KR20190033421A - Phase difference measuring apparatus and phase difference measuring method - Google Patents

Abstract

The present invention provides a phase difference measuring apparatus which contributes to acquisition of a parameter incorporating a phase different of lights penetrating areas of different refractive indices at high precision. The phase difference measuring apparatus (1) comprises an emitting means (10), a slit mask (23), and a detection means (30). The emitting means (10) emits a light to a measurement target (8). The slit mask (23) has slits (23a, 23b, 23c, 24d). The slit (23a) is arranged on the path of a light penetrating a first refractive index area (8a). The slit (23b) is arranged on the path of a light penetrating a second refractive index area (8b), is separated from the slit (23a), and neighbor the slit (23a). The slits (23c, 23d) are arranged on the path of the light penetrating the second refractive index area (8b), are separated from each other, and neighbor each other. The detection means (30) detects a first interference pattern by interference of the light passing through the slits (23a, 23b) and a second interference pattern by interference of the light passing through the slits (23c, 23d).

Description

[0001] PHASE DIFFERENCE MEASURING APPARATUS AND PHASE DIFFERENCE MEASURING METHOD [0002]

The present invention relates to a phase difference measurement apparatus and a phase difference measurement method, and more particularly to a phase difference measurement using an interference fringe.

In recent years, a phase shift mask is used to transfer a pattern with a high resolution to a substrate such as a semiconductor substrate or a display display substrate. In this phase shift mask, a phase shift film for retarding the phase of light in only a half wave period is formed.

Patent Document 1 discloses a measuring device for measuring the phase delay caused by the phase shift film. The measuring apparatus described in Patent Document 1 is characterized in that an irradiation unit for irradiating 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 And a detection unit for detecting the signal.

In this measuring apparatus, 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 having passed through the pair of slits are diffracted and interfered with each other, and the interference fringes generated by the interference are detected by the detection unit.

Since the position of the interference fringe depends on the phase difference between the first light and the second light (in other words, the phase delay due to the phase shift film), the measurement apparatus calculates the phase difference based on the position of the interference fringe.

Japanese Laid-Open Patent Publication No. 2015-187573

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

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

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a phase difference measuring apparatus which contributes to acquisition of a parameter reflecting the phase difference of light transmitted through different refractive index areas with high accuracy.

In order to solve the above problems, a first aspect of the apparatus for measuring a phase difference according to the present invention is a phase difference measuring apparatus for measuring a phase difference between a light transmitted through a first refractive index region of a measurement object having a first refractive index region and a second refractive index region, A first slit disposed on a path of light transmitted through the first refractive index area; and a second slit arranged on a second refractive index area, And a third slit disposed on a path of light transmitted through the second refractive index region and spaced apart from each other and spaced apart from each other at a distance from the first slit, A first slit having a fourth slit, a first interference pattern caused by interference of light passing through the first slit and the second slit, And a detecting means for detecting a second interference pattern by interference of light passing through.

The second aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to the first aspect, wherein the predetermined order of the first interference fringe with respect to the position of the predetermined line of the second interference fringe And a calculation processing means for obtaining a displacement amount of the position of the bright line of the line.

A third aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to the second aspect, wherein the predetermined degree is zero.

A fourth aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to the first aspect further comprising arithmetic processing means and moving means for moving the irradiating means and the slit mask and the detecting means, Wherein the moving means moves one set of the irradiating means, the slit mask and the detecting means to each of a reference position and a measuring position, wherein the reference position is a position at which the light passing through the second refractive index region Wherein the measurement position is a position at which the light passing through the first refractive index region passes through the first slit from the irradiation means and the second slit passes through the second refractive index region from the irradiation means, Is passing through the second slit to the fourth slit, and the detecting means is a position where the light passing through the reference position A first reference interference fringe due to interference of light passing through the first slit and the second slit and a second reference interference fringe due to interference between the third slit and the light passing through the fourth slit are detected , The arithmetic processing means calculates the second interference with respect to the position of the bright line of the second reference interference fringe from the first displacement amount of the position of the bright line of the first interference fringe with respect to the position of the bright line of the first reference interference fringe The second displacement amount of the position of the line of the pattern is subtracted.

The fifth aspect of the apparatus for measuring phase difference related to the present invention is the phase difference measuring apparatus according to any one of the first to fourth aspects, wherein the length along the longitudinal direction of the first slit and the second slit is The length along the longitudinal direction of the slit and the fourth slit is longer than both.

A sixth aspect of the apparatus for measuring phase difference related to the present invention is the phase difference measuring apparatus according to any one of the first to fifth aspects, wherein a pitch between the third slit and the fourth slit Is narrower than the pitch between the second slits.

A seventh aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to any one of the first to sixth aspects, wherein the first slit and the second slit are adjacent to each other in the first direction, The third slit and the fourth slit are adjacent to each other in the first direction and the third slit is adjacent to the second slit in the second direction orthogonal to the first direction.

An eighth aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to any one of the first to seventh aspects, wherein the light passing through the first slit and the second slit, And a separation element for separating light passing through each of the fourth slits.

A ninth aspect of the phase difference measuring apparatus according to the present invention is the phase difference measuring apparatus according to any one of the first to seventh aspects, the phase difference measuring apparatus comprising an image sensor, a Fourier transform lens for forming light from the slit mask on the image sensor And arithmetic processing means for specifying, based on the peak value, whether each peak value of the intensity of light detected by the image sensor represents a bright line of the first interference fringe or the second interference fringe .

A tenth aspect of the phase difference measuring method according to the present invention is a phase difference measuring method for measuring a phase difference between a light transmitted through a first refractive index area of a measurement object having a first refractive index area and a second refractive index area and a light transmitted through the second refractive index area A first slit having a first slit and a second slit; a second slit having a first slit and a second slit; and a second slit, A first interference pattern due to interference of light, a third light having passed through the second refractive index region and the third slit, and a second interference pattern due to interference between the fourth light having passed through the second refractive index region and the fourth slit And a step of detecting the signal.

According to a tenth aspect of the phase difference measuring apparatus and the phase difference measuring method according to the present invention, the position of light and shade of the first interference fringe is determined by the phase difference between the light passing through the first slit and the second slit, (Deviation of the optical axis) of the mask and the detection means. The position of light and shade of the second interference pattern depends on the amount of shift of the optical axis. Therefore, the amount of displacement of the position of the first interference fringe with respect to the position of the bright line of the second interference fringe reflects the phase difference with high accuracy without depending on the shift of the optical axis.

As described above, the phase difference measuring apparatus can contribute to obtaining the parameter (the amount of displacement) that reflects the phase difference with high precision. Therefore, the phase difference can be calculated with high accuracy.

According to the second aspect of the apparatus for measuring phase difference related to the present invention, the amount of displacement obtained by the arithmetic processing means reflects the phase difference with high accuracy. In other words, the phase difference measuring apparatus contributes to the calculation of the phase difference with high precision.

According to the third aspect of the phase difference measuring apparatus according to the present invention, even when the pitch of the bright line of the first interference pattern and the pitch of the bright line of the second interference pattern are different from each other, the amount of displacement can be easily obtained.

According to the fourth aspect of the apparatus for measuring phase difference related to the present invention, it is possible to obtain a parameter (a value obtained by subtracting the second displacement amount from the first displacement amount) that reflects the phase difference with higher precision.

According to the fifth aspect of the apparatus for measuring phase difference related to the present invention, the difference between the intensity of the bright line of the first interference pattern and the intensity of the bright line of the second interference pattern can be reduced.

According to the sixth aspect of the apparatus for measuring phase difference related to the present invention, it is also applicable to a measurement object having a narrow second refractive index area.

According to the seventh aspect of the apparatus for measuring phase difference related to the present invention, it is also applicable to a measurement object having a narrower second refractive index area.

According to the eighth aspect of the apparatus for measuring phase difference related to the present invention, it is possible to separately detect the first interference fringe and the second interference fringe.

According to the ninth aspect of the apparatus for measuring phase difference related to the present invention, since the separation element is not required, the manufacturing cost can be reduced.

1 is a view schematically showing an example of the configuration of a phase difference measuring apparatus.
2 is a plan view schematically showing an example of the configuration of a slit mask.
3 is a flowchart showing an example of the operation of the phase difference measuring apparatus.
4 is a view schematically showing an example of an interference fringe.
5 is a diagram schematically showing an example of an interference fringe.
6 is a flowchart showing an example of the operation of the phase difference measuring apparatus.
7 is a view schematically showing an example of the configuration of a phase difference measuring apparatus at a reference position.
8 is a view schematically showing an example of an interference fringe and a reference interference fringe.
9 is a diagram schematically showing an example of an interference fringe and a reference interference fringe.
10 is a plan view schematically showing an example of the configuration of the slit mask.
11 is a plan view schematically showing an example of the configuration of the slit mask.
12 is a diagram schematically showing an example of the configuration of a phase difference measuring apparatus.

Hereinafter, embodiments will be described in detail with reference to the drawings. For the sake of easy understanding, the dimensions and numbers of the parts are exaggerated or simplified as necessary. In the drawings, parts having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted in the following description.

Fig. 1 is a view schematically showing an example of the configuration of the phase difference measuring apparatus 1. Fig. The phase difference measuring apparatus 1 is a device for measuring a phase difference of light transmitted through a measurement object 8. The measurement object 8 has a first refractive index area 8a and a second refractive index area 8b having different refractive indexes and the phase difference measuring device 1 has a first refractive index area 8a and a second refractive index area 8b, And measures the phase difference of the light transmitted through the measurement object 8 in the region 8b. Hereinafter, the first refractive index area 8a and the second refractive index area 8b are simply referred to as areas 8a and 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 used to form a pattern on a predetermined substrate (such as a semiconductor substrate or a display substrate).

The phase shift mask 80 has a plate-like shape and has regions 8a and 8b having refractive indices different from each other when viewed in a plane (that is, viewed along the thickness direction). For example, the phase shift mask 80 has a base material 81 and a phase shift film 82. The base material 81 is a substrate for supporting the phase shift film 82, and is a translucent substrate having a plate-like shape. The base material 81 is formed of a material having high transmittance (for example, quartz). On one main surface of the base material 81, a phase shift film 82 is formed in a predetermined pattern. The phase shift film 82 may also be referred to as a phase shifter. The phase shift film 82 is formed of a material having a refractive index different from that of the base material 81 and the transmittance of the phase shift film 82 is lower than that of the base material 81. The phase shift film 82 is formed by, for example, tantalum oxide.

In the phase shift mask 80 as described above, the regions where the phase shift film 82 is formed and the regions where the phase shift film 82 is not formed correspond to the regions 8a and 8b, respectively.

When light is irradiated to the regions 8a and 8b of the phase shift mask 80 in the thickness direction, for example, the light is transmitted through the phase shift mask 80 in the regions 8a and 8b. The phase shift film 82 is formed in the region 8a and the phase shift film 82 is not formed in the region 8b so that the phase of the light transmitted through the phase shift mask 80 in the region 8a Is delayed with respect to the phase of the light transmitted through the phase shift mask 80 in the region 8b. Therefore, a phase difference occurs in these lights.

Since the transmittance of the phase shift film 82 is low, the amplitude of the light transmitted through the phase shift mask 80 in the region 8b is smaller than that transmitted through the phase shift mask 80 in the region 8a. When the phase difference is 180 degrees, the light transmitted through the phase shift mask 80 in the regions 8a and 8b is weakened. Thus, the intensity of light transmitted through the region 8a has a distribution that decreases as it diffuses from the center of the region 8a, and weakens the light transmitted through the region 8b on the end side. Thereby, the contrast of the intensity can be improved in the spatial distribution of the light transmitted through the phase shift mask 80. Therefore, in the exposure processing using the phase shift mask 80, the pattern can be transferred to the substrate (semiconductor substrate, display substrate or the like) with high resolution.

<Phase difference measuring device>

<Overview>

The phase difference measuring apparatus 1 is an apparatus for measuring the phase difference. In other words, the phase difference measuring apparatus is a device for measuring the phase delay of light generated by transmitting through the region 8a. In other words, the phase difference measuring apparatus 1 is an apparatus for measuring the phase shift amount (delay) by the phase shift film 82. [

The phase difference measuring apparatus 1 has a holding portion (not shown), and the phase shift mask 80 to be measured is held by the holding portion. In the example of Fig. 1, XYZ coordinates having X, Y, and Z axes orthogonal to each other are added, and the phase shift mask 80 is held in a posture whose thickness direction is along the Z axis direction. In the example of Fig. 1, the Z-axis direction is the vertical direction. In the example of Fig. 1, the phase shift mask 80 has two phase shift films 82 formed thereon, and these two phase shift films 82 are adjacent to each other with an interval in the X axis direction.

The phase difference measuring apparatus 1 includes an irradiating unit 10, an interference fringe generating unit 20, a detecting unit 30, a moving mechanism 40 and a control unit 50. Hereinafter, the outline of these will be described first.

The irradiation unit 10 irradiates the light along the Z-axis direction and makes a part of the phase shift mask 80 enter. Part of the phase shift mask 80 includes both a portion of the region 8a and a portion of the region 8b. The interference fringe generating section 20 interferes with the light transmitted through the part of the phase shift mask 80 to generate an interference fringe. The detection unit 30 detects this interference fringe and outputs the detection result to the control unit 50. [

The control unit 50 calculates the phase difference of the light transmitted through each of the regions 8a and 8b based on the interference fringes detected by the detection unit 30. [ The control unit 50 may judge whether or not the phase difference is within a predetermined range, and when the positive judgment is made, it may be judged that a part of the phase shift mask 80 is properly manufactured. On the other hand, when it is determined that the phase difference is not within the predetermined range, the control section 50 may determine that the phase shift mask 80 is a defective product.

The moving mechanism 40 moves the irradiating unit 10, the interference fringe generating unit 20, and the detecting unit 30 in the XY plane. The moving mechanism 40 has, for example, a ball screw mechanism for the X-axis direction and a ball screw mechanism for the Y-axis direction. The moving mechanism 40 is controlled by the control unit 50.

The moving mechanism 40 can scan the entire surface of the phase shift mask 80 by moving the irradiation section 10, the interference fringe generation section 20 and the detection section 30. [ More specifically, the control unit 50 maintains the arrangement (relative position) of the irradiation unit 10, the interference fringe generation unit 20, and the detection unit 30 in the Z-axis direction, Stop. Thereby, the phase difference measuring apparatus 1 can perform the measurement with respect to a plurality of points of 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 phase shift mask 80 in its entirety. The phase shift mask 80 has, for example, a quadrangular shape when seen from the plane, and the length of the long side is, for example, several hundreds of millimeters [mm], and the length of the short side is, for example, several hundreds [mm].

On the other hand, since the moving mechanism 40 moves the optical system (one set of the irradiating unit 10, the interference fringe generating unit 20, and the detecting unit 30), the moving mechanism 40 The state of the optical axis of each optical element (described later) can be varied. Specifically, the slopes of the optical axes of the optical elements may be shifted from each other, or the axial centers of the optical axes may be shifted from each other. The shift amount may be different for each measurement position.

The position of the light and shade of the interference fringe depends on the phase difference of the light but also on the amount of shift of the optical axis. Therefore, the position of light and shade of the interference fringe can be varied due to the movement of the optical system by the moving mechanism 40. [ Therefore, when the phase difference is calculated based on the position of the interference fringes, an error caused by the shift of the optical axis occurs in the calculated value. In the present embodiment, it is envisaged to suppress such a decrease in the calculation precision.

Hereinafter, each configuration will be described in more detail.

<Investigation Department>

The irradiation unit 10 irradiates a part of the phase shift mask 80 with light. 1, the irradiating unit 10 is opposed to the phase shift mask 80 with a gap in the Z-axis direction, and the light source 11, the condenser lens 12, the band-pass filter 13, A pinhole plate 15, and a condenser lens 16, as shown in Fig.

The light source 11 irradiates light. The light source 11 is, for example, an ultraviolet ray irradiator. As this ultraviolet irradiator, for example, a mercury lamp may be employed. The irradiation / stop of the light of the light source 11 is controlled by the control unit 50.

The condenser lens 12, the band-pass filter 13, the relay lens 14, the pinhole plate 15 and the condenser lens 16 are arranged along the Z-axis direction. The light source 11 and the phase shift mask 80 ) In this order.

The condensing lens 12 is a convex lens, and its focal point is arranged so as to be located in the light source 11. [ The light emitted from the light source 11 is collimated in phase by the condenser lens 12 in the XY plane. The collimated light is incident on the band-pass filter 13. The band-pass filter 13 transmits only light having a predetermined wavelength band (transmission band) out of the parallel light. The wavelength band of the band-pass filter 13 is set to be narrow, and light of a substantially short wavelength (so-called monochromatic light) passes through the band-pass filter 13. [ The light transmitted through the band-pass filter 13 is incident on the relay lens 14.

The relay lens 14 is a convex lens and focuses the incident parallel light on 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 becomes the focal point of the relay lens 14. The light having passed through the pinhole 151 becomes substantially the light irradiated from the point light source and is incident on the condenser lens 16. [ The condenser lens 16 is a convex lens, and its focal point is disposed at a position where it becomes a pinhole 151. [ The condenser lens 16 converts the incident light into parallel light. The irradiation unit 10 irradiates this light onto a part of the phase shift mask 80 along the Z-axis direction.

The interference fringe generation section 20 is disposed on the side opposite to the irradiation section 10 with respect to the phase shift mask 80. In short, the phase shift mask 80 is held between the irradiating unit 10 and the interference fringe generating unit 20. 1, the interference fringe generating section 20 includes an objective lens 21, an image-forming lens 22, and a slit mask 23. In the example shown in Fig. The objective lens 21, the imaging lens 22, and the slit mask 23 are arranged in this order as they are separated from the phase shift mask 80 along the Z-axis direction. The light transmitted through a part of the phase shift mask 80 is expanded through the objective lens 21 and the imaging lens 22 to become parallel light and is incident on the slit mask 23. [

Fig. 2 is a plan view showing an example of the configuration of the slit mask 23. Fig. 2, the phase shift film 82 is also virtually indicated by a chain double-dashed line in order to show the optical positional relationship of the phase shift film 82 with respect to the slit mask 23.

The slit mask 23 has slits 23a to 23d. The slits 23a and 23b have an elongated shape (for example, a rectangular shape) extending in a first direction (Y-axis direction in this case) when viewed in plan view. In short, the slits 23a and 23b are parallel to each other. The slits 23a and 23b are arranged adjacent to each other in a second direction (X-axis direction in this case) perpendicular to the first direction. The slits 23c and 23d have an elongated shape extending in the Y-axis direction when viewed from the plane. In short, the slits 23a to 23d are parallel to each other. The slits 23c and 23d are arranged adjacent to each other in the X-axis direction. In the example of Fig. 1, four slits 23a to 23d are arranged in this order in the X-axis direction.

In the example of Fig. 1, the slit mask 23 has a base 231 and a light-shielding film 232. The substrate 231 is a substrate for supporting the light-shielding film 232, and is a translucent substrate having a plate-like shape. The substrate 231 is formed of a material having high transmittance (for example, quartz). The base material 231 is arranged in a posture whose thickness direction is along the Z-axis direction. On one principal surface of the base material 231, a light-shielding film 232 is formed. The light blocking film 232 is formed of a material that blocks light, and is formed, for example, by chromium. The light shielding film 232 is formed with slits 23a to 23d.

2, the slits 23a and 23b have the same length (along the Y-axis direction) and the width of the slit 23a (width along the X-axis direction) is smaller than the width of the slit 23b wide. In the example of Fig. 2, the lengths of the slits 23c and 23d are the same as each other, and their widths are the same. In short, the slits 23c and 23d have substantially the same shape. The length of the slits 23c and 23d is shorter than the length of both the slits 23a and 23b. The pitch d1 of the slits 23a and 23b is about the same as the pitch d2 of the slits 23c and 23d. The pitch referred to here is the distance between the midline of each slit. The technical significance of these will be described in detail later.

Referring to Fig. 1, light from the imaging lens 22 passes through the slits 23a to 23d. The light having passed through each of the pair of slits 23a and 23b is diffracted and interfered with each other and the light having passed through each of the pair of slits 23c and 23d is diffracted and interfered with each other.

In the example of Fig. 1, a separation element 60 for separating light passing through the slits 23a and 23b and light passing through the slits 23c and 23d, respectively, is formed. The separation element 60 is, for example, a wedge prism arranged at a position opposite to the pair of slits 23c and 23d in the Z-axis direction. 1, a light shielding film 232 is formed on one main surface (one side surface on the side of the phase shift mask 80) of the base 231 and a separation element 60 is formed on the other main surface of the base 231. [ Respectively. The traveling direction of the light that has passed through the slits 23c and 23d is bent by the separation element 60. [ Specifically, the light having passed through the slits 23c and 23d is bent by the wedge prism in the direction away from the light passing through the slits 23a and 23b. The separation element 60 changes the traveling direction to, for example, about several degrees (for example, a comma degree).

The detection unit 30 detects interference between the first interference fringe generated by interference of the light having passed through each of the pair of slits 23a and 23b and the interference of light passing through the pair of slits 23c and 23d And detects the second interference fringe. 1, the detection unit 30 is disposed on the side opposite to the phase shift mask 80 with respect to the interference fringe generation unit 20, and includes a Fourier transform lens 31 and an image sensor 32. [ The Fourier transform lens 31 and the image sensor 32 are arranged in this order as they are separated from the slit mask 23 along the Z-axis direction. Light from the slit mask 23 and the separation element 60 is imaged on the light receiving surface of the image sensor 32 via the Fourier transform lens 31. [ Thereby, the image sensor 32 can detect the first interference fringe and the second interference fringe. The image sensor 32 is, for example, a CCD sensor. The image sensor 32 outputs a detection result (for example, an image) to the control unit 50.

The control unit 50 may be an electronic circuit device, for example, a data processing device and a storage medium. The data processing apparatus may be, for example, an arithmetic processing unit such as a CPU (Central Processor Unit). The storage unit may have a non-temporary storage medium (for example, a ROM (Read Only Memory) or a hard disk) and a temporary storage medium (for example, RAM (Random Access Memory)). In the non-temporary storage medium, for example, a program for specifying a process to be executed by the control section 50 may be stored. By executing this program by the processing apparatus, the control unit 50 can execute the processing specified in the program. Of course, some or all of the processing executed by the control unit 50 may be executed by hardware.

The control unit 50 controls the moving mechanism 40. The control unit 50 obtains a parameter that does not depend on the shift of the optical axis as a parameter (described later) that reflects the phase difference, based on the positions of the first interference fringe and the second interference fringe detected by the detection unit 30. Thereby, the control section 50 can calculate the phase difference with high precision based on the parameter. Hereinafter, specific examples will be described in detail.

<Operation at the time of measurement>

Fig. 3 is a flowchart showing an example of the operation of the phase difference measuring apparatus 1. Fig. First, in step S1, the control unit 50 sets the value k to an initial value (= 1). The value k indicates the number of the plurality of measurement positions P [k].

Next, in step S2, the control unit 50 controls the moving mechanism 40 to move the irradiation unit 10, the interference fringe generation unit 20, and the detection unit 30 to the measurement position P [k]. 1, the measurement position P [k] is a position at which light from the irradiation unit 10 passes through both of a part of the region 8a of the phase shift mask 80 and a part of the region 8b More specifically, the light L1 transmitted through the region 8a (that is, the phase shift film 82) passes through the slit 23a and the region 8b (that is, the phase shift film 82 is formed The light L2 through L4 passing through the slits 23b through 23d passes through the slits 23b through 23d, respectively. In other words, at the measurement position P [k], the slit 23a is disposed on the path of the light L1 that passes through the area 8a, and the slits 23b to 23d are the light passing through the area 8b (L2 to L4).

Next, in step S3, the control unit 50 causes the irradiation unit 10 to emit light. Thereby, the light from the irradiation unit 10 passes through the slit 23a to 23d of the slit mask 23 while passing through a part of the phase shift mask 80, whereby the first interference fringe and the second interference fringe, Receiving surface of the light-receiving element 32. In step S4, the image sensor 32 outputs a detection result (e.g., an image) to the control unit 50. [

The first interference fringe is formed by the light L1 passing through the phase shift film 82 (region 8a) and the slit 23a, the region 8b other than the phase shift film 82, and the slit 23b The interference pattern is generated by the interference of the light L2 that has passed through the interference pattern. Therefore, the position of light and dark of the first interference fringe is a phase difference between the light L1 transmitted through the phase shift film 82 and the light L2 transmitted through the region 8b other than the phase shift film 82 It depends. The position of the light and dark of the first interference pattern also depends on the amount of shift of the optical axis of the optical system.

On the other hand, the second interference fringe is an interference fringe caused by interference between the light L3 passing through the region 8b and the slit 23c and the light L4 passing through the region 8b and the slit 23d It is a pattern. The phase difference between the lights L3 and L4 is ideally zero regardless of the measurement position P [k]. Therefore, the position of the light and shade of the second interference fringe does not depend on the phase difference of the lights L3 and L4, but on the amount of shift of the optical axis of the optical system.

Figs. 4 and 5 schematically show an example of the interference fringe. In the example of Fig. 4, the first interference fringe IF1 due to the interference of the lights L1 and L2 and the second interference fringe IF2 due to the interference of the lights L3 and L4 are shown. In the example of Fig. 4, the bright line of the interference fringe is schematically represented by a rectangle of a long-length image. In the example of Fig. 4, the interference fringe has odd-numbered ghost lines, and the ghost line located at the center corresponds to the 0th ghost line. In the example of Fig. 4, the interference fringe IF0 due to the interference of the light L3 and L4 in the state in which the optical axes of the respective optical systems coincide is indicated by a two-dot chain line. This interference fringe IF0 is not an interference fringe detected by the detection unit 30, but an ideal interference fringe in which the optical axes of the respective optical systems coincide with each other. Fig. 5 schematically shows an example of the intensity of light in the interference fringes (IF0 to IF2). In the example of Fig. 5, the intensities of light in the interference fringes IF0 to IF2 are superimposed.

In the example of Fig. 1, the separation element 60 bends the advancing direction of the light L3, L4 passing through the slits 23c, 23d in a direction tilted to one side in the X-axis direction in the Z-axis direction. Therefore, in the example of Fig. 1, the light L1, L2 is imaged at a position apart from the light L3, L4 on the light-receiving surface of the image sensor 32 in the X-axis direction. Accordingly, the first interference fringe IF1 and the second interference fringe IF2 are imaged at a position apart from each other in the X-axis direction on the light-receiving surface of the image sensor 32. [

However, in the example of Fig. 4, the first interference fringe IF1 and the second interference fringe IF2 are set so that the positional relationship of lightness and darkness of the first interference fringe IF1 and the second interference fringe IF2 is easy to see. Y-axis direction. Of course, it is also possible to actually image the first interference fringe IF1 and the second interference fringe IF2 at a position apart from the Y-axis direction on the light receiving surface of the image sensor 32. [ In short, the separation element 60 may bend the advancing direction of the light L3 or L4 in a direction inclined to one side in the Y-axis direction from the Z-axis direction.

The amount of displacement x1 between the position of the bright line of the interference fringe IF0 and the position of the bright line of the corresponding first interference fringe IF1 is mainly represented by the amount of displacement x0 caused by the phase difference between the lights L1 and L2 And a displacement amount x2 caused by the displacement amount of the optical axis. In short, the amount of displacement x1 is the sum of the amount of displacement x0 and the amount of displacement x2. The position of the corresponding gull line is the position of the gull line of the same order, for example, the position of the gull line of the 0th order. Therefore, the amount of displacement x1 can be also described as the amount of displacement of the position of the bright line of the predetermined order of the first interference fringe IF1 with respect to the position of the bright line of the predetermined order (for example, 0th order) of the interference fringe IF0. The same is true for other displacements. Alternatively, the gland line of the first interference fringe IF1 corresponding to a certain glow line of the interference fringe IF0 can be described as a glow line adjacent to the glow line of the interference fringe IF0 of the first fringe line.

On the other hand, the amount of displacement between the position of the bright line of the interference fringe IF0 and the position of the bright line of the corresponding interference fringe IF2 coincides with the displacement amount x2 caused by the shift of the optical axis. This is because there is almost no phase difference in the light L3 and L4 passing through the region 8b and the first interference fringe IF1 and the second interference fringe IF2 are detected by a common optical system, This is because it works in common for the first interference fringe IF1 and the second interference fringe IF2. That is, the amount of displacement caused by the displacement of the optical axis is observed in the same amount in the first interference fringe IF1 and the second interference fringe IF2.

Thus, in step S5, the control unit 50 calculates the phase difference between the light L1 and the light L2 based on the position of the bright line corresponding to the first interference fringe IF1 and the second interference fringe IF2. Specifically, the control unit 50 specifies the position of the bright line of the interference fringes IF1 and IF2 based on each pixel value (corresponding to the light intensity) of the image from the detection unit 30, (X0) between the position of the bright line of the predetermined order (for example, 0th order) of the first interference fringe IF1 and the second interference fringe IF2. Since this amount of displacement x0 is substantially independent of the amount of displacement of the optical axis different from the amount of displacement x1, it reflects the phase difference of the light L1 and L2 with high accuracy. Then, the control unit 50 calculates the phase difference based on the amount of displacement x0. The relationship between the amount of displacement (x0) and the phase difference is set in advance, and may be determined, for example, by a predetermined relational expression, simulation, or experiment. Alternatively, for example, in the same way as in Patent Document 1, the control unit 50 calculates the quotient (x0 /? X) of the first interference fringe IF1 as the denominator and the numerator as the pitch? X and the amount of displacement x0, The phase difference may be calculated.

Next, in step S6, the control unit 50 determines whether or not the value k is larger than the predetermined value kref. In short, the control unit 50 judges whether or not the measurement at all the measurement positions P [k] has ended. When negative judgment is made, in step S7, the control section 50 adds 1 to the value k and executes steps S2 to S6 again. When an affirmative determination is made in step S7, the control unit 50 ends the processing.

As described above, the control unit 50 does not depend on the position of the bright line of the first interference fringe IF1 and the phase difference between the lights L1 and L2 depending on the phase difference of the lights L1 and L2 and the shift amount of the optical axis And calculates the phase difference between the lights L1 and L2 on the basis of the position of the bright line of the second interference fringe IF2 depending on the displacement amount of the optical axis. Specifically, the control unit 50 finds the amount of displacement x0 that depends on the phase difference of the light L1 and L2, and calculates the phase difference based on the amount of displacement x0, with almost no dependence on the amount of displacement of the optical axis. Therefore, the phase difference of the lights L1 and L2 can be calculated with higher precision.

<Optical characteristics of optical system>

In the example described above, the difference in optical characteristics in each path through which the lights L1 to L4 pass is not taken into consideration. However, actually, the optical characteristics in each path may be different from each other. For example, there are aberrations in the objective lens 21 and the imaging lens 22, and their optical characteristics may be slightly different depending on each path. In this case, for example, the states (e.g., phase) of the lights L1 to L4 when they are incident on the phase shift mask 80 may be different from each other.

Since the above-described shift of the optical axis works in common for each path, it works in common to the lights (L1 to L4), but this optical characteristic may be different in each path, L1 to L4, respectively. Therefore, the difference in the optical characteristics does not act in common to the first interference fringe IF1 and the second interference fringe IF2, but acts separately on the first interference fringe IF1 and the second interference fringe IF2 do. In other words, the amount of displacement caused by the difference in optical characteristics is observed as a different value in the first interference fringe IF1 and the second interference fringe IF2.

Therefore, the amount of displacement x0 obtained by subtracting the amount of displacement x2 from the amount of displacement x1 depends not only on the amount of displacement caused by the phase difference of the light L1, L2, but also on the amount of displacement caused by the difference in optical characteristics. That is, there is room for improvement in the calculation accuracy of the phase difference. Here, it is also desired to suppress the reduction in the calculation accuracy of the phase difference caused by the difference in optical characteristics in the respective paths of the lights L1 to L4.

Fig. 6 is a flowchart showing an example of the operation of the phase difference measuring apparatus 1. Fig. First, in step S11, the control unit 50 controls the moving mechanism 40 to set the optical system (the irradiation unit 10, the interference fringe generation unit 20, and the detection unit 30) to the reference position P [0] . 7 is a view schematically showing an example of the configuration of the phase difference measuring apparatus 1 when the optical system is located at the reference position P [0]. The reference position P [0] is a position at which the light from the irradiation unit 10 passes through the region 8b of the phase shift mask 80. More specifically, the reference position P [0] L4 pass through the slits 23a to 23d, respectively.

Next, in step S12, the control unit 50 causes the irradiation unit 10 to irradiate light. (Hereinafter referred to as a first reference interference fringe IF10) caused by the interference of the light L1 and L2 which has passed through the pair of slits 23a and 23b and the pair of slits 23a and 23b, (Hereinafter referred to as a second reference interference fringe IF20) due to the interference of the light L3 and L4 that have passed through the light receiving portions 23c and 23d is imaged on the light receiving surface of the image sensor 32. [ In step S13, the image sensor 32 detects the first reference interference fringe IF10 and the second reference interference fringe IF20, and outputs the detection result (e.g., an image) to the control unit 50. [ The control unit 50 stores the position of the bright line of the first reference interference fringe IF10 and the second reference interference fringe IF20 in the storage device of the control unit 50. [

Next, the control unit 50 executes steps S14 to S16. Steps S14 to S16 are the same as steps S1, S2, and S4, respectively.

Next, in step S17, the controller 50 determines whether or not the positions of the first interference fringe IF1 and the second interference fringe IF2 detected in step S16 and the positions of the first reference interference fringe IF10 (L1, L2) at the measurement position P [k] on the basis of the position of the first reference interference fringe pattern IF20 and the position of the second reference interference fringe IF20. Hereinafter, this will be described in detail.

Figs. 8 and 9 are diagrams schematically showing an example of the first interference fringe IF1, the second interference fringe IF2, the first reference interference fringe IF10 and the second reference interference fringe IF20. 9 shows an example of the intensity of light in the first interference fringe IF1, the second interference fringe IF2, the first reference interference fringe IF10 and the second reference interference fringe IF20. The first interference fringe IF1 and the first reference interference fringe IF10 are interference fringes due to the interference of the light L1 and L2 at the measurement position P [k] and the reference position P [0], respectively. Therefore, the optical characteristics of the path through which the lights L1 and L2 pass are common to the first interference fringe IF1 and the first reference interference fringe IF10. Therefore, in the amount of displacement x10 between the position of the bright line of the first interference fringe IF1 and the position of the bright line of the corresponding first reference interference fringe IF10, the influence of the optical characteristics of the path disappears. In short, the amount of displacement x10 is hardly dependent on the optical characteristics (for example, aberration) of the path.

On the other hand, the phase difference of the lights L1 and L2 incident on the pair of slits 23a and 23b is substantially zero in the reference position P [0] (FIG. 7), while the measurement position P [k] ) Takes a value corresponding to the phase delay due to the phase shift film 82. The state of the optical axis of the optical system is different in the reference position P [0] and the measurement position P [k]. Therefore, the displacement x10 depends on the phase difference of the light L1, L2 at the measurement position P [k] and the displacement of the optical axis of the optical system.

The second interference fringe IF2 and the second reference interference fringe IF20 are interference fringes due to the interference of the light L3 and L4 at the measurement position P [k] and the reference position P [0], respectively. Therefore, the optical characteristics of the paths of the lights L3 and L4 commonly act on the second interference fringe IF2 and the second reference interference fringe IF20. Therefore, in the amount of displacement x20 between the position of the bright line of the second interference fringe IF2 and the position of the bright line of the corresponding second reference interference fringe IF20, the influence of the optical characteristics of the path disappears. In short, the amount of displacement x20 hardly depends on the optical characteristics (for example, aberration) of the path.

The retardation of the light beams L3 and L4 incident on the slits 23c and 23d is substantially equal to each other in the reference position P [0] and the measurement position P [k]. Therefore, the amount of displacement x20 depends on the amount of shift of the optical axis of the optical system, and does not depend on the phase difference of the light beams L3 and L4.

The first reference interference fringe IF10 and the second reference interference fringe IF20 are detected as a common optical system at the reference position P [0], and the first interference fringe IF1 and the second interference fringe IF2 are measured The amount of shift of the optical axis at the measurement position P [k] with respect to the reference position P [0] is detected by the first interference fringe IF1 and the second interference fringe IF2 The same amount of displacement is observed. In short, the amount of displacement x10 is the sum of the amount of displacement x0 that depends on the phase difference of light L1, L2 and the amount of displacement x20 that depends on the amount of displacement of the optical axis. Therefore, the amount of displacement x0 obtained by subtracting the amount of displacement x20 from the amount of displacement x10 reflects the phase difference of the light L1, L2 with higher precision.

The control unit 50 first obtains the amount of displacement x10 of the position of the bright line corresponding to the first interference fringe IF1 detected in step S16 and the first reference interference fringe IF10 detected in step S13, Similarly, the displacement amount x20 of the position of the bright line corresponding to the second interference fringe IF2 detected in step S16 and the second reference interference fringe IF20 detected in step S13 is found. Next, the control unit 50 obtains the amount of displacement x0 by subtracting the amount of displacement x20 from the amount of displacement x10, and obtains the phase difference between the lights L1 and L2 as described above based on the amount of displacement x0 . For example, the control unit 50 may obtain the phase difference based on the quotient and the numerator of the pitch? X and the amount of displacement x0 of the first interference fringe IF1, respectively.

Next, in step S18, the control unit 50 determines whether or not the value k is larger than the predetermined value kref. When a negative determination is made in step S18, in step S19, the control section 50 adds 1 to the value k. Next, the control unit 50 executes steps S15 to S18 again. When an affirmative determination is made in step S18, the control unit 50 ends the operation.

As described above, the control unit 50 determines whether or not the amount of displacement x10 between the gland lines corresponding to the first interference fringe IF1 and the first reference interference fringe IF10, and the amount of displacement x10 between the second interference fringe IF2 and the second reference interference fringe IF10, The phase difference is calculated based on the amount of displacement x20 between the gull lines corresponding to each other of the pattern IF20. More specifically, the control unit 50 calculates the phase difference based on the displacement amount x0 obtained by subtracting the displacement amount x20 from the displacement amount x10. Since the influence of the difference in the optical characteristics in each path of the optical system is eliminated in the displacement amounts (x10 and x20), the amount of displacement x0 is substantially independent of the difference in the optical characteristics, L2. Therefore, the phase difference can be calculated with higher accuracy.

When a plurality of phase shift masks 80 are sequentially brought into the phase difference measuring apparatus 1 according to the operation of Fig. 6, the first reference interference fringe IF10 and the second reference interference fringe IF20 Detection (steps S11 to S13) is performed for each phase shift mask 80. However, this detection does not need to be performed for each phase shift mask 80 one by one. The detection of the first reference interference fringe IF10 and the second reference interference fringe IF20 is performed only once and the detected first reference interference fringe IF10 and the second reference interference fringe IF20 are detected by a plurality of phase shift masks IF10, (80). The first reference interference fringe IF10 and the second reference interference fringe IF20 may be detected and updated for each of the N phase shift masks 80. [

<Slit mask>

&Lt; Width of slits 23a and 23b &gt;

In the phase shift mask 80, the transmittance of the phase shift film 82 is smaller than the transmittance of the base material 81. For example, the ratio of the transmittance of the phase shift film 82 to the transmittance of the base material 81 is, for example, several%. Therefore, the amount of light L1 transmitted through the region 8a becomes smaller than the light L2 transmitted through the region 8b. Therefore, the amount of light L1 incident on the slit 23a becomes smaller than the amount of light L2 incident on the slit 23b. The greater the difference in the amount of light between the lights L1 and L2, the worse the contrast of the first interference fringe IF1 caused by the interference of the lights L1 and L2.

Therefore, it is also desirable to determine the size of the slit 23a in order to improve the contrast of the first interference fringe IF1. 2, the lengths (along the longitudinal direction) of the slits 23a and 23b are the same as each other and the width of the slit 23a is wider than the width of the slit 23d . According to this, the light amount difference between the lights L1 and L2 passing through the slits 23a and 23b can be made smaller. Therefore, the contrast of the first interference fringe IF1 due to the interference of the lights L1 and L2 passing through the slits 23a and 23b can be improved.

&Lt; Lengths of slits 23a to 23d &gt;

As described above, since the transmittance of the phase shift film 82 is smaller than the transmittance of the base material 81, the amount of the light L2 through L4 passing through the region 8b is smaller than that of the light passing through the region 8a L1). Therefore, the amount of light (for example, the total amount) in the second interference fringe IF2 by the lights L3 and L4 is the sum of the amounts of light in the first interference fringe IF1 by the lights L1 and L2 (For example, the total amount). When the light amount difference between the first interference fringe IF1 and the second interference fringe IF2 is large, it is necessary to employ a sensor having a wide measurement range as the image sensor 32. [ Such a sensor is expensive.

Therefore, it is also desirable to determine the size of the slits 23a to 23d in order to reduce the light amount difference between the first interference fringe IF1 and the second interference fringe IF2. In the example of Fig. 2, the lengths of the slits 23c and 23d are equal to each other, and the length of each of the slits 23a and 23b is longer than the length of each of the slits 23c and 23d. This can reduce the amount of the light L3 and L4 passing through the slits 23c and 23d so that the difference in amount of light between the first interference fringe IF1 and the second interference fringe IF2 can be reduced . As a result, a sensor having a narrower measurement range than that of the image sensor 32 can be employed. Therefore, the cost of the image sensor 32 can be reduced.

<The pitch of the slits 23a and 23b and the pitch of the slits 23c and 23d>

10 is a plan view showing an example of the configuration of the slit mask 23. Fig. In the example of Fig. 10, the pitch d2 of the slits 23c and 23d is narrower than the pitch d1 of the slits 23a and 23b. Since the pitch of light and shade of the interference fringe is inversely proportional to the pitch of the slit, the pitch of the lightness of the second fringe pattern IF2 becomes longer than the pitch of the lightness of the first fringe pattern. However, the position of the zero-th order line of the first interference fringe IF1 and the second interference fringe IF2 does not depend on the pitch of the slits. Therefore, as described above, the control unit 50 calculates the phase difference based on the amount of displacement x0 between the zero-th order line of the first interference fringe IF1 and the second interference fringe IF2, Can be calculated.

In addition, since the pitch d2 of the slits 23c and 23d is made narrower than the pitch d1 of the slits 23a and 23b, the gap between the adjacent phase shift films 82 in the X- (p1) can be made narrower. In other words, the present phase difference measuring apparatus 1 can also be used for the phase shift mask 80 in which the gap p1 (that is, the width of the region 8b in the X-axis direction) is narrower. In other words, the phase difference measuring apparatus 1 can measure the more detailed phase shift mask 80 as well.

&Lt; Positional relation between pair of slits 23a and 23b and pair of slits 23c and 23d &gt;

In the example of Fig. 2, the slits 23a to 23d are arranged in the X-axis direction. However, it is not necessarily limited to this. For example, the pair of slits 23a and 23b may be arranged so as not to overlap the pair of slits 23c and 23d when viewed along the Y-axis direction. In other words, the pair of slits 23c and 23d may be disposed at positions displaced from the pair of slits 23a and 23b in the Y-axis direction. 11 is a plan view showing an example of the configuration of the slit mask 23. Fig.

11, the pair of slits 23a and 23b are adjacent to each other in the X-axis direction, and the pair of slits 23c and 23d are also adjacent to each other in the X-axis direction. The slits 23b and 23c are arranged adjacent to each other in the Y-axis direction.

According to this, the slits 23b and 23c are not adjacent to each other in the X-axis direction but neighbor to each other in the Y-axis direction. Therefore, the phase difference measuring apparatus 1 can also be applied to the phase shift mask 80 in which the gap p1 between the adjacent phase shift films 82 in the X-axis direction is narrower. In other words, the phase difference measuring apparatus 1 can measure the more detailed phase shift mask 80 as well.

<Separation of Interference Pattern by Algorithm>

In the example described above, the separation element 60 images the image of the first interference fringe IF1 and the second interference fringe IF2 on the image sensor 32 at a position separated from each other. However, the separation element 60 is not necessarily required. 12 is a diagram showing an example of a conceptual configuration of the phase difference measuring apparatus 1A. The phase difference measuring apparatus 1A is different from the phase difference measuring apparatus 1 in that the separating element 60 is provided. In the phase difference measuring apparatus 1A, the separation element 60 is not formed. Therefore, the first interference fringe IF1 and the second interference fringe IF2 are imaged on the image sensor 32 at the same position.

Therefore, in the image captured by the image sensor 32, the first interference fringe IF1 and the second interference fringe IF2 coexist in the same area. The control unit 50 may specify the positions of the bright lines of the first interference fringe IF1 and the second interference fringe IF2 based on the image from the image sensor 32. [ For example, since the amount of light L1, L2 having passed through the slits 23a, 23b differs from the amount of light L3, L4 passing through the slits 23c, 23d, the first interference fringes IF1 and 2 intensity of the corresponding order of the interference fringes IF2 are different from each other. Whether the intensity of the first line of the first interference fringe IF1 or the second line of the second interference fringe IF2 is high depends on the shape of the slit mask 23 in advance. Further, in general, in one interference fringe, as the degree becomes larger, the intensity of the bright line decreases. In other words, in one interference fringe, the intensity of the zero-th order ghost line is higher than the intensity of the ghost line of the other orders.

For example, the control unit 50 determines whether each peak value of the pixel value (in other words, the intensity of light) in the image indicates which of the first interference fringe IF1 and the second fringe IF2 represents the bright line Based on the peak value. For example, when the intensity of the bright line of the second interference fringe IF2 is higher than the intensity of the bright line of the first interference fringe IF1, the control unit 50 determines that the intensity The high position may be determined as the position of the zero-th order line of the second interference fringe IF2. The pitch between the bright lines of the second interference fringe IF2 is determined in advance according to the pitch between the slits 23c and 23d, the wavelength of the light, and the focal length of the Fourier transform lens 31. [ Therefore, when the position of the zero-th order line of the interference fringe IF2 is determined, the position of the line of the other orders can be estimated. For example, the control unit 50 estimates the position where the predetermined pitch is added to the position of the zero-th gaming line as the position of the primary gaming line. The control unit 50 specifies the position where the intensity takes the peak value in the vicinity of the position assumed to be the position of the primary bright line by the position of the primary bright line. The control unit 50 can specify the positions of the gland lines of other orders in the same manner.

The zero-th order line of the first interference fringe IF1 is located between the zero-th order line of the second interference fringe IF2 and the first-order (or -1st) line of sight. Thus, the control unit 50 sets the position where the intensity takes the peak value between the zero-th order line of the specific second interference fringe IF2 and the first-order (or first-order) line of sight, as the first interference fringe IF1, As the position of the zero-th line of the line. Since the pitch between the bright lines of the first interference fringe IF1 is predetermined as well, the controller 50 specifies the position of the m-th bright line of the first interference fringe IF1 in the same manner as the second interference fringe IF2 .

As described above, the control unit 50 can specify the position of the bright line of the first interference fringe IF1 and the bright line of the second interference fringe IF2. The control unit 50 obtains displacement amounts x0 of the gland lines corresponding to the first interference fringe IF1 and the second interference fringe IF2. Thus, the displacement amount x0 reflecting the phase difference with high precision can be obtained.

The controller 50 may move the optical system to the reference position P [0] and specify the position of the bright line of the first reference interference fringe IF10 and the second reference interference fringe IF20 in the same manner as described above. Then, the control unit 50 moves the optical system to the measurement position P [k] and identifies the positions of the bright lines of the first interference fringe IF1 and the second interference fringe IF2 in the same manner as described above. The control unit 50 calculates the amount of displacement x0 (x0) as described above based on the first interference fringe IF1, the second interference fringe IF2, the first reference interference fringe IF10 and the second reference interference fringe IF20, ). Thereby, the displacement amount x0 reflecting the phase difference with higher accuracy can be obtained.

In the above-described example, the phase shift mask 80 is exemplified as the measurement object 8, but it is not necessarily limited thereto. In other words, the phase difference measuring apparatus 1 can measure the phase difference of the light passing through the different refractive index areas with respect to the measurement object 8 having the refractive index distribution. As another example of the measurement object 8, mineral or the like is exemplified.

As described above, the substrate holding apparatus and the substrate processing apparatus have been described in detail, but the above description is an example in all aspects, and the disclosure is not limited thereto. The above-described various modifications may be applied in combination as long as they do not contradict each other. It is to be understood that many modifications, which are not illustrated, can be made without departing from the scope of this disclosure.

1: phase difference measuring device
8: Measurement object
8a: first refractive index area
8b: the second refractive index area
10: Investigation means (Investigation section)
23: Slit mask
23a: a first slit (slit)
23b: the second slit (slit)
23c: third slit (slit)
23d: fourth slit (slit)
30: Detection means (detection section)
31: Fourier transform lens
32: Image sensor
40:
50: operation processing means (control section)
60:
IF1: first interference pattern (interference pattern)
IF2: second interference pattern (interference pattern)
IF10: First reference interference fringe (reference interference fringe)
IF20: second reference interference fringe (reference interference fringe)
P [0]: Reference position
P [k]: Measurement position

Claims (10)

A phase difference measuring apparatus for measuring a phase difference between light transmitted through a 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,
Irradiating means for irradiating the measurement object with light,
A first slit disposed on a path of light passing through the first refractive index region and a second slit disposed on a path of light passing through the second refractive index region and adjacent to the first slit with an interval therebetween; A slit mask disposed on the path of the light transmitted through the second refractive index region and having third and fourth slits adjacent to each other with an interval therebetween,
A first interference fringe caused by interference of light passing through each of the first slit and the second slit and a second interference fringe due to interference of light passing through the third slit and the fourth slit, And the phase difference measuring device. The method according to claim 1,
Further comprising arithmetic processing means for obtaining a displacement amount of a position of a bright line of the predetermined order of the first interference fringe with respect to a position of a predetermined line of the second interference fringe. 3. The method of claim 2,
And the predetermined order is zero degree. The method according to claim 1,
An arithmetic processing means,
Further comprising moving means for moving said irradiating means, said slit mask and said detecting means,
The moving means moves one set of the irradiating means, the slit mask and the detecting means to each of the reference position and the measuring position,
Wherein the reference position is a position at which light passing through the second refractive index area from the irradiation means passes through the first slit to the fourth slit,
Wherein the measurement position is a position in which light passing through the first refractive index region from the irradiation means passes through the first slit and light passing through the second refractive index region from the irradiation means passes through the second slit Lt; / RTI &gt;
Wherein the detection means detects the first reference interference fringe due to the interference of the light passing through the first slit and the second slit at the reference position and the second reference interference fringe due to the interference of the light passing through the third slit and the fourth slit Detecting a second reference interference fringe,
The arithmetic processing means calculates the second interference fringe pattern from the first displacement amount of the position of the bright line of the first interference fringe to the position of the bright line of the first reference interference fringe, And the second displacement amount of the position of the bright line in the second image. 5. The method according to any one of claims 1 to 4,
The length along the longitudinal direction of the first slit and the length of the second slit is longer than the length along the longitudinal direction of the third slit and the fourth slit. 5. The method according to any one of claims 1 to 4,
And the pitch between the third slit and the fourth slit is narrower than the pitch between the first slit and the second slit. 5. The method according to any one of claims 1 to 4,
Wherein the first slit and the second slit are adjacent to each other in the first direction, the third slit and the fourth slit are adjacent to each other in the first direction, and the third slit is adjacent to the second slit and the second slit, And is adjacent in a second direction orthogonal to the first direction. 5. The method according to any one of claims 1 to 4,
Further comprising a separation element for separating light passing through each of the first slit and the second slit and light passing through the third slit and the fourth slit, respectively. 5. The method according to any one of claims 1 to 4,
An image sensor,
A Fourier transform lens for forming light from the slit mask on the image sensor,
And arithmetic processing means for specifying, based on the peak value, which peak value of the intensity of the light detected by the image sensor represents the bright line of the first interference fringe or the second interference fringe, Measuring device. A phase difference measuring method for measuring a phase difference between light transmitted through a 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 step of irradiating the measurement object with light;
A first interference pattern due to interference between the first light having passed through the first refractive index region and the first slit, the second light having passed through the second refractive index region and the second slit, and a second interference pattern caused by interference between the second refractive index region and the third slit And a second interference fringe caused by interference between the third light having passed through the fourth slit and the fourth light having passed through the second slit and the second refractive index region.

Images