KR20240059563A - Phase difference measuring apparatus and phase difference measuring method - Google Patents

Abstract

[Task] Measure the phase shift amount of light passing through different refractive index regions with high precision.
[Solution] The phase difference measuring device 1 includes an irradiation unit 10, a slit mask 23, a sensor 25, and an arithmetic processing unit 50. The irradiation unit 10 irradiates light to the measurement object 8. The slit mask 23 includes a first slit 23a, a second slit 23b adjacent to the first slit 23a at a first interval, and a second slit 23b adjacent to the second slit 23b at a second interval. It has 3 slits 23c. The sensor 25 detects an interference pattern caused by interference of light that has passed through the slit mask 23. The arithmetic processing unit 50 provides a first phase of the first frequency component corresponding to the third interval or the first interval between the first slit 23a and the third slit 23c, and a second phase corresponding to the second interval. The second phase of the frequency component is determined based on the interference pattern, and the phase shift amount is determined based on the first phase and the second phase.

Description

Phase difference measurement device and phase difference measurement method {PHASE DIFFERENCE MEASURING APPARATUS AND PHASE DIFFERENCE MEASURING METHOD}

This disclosure relates to a phase difference measurement device and a phase difference measurement method.

In recent years, phase shift masks have been used to transfer patterns with high resolution to substrates such as semiconductor substrates or display substrates. A phase shift film that delays the phase of light by half a wavelength is formed on this phase shift mask.

Patent Document 1 and Patent Document 2 disclose a measuring device for measuring the phase delay caused by this phase shift film. The measuring device described in Patent Document 1 includes an irradiation unit that irradiates light to a phase shift mask (a phase difference mask in Patent Document 1), a slit mask having a pair of slits, and an interference pattern caused by light passing through the pair of slits. It is equipped with a detection unit that detects.

In this measuring device, the first light passing through the phase shift film passes through one slit, and the second light passing through the phase shift mask at a position adjacent to the phase shift film passes through the other slit. The first light and the second light that pass through a pair of slits diffract and interfere with each other, and an interference pattern generated by the interference is detected by the detection unit.

Since the position of this interference fringe depends on the amount of phase shift between the first light and the second light (that is, the phase delay caused by the phase shift film), the measuring device calculates the amount of phase shift based on the position of this interference fringe.

Japanese Patent Publication No. 2015-187573 Japanese Patent Publication No. 2019-56631

Consider the case of measuring the entire surface of a phase shift mask. For example, by moving the optical system (a set of irradiation section, slit mask, and detection section) relative to the phase shift mask, the optical system can scan the entire surface of the phase shift mask and perform measurements at each measurement position.

However, since the inertial force accompanying the movement of the optical system acts on the optical system, deviation from the optical axis of the optical system (inclination of the optical axis or positional deviation of the optical axis) may occur at each measurement position. Since the position of the interference fringe also depends on the amount of deviation of the optical axis, it is difficult to calculate the amount of phase shift with high precision based on the position of the interference fringe. In other words, the position of this interference fringe does not reflect the amount of phase shift with high precision.

Therefore, the present disclosure aims to provide a technique for measuring the phase shift amount of light passing through different refractive index regions with high precision.

The first aspect is a phase difference for measuring the amount of phase shift, which is the phase difference between light transmitted through the first refractive index region of a measurement object having a first refractive index region and a second refractive index region, and light transmitted through the second refractive index region. A measuring device, comprising: an irradiator that irradiates light to the object to be measured; a first slit; a second slit adjacent to the first slit at a first interval; and a third slit adjacent to the second slit at a second interval. A slit mask having a slit mask, wherein the first slit is located on a path of light passing through the first refractive index region, and the second slit and the third slit are located on a path of light passing through the second refractive index region, respectively. a sensor that detects an interference pattern caused by interference of light passing from the first slit to the third slit, respectively, in the interference pattern, and a third interval between the first slit and the third slit, or The first phase of the first frequency component corresponding to the first interval and the second phase of the second frequency component corresponding to the second interval are obtained based on the interference pattern, and the first phase and the second and an arithmetic processing unit that calculates the phase shift amount based on the phase.

A second aspect is the phase difference measuring device according to the first aspect, wherein the first gap between the first slit and the second slit is wider than the second gap between the second slit and the third slit.

A third aspect is the phase difference measuring device according to the first aspect or the second aspect, wherein the transmittance of the first refractive index region is lower than the transmittance of the second refractive index region, and the width of the first slit is that of the second slit. wider than the width, and the width of the second slit is wider than the width of the third slit.

A fourth aspect is the phase difference measuring device according to the third aspect, wherein the calculation processing unit determines the first phase of the first frequency component corresponding to the first interval.

A fifth aspect is a phase difference measurement device according to any one of the first to fourth aspects, wherein the irradiation unit irradiates light having a plurality of peak wavelengths, and the calculation processing unit radiates light having a plurality of peak wavelengths, and the calculation processing unit determines the phase difference based on the interference pattern. The first phase and the second phase are determined for each peak wavelength, and the phase shift amount is determined for each peak wavelength based on the first phase and the second phase.

A sixth aspect is a phase difference measuring device according to any one of the first to fifth aspects, further comprising a moving mechanism that moves the irradiation unit, the slit mask, and the sensor, and the moving mechanism includes the irradiation unit. , moving a set of the slit mask and the sensor to each of a reference position and a measurement position, wherein the measurement position is such that light passing through the first refractive index region passes through the first slit, and the second refractive index region is a position where light passing through passes through the second slit and the third slit, respectively, and the reference position is a position where light passing through the second refractive index region passes from the first slit to the third slit, respectively. The sensor detects a reference interference pattern that is an interference pattern caused by interference of light passing through the third slit from the first slit at the reference position, and the calculation processing unit detects the first of the reference interference patterns. The first reference phase of the frequency component and the second reference phase of the second frequency component in the reference interference pattern are obtained based on the reference interference pattern, and the first phase, the first reference phase, and the second reference phase are determined based on the reference interference pattern. Based on the phase and the second reference phase, the phase shift amount is obtained.

A seventh aspect is the phase difference measuring device according to the sixth aspect, wherein the transmittance of the first refractive index region is lower than the transmittance of the second refractive index region, and the calculation processing unit performs Fourier transform on the reference interference pattern to obtain a reference amplitude. Obtain a spectrum and a reference phase spectrum, obtain a first frequency of the first frequency component and a second frequency of the second frequency component based on the reference amplitude spectrum, and obtain the first frequency obtained based on the reference amplitude spectrum. And based on the second frequency and the reference phase spectrum, the first reference phase and the second reference phase are obtained, Fourier transform is performed on the interference pattern to obtain a phase spectrum, and based on the reference amplitude spectrum, Based on the obtained first and second frequencies and the phase spectrum, the first phase and the second phase are determined.

An eighth aspect is a phase difference measurement device according to any one of the first to sixth aspects, wherein the calculation processing unit performs Fourier transform on the interference pattern to determine the first phase of the first frequency component and the The second phase of the second frequency component is obtained.

A ninth aspect is a phase difference measurement device according to any one of the first to sixth aspects, wherein the calculation processing unit includes a phase variable of the frequency component corresponding to the first interval, and a phase variable of the second frequency component. and calculating a calculated interference pattern by substituting the phase variable of the frequency component corresponding to the third interval into a predetermined function, and calculating a degree of similarity between the interference pattern and the calculated interference pattern, while changing the phase variable. , the first phase and the second phase are obtained based on the phase variable used to calculate the calculated interference pattern similar to the interference pattern.

The tenth aspect is a phase difference for measuring a phase shift amount, which is the phase difference between light passing through the first refractive index region of a measurement object having a first refractive index region and a second refractive index region, and light passing through the second refractive index region. A measuring method comprising: a step of irradiating light to the measurement object, light passing through the first refractive index area and a first slit, the second refractive index area, and a second refractive index area adjacent to the first slit at a first interval. 2. A process of detecting an interference pattern caused by interference between light passing through a slit, the second refractive index region, and a third slit adjacent to the second slit at a second interval, among the interference patterns, A third interval between the third slit and the first slit or a first phase of a first frequency component corresponding to the first interval, and a second phase of a second frequency component corresponding to the second interval, It includes a step of determining the phase shift amount based on the interference pattern, and a step of determining the phase shift amount based on the first phase and the second phase.

According to the first and tenth aspects, the first phase depends on the amount of phase shift and the misalignment of the optical axis, and the second phase has little dependence on the amount of phase shift and depends on the misalignment of the optical axis. Since the calculation processing unit determines the phase shift amount based on the first phase and the second phase, the influence of optical axis deviation can be suppressed and the phase shift amount can be obtained with higher precision.

According to the second aspect, the first gap between the first slit and the second slit is wide, so it is easy to position the first slit within the first refractive index region. Additionally, because the second gap between the second slit and the third slit is narrow, it is easy to position the second slit and the third slit within the second refractive index region.

According to the third aspect, since the transmittance of the first refractive index region is lower than the transmittance of the second refractive index region, the amount of light transmitted through the first refractive index region is lower than the amount of light transmitted through the second refractive index region. On the other hand, since the width of the first slit is wider than the width of the second slit, the amount of light passing through the first slit (hereinafter referred to as first light) and the light passing through the second slit (hereinafter referred to as second light) It is possible to reduce the difference in light intensity. For this reason, the amplitude of the first frequency component resulting from interference between the first light and the second light can be increased. Therefore, it is easy for the calculation processing unit to specify the first frequency component from the interference pattern.

Additionally, since the width of the third slit is narrower than that of the second slit, the shape of the envelope of the interference pattern can be made flatter. As a result, the number of intensity peaks (i.e., the number of fringes) in the interference pattern can be increased. Therefore, the calculation processing unit is easy to specify the first frequency component and the second frequency component from the interference pattern.

According to the fourth aspect, since the first frequency component is generated by interference of the first light and the second light that passed through the first slit and the second slit, respectively, which are wider than the third slit, the arithmetic processing unit generates the first frequency component from the interference pattern. 1 It is easy to specify frequency components.

According to the fifth aspect, the phase shift amount of each peak wavelength can be obtained by detecting the interference pattern once.

According to the sixth aspect, the influence of misalignment of the optical axis and differences between paths in optical characteristics can be suppressed, and the phase shift amount can be obtained with higher precision.

According to the seventh aspect, at the measurement position, the first light transmits through the first refractive index region with low transmittance, so the peak value of the intensity in the interference pattern is relatively low. Meanwhile, at the reference position, the first light transmits through the second refractive index region with high transmittance, so the peak value of the intensity in the reference interference pattern is relatively high. For this reason, the influence of noise on the reference interference pattern is relatively small. Since the calculation processing unit determines the first frequency and the second frequency using a reference phase spectrum obtained based on a reference interference pattern with a small effect of noise, the first frequency and the second frequency can be obtained with higher precision.

According to the eighth aspect, the first phase and the second phase can be obtained with high precision.

According to the ninth aspect, the first phase and the second phase can be obtained from the interference pattern.

1 is a diagram schematically showing an example of the configuration of a phase difference measurement device.
Figure 2 is a plan view showing an example of the configuration of a slit mask.
Fig. 3 is a flow chart showing a first example of the operation of the phase difference measurement device.
Figure 4 is a diagram schematically showing an example of an interference pattern detected by a sensor.
Figure 5 is a diagram schematically showing an example of the amplitude spectrum of an interference pattern.
FIG. 6 is a flow chart showing an example of a method for calculating the first phase and the second phase according to the first embodiment.
Figure 7 is a graph schematically showing an example of a phase spectrum.
Fig. 8 is a flow chart showing another example of the method for calculating the first phase and the second phase according to the first embodiment.
Figure 9 is a graph schematically showing an example of an amplitude spectrum.
Fig. 10 is a flow chart showing a second example of the operation of the phase difference measuring device.
FIG. 11 is a diagram schematically showing an example of the configuration of a phase difference measuring device when the optical system is located at the reference position.
Fig. 12 is a flow chart showing an example of a method for calculating the reference phase.
Figure 13 is a graph schematically showing an example of a reference phase spectrum.
Fig. 14 is a flow chart showing an example of a method for calculating the first phase and the second phase according to the second embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings. Additionally, in the drawings, for ease of understanding, the dimensions and numbers of each part are exaggerated or simplified as necessary. In addition, parts having the same structure and function are given the same symbols, and duplicate descriptions are omitted in the following description. Additionally, in the drawings, XYZ orthogonal coordinates are appropriately indicated to indicate the positional relationship of each component. For example, the Z-axis is arranged along the vertical direction, and the X-axis and Y-axis are arranged along the horizontal direction.

In addition, in the description shown below, the same components are denoted by the same symbols, and their names and functions are also assumed to be the same. Therefore, detailed descriptions of them may be omitted to avoid duplication.

In addition, in the description described below, although ordinal numbers such as “first” or “second” may be used, these terms are used for convenience in order to facilitate understanding of the content of the embodiment, There is no limitation to the order that can occur by these ordinal numbers.

When expressions expressing relative or absolute positional relationships (e.g., “in one direction,” “along one direction,” “parallel,” “orthogonal,” “center,” “concentric,” “coaxial,” etc.) are used, the Unless otherwise specified, the expression not only strictly represents the positional relationship, but also represents a relatively displaced state in terms of angle or distance within a range that can achieve tolerance or the same level of function. When expressions that indicate the same state (e.g., “same,” “identical,” “homogeneous,” etc.) are used, the expression not only indicates the strictly identical state quantitatively, but also contains tolerances, unless otherwise specified. Alternatively, it may also indicate a state in which a car exists that can achieve the same level of functionality. When an expression representing a shape (for example, “square shape” or “cylindrical shape”) is used, the expression not only strictly represents the shape geometrically, but also has the same degree of effect, unless otherwise specified. To the extent that can be obtained, shapes having, for example, irregularities or chamfers, etc. are also shown. When expressions such as “have,” “have,” “have,” “include,” or “have” are used to describe one component, the expression is not an exclusive expression that excludes the presence of other components. . When the expression “at least one of A, B, and C” is used, the expression means only A, only B, only C, any two of A, B, and C, and all of A, B, and C. Includes.

<First embodiment>

FIG. 1 is a diagram schematically showing an example of the configuration of the phase difference measurement device 1. This phase difference measuring device 1 is a device that measures the phase difference of light that has transmitted through the measurement object 8. This measurement object 8 has a first refractive index region 8A and a second refractive index region 8B with different refractive indices. The phase difference measuring device 1 measures the phase difference between the light that passed through the first refractive index region 8A and the light that passed through the second refractive index region 8B. Hereinafter, the first refractive index area 8A and the second refractive index area 8B are simply referred to as area 8A and area 8B, respectively.

＜Measurement object＞

First, an example of the measurement object 8 will be described in detail. The measurement object 8 is, for example, a phase shift mask 80. The phase shift mask 80 is a type of photomask and is used in an exposure device (not shown). The exposure apparatus can transfer a pattern to a given substrate (not shown) by performing exposure processing on the given substrate (not shown) using the phase shift mask 80. The predetermined substrate is, for example, various substrates such as a semiconductor substrate or a substrate for a flat panel display.

The phase shift mask 80 has a plate-like shape, and has regions 8A and 8B with different refractive indices when viewed in a plan view (that is, when viewed along the thickness direction). For example, the phase shift mask 80 includes a substrate 81, a phase shift film 82, and a shielding film 83. The substrate 81 has transparency to exposure light (for example, ultraviolet rays such as i-rays) and is made of, for example, quartz glass. The base material 81 has a plate-shaped shape, for example, a rectangular shape in plan view. The length of one side of the phase shift mask 80 is set to several meters, for example. As a more specific example, the lengths of the vertical and horizontal sides of the phase shift mask 80 are approximately 1.8 m and approximately 2.0 m, respectively, and the thickness of the phase shift mask 80 is approximately 21 mm.

The phase shift film 82 is formed in a predetermined pattern on one main surface of the substrate 81. The phase shift film 82 has translucency for exposure light, but its transmittance is lower than that of the substrate 81. The transmittance of the phase shift film 82 is, for example, several percent (more specifically, 5% to 10%). The phase shift film 82 is formed of, for example, tantalum oxide.

The shielding film 83 is formed in a predetermined pattern on the phase shift film 82, for example. This shielding film 83 is formed in an area inside the outline of the phase shift film 82 in plan view. The shielding film 83 has light-shielding properties against exposure light and is formed of, for example, chromium or chromium oxide.

In this phase shift mask 80, the area of the substrate 81 that is not covered by the phase shift film 82 corresponds to the area 8B and is covered by the shielding film 83 in the phase shift film 82. The area that does not correspond to area 8A. Since the transmittance of the phase shift film 82 is lower than that of the substrate 81, the transmittance of the region 8A is lower than that of the region 8B. Additionally, the phase shift film 82 shifts the phase of the light that passed through the region 8A by about 180 degrees with respect to the phase of the light that passed through the region 8B. That is, ideally, the phase difference between the light passing through the area 8A and the light passing through the area 8B is 180 degrees. Hereinafter, the phase difference is also called the phase shift amount θ by the area 8A.

When this phase shift mask 80 is mounted on an exposure apparatus and exposure is performed with the exposure apparatus, on a predetermined substrate to be exposed, the light transmitted through the region 8A and the light transmitted through the region 8B are the same. There is interference at the boundary, and as a result, the contrast of the projection image of the area 8B can be increased. Therefore, by using the phase shift mask 80, the exposure apparatus can transfer a pattern to a predetermined substrate with higher resolution compared to the case where the phase shift mask 80 is not used.

In this phase shift mask 80, the thickness of the phase shift film 82 in the region 8A is directly related to the transfer ability. For example, when the thickness of the phase shift film 82 in the region 8A deviates from the designed value, the phase shift amount θ by the region 8A deviates by 180 degrees. As a result, the effect of interference is reduced, the resolution is lowered, and the resolution of the pattern on the transferred substrate becomes unstable, ultimately causing many problems, such as lowering the manufacturing yield and damaging the quality of the product. raise it up Therefore, in order to determine whether the phase shift mask 80 is good or bad, it is desirable to measure the phase shift amount θ due to the region 8A formed in the phase shift mask 80 and properly manage the mask manufacturing process.

＜Phase difference measurement device＞

＜Overview＞

The phase difference measuring device 1 is a device that measures the above-described phase shift amount θ. In other words, the phase difference measuring device 1 is a device that measures the phase delay of light generated by passing through the area 8A. When the measurement target is a photomask (for example, the phase shift mask 80), the phase difference measurement device 1 may also be called a photomask inspection device.

The phase difference measuring device 1 includes a holding portion 90. The phase shift mask 80 that is the measurement target is held by this holding portion 90. In addition, in the example of FIG. 1, XYZ coordinates having X-axis, Y-axis, and Z-axis orthogonal to each other are added. The Z-axis direction is set to the vertical direction, for example. The holding portion 90 holds the phase shift mask 80 in an attitude in which the thickness direction of the phase shift mask 80 follows the Z-axis direction.

The phase difference measuring device 1 includes an irradiation unit 10, a detection unit 20, a moving mechanism 40, and a control unit 50. Below, an outline of these will first be described.

The irradiation unit 10 irradiates light along the Z-axis direction and makes it enter a part of the phase shift mask 80. This part of the phase shift mask 80 includes both a part of the area 8A and a part of the area 8B. This irradiation unit 10 is controlled by the control unit 50.

As will be described in detail later, the detection unit 20 generates an interference pattern by interfering with each other the light that has passed through this part of the phase shift mask 80. The detection unit 20 detects this interference pattern and outputs an electrical signal representing the detection result to the control unit 50.

As will be described in detail later, the control unit 50 calculates the phase shift amount θ by the area 8A based on the interference pattern detected by the detection unit 20. The control unit 50 determines whether the phase shift amount θ is within a predetermined range, and when a positive judgment is made, it may be determined that the part of the phase shift mask 80 is appropriately manufactured. On the other hand, when the control unit 50 determines that the phase shift amount θ is not within a predetermined range, it may determine that the phase shift mask 80 is a defective product.

The moving mechanism 40 moves the irradiation unit 10 and the detection unit 20 in the XY plane. The moving mechanism 40 may include, for example, a motor as a drive source, and has, for example, a ball screw mechanism for the X-axis direction and a ball screw mechanism for the Y-axis direction. This moving mechanism (40) is controlled by the control unit (50).

By the moving mechanism 40 moving the irradiation unit 10 and the detection unit 20, the entire surface of the phase shift mask 80 can be scanned. Specifically, the moving mechanism 40 is under the control of the control unit 50, and measures each of the irradiation unit 10 and the detection unit 20 while maintaining the alignment (relative position) of the irradiation unit 10 and the detection unit 20 in the Z-axis direction. stop in position. Thereby, the phase difference measuring device 1 can measure a plurality of locations within the phase shift mask 80.

According to this, even if the area of the phase shift mask 80 is large, measurement can be performed by scanning the entire phase shift mask 80.

Hereinafter, each configuration will be described in more detail.

＜Investigation Department＞

The irradiation unit 10 irradiates light to a portion of the phase shift mask 80. In the example of FIG. 1, the irradiation unit 10 faces the phase shift mask 80 at an interval in the Z-axis direction, and includes a light source 11, a condenser lens 12, a relay lens 14, and a pinhole plate ( 15) and a condenser lens (16).

The light source 11 irradiates light. The light source 11 is, for example, an ultraviolet irradiator. The light source 11 may radiate light having multiple peak wavelengths. As a plurality of peak wavelengths, for example, the peak wavelength of the i-line (365 nm), the peak wavelength of the h-line (405 nm), and the peak wavelength of the g-line (436 nm) can be applied. As this ultraviolet irradiator, for example, a mercury lamp can be applied. This light source 11 is controlled by the control unit 50.

The condenser lens 12, relay lens 14, pinhole plate 15, and condenser lens 16 are arranged along the Z-axis direction, between the light source 11 and the phase shift mask 80, in this order. It is placed.

The converging lens 12 is a convex lens and is arranged so that its focus is located on the light source 11. The light irradiated from the light source 11 becomes parallel light whose phase is aligned in the XY plane by the condenser lens 12, and this parallel light enters the relay lens 14.

The relay lens 14 is a convex lens and focuses incident parallel light onto the pinhole 151 of the pinhole plate 15. The pinhole 151 penetrates the pinhole plate 15 in its thickness direction. The pinhole plate 15 is disposed at a position where the pinhole 151 is the focus of the relay lens 14. The light passing through the pinhole 151 essentially becomes light emitted from a point light source and enters the condenser lens 16. The condenser lens 16 is a convex lens, and its focus is placed at a position where the pinhole 151 is. The condenser lens 16 converts the incident light into parallel light. The irradiation unit 10 irradiates this light to a portion of the phase shift mask 80 along the Z-axis direction.

＜Detection section＞

The detection unit 20 is disposed on the side opposite to the irradiation unit 10 with respect to the phase shift mask 80, and faces the phase shift mask 80 at a distance in the Z-axis direction. That is, the phase shift mask 80 is held by the holding part 90 between the irradiation part 10 and the detection part 20. In the example of FIG. 1, the detection unit 20 includes an objective lens 21, an imaging lens 22, a slit mask 23, a Fourier transform lens 24, and a sensor 25. The objective lens 21, imaging lens 22, slit mask 23, Fourier transform lens 24, and sensor 25 are arranged in this order as they move away from the phase shift mask 80 along the Z-axis direction. It is done.

The objective lens 21 and the imaging lens 22 are, for example, convex lenses. The light that has passed through this part of the phase shift mask 80 is expanded through the objective lens 21 and the imaging lens 22 and enters the slit mask 23.

FIG. 2 is a plan view showing an example of the configuration of the slit mask 23. Additionally, in FIG. 2, in order to show the optical positional relationship of the phase shift film 82 with respect to the slit mask 23, an image of the phase shift film 82 is also shown virtually as a two-dot chain line.

The slit mask 23 has a first slit 23a, a second slit 23b, and a third slit 23c. Each of the first slit 23a, the second slit 23b, and the third slit 23c has an elongated shape (for example, a rectangle) extending in the first direction (here, the Y-axis direction) in plan view. Have. That is, the first slit 23a, the second slit 23b, and the third slit 23c are parallel to each other. The lengths of the first slit 23a, the second slit 23b, and the third slit 23c in the longitudinal direction may be the same. The first slit 23a, the second slit 23b, and the third slit 23c are arranged adjacent to each other in a second direction perpendicular to the first direction (here, the X-axis direction). The second slit 23b is located between the first slit 23a and the third slit 23c. Hereinafter, the second direction is also called the arrangement direction.

In the example of FIG. 1, the slit mask 23 includes a substrate 231 and a shielding film 232. The substrate 231 is a substrate for supporting the shielding film 232 and is a light-transmitting substrate having a plate-like shape. The substrate 231 is made of a material with high transmittance (for example, quartz). The base material 231 is arranged so that its thickness direction follows the Z-axis direction. The base material 231 has, for example, a rectangular shape in plan view, and one side is set to, for example, about several tens of mm (for example, about 20 mm). A shielding film 232 is formed on one main surface of the substrate 231. The shielding film 232 is formed of a material that blocks light, for example, chromium. In the shielding film 232, a first slit 23a, a second slit 23b, and a third slit 23c are formed.

As shown in FIG. 2, the first gap d1 between the first slit 23a and the second slit 23b is different from the second gap d2 between the second slit 23b and the third slit 23c. That is, the second slit 23b is adjacent to the first slit 23a at a first spacing d1 in the array direction, and the third slit 23c is a second slit 23c that is different from the first spacing d1 in the array direction. It is adjacent to the second slit 23b at a distance d2. Here, the first spacing d1 is the spacing between the center position of the first slit 23a and the center position of the second slit 23b in the array direction, and the second spacing d2 is the spacing between the center position of the second slit 23b in the array direction. This is the distance between the center position of (23b) and the center position of the third slit (23c).

Referring to FIG. 1, light from the imaging lens 22 passes through the first slit 23a, the second slit 23b, and the third slit 23c. Light passing through the first slit 23a, the second slit 23b, and the third slit 23c interfere with each other. Hereinafter, the light passing through the first slit 23a is also called light La, the light passing through the second slit 23b is also called light Lb, and the light passing through the third slit 23c is also called light Lc. .

The Fourier transform lens 24 is, for example, a convex lens. The focal length of the Fourier transform lens 24 may be set to, for example, hundreds of mm (eg, 200 mm). Light from the slit mask 23 is refracted by the Fourier transform lens 24 and enters the light-receiving surface of the sensor 25. For this reason, an interference pattern is formed on the light-receiving surface of the sensor 25 by the light La, light Lb, and light Lc that passed through the first slit 23a, the second slit 23b, and the third slit 23c, respectively. do.

The sensor 25 generates an image representing an interference pattern by detecting the intensity of light incident on the light-receiving surface for each light-receiving element (pixel). The sensor 25 is, for example, a CCD sensor or a CMOS sensor. The sensor 25 outputs an electrical signal representing the detection result (i.e., an image representing an interference pattern) to the control unit 50 .

＜Control section＞

The control unit 50 can control the phase difference measurement device 1 as a whole. For example, the control unit 50 controls the irradiation of light by the irradiation unit 10 and the movement by the movement mechanism 40, as described above. Additionally, the control unit 50 also functions as an arithmetic processing unit that calculates the phase shift amount θ by the area 8A based on the interference pattern detected by the sensor 25. The method of calculating the phase shift amount θ will be described in detail later.

The control unit 50 is an electronic circuit device and may have, for example, a data processing device and a storage unit. For example, the data processing device may be an arithmetic processing device such as a CPU (Central Processor Unit). The storage unit may include a non-transitory storage unit (for example, ROM (Read Only Memory) or a hard disk) and a temporary storage unit (for example, RAM (Random Access Memory)). In the non-transitory storage unit, for example, a program that specifies the processing to be executed by the control unit 50 may be stored. When the processing device executes this program, the control unit 50 can execute the processing specified in the program. Of course, part or all of the processing executed by the control unit 50 may be executed by a dedicated hardware circuit.

＜Operation during measurement＞

FIG. 3 is a flow chart showing a first example of the operation of the phase difference measurement device 1. First, in step S1, the control unit 50 sets the value k to the initial value (=1). This value k represents the number of a plurality of measurement positions P[k].

Next, in step S2, the control unit 50 controls the moving mechanism 40 to move one set of the irradiation unit 10 and the detection unit 20 to the measurement position P[k]. Referring to FIG. 1, this measurement position P[k] is a position where light from the irradiation unit 10 transmits both a part of the area 8A and a part of the area 8B of the phase shift mask 80. , More specifically, the measurement position P[k] is such that the light La passes through the area 8A (i.e. the phase shift film 82) and the first slit 23a, and the light Lb passes through the area 8B (i.e. This is the position where light Lc passes through the area (where the phase shift film 82 is not formed) and the second slit 23b, and the light Lc passes through the area 8B and the third slit 23c. In other words, at the measurement position P[k], the first slit 23a is located on the path of light passing through the area 8A, and the second slit 23b and the third slit 23c are located in the area 8B. are each located on the path of light passing through.

Next, in step S3, the control unit 50 causes the irradiation unit 10 to irradiate light. Light from the irradiation unit 10 passes through a portion of the phase shift mask 80 and the first slit 23a, second slit 23b, and third slit 23c of the slit mask 23. Light La, light Lb, and light Lc that passed through the slit mask 23 interfere with each other, forming an interference pattern on the light receiving surface of the sensor 25.

Then, in step S4, the sensor 25 detects the interference pattern of the light-receiving surface and outputs an electrical signal (for example, an image) representing the detection result to the control unit 50.

FIG. 4 is a diagram schematically showing an example of an interference pattern detected by the sensor 25. In Figure 4, the horizontal axis represents the position of the X-axis, and the vertical axis represents the intensity of light. As shown in FIG. 4, the interference pattern includes a plurality of frequency components. Figure 5 is a diagram schematically showing an example of the amplitude spectrum of an interference pattern. As shown in FIG. 5, the interference pattern includes at least the frequency component F1, frequency component F2, and frequency component F3 described below. The frequency component F1 is a component generated by interference between light La and light Lb, the frequency component F2 is a component generated by interference between light Lb and light Lc, and the frequency component F3 is a component generated by interference between light Lc and light La. It is a component generated by .

Since the frequency component F1 is generated by interference between light La and light Lb, the frequency f1 of the frequency component F1 depends on the first gap d1 between the first slit 23a and the second slit 23b. Specifically, the frequency f1 increases as the first interval d1 becomes wider.

The phase ϕ1 of the frequency component F1 generated by the interference of light La and light Lb corresponds to the position of the frequency component F1 on the X-axis in the interference pattern. This phase ϕ1 depends on the phase difference between the light La and the light Lb in the slit mask 23 (that is, the phase shift amount θ due to the region 8A).

Phase ϕ1 actually depends not only on the phase shift amount θ but also on the misalignment of the optical axis. The optical axis deviation referred to here refers to, for example, the optical axis deviation of various optical elements (for example, the objective lens 21, etc.) belonging to the detection unit 20. Since the amount of deviation of the optical axis may vary depending on movement by the moving mechanism 40, the amount of deviation of the optical axis at a plurality of measurement positions P[k] may be different from each other.

Since the frequency component F2 is generated by interference between the light Lb and the light Lc, the frequency f2 of the frequency component F2 depends on the second gap d2 between the second slit 23b and the third slit 23c. When the second gap d2 is narrower than the first gap d1, the frequency f2 is lower than the frequency f1.

The phase ϕ2 of the frequency component F2 generated by the interference of light Lb and light Lc corresponds to the position of the frequency component F2 on the X-axis in the interference pattern. This phase phi2 depends on the phase difference between the light Lb and the light Lc in the slit mask 23. Since both light Lb and light Lc transmit through region 8B, this phase difference is substantially zero. Additionally, in reality, the phase ϕ2 also depends on the deviation of the optical axis.

Since the frequency component F3 is generated by interference between light Lc and light La, the frequency f3 of the frequency component F3 depends on the third gap d3 (=d1+d2) between the third slit 23c and the first slit 23a. Because the third interval d3 is wider than the first interval d1, the frequency f3 is higher than the frequency f1.

The phase ϕ3 of the frequency component F3 generated by interference between light Lc and light La corresponds to the position of the frequency component F3 on the X-axis in the interference pattern. This phase ϕ3 depends on the phase difference between the light Lc and the light La in the slit mask 23 (that is, the phase shift amount θ due to the region 8A). In reality, the phase ϕ3 also depends on the misalignment of the optical axis.

It is believed that the influence of optical axis deviation commonly occurs from light La to light Lc. For this reason, the amount resulting from the deviation of the optical axis at the same measurement position P[k] is common to all of phase phi 1, phase phi 2, and phase phi 3. Accordingly, the value obtained by subtracting phase ϕ2 from phase ϕ1 and the value obtained by subtracting phase ϕ2 from phase ϕ3 almost do not include the amount due to misalignment of the optical axis and become values dependent on the phase shift amount θ. In other words, if the control unit 50 can obtain phases ϕ1 and phase ϕ2, or phases ϕ2 and phase ϕ3, it can obtain the phase shift amount θ with high precision.

There, in step S5, the control unit 50 determines the first phase (phase phi 1 or phase phi 3) and the second phase (phase phi 2) based on the interference pattern measured by the sensor 25. Here, as an example, the control unit 50 determines phase phi 1 and phase phi 2.

Fig. 6 is a flow chart showing an example of a method for calculating the first phase and the second phase according to the first embodiment. That is, the flow chart in FIG. 6 shows an example of the specific operation of step S5 in FIG. 3. In the example of FIG. 6, in step S51, the control unit 50 performs Fourier transform on the interference pattern to obtain a phase spectrum. Figure 7 is a graph schematically showing an example of a phase spectrum. The horizontal axis of Figure 7 represents frequency, and the vertical axis represents phase. Additionally, FIG. 7 shows simulation results when the light irradiated by the irradiation unit 10 includes a plurality of peak wavelengths. For this reason, in the example of Fig. 7, frequency f1i, frequency f1h, frequency f1g, frequency f2i, frequency f2h, frequency f2g, phase ϕ1i, phase ϕ1h, phase ϕ1g, phase ϕ2i, phase ϕ2h and phase ϕ2g are shown. Below, for simplicity, the case where light has a single peak wavelength is first described, and the case where light has multiple peak wavelengths is described later. Here, as an example, the frequencies f1, frequency f2, phase phi1, and phase phi2 corresponding to a single peak wavelength are frequency f1i, frequency f2i, phase phi1i, and phase phi2i, respectively. Additionally, the phase difference measurement device 1 may have an optical filter (for example, a band-pass filter) that transmits a predetermined wavelength range including a single peak wavelength. The optical filter is installed between the condenser lens 12 and the relay lens 14, for example. The light that passes through the optical filter is substantially short-wavelength light.

However, the frequency f1 of the frequency component F1 depends not only on the first distance d1 between the first slit 23a and the second slit 23b, but also on the wavelength λ of light and the focal length fd of the Fourier transform lens 24. The same applies to the frequency f2 of the frequency component F2. Specifically, the frequency f1 and frequency f2 are expressed by the following equations.

f1=d1/(λ·fd)

f2=d2/(λ·fd)... (One)

Since the first spacing d1, the second spacing d2, the wavelength λ, and the focal length fd are already known in design, the frequencies f1 and f2 can be calculated in advance. The values of frequency f1 and frequency f2 may be stored in advance in, for example, a nonvolatile storage unit (e.g., flash memory or hard disk, etc.) of the control unit 50.

Next, in step S52, the control unit 50 determines the phase phi of the frequency component F1 and the phase phi 2 of the frequency component F2 based on the phase spectrum. Specifically, the control unit 50 determines the phase ϕ1 based on the frequency f1 read from the storage unit and the phase spectrum obtained in step S51, and the frequency f2 read from the storage unit and the phase spectrum obtained in step S51. Based on this, the phase ϕ2 is obtained. That is, in the phase spectrum, the control unit 50 specifies the phase when the frequency becomes frequency f1 as phase ϕ1, and specifies the phase when the frequency becomes frequency f2 as phase ϕ2.

Next, in step S6, the control unit 50 determines the phase shift amount θ based on phase phi 1 and phase phi 2. Specifically, the control unit 50 calculates the phase shift amount θ (=ϕ1-ϕ2) by subtracting phase ϕ2 from phase ϕ1. As described above, phase ϕ1 includes the amount of phase shift θ and the amount due to the misalignment of the optical axis, and phase ϕ2 does not include the amount of phase shift θ but includes the amount due to the misalignment of the optical axis, so phase ϕ1 At the value obtained by subtracting phase ϕ2 from , most of the amount due to deviation of the optical axis is canceled.

Next, in step S7, the control unit 50 determines whether the value k is greater than the predetermined value kref. That is, the control unit 50 determines whether measurement at all measurement positions P[k] has been completed. If a negative judgment is made, in step S8, the control unit 50 adds 1 to the value k and executes steps S2 to S7 again. If a positive judgment is made in step S7, the control unit 50 ends the process.

As described above, in the phase difference measurement device 1, the interference pattern is formed by the light La, light Lb, and light Lc that passed through the first slit 23a, the second slit 23b, and the third slit 23c, respectively. is detected (step S4). For this reason, the detected interference pattern includes a frequency component F1 due to the interference of the light La and the light Lb, a frequency component F2 due to the interference of the light Lb and the light Lc, and a frequency component due to the interference of the light Lc and the light La. Component F3 is included. Since light La transmits through the region 8A, and light Lb and light Lc transmit through the region 8B, the phase ϕ1 of the frequency component F1 depends on the phase shift amount θ due to the region 8A, and the phase of the frequency component F2 Phase ϕ2 has little dependence on the phase shift amount θ. Additionally, phase ϕ1 and phase ϕ2 include the amount due to misalignment of the optical axis.

The control unit 50 determines, for example, phase phi 1 and phase phi 2 based on the interference pattern detected at one measurement position P[k] (step S5). For this reason, the phase phi 1 and the phase phi 2 commonly include the quantity resulting from the deviation of the optical axis at the one measurement position P[k]. Additionally, the control unit 50 calculates the phase shift amount θ by subtracting phase ϕ2 from phase ϕ1, so that the amount due to the optical axis misalignment included in phase ϕ1 can be more accurately subtracted to phase ϕ2. For this reason, the value obtained by subtracting phase ϕ2 from phase ϕ1 almost does not include the amount due to misalignment of the optical axis. That is, the control unit 50 can suppress the influence of optical axis deviation and calculate the phase shift amount θ with higher precision.

Additionally, in the above-described example, the control unit 50 performs Fourier transform on the interference pattern to obtain the frequency component F1 and frequency component F2 (step S51). For this reason, the control unit 50 can obtain the frequency component F1 and the frequency component F2 with high accuracy, and can obtain the phase ϕ1 and phase ϕ2 with even higher accuracy. As a result, the control unit 50 can calculate the phase shift amount θ with higher precision.

＜Specification of the frequency of the frequency component＞

In the above example, the frequencies f1 and f2 are calculated in advance and stored in the storage unit. However, the first spacing d1, the second spacing d2, the wavelength λ, and the focal length fd may vary due to manufacturing variations, and may also vary due to factors such as deterioration over time or thermal deformation. For this reason, the values of the frequency f1 and frequency f2 calculated in advance may deviate from the actual values.

Therefore, the control unit 50 may determine the frequencies f1 and f2 based on the interference pattern detected by the sensor 25.

Fig. 8 is a flow chart showing another example of the method for calculating the first phase and the second phase according to the first embodiment. That is, the flow chart in FIG. 8 shows another example of the specific operation of step S5 in FIG. 3. First, the control unit 50 executes step S51. More specifically, the control unit 50 performs Fourier transform on the interference pattern to obtain an amplitude spectrum and a phase spectrum. Figure 9 is a graph schematically showing an example of an amplitude spectrum. The horizontal axis of Figure 9 represents frequency, and the vertical axis represents amplitude. Additionally, in the example of FIG. 9, frequencies f1i, frequency f1h, frequency f1g, frequency f2i, frequency f2h, and frequency f2g are shown. As in FIG. 7, these will be described later.

Next, in step S53, the control unit 50 specifies the frequency f1 and frequency f2 based on the amplitude spectrum. For example, the control unit 50 specifies the peak value of the amplitude within a predetermined frequency range R1 corresponding to the frequency f1, and specifies the frequency at which the amplitude reaches the peak value as the frequency f1. The frequency range R1 is, for example, a range centered on the design value of the frequency f1, and can be set to a range that the frequency f1 can take. Similarly, the control unit 50 specifies the peak value of the amplitude within a predetermined frequency range R2 corresponding to the frequency f2, and specifies the frequency at which the amplitude reaches the peak value as the frequency f2. The frequency range R2 is, for example, a range centered on the design value of the frequency f2, and is set to a range that the frequency f2 can take. Additionally, the frequency range R1 and frequency range R2 are set so as not to overlap each other.

Next, the control unit 50 executes step S52. However, the control unit 50 determines the phases phi 1 and phase phi 2 based on the specified frequencies f1 and f2 in step S53 and the phase spectrum determined in step S51.

As described above, the control unit 50 determines the frequencies f1 and f2 based on the interference pattern detected by the sensor 25. For this reason, the control unit 50 can obtain the frequency f1 and frequency f2 with higher precision. Since the control unit 50 uses these frequencies f1 and f2 to specify phase phi 1 and phase phi 2, it is possible to obtain phases phi 1 and phase phi 2 with higher precision. Accordingly, the control unit 50 can obtain the phase shift amount θ with higher precision.

＜Spacing of slits＞

Next, the first gap d1 between the first slit 23a and the second slit 23b and the second gap d2 between the second slit 23b and the third slit 23c will be explained. As described above, the first interval d1 and the second interval d2 define the frequency f1 and frequency f2, respectively. Specifically, the frequency f1 is proportional to the first interval d1, and the frequency f2 is proportional to the second interval d2 (see also equation (1)).

And, as can be understood from the amplitude spectrum in FIG. 9, as the difference between the frequencies f1 and f2 increases, the peak values of the amplitudes corresponding to the frequencies f1 and f2 respectively fall apart from each other. For this reason, it is easy for the control unit 50 to specify both peak values from the amplitude spectrum. In other words, the control unit 50 is easy to specify the frequency f1 and frequency f2. Therefore, the difference between the first interval d1 and the second interval d2 is set to a value that can specify both peak values in the amplitude spectrum. For example, the smaller interval among the first interval d1 and the second interval d2 may be 70% or less of the larger interval. As a specific example, the first spacing d1 is, for example, about 1 mm, and the second spacing d2 is, for example, about 0.5 mm.

<Slit spacing size>

Next, an example of the magnitude relationship between the first interval d1 and the second interval d2 will be described. In the example of FIG. 2, the first spacing d1 is set to be wider than the second spacing d2.

However, as shown in FIG. 1, the light passing through the area 8A passes through the first slit 23a, and the light passing through the area 8B passes through the second slit 23b and the third slit 23c, respectively. ) passes through. For this reason, as shown in FIG. 2, on the slit mask 23, the first slit 23a is located within (on) the area 8A, and the second slit 23b and the third slit 23c is located within (above) area 8B. In other words, on the slit mask 23, one end 82a of (on) the area 8B needs to be located between the first slit 23a and the second slit 23b, and the other end 82a needs to be located between the first slit 23a and the second slit 23b. The end 82b needs to be located on the opposite side of the second slit 23b with respect to the third slit 23c.

In the example of FIG. 2, since the first gap d1 is wider than the second gap d2, compared to the case where the first gap d1 is narrower than the second gap d2, the upper end 82a of the area 8B is connected to the first slit 23a. ) and the second slit (23b). Additionally, since the second gap d2 is narrower than the first gap d1, it is easy to position the second slit 23b and the third slit 23c within the area 8B. In other words, the positional accuracy of the irradiation unit 10 and the detection unit 20 required for each measurement position P[k] can be relaxed.

Moreover, even if the phase shift mask 80 with a narrower width of the area 8B is the object of measurement, the second slit 23b and the third slit 23c can be positioned within the image of the area 8B. In other words, the lower limit of the pattern spacing (width of the region 8B) of the phase shift mask 80 that can measure the phase shift amount θ by the phase difference measuring device 1 can be made smaller.

＜Width of slit＞

Next, an example of the size relationship between the width wa of the first slit 23a, the width wb of the second slit 23b, and the width wc of the third slit 23c will be described. The width wa is the width of the first slit 23a in the array direction (here, the X-axis direction), the width wb is the width of the second slit 23b in the array direction, and the width wc is the array direction. This is the width of the third slit 23c in . In the example of Figure 2, the width wa is wider than the width wb. Since the light La transmits through the phase shift film 82 (that is, the region 8A) with a low transmittance, the amount of light becomes small. Therefore, if the width wa and the width wb are about the same, the amplitude of the frequency component F1 resulting from interference between light La and light Lb becomes small. In the example of FIG. 2, since the width wa is wider than the width wb, a decrease in the amount of light La passing through the first slit 23a can be suppressed, and the amplitude of the frequency component F1 can be increased. Therefore, the control unit 50 can easily specify the frequency component F1 from the interference pattern, and obtain the phase phi1 with higher precision.

Moreover, in the example of FIG. 2, the width wb of the second slit 23b is wider than the width wc of the third slit 23c. For this reason, the amount of light Lb passing through the second slit 23b can be increased. Therefore, each peak value of intensity due to interference between light La and light Lb can be increased. According to this, the influence of noise on the first frequency component can be reduced, and the control unit 50 can specify the phase phi 1 with higher precision.

However, the width wa, wb, and wc also affect the shape of the envelope E1 (see FIG. 4) of the interference pattern. Specifically, as the width wa, wb, and wc become wider, the envelope E1 has a steeper convex shape. In the example of Fig. 4, envelope E11, which is steeper than envelope E1, is also schematically shown. As the envelope E1 becomes steeper, each peak value of intensity in the interference pattern below the envelope E1 becomes smaller. For this reason, the amplitude of each frequency component may become small, and the specific accuracy of the frequency component from the interference pattern may decrease. It is also understandable that as the envelope E1 becomes steeper, the number of peaks of intensity in the interference pattern (i.e., the number of fringes in the interference pattern) decreases. In this case, the actual range in the X-axis direction of the interference pattern that is the subject of Fourier transform is narrowed. As a result, the specific accuracy of the frequency component decreases.

In contrast, in the example of FIG. 2, the width wc of the third slit 23c is set to be narrower than the width wb of the second slit 23b. For this reason, the shape of the envelope E1 can be made more gently convex. Therefore, the peak value of each intensity below the envelope E1 can be increased, and the actual range of the interference pattern in the X-axis direction can also be expanded. Accordingly, the control unit 50 can specify each frequency component from the interference pattern with higher precision. Furthermore, the control unit 50 can obtain the phase shift amount θ with higher precision.

＜Multiple peak wavelengths＞

Next, a case where the light irradiated by the irradiation unit 10 has multiple peak wavelengths will be described. For example, the light has a first peak wavelength λi, a second peak wavelength λh, and a third peak wavelength λg. The first peak wavelength λi is, for example, the i-line wavelength, the second peak wavelength λh is, for example, the h-line wavelength, and the third peak wavelength λg is, for example, the g-line wavelength. Hereinafter, the end of the sign of the peak wavelength is added at the end of the sign of light having each peak wavelength. For example, the light with the first peak wavelength λi among the lights La is called light Lai, the light with the first peak wavelength λi among the lights Lb is called light Lbi, and the light with the first peak wavelength λi among the lights Lc is called light. It is called optical Lci.

When the light irradiated by the irradiation unit 10 has a plurality of peak wavelengths, the interference pattern detected by the sensor 25 includes frequency components due to interference for each peak wavelength. For example, as shown in FIGS. 7 and 9, the interference pattern includes a plurality of frequency components.

The frequency component F1i is a component generated by interference of light Lai and light Lbi having the first peak wavelength λi. For this reason, the frequency f1i of the frequency component F1i is determined by the first interval d1, the first peak wavelength λi, and the focal length fd (see also equation (1)). The phase ϕ1i of the frequency component F1i depends on the phase difference between the light Lai and the light Lbi in the slit mask 23 (that is, the phase shift amount θ of the area 8A with respect to the light of the first peak wavelength λi). In reality, the phase ϕ1i also depends on the misalignment of the optical axis. Hereinafter, the phase shift amount θ for light having the first peak wavelength λi is also called the phase shift amount θi.

The frequency component F2i is a component generated by interference of light Lbi and light Lci having the first peak wavelength λi. For this reason, the frequency f2i of the frequency component F2i is determined by the second interval d2, the first peak wavelength λi, and the focal length fd. The phase ϕ2i of the frequency component F2i depends on the phase difference between the light Lbi and the light Lci in the slit mask 23. The phase difference is essentially zero. In reality, the phase ϕ2i depends on the misalignment of the optical axis.

For this reason, if the phase ϕ1i and the phase ϕ2i can be obtained, the phase shift amount θi can be obtained with high accuracy based on the phase ϕ1i and the phase ϕ2i.

The frequency component F1h is a component generated by interference of light Lah and light Lbh having the second peak wavelength λh. For this reason, the frequency f1h of the frequency component F1h is determined by the first interval d1, the second peak wavelength λh, and the focal length fd. The phase ϕ1h of the frequency component F1h depends on the phase difference between the light Lah and the light Lbh in the slit mask 23 (that is, the phase shift amount θ of the region 8A with respect to the light of the second peak wavelength λh). In reality, the phase ϕ1h also depends on the misalignment of the optical axis. Hereinafter, the phase shift amount θ for light having the second peak wavelength λh is called the phase shift amount θh.

The frequency component F2h is a component generated by interference of light Lbh and light Lch having the second peak wavelength λh. For this reason, the frequency f2h of the frequency component F2h is determined by the second interval d2, the second peak wavelength λh, and the focal length fd. The phase phi2h of the frequency component F2h depends on the phase difference between the light Lbh and the light Lch in the slit mask 23. The phase difference is essentially zero. Also, in reality, the phase ϕ2h depends on the deviation of the optical axis.

The phase ϕ1h depends on the phase shift amount θh and the optical axis misalignment, and the phase ϕ2h does not depend on the phase shift amount θh but depends on the optical axis misalignment. For this reason, if the phase ϕ1h and the phase ϕ2h can be obtained, the phase shift amount θh can be obtained with high accuracy based on the phase ϕ1h and the phase ϕ2h.

The frequency component F1g is a component generated by interference between light Lag and light Lbg having the third peak wavelength λg. For this reason, the frequency f1g of the frequency component F1g is determined by the first interval d1, the third peak wavelength λg, and the focal length fd. The phase ϕ1g of the frequency component F1g depends on the phase difference between the light Lag and the light Lbg in the slit mask 23 (that is, the phase shift amount θ of the region 8A with respect to the third peak wavelength λg). In reality, the phase ϕ1g also depends on the misalignment of the optical axis. In addition, hereinafter, the phase shift amount θ with respect to the light having the third peak wavelength λg is called the phase shift amount θg.

The frequency component F2g is a component generated by interference between light Lbg and light Lcg. For this reason, the frequency f2g of the frequency component F2g is determined by the second interval d2, the third peak wavelength λg, and the focal length fd. The phase ϕ2g of the frequency component F2g depends on the phase difference between the light Lbg and the light Lcg in the slit mask 23. The phase difference is essentially zero. In reality, the phase ϕ2g depends on the misalignment of the optical axis.

The phase ϕ1g depends on the phase shift amount θg and the misalignment of the optical axis, and the phase ϕ2g does not depend on the phase shift amount θg but depends on the misalignment of the optical axis. For this reason, if the phase ϕ1g and the phase ϕ2g can be obtained, the phase shift amount θg can be obtained with high accuracy based on the phase ϕ1g and the phase ϕ2g.

Additionally, in reality, the frequency component F3 generated by the interference between light Lc and light La is also included in the interference pattern for each peak wavelength, similar to the frequency components F1 and F2 described above. Here, for simplicity, description of the frequency component F3 is omitted.

The control unit 50 determines phase ϕ1i, phase ϕ1h, phase ϕ1g, phase ϕ2i, phase ϕ2h, and phase ϕ2g based on the interference pattern detected by sensor 25, and determines phase shift amount θi and phase ϕ2g based on these. The shift amount θh and the phase shift amount θg may be obtained.

A specific example of phase calculation is as shown in FIG. 6 or FIG. 8. However, in step S52, the control unit 50 controls the frequency f1i, the frequency f1h, the frequency f1g, the frequency f2i, the frequency f2h, and the frequency f2g, and based on the phase spectrum, phase ϕ1i, phase ϕ1h, phase ϕ1g, phase ϕ2i, phase ϕ2h, and Find the phase ϕ2g. This specification method is the same as the specification method of phase phi 1 based on frequency f1 and the phase spectrum and the specification method of phase phi 2 based on frequency f2 and phase spectrum.

Then, in step S6, the control unit 50 calculates the phase shift amount θi based on the phase ϕ1i and the phase ϕ2i, calculates the phase shift amount θh based on the phase ϕ1h and the phase ϕ2h, and calculates the phase shift amount θh based on the phase ϕ1g and the phase ϕ2g. Thus, the phase shift amount θg is calculated. This calculation method is the same as the calculation method of the phase shift amount θ (=ϕ1-ϕ2) based on phase ϕ1 and phase ϕ2.

As described above, the irradiation unit 10 irradiates light containing a plurality of peak wavelengths to the phase shift mask 80, and the sensor 25 detects light that has passed through the slit mask 23 from the phase shift mask 80. The interference pattern formed by La, light Lb, and light Lc is detected. Based on the interference pattern detected by the sensor 25, the control unit 50 determines the first phase of the first frequency component corresponding to the first interval d1 (i.e., phase ϕ1i, phase ϕ1h, and phase ϕ1g) for each peak wavelength. ) is obtained, and for each peak wavelength, the second phase of the second frequency component corresponding to the second interval d2 (i.e., phase ϕ2i, phase ϕ2h, and phase ϕ2g) is obtained. Then, the control unit 50 determines the phase shift amount θ (that is, the phase shift amount θi, the phase shift amount θh, and the phase shift amount θg) based on the first phase and the second phase for each peak wavelength.

For comparison, a case where light for each peak wavelength is sequentially irradiated to the phase shift mask 80 will be described. The irradiation unit 10 may output light by changing the wavelength of light. For example, the irradiation unit 10 irradiates short-wavelength light having a first peak wavelength λi. At this time, the sensor 25 detects an interference pattern corresponding to the first peak wavelength λi. Next, the irradiation unit 10 irradiates short-wavelength light having a second peak wavelength λh. At this time, the sensor 25 detects an interference pattern corresponding to the second peak wavelength λh. Finally, the irradiation unit 10 irradiates short-wavelength light having the third peak wavelength λg. At this time, the sensor 25 detects an interference pattern corresponding to the third peak wavelength λg. Then, the control unit 50 determines the phase shift amount θ for each peak wavelength based on the interference pattern corresponding to each peak wavelength. In this case, it is necessary for the irradiation unit 10 to irradiate light at different timings and for the sensor 25 to detect the interference pattern each time. For this reason, the time required to calculate the plurality of phase shift amounts θ corresponding to the plurality of peak wavelengths respectively becomes long. In addition, the control unit 50 needs to perform processing such as Fourier transform for each of the plurality of interference patterns corresponding to the plurality of peak wavelengths, and the processing load of the control unit 50 becomes heavy.

In contrast, in the above-described example, the irradiation unit 10 irradiates light containing a plurality of peak wavelengths to the phase shift mask 80, and the sensor 25 only needs to detect the interference pattern by 1 degree. Therefore, the phase difference measuring device 1 can obtain a plurality of phase shift amounts corresponding to a plurality of peak wavelengths in a short time. Additionally, the processing load of the control unit 50 can be lightened.

＜Optical characteristics of optical systems＞

In the above-described example, the differences in optical characteristics of the plurality of paths through which light La, light Lb, and light Lc respectively pass are not considered. However, in reality, the optical characteristics of each path may be different from each other. For example, the objective lens 21 and the imaging lens 22 have aberrations, and their optical characteristics may be slightly different depending on each path. In this case, for example, the states (e.g., phases) of light La, light Lb, and light Lc when incident on the phase shift mask 80 may be different from each other.

Since the above-mentioned optical axis deviation acts commonly for each path, it acts commonly for light La, light Lb, and light Lc. However, since this optical characteristic may be different for each path, the difference in this optical characteristic is It acts separately on light La, light Lb, and light Lc.

Therefore, for example, the value obtained by subtracting phase phi2 from phase phi1 depends not only on the phase shift amount θ but also on differences between paths in optical characteristics. In other words, there is still room for improvement in the calculation accuracy of the phase shift amount θ. Here, an attempt is made to suppress a decrease in the calculation accuracy of the phase shift amount θ due to differences in optical characteristics in the respective paths of light La, light Lb, and light Lc. In addition, for the sake of simplicity, hereinafter, a mode in which the irradiation unit 10 irradiates light having a single peak wavelength to the phase shift mask 80 will be described.

FIG. 10 is a flow chart showing a second example of the operation of the phase difference measuring device 1. Here, an aspect in which phase phi 1 is applied as the first phase will be described. First, in step S11, the control unit 50 controls the moving mechanism 40 to move the optical system (a set of the irradiation unit 10 and the detection unit 20) to the reference position P[0]. FIG. 11 is a diagram schematically showing an example of the configuration of the phase difference measurement device 1 when the optical system is located at the reference position P[0]. This reference position P[0] is a position at which the light from the irradiation unit 10 passes only the area 8B of the phase shift mask 80. More specifically, the light passing through the area 8B is each This is the position where it passes through the first slit (23a), the second slit (23b), and the third slit (23c).

Next, in step S12, the control unit 50 irradiates light to the irradiation unit 10. By irradiation of this light, light La, light Lb, and light Lc form an interference pattern on the light-receiving surface of the sensor 25. Then, in step S13, the sensor 25 detects an interference pattern (hereinafter referred to as a reference interference pattern) and outputs an electrical signal (for example, an image) representing the detection result to the control unit 50.

Next, in step S14, the control unit 50 determines the reference phase ϕ10 of the frequency component F1 (corresponding to the first reference phase) and the reference phase ϕ20 of the frequency component F2 based on the reference interference pattern detected by the sensor 25. Find (equivalent to the second reference phase).

Fig. 12 is a flow chart showing an example of a method for calculating the reference phase. In the example of Fig. 12, in step S141, the control unit 50 performs Fourier transformation on the reference interference pattern to obtain an amplitude spectrum (hereinafter referred to as a reference amplitude spectrum) and a phase spectrum (hereinafter referred to as a reference phase spectrum). .

Next, in step S142, the control unit 50 determines the frequency f1 and frequency f2 based on the reference amplitude spectrum. The method for specifying the frequency f1 and frequency f2 is the same as step S53 in FIG. 9. Specifically, the control unit 50 specifies the peak value of the amplitude within the frequency range R1 from the reference amplitude spectrum, and specifies the frequency at which the amplitude reaches the peak value as the frequency f1. Similarly, the control unit 50 specifies the peak value of the amplitude within the frequency range R2 from the reference amplitude spectrum, and specifies the frequency at which the amplitude reaches the peak value as the frequency f2.

Next, in step S143, the control unit 50 determines the reference phase phi 10 and the reference phase phi 20 based on the frequency f1, the frequency f2, and the reference phase spectrum. Figure 13 is a graph schematically showing an example of a reference phase spectrum. The control unit 50 specifies the phase when the frequency becomes the specific frequency f1 in step S142 as the reference phase ϕ10, and specifies the phase when the frequency becomes the specific frequency f2 in step S142 as the reference phase ϕ20. In short, the method for specifying the reference phase ϕ10 and the reference phase ϕ20 is the same as step S52 in FIG. 8.

Next, in step S15, the control unit 50 sets the value k as the initial value, similarly to step S1. Next, in step S16, the moving mechanism 40 moves one set of the irradiation unit 10 and the detection unit 20 to the measurement position P[k], similarly to step S2. Next, in step S17, the sensor 25 detects the interference pattern by light La, light Lb, and light Lc, similarly to step S4.

Next, in step S18, the control unit 50 determines the phase phi 1 and the phase phi 2 based on the interference pattern detected by the sensor 25 in step S17. The calculation method of phase ϕ1 and phase ϕ2 is the same as in FIG. 6. However, here, the control unit 50 may determine the phase phi 1 and the phase phi 2 using the values of the frequency f1 and frequency f2 determined in step S142. That is, the values of frequency f1 and frequency f2 obtained based on the reference interference pattern detected at the measurement position P[0] are also applied to the interference pattern detected at each measurement position P[k].

This is because, as will be explained next, the specific accuracy of the frequencies f1 and f2 is higher when a reference interference pattern is used. That is, at the measurement position P[k], light La transmits through the area 8A with low transmittance, while at the measurement position P[0], light La transmits through the area 8B with high transmittance. For this reason, the intensity peak in the reference interference pattern becomes larger than that of the interference pattern. Accordingly, the influence of noise is small on the reference interference pattern, and the control unit 50 can specify the frequency f1 and frequency f2 with higher precision from the reference interference pattern.

There, the control unit 50 determines the phases phi 1 and phase phi 2 based on the frequencies f1 and frequencies f2 obtained based on the reference interference pattern and the phase spectrum of the interference pattern. For this reason, the control unit 50 can obtain phase phi 1 and phase phi 2 with higher precision.

Next, in step S19, the phase shift amount θ at the measurement position P[k] is determined based on the phases ϕ1 and phase ϕ2 determined in step S17 and the reference phase ϕ10 and reference phase ϕ20 determined in step S14. Specifically, the control unit 50 calculates the phase shift amount θ using the following equation.

θ=(ϕ1-ϕ10)-(ϕ2-ϕ20)... (2)

The phase ϕ1 is determined by the phase shift amount θ, the amount due to the deviation of the optical axis at the measurement position P[k] (hereinafter referred to as the measurement deviation amount), and the difference between the paths of light La and light Lb in optical characteristics. It includes a quantity (hereinafter referred to as the first path car). The reference phase ϕ10 includes the amount corresponding to the deviation of the optical axis of the measurement position P[0] (hereinafter referred to as the reference deviation amount) and the first path difference. For this reason, the value (ϕ1-ϕ10) is expressed as (phase shift amount θ + measured deviation amount - reference deviation amount), and most of the first path difference is canceled.

On the other hand, the phase phi2 includes the amount of measurement deviation and the difference in optical characteristics between the paths of the light Lb and the light Lc (hereinafter referred to as the second path difference). The reference phase ϕ20 includes the reference deviation amount and the second path difference. For this reason, the value (ϕ2-ϕ20) is expressed as (measurement deviation amount - reference deviation amount), and most of the second path difference is canceled.

In the value of the right-hand side of equation (2), most of the measurement deviation amount and reference deviation amount are also canceled, and as a result, the right-hand side of equation (2) includes the measurement deviation amount, reference deviation amount, first path difference, and second path difference. Instead, it includes the phase shift amount θ. Accordingly, the control unit 50 can obtain the phase shift amount θ with higher precision.

Next, in step S20, the control unit 50 determines whether the value k is greater than the predetermined value kref. When a negative judgment is made in step S20, the control unit 50 adds 1 to the value k in step S21. Next, the control unit 50 executes steps S16 to S20 again. When a positive judgment is made in step S20, the control unit 50 ends the operation.

As described above, the control unit 50 calculates the phase shift amount θ based on the interference pattern and the reference interference pattern. Specifically, the control unit 50 obtains the reference phase ϕ10 and the reference phase ϕ20 from the reference interference pattern, obtains the phase ϕ1 and phase ϕ2 from the interference pattern, and calculates the Find the phase shift amount θ. Specifically, the control unit 50 determines the difference between the value obtained by subtracting the reference phase ϕ10 from the phase ϕ1 and the value obtained by subtracting the reference phase ϕ20 from the phase ϕ2 as the phase shift amount θ. As a result, the control unit 50 can suppress both the influence of optical axis deviation and the influence of differences in optical characteristics in each path of the optical system, and obtain the phase shift amount θ with higher accuracy.

In addition, when a plurality of phase shift masks 80 are sequentially loaded into the phase difference measurement device 1, according to the operation in FIG. 10, detection of the reference interference pattern is performed for each phase shift mask 80. However, this detection does not need to be performed for each phase shift mask 80. Detection of the reference interference pattern is performed only once, and the detected reference interference pattern may be commonly used for a plurality of phase shift masks 80. Additionally, a reference interference pattern may be detected for each N phase shift mask 80 and updated.

In addition, in the above-mentioned example, the phase shift amount θ is calculated based on phase phi 1 and phase phi 2, but the phase shift amount θ may be calculated based on phase phi 2 and phase phi 3. In this case, the control unit 50 determines the reference phase ϕ20 (corresponding to the second reference phase) of the frequency component F2 and the reference phase ϕ30 (corresponding to the first reference phase) of the frequency component F3 based on the reference interference pattern. Then, the control unit 50 determines the phase shift amount θ{=ϕ3-ϕ30-(ϕ2-ϕ20)} based on the phase ϕ3, the reference phase ϕ30, the phase ϕ2, and the reference phase ϕ20.

Additionally, since the value of the frequency f1 and the value of the frequency f2 can be calculated in advance, the previously calculated value of the frequency f1 and the value of the frequency f2 may be used.

When the light irradiated by the irradiation unit 10 has a plurality of peak wavelengths, the phase difference measuring device 1 determines the first phase, the second phase, the first reference phase, and the second reference phase for each peak wavelength. In the example of Figure 13, the reference phase ϕ10i and the reference phase ϕ20i corresponding to the first peak wavelength λi, the reference phase ϕ10h and the reference phase ϕ20h corresponding to the second peak wavelength λh, and the reference phase corresponding to the third peak wavelength λg. ϕ10g and reference phases ϕ20g are also shown. Then, the control unit 50 determines the phase shift amount θ based on the first phase, first reference phase, second phase, and second reference phase for each peak wavelength. For example, with respect to the first peak wavelength λi, the control unit 50 sets the phase shift amount θi{=ϕ1i-ϕ10i-(ϕ2i-ϕ20i)} based on the phase ϕ1i, the reference phase ϕ10i, the phase ϕ2i, and the reference phase ϕ20i. Find . According to this, the phase difference measurement device 1 can determine the phase shift amount θ with higher precision for each peak wavelength.

＜Second Embodiment＞

In the first embodiment, the control unit 50 performed Fourier transform on the interference pattern to obtain the first phase (e.g., phase phi 1) and the second phase (e.g., phase phi 2). However, the control unit 50 does not necessarily need to perform Fourier transform on the interference pattern. In the second embodiment, another algorithm for calculating the first phase and the second phase will be described.

The configuration of the phase difference measurement device 1 according to the second embodiment is the same as that of the first embodiment. The operation of the phase difference measurement device 1 according to the second embodiment is the same as that in FIG. 3, except for the specific example of step S5. That is, the method of calculating the first phase and the second phase by the control unit 50 is different from the first embodiment. Below, first, the idea of the method for calculating the first phase and the second phase according to the second embodiment will be explained.

The interference pattern formed on the light-receiving surface of the sensor 25 can be expressed as a predetermined function. The predetermined function can be simply expressed by the following equation.

Here, I(x) represents an interference pattern formed on the light-receiving surface of the sensor 25. x represents the position in the X-axis direction. The first term in equation (3) is a term representing the interference pattern caused by the interference of light La and light Lb, and the second term in equation (3) is the interference caused by interference between light Lb and light Lc. It is a term representing a pattern, and the third term of equation (3) is a term representing an interference pattern generated by interference between light Lc and light La. In addition, for simplicity here, the light emitted by the irradiation unit 10 is assumed to have a single peak wavelength.

α1, α2, and α3 represent the weighting coefficients of terms 1 to 3, respectively. The weighting coefficient α1 is a value reflecting the light quantity of light La and light Lb, the weighting coefficient α2 is a value reflecting the light quantity of light Lb and light Lc, and the weighting coefficient α3 is a value reflecting the light quantity of light Lc and light La. In other words, the weighting coefficient α1 is a value reflecting the width wa and the width wb, the weighting coefficient α2 is a value reflecting the width wb and the width wc, and the weighting coefficient α3 is a value reflecting the width wc and the width wa. Since the width wa, width wb and width wc are already known, weighting coefficient α1, weighting coefficient α2 and weighting coefficient α3 can be set in advance.

Here, the light emitted by the irradiation unit 10 has a single peak wavelength (wavelength λ). The wavelength λ is already known. The focal length fd of the Fourier transform lens 24 is also already known. The first interval d1, the second interval d2, and the third interval d3 are also already known.

In addition, w1 is a value reflecting the width wa of the first slit 23a and the width wb of the second slit 23b, and is a value between the width wa and the width wb (for example, the average value of the width wa and the width wb). . w2 is a value reflecting the width wb of the second slit 23b and the width wc of the third slit 23c, and is a value between the width wb and the width wc (for example, the average value of the width wb and the width wc). w3 is a value reflecting the width wc of the third slit 23c and the width wa of the first slit 23a, and is a value between the width wc and the width wa (for example, the average value of the width wc and the width wa).

In equation (3), phase ϕ1, phase ϕ2, and phase ϕ3 are taken as variables. Hereinafter, phase ϕ1, phase ϕ2, and phase ϕ3 as variables are called phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3, respectively. Additionally, the interference pattern I(x) calculated based on the phase variable ϕc1, phase variable ϕc2, phase variable ϕc3, and equation (3) is called the calculated interference pattern Ic(x).

If the interference pattern I(x) detected by the sensor 25 matches the calculated interference pattern Ic(x), the phase variables ϕc1, phase variable ϕc2, and phase variables ϕc3 used in the calculated interference pattern Ic(x) The values of can be considered to coincide with phase ϕ1, phase ϕ2, and phase ϕ3, respectively.

Therefore, as described in detail below, the control unit 50 specifies a calculated interference pattern Ic(x) similar to the interference pattern I(x), and determines the phase variable ϕc1 used in calculating the calculated interference pattern Ic(x). , the phase variable ϕc2 and the phase variable ϕc3 are specified as phase ϕ1, phase ϕ2, and phase ϕ3, respectively. Then, as in the first embodiment, the control unit 50 calculates the phase shift amount θ by subtracting phase phi 2 from phase phi 1 (step S6). Alternatively, the control unit 50 may obtain the phase shift amount θ by subtracting phase phi2 from phase phi3 (step S6).

Fig. 14 is a flow chart showing an example of a method for calculating the first phase and the second phase according to the second embodiment. That is, the flow chart in FIG. 14 shows an example of the specific operation of step S5 in FIG. 3. In step S501, the control unit 50 sets the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3. For example, first, the control unit 50 sets the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3 to their respective initial values. The initial value of the phase variable ϕc1 is, for example, the minimum value of the first predetermined range for the phase variable ϕc1. The first predetermined range is a range that takes into account the variation in the thickness of the phase shift film 82, the variation in the amount of deviation of the optical axis, and the variation in the difference between paths in optical characteristics, and is a range of values that can take the phase ?1. The first predetermined range is set in advance, and the initial value of the phase variable ?c2, for example, stored in the storage unit, is, for example, the minimum value of the second predetermined range that the phase ?2 can take. The second predetermined range is set in advance and stored, for example, in a storage unit. The initial value of the phase variable ϕc3 is, for example, the minimum value of the third predetermined range that the phase ϕ3 can take. The third predetermined range is set in advance and stored, for example, in a storage unit.

Next, in step S502, the control unit 50 substitutes the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3 set in step S501 into equation (3) to calculate the calculated interference pattern Ic(x).

Next, in step S503, the control unit 50 calculates the degree of similarity between the interference pattern I(x) detected by the sensor 25 in step S4 and the calculated interference pattern Ic(x) calculated in step S502. . The similarity is not particularly limited, but for example, the sum of squares of the intensity difference at each position x, the sum of the absolute value of the intensity difference at each position x, or the interference pattern. It may be a correlation function between I(x) and the calculated interference pattern Ic(x). The higher the similarity, the more similar the calculated interference pattern Ic(x) is to the interference pattern I(x).

Next, in step S504, the control unit 50 determines whether the degree of similarity has been calculated for all combinations of phase variables ϕc1, phase variables ϕc2, and phase variables ϕc3.

If all similarities have not yet been calculated, the control unit 50 executes step S501 again. In step S501, the control unit 50 changes the value of one of the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3 within the corresponding predetermined range. For example, the control unit 50 adds a predetermined value to each one.

Next, the control unit 50 executes steps S502 and S503. By repeatedly executing steps S501 to S503, the control unit 50 can calculate the degree of similarity for all combinations of the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3.

When the degree of similarity has been calculated for all combinations, in step S505, the control unit 50 specifies the first phase and the second phase based on the degree of similarity. Here, phase ϕ1 is applied as the first phase. The second phase is phase ϕ2. For example, the control unit 50 specifies the highest similarity among the plurality of similarities, and specifies the phase variable ϕc1 and phase variable ϕc2 used to calculate the highest similarity as phase ϕ1 and phase ϕ2, respectively. That is, since the phase variable ϕc1 and phase variable ϕc2 used to calculate the calculated interference pattern Ic(x) that is most similar to the interference pattern I(x) are considered to be equivalent values to the actual phase ϕ1 and phase ϕ2, the control unit 50 These phase variables ϕc1 and phase variable ϕc2 are specified as phase ϕ1 and phase ϕ2, respectively.

Then, similarly to the first embodiment, the control unit 50 determines the phase shift amount θ based on the first phase and the second phase (step S6).

Additionally, the control unit 50 may specify the phase variables ϕc2 and phase variables ϕc3 used in calculating the highest similarity as phase ϕ2 and phase ϕ3, respectively, and calculate the phase shift amount θ based on the phases ϕ2 and phase ϕ3.

As described above, in the second embodiment, the control unit 50 calculates the interference pattern Ic(x) by substituting the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3 into a predetermined function, and calculates the interference pattern I(x) ) and the calculated interference pattern Ic(x) (steps S502 and S503) are repeatedly performed while changing the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3. Then, the control unit 50 calculates the first phase (i.e., phase Find the second phase (i.e. phase ϕ1 or phase ϕ3) and the second phase (i.e. phase ϕ2). For this reason, the control unit 50 can specify phase phi 1 and phase phi 2, or phase phi 2 and phase phi 3, based on the interference pattern I(x) detected by sensor 25.

Also, in the second embodiment, the control unit 50 determines the phase shift amount θ based on the first phase and the second phase, so, similarly to the first embodiment, the phase shift amount θ is determined with higher precision. You can. In addition, since the control unit 50 determines the first phase and the second phase based on the interference pattern I(x) detected at once, the phase shift amount θ can be obtained in a short time, similar to the first embodiment. Also, the processing load of the control unit 50 can be lightened.

In addition, the control unit 50 may calculate the phase shift amount θ based on the first phase, the second phase, the first reference phase, and the second reference phase, similarly to the operation in FIG. 10 of the first embodiment. As a specific example of the method for calculating the first reference phase and the second reference phase (step S14) in this case, the flow chart in FIG. 14 can be applied. That is, the control unit 50 calculates the calculated interference pattern Ic(x) based on equation (3) while changing the phase variable ϕc1, phase variable ϕc2, and phase variable ϕc3. Then, the control unit 50 determines the degree of similarity between the reference interference pattern detected by the sensor 25 and the calculated interference pattern Ic(x), and sets the phase variable ϕc1 and phase variable ϕc2 to the reference phase ϕ10, respectively, based on the similarity. and reference phase ϕ20. Alternatively, the control unit 50 specifies the phase variable ϕc2 and phase variable ϕc3 as the reference phase ϕ20 and the reference phase ϕ30, respectively, based on their similarity.

As described above, the phase difference measurement device 1 and the phase difference measurement method have been described in detail, but the above description is illustrative in all aspects and the disclosure is not limited thereto. In addition, the various modifications described above can be applied in combination as long as they do not contradict each other. In addition, it is interpreted that many modifications that are not illustrated can be assumed without departing from the disclosed scope.

1: Phase difference measurement device
8: Measurement object
8A: first refractive index region
8B: second refractive index region
10: Investigation Department
23: Slit mask
23a: first slit (slit)
23b: second slit (slit)
23c: third slit (slit)
25: sensor
40: moving mechanism
50: Operation processing unit (control unit)
d1: first interval
d2: second interval
d3: third interval
F1, F1i, F1h, F1g, F3: first frequency component (frequency component)
F2, F2i, F2h, F2g: second frequency component (frequency component)
P[0]: Reference position
P[k]: Measurement position
ϕ1, ϕ1i, ϕ1h, ϕ1g, ϕ3: first phase (phase)
ϕ2, ϕ2i, ϕ2h, ϕ2g: 2nd phase (phase)
ϕ10, ϕ10i, ϕ10h, ϕ10g, ϕ30: first reference phase (reference phase)
ϕ20, ϕ20i, ϕ20h, ϕ20g: 2nd reference phase (reference phase)
θ1, θ1i, θ1h, θ1g: Phase shift amount

Claims (10)

A phase difference measuring device for measuring a phase shift amount, which is the phase difference between light transmitted through the first refractive index region of a measurement object having a first refractive index region and a second refractive index region, and light transmitted through the second refractive index region,
an irradiation unit that irradiates light to the measurement object,
a slit mask having a first slit, a second slit adjacent to the first slit at a first distance, and a third slit adjacent to the second slit at a second distance;
In a state where the first slit is located on a path of light passing through the first refractive index region, and the second slit and the third slit are respectively located on a path of light passing through the second refractive index region, A sensor that detects an interference pattern caused by interference of light passing from the first slit to the third slit, respectively;
In the interference pattern, a third interval between the first slit and the third slit or a first phase of a first frequency component corresponding to the first interval, and a second phase of a second frequency component corresponding to the second interval An arithmetic processing unit that determines two phases based on the interference pattern and determines the phase shift amount based on the first phase and the second phase.
A phase difference measuring device comprising: In claim 1,
The first gap between the first slit and the second slit is wider than the second gap between the second slit and the third slit. In claim 1 or claim 2,
The transmittance of the first refractive index region is lower than the transmittance of the second refractive index region,
The width of the first slit is wider than the width of the second slit,
A phase difference measuring device wherein the width of the second slit is wider than the width of the third slit. In claim 3,
The phase difference measuring device wherein the calculation processing unit determines the first phase of the first frequency component corresponding to the first interval. In claim 1 or claim 2,
The irradiation unit irradiates light having a plurality of peak wavelengths,
The calculation processing unit determines the first phase and the second phase for each peak wavelength based on the interference pattern, and determines the phase shift amount based on the first phase and the second phase for each peak wavelength. Phase contrast measurement device. In claim 1 or claim 2,
further comprising a moving mechanism that moves the irradiation unit, the slit mask, and the sensor,
The moving mechanism moves a set of the irradiation unit, the slit mask, and the sensor to each of a reference position and a measurement position,
The measuring position is a position where light passing through the first refractive index region passes through the first slit, and light passing through the second refractive index region passes through the second slit and the third slit, respectively,
The reference position is a position where light passing through the second refractive index region passes from the first slit to the third slit, respectively,
The sensor detects a reference interference pattern, which is an interference pattern caused by interference of light passing from the first slit to the third slit, at the reference position,
The operation processing unit,
Obtaining a first reference phase of the first frequency component in the reference interference pattern and a second reference phase of the second frequency component in the reference interference pattern based on the reference interference pattern,
A phase difference measuring device that determines the phase shift amount based on the first phase, the first reference phase, the second phase, and the second reference phase. In claim 6,
The transmittance of the first refractive index region is lower than the transmittance of the second refractive index region,
The operation processing unit,
Perform Fourier transform on the reference interference pattern to obtain a reference amplitude spectrum and a reference phase spectrum,
Based on the reference amplitude spectrum, the first frequency of the first frequency component and the second frequency of the second frequency component are obtained,
Obtaining the first reference phase and the second reference phase based on the first frequency and the second frequency obtained based on the reference amplitude spectrum and the reference phase spectrum,
Performing Fourier transform on the interference pattern to obtain a phase spectrum,
A phase difference measuring device, wherein the first frequency and the second frequency are determined based on the reference amplitude spectrum, and the first phase and the second phase are determined based on the phase spectrum. In claim 1 or claim 2,
The operation processing unit,
A phase difference measurement device that performs Fourier transform on the interference pattern to obtain the first phase of the first frequency component and the second phase of the second frequency component. In claim 1 or claim 2,
The calculation processing unit,
Substituting the phase variable of the frequency component corresponding to the first interval, the phase variable of the second frequency component, and the phase variable of the frequency component corresponding to the third interval into a predetermined function to calculate a calculated interference pattern, and calculating the interference pattern. Processing for calculating the similarity between a pattern and the calculated interference pattern is performed while changing the phase variable,
A phase difference measurement device that determines the first phase and the second phase based on the phase variable used to calculate the calculated interference pattern similar to the interference pattern. A phase difference measurement method for measuring a phase shift amount, which is the phase difference between light transmitted through the first refractive index region of a measurement object having a first refractive index region and a second refractive index region, and light transmitted through the second refractive index region,
A process of irradiating light to the measurement object,
Light passing through the first refractive index area and the first slit, the second refractive index area, and light passing through the second slit adjacent to the first slit at a first distance, the second refractive index area, and , a process of detecting an interference pattern caused by interference of light passing through a third slit adjacent to the second slit at a second distance;
In the interference pattern, a third interval between the third slit and the first slit or a first phase of a first frequency component corresponding to the first interval, and a second phase of a second frequency component corresponding to the second interval 2. A process of determining phase based on the interference pattern;
Step of calculating the phase shift amount based on the first phase and the second phase
A phase difference measurement method comprising:

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