. After the scanning in each unit area is completed, the objective lens 3 is moved further downward by λ / 8. Thereby, the measuring object S further moves upward so as to approach the focal position of the objective lens 3. In this state, the laser beam is scanned in the X direction and the Y direction within each unit region.

  The same operation is repeated until the measurement object S moves sufficiently above the focal position of the objective lens 3. Thereby, the position of the measuring object S in the Z direction and the received light intensity are obtained for each pixel on the entire surface of the measuring object S. The obtained position of the measuring object S in the Z direction and the received light intensity are stored in the work memory 230 of FIG.

  Based on the position in the Z direction of the measuring object S and the received light intensity stored in the work memory 230, a superimposed received light intensity distribution for each pixel is generated. Further, a confocal light reception intensity distribution component and an interference light reception intensity distribution component for each pixel are extracted from the superimposed light reception intensity distribution for each pixel.

  Confocal height data is generated based on the peak position in the extracted confocal received light intensity distribution component. Further, interference height data is generated based on the first to fourth intensities I1 to I4 in FIG. 5B in the extracted received light intensity distribution components of the interference method. The generated confocal height data and interference height data are stored in the work memory 230. In the above measurement, the objective lens 3 is moved at an interval of λ / 8 in the Z direction, but is not limited to this. The objective lens 3 may be moved in the Z direction at intervals smaller than λ / 8, for example.

  In addition to the objective lens 3 that is an interference type objective lens, a non-interference type objective lens can be attached to the measurement unit 100 in FIG. It is possible to selectively dispose the objective lens 3 and the non-interference objective lens in the optical path of the laser light irradiated on the surface of the measuring object S and the laser light reflected by the measuring object S.

  When the objective lens 3 is arranged in the optical path, as described above, the superimposed light reception intensity distribution of FIG. On the other hand, when the non-interfering objective lens is arranged in the optical path, the light receiving element 30 can obtain the confocal light receiving intensity distribution of FIG.

  The user can specify to the CPU 210 in FIG. 1 which of the objective lens 3 and the non-interference objective lens is arranged in the optical path. Alternatively, the CPU 210 may determine which of the objective lens 3 and the non-interfering objective lens is arranged in the optical path. For example, when the received light intensity distribution obtained by the light receiving element 30 has a superimposed component of a relatively high frequency component and a relatively low frequency component, the CPU 210 determines that the objective lens 3 is disposed in the optical path. On the other hand, if the received light intensity distribution obtained by the light receiving element 30 has a relatively low frequency component and does not have a relatively high frequency component, the CPU 210 determines that the non-interfering objective lens is disposed in the optical path. .

  When the objective lens 3 is arranged on the optical path, the CPU 210 receives the confocal light reception intensity distribution of FIG. 5A extracted from the superimposed light reception intensity distribution and the interference light reception of FIG. 5B. Based on the intensity distribution, processing for generating confocal height data and interference height data is performed. On the other hand, when the non-interfering objective lens is disposed in the optical path, the CPU 210 performs processing for generating confocal height data based on the confocal light reception intensity distribution of FIG. .

(9) Height shape measurement process FIG. 8 is a flowchart showing the height shape measurement process. The height shape measurement process by the CPU 210 will be described with reference to FIG. The CPU 210 obtains a superimposed received light intensity distribution in the Z direction for each pixel (step S1). Next, the CPU 210 extracts a confocal light intensity distribution component and an interference light intensity distribution component from the obtained superimposed light intensity distribution (step S2).

  Thereafter, the CPU 210 performs correction processing on the extracted confocal light reception intensity distribution component and interference light reception intensity distribution component (step S3). Here, when a confocal light intensity distribution component is extracted by applying a low-pass filter to the superimposed light intensity distribution, correction processing is not performed on the light intensity distribution component of the confocal system. . When a confocal light intensity distribution component is extracted by applying a morphological filter to the superimposed light intensity distribution, a correction process is performed to remove a high frequency component from the confocal light intensity distribution component. . The interference-type received light intensity distribution component is subjected to a correction process for making the amplitudes of a plurality of peaks substantially uniform.

  Next, the CPU 210 generates confocal height data based on the peak position in the confocal received light intensity distribution component (step S4). Further, the CPU 210 generates interference height data based on the first to fourth intensities I1 to I4 in FIG. 5B in the received light intensity distribution component of the interference method (step S5).

  Finally, the CPU 210 generates shape data indicating the height shape of the surface of the measuring object S by synthesizing the confocal height data and the interference height data (step S6). Thereby, the height shape of the measuring object S is measured. Here, the synthesis of the confocal height data and the interference height data is performed by adding the interference height data to the confocal height data.

  In addition, when the numerical aperture of the objective lens 3 is small or the aberration of the objective lens 3 is large, the accuracy of connection between the confocal height data and the interference height data is lowered. In this case, a known unwrapping process may be performed on the interference height data based on the assumption that the height of one pixel and a pixel adjacent to the pixel is continuously changing.

(10) Effect In the shape measuring apparatus 500 according to the present embodiment, the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are respectively extracted from the superimposed received light intensity distribution. According to the confocal height data calculated based on the light reception intensity distribution component of the confocal system, there is no inconvenience that a plurality of positions having a distance difference that is an integral multiple of λ / 2 cannot be identified. Moreover, according to the interference height data calculated based on the received light intensity distribution component of the interference method, a higher resolution than the confocal height data can be obtained within the range of λ / 2.

  Accordingly, by generating shape data using the interference height data and the confocal height data for a plurality of portions of the measuring object S, a plurality of positions having a distance difference that is an integral multiple of λ / 2 are identified. The position can be detected with higher resolution. In this case, since the interference-type received light intensity distribution component and the confocal-type received light intensity distribution component are separated from the superimposed received light intensity distribution, interference height data and confocal height data can be accurately calculated. . As a result, the height shape of the surface of the measuring object S can be accurately measured.

(11) Other Embodiments (11-1) In the above embodiment, the XY scanning optical system 20 is controlled to scan the laser light on the measuring object S in the X direction and the Y direction. However, it is not limited to this. The laser beam may be scanned on the measurement object S in the X direction and the Y direction by moving the stage 60.

  (11-2) In the above embodiment, the relative position of the measuring object S with respect to the objective lens 3 in the Z direction is changed by moving the objective lens 3 in the Z direction. However, the present invention is not limited to this. The relative position of the measuring object S with respect to the objective lens 3 in the Z direction may be changed by moving the stage 60 in the Z direction.

  (11-3) In the above embodiment, the CPU 210 of the PC 200 may have the function of the control unit 300. In this case, the control unit 300 may not be provided.

  (11-4) In the above embodiment, line light (for example, elongated light extending in the X direction) may be used as the laser light. In this case, instead of the XY scan optical system 20, a Y scan optical system that does not perform scanning in the X direction is used. Further, instead of the light receiving element 30, a line CCD camera or the like including a plurality of light receiving elements arranged in a direction corresponding to the X direction is used.

  The size of the light receiving surface in the direction corresponding to the Y direction of each light receiving element of the line CCD camera is generally several tens of μm. In this case, the light receiving surface of the line CCD camera is disposed at the focal position of the lens 2. When the surface of the observation object S is at the focal position of the objective lens 3, the line light reflected by the observation object S is collected on the light receiving surface of the line CCD camera. Thereby, most of the line light reflected by the observation object S enters the light receiving surface of the line CCD camera.

  On the other hand, when the observation object S is at a position out of the focal position of the objective lens 3, the line light reflected by the observation object S is condensed at a position before or after the light receiving surface of the line CCD camera. Thereby, only part of the line light reflected by the observation object S enters the light receiving surface of the line CCD camera. Therefore, it is not necessary to arrange the pinhole member 7 in front of the line CCD camera.

  Alternatively, instead of providing the laser light source 10 and the XY scan optical system 20, a point light source scanned in the X direction and the Y direction may be provided.

  Alternatively, a surface light source and a disk-shaped rotating member formed with a plurality of pinholes may be provided. In this case, the planar light output from the surface light source becomes linear light by passing through the pinhole of the rotating member. Here, the plurality of pinholes are formed in the rotating member such that all the pixels in the unit region of the measuring object S are irradiated while the rotating member makes one rotation.

(12) Correspondence between each component of claim and each part of embodiment The following describes an example of a correspondence between each component of the claim and each part of the embodiment. It is not limited.

  The measuring object S is an example of the measuring object, the shape measuring device 500 is an example of the shape measuring device, the measuring unit 100 is an example of the received light intensity distribution acquiring unit, and the interference height data is the first data. It is an example, and the confocal height data is an example of the second data. The CPU 210 is an example of a calculation unit and a processing unit, the laser light source 10 is an example of a light source, the light receiving element 30 is an example of a light receiving element, and the objective lens 3 is an example of an interference type objective lens.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

  The present invention can be effectively used in various shape measuring apparatuses and shape measuring methods.

1, 2, 31, 34 Lens 3 Objective lens 4 Half mirror 5 Mirror 7 Pinhole member 10 Laser light source 20 XY scan optical system 30 Light receiving element 32 Beam splitter 33 Reference mirror 60 Stage 61 Stage operation unit 62 Stage drive unit 63 Lens driving unit 100 Measuring unit 200 PC
210 CPU
220 ROM
230 Working Memory 240 Storage Device 300 Control Unit 400 Display Unit 500 Shape Measuring Device La Average Line Lc Curve Le Envelope Le1 Upper Envelope Le2 Lower Envelope S Measurement Object

Claims (11)

A shape measuring device for measuring the shape of the surface of a measurement object,
By irradiating a plurality of portions on the surface of the measurement object and receiving the light reflected by the plurality of portions, the plurality of portions are shared with the received intensity distribution component of the interference method in the light irradiation direction. A received light intensity distribution acquisition unit for acquiring a superimposed received light intensity distribution having a superimposed waveform with a received light intensity distribution component of a focus method;
Interference-type received light intensity distribution components and confocal-type received light intensity distribution components are respectively extracted from the superimposed received light intensity distribution acquired by the received light intensity distribution acquisition unit, and based on the extracted interference-type received light intensity distribution components The first data indicating the position in the light irradiation direction can be calculated for a plurality of portions, and the positions in the light irradiation direction can be determined for the plurality of portions based on the extracted confocal light intensity distribution components. A calculation unit configured to be able to calculate the second data to be shown
A shape measuring apparatus comprising: a processing unit that generates shape data indicating a shape of a surface of the measurement object using first and second data for the plurality of portions. The shape measuring apparatus according to claim 1, wherein the calculation unit calculates first data from the extracted light reception intensity distribution component of the interference method by a phase shift interference method. The shape measuring apparatus according to claim 1, wherein the calculation unit calculates, as second data, a position corresponding to the peak of the extracted confocal light intensity distribution component. The calculation unit extracts a confocal received light intensity distribution component from the superimposed received light intensity distribution by applying a frequency filter to the superimposed received light intensity distribution acquired by the received light intensity distribution acquiring unit. The shape measuring device according to any one of the above. The shape measuring apparatus according to claim 4, wherein the frequency filter includes a low-pass filter. The calculation unit extracts a confocal received light intensity distribution component from the superimposed received light intensity distribution by applying a morphological filter to the superimposed received light intensity distribution acquired by the received light intensity distribution acquiring unit. The shape measuring device according to claim 5. The shape according to any one of claims 1 to 6, wherein the calculation unit extracts an interference-type received light intensity distribution component from the superimposed received light intensity distribution by making the amplitude of the extracted received light intensity distribution component uniform. measuring device. The shape measurement apparatus according to claim 1, wherein the processing unit generates shape data by adding first data to second data for the plurality of portions. The shape measuring apparatus according to claim 1, wherein the processing unit performs unwrapping processing on the first data so that each of the plurality of portions is continuously connected to adjacent portions. . The received light intensity distribution acquisition unit includes a light source that generates light, a light receiving element, and an optical path through which light irradiated to the measurement target and reflected light from the measurement target pass, and can be disposed in the optical path Including an interference type objective lens,
Light generated by the light source is applied to the measurement object through the interference objective lens, and reflected light from the measurement object is guided to the light receiving element, and a superimposed light reception intensity distribution is obtained by the light receiving element. The shape measuring apparatus according to claim 1, configured as described above. A shape measuring method for measuring the shape of the surface of a measurement object,
By irradiating a plurality of portions on the surface of the measurement object and receiving the light reflected by the plurality of portions, the plurality of portions are shared with the received intensity distribution component of the interference method in the light irradiation direction. Obtaining a superimposed received light intensity distribution having a superimposed waveform with a focus type received light intensity distribution component;
Extracting an interference-type received light intensity distribution component and a confocal-type received light intensity distribution component from the acquired superimposed received light intensity distribution; and
Calculating first data indicating positions in the light irradiation direction for the plurality of portions based on the extracted light-receiving intensity distribution components of the interference method;
Calculating respective second data indicating positions in the light irradiation direction for the plurality of portions based on the extracted confocal received light intensity distribution components;
Generating shape data indicating the shape of the surface of the measurement object using the first and second data for the plurality of portions.

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