KR102045680B1 - Phase difference measuring apparatus and phase difference measuring method - Google Patents

Abstract

(Problem) Provided is a phase difference measuring apparatus that contributes to acquisition of a parameter in which the phase difference of light passing through different refractive index regions is accurately reflected.
(Remedy means) The phase difference measuring apparatus 1 includes an irradiation means 10, a slit mask 23, and a detection means 30. The irradiation means 10 irradiates light to the measurement object 8. The slit mask 23 has slits 23a to 23d. The slit 23a is disposed on a path of light passing through the first refractive index region 8a. The slits 23b are disposed on a path of light passing through the second refractive index region 8b and are adjacent to the slits 23a at intervals. The slits 23c and 23d are respectively disposed on the paths of light transmitted through the second refractive index region 8b, and are adjacent to each other at intervals. The detection means 30 detects the 1st interference fringe by the interference of the light which passed through the slit 23a, 23b, respectively, and the 2nd interference fringe by the interference of the light which respectively passed through the slit 23c, 23d.

Description

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

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

In recent years, a phase shift mask is used to transfer a pattern with high resolution with respect to a board | substrate, such as a semiconductor substrate or a board | substrate for display displays. In this phase shift mask, the phase shift film which delays the phase of light only half wavelength is formed.

Patent document 1 is disclosed as a measuring apparatus which measures the delay of the phase by this phase shift film. The measuring device described in Patent Literature 1 includes an irradiation part for irradiating light to a phase shift mask (a phase difference mask in Patent Literature 1), a slit mask having a pair of slits, and an interference fringe by light passing through the pair of slits. It is provided with the detection part which detects.

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 passes through the other slit at a position adjacent to the phase shift film. The first light and the second light passing through the pair of slits are diffracted to interfere with each other, and the interference fringe generated by the interference is 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 delay of the phase by the phase shift film), the measuring device calculates the phase difference based on the position of the interference fringe.

Japanese Unexamined 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 (one set of irradiation unit, slit mask and detection unit) with respect to the phase shift mask, the optical system can scan the entire surface of the phase shift mask and measure at each measurement position.

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

Then, an object of this invention is to provide the phase difference measuring apparatus which contributes to acquisition of the parameter which reflected the phase difference of the light which permeate | transmits a different refractive index area with high precision.

In order to solve the said subject, the 1st aspect of the phase difference measuring apparatus which concerns on this invention is the light which permeate | transmitted the said 1st refractive index area | region of the measurement object which has a 1st refractive index area | region and a 2nd refractive index area | region, and the said 2nd refractive index area | region A phase difference measuring device for measuring a phase difference between light transmitted through a light source, comprising: irradiation means for irradiating light to the measurement object, a first slit disposed on a path of light passing through the first refractive index area, and a second refractive index area A second slit disposed on a path of light that transmits light and is adjacent to the first slit at intervals, and a third slit that is disposed on a path of light transmitted through the second refractive index area and adjacent to each other, and A slit mask having a fourth slit, a first interference fringe caused by interference of light passing through the first slit and the second slit, and the third slit and the fourth slit, respectively. And a detecting means for detecting a second interference pattern by interference of light passing through.

A second aspect of the phase difference measuring apparatus according to the present invention is a phase difference measuring apparatus according to the first aspect, wherein the predetermined degree of the first interference fringe is relative to a position of a bright line of a predetermined degree of the second interference fringe. It further comprises arithmetic processing means for calculating the displacement amount of the position of the bright line.

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

A fourth aspect of the phase difference measuring device according to the present invention is a phase difference measuring device according to the first aspect, further comprising: arithmetic processing means, moving means for moving the irradiation means, the slit mask, and the detection means; The moving means moves the set of the irradiation means, the slit mask and the detection means to each of a reference position and a measurement position, wherein the reference position is such that light passing from the irradiation means through the second refractive index region is A position passing through the first slit to the fourth slit, and in the measurement position, light passing through the first refractive index region from the irradiation means passes through the first slit, and from the irradiation means, the second refractive index region Light passing through the light passes through the second to fourth slits, and the detection means is the reference position. Wherein the first reference interference fringe is detected by interference of light passing through the first slit and the second slit, and the second reference interference fringe is detected by interference of light passing through the third slit and the fourth slit. And the arithmetic processing means performs 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 at the position of the bright line of the pattern is subtracted.

A fifth aspect of the phase difference measuring device according to the present invention is the phase difference measuring device according to any one of the first to fourth aspects, wherein a length along the longitudinal direction of the first slit and the second slit is the third. It is longer than both the slit and the length along the longitudinal direction of the said fourth slit.

A sixth aspect of the phase difference measuring device according to the present invention is the phase difference measuring device according to any one of the first to fifth aspects, wherein a pitch between the third slit and the fourth slit is the first slit and the above. Narrower than the pitch between the second slits.

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

An eighth aspect of the phase difference measuring apparatus according to the present invention is a phase difference measuring apparatus according to any one of the first to seventh aspects, wherein the light passes through the first slit and the second slit, respectively, and the third slit. And a separating element that separates the light passing through the fourth slit, respectively.

A ninth aspect of the phase difference measuring device according to the present invention is a phase difference measuring device according to any one of the first to seventh aspects, wherein the image sensor and a Fourier transform lens for forming light from the slit mask into the image sensor And arithmetic processing means for specifying, based on the peak value, each peak value of the intensity of light detected by the image sensor indicates which of the bright lines of the first and second interference fringes. .

A tenth aspect of the phase difference measuring method according to the present invention is a 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 phase difference measuring method for measuring a light source, the method comprising: irradiating light to the measurement object, first light passing through the first refractive index region and the first slit, and second passing through the second refractive index region and the second slit. A second interference fringe caused by interference of a first interference fringe due to interference of light, a third light passing through the second refractive index region and a third slit, and a fourth light passing through the second refractive index region and a fourth slit; The process of detecting is provided.

According to the 1st aspect of the phase difference measuring apparatus which concerns on this invention, and the 10th aspect of the phase difference measuring method, the position of the contrast of a 1st interference fringe is the phase difference of the light which respectively passed the 1st slit and the 2nd slit, irradiation means, a slit It depends on the deviation of the mask and the detection means (deviation of the optical axis). The position of the contrast of the second interference fringe depends on the amount of deviation 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 almost does not depend on the deviation of the optical axis, and reflects the phase difference with high precision.

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

According to the 2nd aspect of the phase difference measuring apparatus which concerns on this invention, the displacement amount calculated | required by arithmetic processing means reflects a phase difference with high precision. In short, the phase difference measuring device contributes to the calculation of the phase difference with high precision.

According to the 3rd aspect of the phase difference measuring apparatus which concerns on this invention, even if the pitch of the bright line of a 1st interference fringe and the pitch of the bright line of a 2nd interference fringe are mutually different, it is easy to calculate the displacement amount.

According to the 4th aspect of the phase difference measuring apparatus which concerns on this invention, the parameter (value which subtracted the 2nd displacement amount from the 1st displacement amount) which reflects a phase difference with higher precision can be obtained.

According to the 5th aspect of the phase difference measuring apparatus which concerns on this invention, the difference of the intensity | strength of the bright line of a 1st interference fringe, and the intensity of the bright line of a 2nd interference fringe can be reduced.

According to the 6th aspect of the phase difference measuring apparatus which concerns on this invention, it is applicable also to the measurement object with a narrow width | variety of a 2nd refractive index area | region.

According to the 7th aspect of the phase difference measuring apparatus which concerns on this invention, it is applicable also to the measurement object whose width | variety of a 2nd refractive index area | region is narrower.

According to the 8th aspect of the phase difference measuring apparatus which concerns on this invention, a 1st interference fringe and a 2nd interference fringe can be isolate | separated and detected.

According to the 9th aspect of the phase difference measuring apparatus which concerns on this invention, since a separate element is not needed, manufacturing cost can be reduced.

1 is a diagram 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 diagram 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.
It is a figure which shows roughly an example of the structure of the phase difference measuring apparatus in a reference position.
8 is a diagram 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 illustrating an example of a configuration of a slit mask.
11 is a plan view schematically illustrating an example of a configuration of a slit mask.
It is a figure which shows schematically an example of a structure of a phase difference measuring apparatus.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment is described in detail, referring drawings. In order to facilitate understanding, the dimensions and numbers of the parts are exaggerated or simplified as necessary. In addition, in the figure, the same code | symbol is attached | subjected about the part which has the same structure and function, and the overlapping description is abbreviate | omitted in the following description.

1 is a diagram schematically showing an example of the configuration of the phase difference measuring apparatus 1. This retardation measuring device 1 is a device for measuring the retardation of light transmitted through the measurement target 8. This measurement object 8 has the 1st refractive index area | region 8a and the 2nd refractive index area | region 8b from which refractive indices differ, and the phase difference measuring apparatus 1 is the 1st refractive index area | region 8a and the 2nd refractive index, respectively. In the region 8b, the phase difference of the light transmitted through the measurement target 8 is measured. In the following, the first refractive index region 8a and the second refractive index region 8b are simply referred to as regions 8a and 8b, respectively.

<Measurement object>

First, an example of the measurement object 8 is explained in full detail. The measurement object 8 is a phase shift mask 80, for example. The phase shift mask 80 is a kind of photomask and is used to form a pattern on a predetermined substrate (semiconductor substrate or display substrate).

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

In such a phase shift mask 80, the area | region in which the phase shift film 82 was formed, and the area | region in which the phase shift film 82 was not formed are corresponded to the area | regions 8a and 8b, respectively.

When light is irradiated to the area | region 8a, 8b of the phase shift mask 80, for example in the thickness direction, light passes through the phase shift mask 80 in each area | region 8a, 8b. Since the phase shift film 82 is formed in the area | region 8a, and the phase shift film 82 is not formed in the area | region 8b, the phase of the light which permeate | transmitted the phase shift mask 80 in the area | region 8a is carried out. 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 arises 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 the light 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 areas 8a and 8b is weakened. Therefore, 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 each other with the light transmitted through the region 8b on the end side thereof. Thereby, the contrast of the intensity | strength can be improved in the spatial distribution of the light which permeate | transmitted the phase shift mask 80. FIG. Therefore, in the exposure process using the phase shift mask 80, a pattern can be transferred to a board | substrate (semiconductor board | substrate, a board | substrate for display, etc.) with high resolution.

<Phase difference measuring device>

<Summary>

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

The phase difference measuring apparatus 1 has the holding part which illustration is abbreviate | omitted, and the phase shift mask 80 used as a measurement object is hold | maintained by this holding part. In the example of FIG. 1, the XYZ coordinate which has the X-axis, Y-axis, and Z-axis orthogonal to each other is added, and the phase shift mask 80 is hold | maintained in the attitude | position along the Z-axis direction. In the example of FIG. 1, the Z axis direction is a vertical direction. In the example of FIG. 1, two phase shift films 82 are formed in the phase shift mask 80, and these two phase shift films 82 are adjacent at intervals in the X axis direction.

The phase difference measuring apparatus 1 is provided with the irradiation part 10, the interference fringe generation part 20, the detection part 30, the moving mechanism 40, and the control part 50. As shown in FIG. Below, these outline | summary is demonstrated first.

The irradiation unit 10 irradiates light along the Z axis direction and enters a part of the phase shift mask 80. The said part of phase shift mask 80 contains both a part of area | region 8a and a part of area | region 8b. The interference fringe generating unit 20 interferes with light transmitted through the part of the phase shift mask 80 to each other 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 part 50 calculates the phase difference of the light which permeate | transmitted the area | regions 8a and 8b based on the interference fringe detected by the detection part 30, respectively. The controller 50 determines whether the phase difference is within a predetermined range, and when affirmative determination is made, the part of the phase shift mask 80 may be determined to be appropriately manufactured. On the other hand, when the control part 50 judges that a phase difference does not exist in a predetermined range, you may judge that the phase shift mask 80 is a defective article.

The moving mechanism 40 moves the irradiation part 10, the interference fringe generation part 20, and the detection part 30 in an XY plane. The moving mechanism 40 has, for example, a ball screw mechanism in the X axis direction, a ball screw mechanism in the Y axis direction, and the like. This moving mechanism 40 is controlled by the controller 50.

The moving mechanism 40 can scan the whole surface of the phase shift mask 80 by moving the irradiation part 10, the interference fringe generation part 20, and the detection part 30. FIG. Specifically, the control unit 50 maintains the alignment (relative position) in the Z axis direction of the irradiation unit 10, the interference fringe generation unit 20, and the detection unit 30, and at the respective measurement positions. Stop it. Thereby, the phase difference measuring apparatus 1 can measure a some point of the phase shift mask 80. FIG.

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 whole surface. The phase shift mask 80 has a rectangular shape, for example in plan view, the length of the long side is, for example, several thousand [mm], and the length of the short side is, for example, several hundred [mm].

On the other hand, since the moving mechanism 40 moves the optical system (one set of the irradiating portion 10, the interference fringe generating portion 20, and the detecting portion 30), the moving mechanism 40 belongs to the optical system due to the inertial force or the like accompanying the movement. The state of the optical axis of each optical element (described later) may vary. Specifically, the inclination of the optical axis of each optical element may shift | deviate from each other, or the axis of an optical axis may mutually shift | deviate. The amount of deviation may be different for each measurement position.

The position of the contrast of the interference fringe depends on the phase difference of the light, but also on the amount of deviation of the optical axis. Therefore, due to the movement of the optical system by the moving mechanism 40, the position of the contrast of the interference fringe can be varied. Therefore, when the phase difference is calculated based on the position of the interference fringe, an error caused by the deviation of the optical axis occurs in the calculated value. In this embodiment, suppression of such a fall of calculation precision is also prayed.

Hereinafter, each structure is demonstrated more concretely.

<Irradiation department>

The irradiation unit 10 irradiates a part of the phase shift mask 80 with light. In the example of FIG. 1, the irradiation unit 10 faces the phase shift mask 80 at intervals in the Z axis direction, and the light source 11, the condenser lens 12, the band pass filter 13, and the relay lens are opposed to each other. 14, the pinhole plate 15, and the condenser lens 16 are provided.

The light source 11 irradiates light. The light source 11 is an ultraviolet irradiator, for example. As this ultraviolet irradiator, a mercury lamp can be employ | adopted, for example. Irradiation / stop of the light of the light source 11 is controlled by the control part 50.

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

The condenser lens 12 is a convex lens, and is disposed so that its focus is located on the light source 11. The light irradiated from the light source 11 becomes parallel light in which phases are aligned in the XY plane by the condenser lens 12, and the parallel light is incident on the band pass filter 13. The band pass filter 13 transmits only light having a predetermined wavelength band (transmission band) among the parallel lights. The wavelength band of the band pass filter 13 is set narrow, and substantially short wavelength light (so-called monochromatic light) passes through the band pass filter 13. Light passing 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 the thickness direction. The pinhole plate 15 is disposed at a position where the pinhole 151 is the focal point of the relay lens 14. Light passing through the pinhole 151 becomes light irradiated from the point light source substantially and is incident on the condenser lens 16. The condenser lens 16 is a convex lens, and is disposed at a position at which the focal point becomes the pinhole 151. The condenser lens 16 converts the incident light into parallel light. The irradiation unit 10 irradiates this light to a part of the phase shift mask 80 along the Z axis direction.

The interference fringe generator 20 is disposed on the side opposite to the irradiator 10 with respect to the phase shift mask 80. In other words, the phase shift mask 80 is held between the irradiating portion 10 and the interference fringe generating portion 20. In the example of FIG. 1, the interference fringe generator 20 includes an objective lens 21, an imaging lens 22, and a slit mask 23. The objective lens 21, the imaging lens 22, and the slit mask 23 are arranged in this order as they fall from the phase shift mask 80 along the Z axis direction. The light transmitted through the part of the phase shift mask 80 is enlarged through the objective lens 21 and the imaging lens 22 to become parallel light, and is incident on the slit mask 23.

2 is a plan view illustrating an example of a configuration of the slit mask 23. In addition, in FIG. 2, in order to show the optical positional relationship of the phase shift film | membrane 82 with respect to the slit mask 23, the phase shift film | membrane 82 is also shown by virtually double-dotted line.

The slit mask 23 has slits 23a to 23d. The slits 23a and 23b have a long shape (for example, a rectangle) extending in the first direction (here, the Y axis direction) when viewed in a plan view. In short, the slits 23a and 23b are parallel to each other. The slits 23a and 23b are arranged next to each other in a second direction (here, the X axis direction) orthogonal to the first direction. The slits 23c and 23d have a long shape extending in the Y axis direction when viewed in a plan view. In short, the slits 23a to 23d are parallel to each other. The slits 23c and 23d are arranged next 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 substrate 231 and a light shielding film 232. The base material 231 is a substrate for supporting the light shielding film 232, and is a light-transmissive substrate having a plate shape. The substrate 231 is formed of a material having high transmittance (for example, quartz). The base material 231 is arrange | positioned at the posture along the Z axis direction in the thickness direction. The light shielding film 232 is formed in one main surface of the base material 231. The light shielding film 232 is formed of a material that blocks light, and is formed of, for example, chromium. Slits 23a to 23d are formed in the light shielding film 232.

In the example of FIG. 2, the lengths (lengths along the Y axis direction) of the slits 23a and 23b are about the same, and the widths (widths along the X axis direction) of the slits 23a are larger than the widths of the slits 23b. wide. In the example of FIG. 2, the lengths of the slits 23c and 23d are about the same as each other, and the widths are also about the same as each other. In short, the slits 23c and 23d have substantially the same shape. The lengths of the slits 23c and 23d are shorter than the lengths 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. In addition, the pitch here is the distance between connecting the midline of each slit. These technical meanings are described in detail later.

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

In the example of FIG. 1, the separating element 60 which isolate | separates the light which passed through the slit 23a, 23b, respectively, and the light which passed through the slit 23c, 23d, from each other is formed. The separating element 60 is, for example, a wedge prism and is disposed at a position opposite to the pair of slits 23c and 23d in the Z axis direction. In the example of FIG. 1, the light shielding film 232 is formed in one main surface (one main surface of the phase shift mask 80 side) of the base material 231, and the separation element 60 is provided in the other main surface of the base material 231. Is arranged. The traveling direction of the light passing through the slits 23c and 23d, respectively, is bent by the separating element 60. Specifically, the light passing through the slits 23c and 23d is bent by the wedge prism in a direction away from the light passing through the slits 23a and 23b. The separating element 60 changes the advancing direction to about a few degrees (for example, comma number), for example.

The detection unit 30 generates the first interference fringe generated by the interference of light passing through the pair of slits 23a and 23b, respectively, and the interference generated by the light passing through the pair of slits 23c and 23d, respectively. The second interference fringe is detected. In the example of FIG. 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 fall away from the slit mask 23 along the Z axis direction. Light from the slit mask 23 and the separating 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 a 1st interference fringe and a 2nd interference fringe. The image sensor 32 is a CCD sensor, for example. The image sensor 32 outputs the detection result (for example, image) to the control part 50.

The control part 50 may have a data processing apparatus and a storage medium as an electronic circuit device, for example. The data processing device may be, for example, an arithmetic processing device such as a central processor unit (CPU). The storage unit may have a non-transitory storage medium (for example, a ROM (Read Only Memory) or a hard disk) and a temporary storage medium (for example, a random access memory (RAM)). In the non-transitory storage medium, for example, a program that defines a process to be executed by the control unit 50 may be stored. By the processor executing this program, the control unit 50 can execute the processing prescribed in the program. Of course, some or all of the processing executed by the controller 50 may be executed by hardware.

The control unit 50 controls the moving mechanism 40. Moreover, the control part 50 calculates | requires the parameter which does not depend well on an optical axis shift as a parameter (after-mentioned) which reflected the phase difference based on the position of the 1st interference fringe and the 2nd interference fringe detected by the detection part 30. FIG. Thereby, the control part 50 can calculate a phase difference with high precision based on the said parameter. A specific example is explained in full detail below.

<Operation at the time of a measurement>

3 is a flowchart showing an example of the operation of the phase difference measuring apparatus 1. First, in step S1, the control part 50 sets the value k to an initial value (= 1). This value k shows the number of several measuring position P [k].

Next, in step S2, the control part 50 controls the moving mechanism 40, and moves the irradiation part 10, the interference fringe generation part 20, and the detection part 30 to the measurement position P [k]. This measurement position P [k] is a position which the light from the irradiation part 10 transmits both part of the area | region 8a of the phase shift mask 80, and a part of area | region 8b with reference to FIG. More specifically, the light L1 transmitted through the region 8a (ie, the phase shift film 82) passes through the slit 23a, and the region 8b (ie, the phase shift film 82 is not formed). The light L2 through L4 that have passed through the unlit regions pass through the slits 23b to 23d, respectively. In other words, in the measurement position P [k], the slit 23a is arrange | positioned on the path | route of the light L1 which permeate | transmits the area | region 8a, and the slit 23b-23d is the light which permeate | transmits the area | region 8b. It is arrange | positioned on the path | route of L2-L4, respectively.

Next, in step S3, the control part 50 irradiates the irradiation part 10 with light. As a result, the first interference fringe and the second interference fringe pass through the slits 23a to 23d of the slit mask 23 while the light from the irradiating portion 10 passes through a part of the phase shift mask 80. It forms in the light receiving surface of (32). In step S4, the image sensor 32 outputs the detection result (for example, image) to the control unit 50.

By the way, the 1st interference fringe is the light L1 which passed the phase shift film 82 (region 8a) and the slit 23a, the area | region 8b other than the phase shift film 82, and the slit 23b. ) Is an interference fringe generated by interference of light L2 passing through Therefore, the position of the contrast of the first interference fringe is determined by the 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. Depends. The position of the contrast of the first interference fringe also depends on the amount of deviation of the optical axis of the optical system.

On the other hand, the second interference fringe is interference generated by interference of light L3 passing through the region 8b and the slit 23c and 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 contrast of the second interference fringe does not depend on the phase difference between the lights L3 and L4, but depends on the amount of shift of the optical axis of the optical system.

4 and 5 schematically show an example of an 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 typically shown by the long rectangle. In the example of FIG. 4, the interference fringe has an odd number of bright lines, and the bright line located in the center corresponds to the 0th bright line. In addition, in the example of FIG. 4, the interference fringe IF0 by the interference of the lights L3 and L4 in the state where the optical axis of each optical system was coincided is shown by the dashed-dotted 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. 5 schematically shows an example of the intensity of light in the interference fringes IF0 to IF2. In the example of FIG. 5, the intensity of light in the interference fringes IF0 to IF2 is shown overlapping.

In the example of FIG. 1, the separating element 60 bends the traveling direction of the lights L3 and L4 that have passed through the slits 23c and 23d in a direction inclined to one side of the X-axis direction from the Z-axis direction. Therefore, in the example of FIG. 1, the lights L1 and L2 are formed at positions separated from the light L3 and L4 in the X axis direction on the light receiving surface of the image sensor 32. Therefore, the first interference fringe IF1 and the second interference fringe IF2 are imaged at positions apart in the X-axis direction on the light receiving surface of the image sensor 32.

However, in the example of FIG. 4, in order to make it easier to see the positional relationship between the contrasts of the first and second interference fringes IF1 and IF2, the first and second interference fringes IF1 and IF2 are arranged. It is shown in the position away in the Y-axis direction. Of course, you may actually form the 1st interference fringe IF2 and the 2nd interference fringe IF2 in the position which fell to the Y-axis direction in the light receiving surface of the image sensor 32. As shown in FIG. That is, the separating element 60 may bend the advancing direction of the lights L3 and L4 in the direction inclined to one side of the Y-axis direction from the Z-axis direction.

By the way, in the displacement amount 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, the displacement amount x0 mainly caused by the phase difference between the lights L1 and L2. ) And the displacement amount x2 caused by the displacement amount of the optical axis. In other words, the displacement amount x1 is the sum of the displacement amount x0 and the displacement amount x2. In addition, the position of a corresponding bright line is a position of the bright line of the same order, for example, it is a position of the 0th bright line. Therefore, the displacement amount x1 can also be described as the displacement amount of the position of the bright line of the predetermined order of the 1st 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 applies to other displacement amounts. Or the bright line of the 1st interference fringe IF1 corresponding to the bright line of the interference fringe IF0 can also be described as the bright line which adjoins the bright line of the interference fringe IF0 among the bright lines of a 1st interference fringe.

On the other hand, the displacement amount 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 deviation of the optical axis. This is because there is almost no phase difference in the lights L3 and L4 passing through the region 8b, and since the first interference fringe IF2 and the second interference fringe IF2 are detected by a common optical system, the optical axis shifts. This is because the first interference fringe IF1 and the second interference fringe IF2 act in common. In other words, it is because the amount of displacement caused by the deviation of the optical axis is observed in the same amount in the first interference pattern IF1 and the second interference pattern IF2.

So, in step S5, the control part 50 calculates the phase difference of the lights L1 and L2 based on the position of the bright line corresponding to each other of the 1st interference fringe IF1 and the 2nd interference fringe IF2. Specifically, the control part 50 specifies the position of the bright line of the interference fringes IF1 and IF2 based on each pixel value (equivalent to the intensity of light) of the image from the detection part 30, and this 1st interference fringe The displacement amount x0 between the position of the bright line of the predetermined order (for example, 0th order) of the IF1 and the second interference fringe IF2 is obtained. Since the displacement amount x0 hardly depends on the displacement amount of the optical axis differently from the displacement amount x1, the displacement amount x0 reflects the phase difference between the lights L1 and L2 with high accuracy. And the control part 50 calculates a phase difference based on this displacement amount x0. The relationship between the displacement amount x0 and the phase difference is set in advance, and may be determined by, for example, a predetermined relationship, simulation or experiment. Or, for example, similarly to patent document 1, the control part 50 has the quotient (x0 / deltax) which made the pitch (DELTA) x and the displacement amount (x0) between the bright lines of the 1st interference fringe (IF1) into denominator and a molecule, respectively. You may calculate a phase difference based on.

Next, in step S6, the control part 50 determines whether the value k is larger than the predetermined value kref. In short, the control part 50 determines whether the measurement in all the measurement positions P [k] is complete | finished. If a negative judgment is made, in step S7, the controller 50 adds 1 to the value k, and executes steps S2 to S6 again. If affirmative judgment is made in step S7, the control part 50 complete | finishes a process.

As mentioned above, the control part 50 does not depend on the position of the bright line of the 1st interference fringe IF1 which depended on the phase difference of the light L1, L2, and the optical axis shift | deviation, and the phase difference of the light L1, L2. Instead, the phase difference between the lights L1 and L2 is calculated based on the position of the bright lines of the second interference fringe IF2 depending on the amount of displacement of the optical axis. Specifically, the control part 50 obtains the displacement amount x0 which depended on the phase difference of the light L1, L2 hardly dependent on the shift amount of an optical axis, and calculates a phase difference based on this displacement amount x0. Therefore, the phase difference of the lights L1 and L2 can be calculated with higher precision.

<Optical characteristics of the optical system>

In the above-mentioned example, the difference of the optical characteristic in each path | route which light L1-L4 passes is not considered. In reality, however, optical characteristics in 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 slightly differ along each path. In this case, for example, states (for example, phases) of the lights L1 to L4 at the time of being incident on the phase shift mask 80 may be different from each other.

Since the above-described misalignment of the optical axes acts in common for each path, it works in common for the lights L1 to L4. However, since the optical properties may be different in each path, the difference in the optical properties is different from the light ( L1 to L4) act individually. Therefore, the difference in the optical characteristics does not act in common with the first interference fringe IF2 and the second interference fringe IF2, but acts separately for the first interference fringe IF1 and the second interference fringe IF2. do. In short, the amount of displacement resulting from the difference in the optical properties is observed at different values in the first interference fringe IF1 and the second interference fringe IF2.

Therefore, the displacement amount x0 obtained by subtracting the displacement amount x2 from the displacement amount x1 depends not only on the displacement amount caused by the phase difference between the lights L1 and L2 but also on the displacement amount caused by the difference in the optical characteristics. In short, there is room for improvement in the calculation accuracy of the phase difference. In this case, it is also intended to suppress a decrease in the calculation accuracy of the phase difference caused by the difference in the optical characteristics in the respective paths of the lights L1 to L4.

6 is a flowchart showing an example of the operation of the phase difference measuring apparatus 1. First, in step S11, the control unit 50 controls the moving mechanism 40 to set the optical system (one set of the irradiating unit 10, the interference fringe generating unit 20, and the detecting unit 30) to the reference position P [0]. Move it. 7 is a diagram 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]. This reference position P [0] is a position at which the light from the irradiation section 10 passes through the region 8b of the phase shift mask 80, and more specifically, the light L1 through the region 8b. L4) is a position passing through the slits 23a to 23d, respectively.

Next, in step S12, the control part 50 irradiates the irradiation part 10 with light. By the irradiation of this light, an interference fringe (hereinafter referred to as a first reference interference fringe IF10) and an pair of slits caused by interference of the lights L1 and L2 passing through the pair of slits 23a and 23b. An interference fringe (hereinafter referred to as a second reference interference fringe IF20) due to the interference of the lights L3 and L4 passing through the 23c and 23d is formed 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 (for example, an image) to the controller 50. The control unit 50 stores the positions of the bright lines 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 part 50 performs steps S14-S16. Steps S14 to S16 are the same as step S1, S2 and S4, respectively.

Next, in step S17, the controller 50 controls the positions of the first interference fringe IF1 and the second interference fringe IF2 detected in step S16, and the first reference interference fringe IF10 detected in step S13. ) And the phase difference of the lights L1 and L2 at the measurement position P [k] based on the position of the 2nd reference interference fringe IF20. It demonstrates concretely below.

8 and 9 are diagrams schematically showing examples of the first interference fringe IF1, the second interference fringe IF2, the first reference interference fringe IF10 and the second reference interference fringe IF20. In FIG. 9, an example of the intensity of the light in the 1st interference fringe IF1, the 2nd interference fringe IF2, the 1st reference interference fringe IF10, and the 2nd reference interference fringe IF20 is shown. The 1st interference fringe IF1 and the 1st reference interference fringe IF10 are interference fringes by the interference of the lights L1 and L2 in 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 displacement amount x10 between the position of the bright line of the 1st interference fringe IF1 and the position of the bright line of the corresponding 1st reference interference fringe IF10, the influence of the optical characteristic of the said path | route disappears. In short, the displacement amount x10 is hardly dependent on the optical properties (eg aberration) of the path.

In contrast, the phase difference of the lights L1 and L2 incident on the pair of slits 23a and 23b, respectively, is almost zero at the reference position P [0] (FIG. 7), while the measurement position P [k] (FIG. 1). ), The value according to the phase delay by the phase shift film 82 is taken. The state of the optical axis of the optical system is different at the reference position P [0] and the measurement position P [k]. Therefore, the displacement amount x10 depends on the phase difference of the lights L1 and L2 in the measurement position P [k], and the shift amount of the optical axis of an optical system.

The second interference fringe IF2 and the second reference interference fringe IF20 are interference fringes caused by interference of the lights 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 act in common with the second interference fringe IF2 and the second reference interference fringe IF20. Therefore, in the displacement amount x20 between the position of the bright line of the 2nd interference fringe IF2, and the position of the bright line of the corresponding 2nd reference interference fringe IF20, the influence of the optical characteristic of the said path | route disappears. In other words, the displacement amount x20 hardly depends on the optical properties (eg aberration) of the path.

Moreover, the phase differences of the lights L3 and L4 incident on the slits 23c and 23d, respectively, are substantially equal to each other at the reference position P [0] and the measurement position P [k]. Therefore, the displacement amount x20 hardly depends on the phase difference of the lights L3 and L4, but depends on the amount of displacement of the optical axis of the optical system.

The first reference interference fringe IF10 and the second reference interference fringe IF20 are detected by a common optical system at the reference position P [0], and the first interference fringe IF1 and the second interference fringe IF2 are measured. Since it is detected by a common optical system at the position P [k], the amount of deviation of the optical axis at the measurement position P [k] relative to the reference position P [0] is determined by the first interference fringe IF1 and the second interference fringe IF2. Is observed as the same displacement amount. In other words, the displacement amount x10 is the sum of the displacement amount x0 depending on the phase difference between the lights L1 and L2 and the displacement amount x20 depending on the displacement amount of the optical axis. Therefore, the displacement amount x0 which subtracted the displacement amount x20 from the displacement amount x10 reflects the phase difference of the lights L1 and L2 with higher precision.

Therefore, first, the control part 50 calculates the displacement amount x10 of the position of the bright line corresponding to each other of the 1st interference fringe IF1 detected by step S16, and the 1st reference interference fringe IF10 detected by step S13, Similarly, the displacement amount x20 of the position of the bright line corresponding to each other of the 2nd interference fringe IF2 detected by step S16 and the 2nd reference interference fringe IF20 detected by step S13 is calculated | required. Next, the control part 50 calculates the displacement amount x0 by subtracting the displacement amount x20 from the displacement amount x10, and calculates the phase difference of the light L1, L2 as mentioned above based on this displacement amount x0. . For example, the controller 50 may obtain the phase difference based on the quotient and the numerator of the pitch Δx and the displacement amount x0 of the first interference fringe IF1, respectively.

Next, in step S18, the control part 50 determines whether the value k is larger than the predetermined value kref. When a negative judgment is made in step S18, in step S19, the control part 50 adds 1 to the value k. Next, the control part 50 performs steps S15-S18 again. When affirmative judgment is made in step S18, the control part 50 complete | finishes an operation.

As described above, the control unit 50 includes the displacement amount x10 between the bright lines corresponding to each other of the first interference fringe IF1 and the first reference interference fringe IF10, and the second interference fringe IF2 and the second reference interference. The phase difference is calculated based on the displacement amount x20 between bright lines corresponding to the patterns IF20. Specifically, the control part 50 calculates a phase difference based on the displacement amount x0 which subtracted the displacement amount x20 from the displacement amount x10. In the displacement amounts x10 and x20, since the influence of the difference of the optical characteristic in each path | route of the optical system has disappeared, the displacement amount x0 hardly depends on the difference of the said optical characteristic, and it has high precision with the light L1, Reflects the phase difference of L2). Therefore, the phase difference can be calculated with higher precision.

In addition, when a plurality of phase shift masks 80 are sequentially loaded 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 are obtained. Detection (steps S11 to S13) is performed for each phase shift mask 80. By the way, this detection need not be carried out for each sheet of the phase shift mask 80. The detection of the first reference interference fringe IF10 and the second reference interference fringe IF20 is carried out only once, and the detected first reference interference fringe IF10 and the second reference interference fringe IF20 are provided with a plurality of phase shift masks. You may use in common about (80). The first reference interference fringe IF10 and the second reference interference fringe IF20 may be detected for each of the N phase shift masks 80 and updated.

<Slit mask>

<Width of slit 23a, 23b>

In the phase shift mask 80, the transmittance of the phase shift film 82 is smaller than that of the base material 81. For example, the ratio of the transmittance | permeability of the phase shift film 82 with respect to the transmittance | permeability of the base material 81 is about several%, for example. Therefore, the amount of light L1 passing through the region 8a becomes smaller than the light L2 passing 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. And the larger the light quantity difference 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, in order to improve the contrast of the first interference fringe IF1, the size of the slit 23a is determined. In the example of FIG. 2, the lengths (lengths along the length direction) of the slits 23a and 23b are about the same, and the width of the slits 23a is wider than the widths (width along the width direction) of the slit 23d. . According to this, the light quantity difference of the lights L1 and L2 which passed the slit 23a, 23b can also be made smaller. Therefore, the contrast of the 1st interference fringe IF1 by the interference of the light L1, L2 which passed the slit 23a, 23b can be improved.

<Length of Slits 23a to 23d>

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 light L2 to L4 passing through the region 8b is determined by the light passing through the region 8a ( Less than the amount of L1). Therefore, the amount (for example, the total amount) of light in the second interference fringe IF2 by the lights L3 and L4 is the amount of light in the first interference fringe IF1 by the lights L1 and L2. Greater than (eg total). In the case where the light quantity 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 sensors are expensive.

Therefore, in order to reduce the light quantity difference between the 1st interference fringe IF1 and the 2nd interference fringe IF2, it is prayed to determine the size of the slit 23a-23d. In the example of FIG. 2, the lengths of the slits 23c and 23d are about the same, and the lengths of the slits 23a and 23b are longer than the respective lengths of the slits 23c and 23d. According to this, since the quantity of the lights L3 and L4 which pass through the slit 23c, 23d can be reduced, the light quantity difference between the 1st interference fringe IF1 and the 2nd interference fringe IF2 can be reduced. . Thereby, the sensor with a narrower measurement range can be adopted as the image sensor 32. Therefore, the cost of the image sensor 32 can be reduced.

<Pitch of Slits 23a and 23b and Pitch of Slits 23c and 23d>

10 is a plan view illustrating an example of a configuration of the slit mask 23. 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 the contrast of the interference fringe is inversely proportional to the pitch of the slit, the pitch of the contrast of the second interference fringe IF2 is longer than the pitch of the contrast of the first interference fringe. However, the position of the 0th order bright line of the 1st interference fringe IF1 and the 2nd interference fringe IF2 does not depend on the pitch of a slit. Therefore, the controller 50 calculates the phase difference based on the displacement amount x0 between the 0th order bright lines of the first interference fringe IF1 and the second interference fringe IF2 as described above, thereby calculating the phase difference with high accuracy. Can be calculated.

In addition, since the pitch d2 of the slits 23c and 23d is narrower than the pitch d1 of the slits 23a and 23b, the gap between the neighboring phase shift films 82 in the X-axis direction is compared with the reverse. (p1) can be made narrower. In other words, the phase difference measuring device 1 can be used also for the phase shift mask 80 having a narrower gap p1 (ie, the width in the X-axis direction of the region 8b). In other words, the phase difference measuring apparatus 1 can also measure the finer phase shift mask 80.

<Position relation between pair of slits 23a and 23b and pair of slits 23c and 23d>

In the example of FIG. 2, the slits 23a to 23d are arranged side by side in the X axis direction. By the way, it is not necessarily limited to this. For example, the pair of slits 23a and 23b may be disposed so as not to overlap with 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 shifted from the pair of slits 23a and 23b in the Y axis direction. 11 is a plan view illustrating an example of a configuration of the slit mask 23.

In the example of FIG. 11, the pair of slits 23a and 23b are adjacent in the X axis direction, and the pair of slits 23c and 23d are also adjacent in the X axis direction. Moreover, in the slit 23b, 23c, they are arrange | positioned adjacent to each other in the Y-axis direction.

According to this, the slits 23b and 23c do not neighbor in the X axis direction, but are adjacent in the Y axis direction. Therefore, the phase difference measuring apparatus 1 is applicable also to the phase shift mask 80 in which the clearance gap p1 of the adjacent phase shift film 82 in a X-axis direction is narrower. In other words, the phase difference measuring apparatus 1 can also measure the finer phase shift mask 80.

<Separation of interference fringe by algorithm>

In the above-mentioned example, the isolation | separation element 60 forms the image sensor 32 in the position which isolate | separated 1st interference fringe IF1 and 2nd interference fringe IF2 from each other. By the way, the isolation element 60 is not necessarily required. 12 is a diagram illustrating an example of a conceptual configuration of the phase difference measuring apparatus 1A. The phase difference measuring device 1A is different from the phase difference measuring device 1 in that the separation element 60 is present. In this phase difference measuring apparatus 1A, the separating element 60 is not formed. Therefore, the first interference fringe IF1 and the second interference fringe IF2 are formed in the image sensor 32 at the same position.

Therefore, in the image which the image sensor 32 picks up, the 1st interference fringe IF1 and the 2nd interference fringe IF2 are mixed in the same area. The control part 50 may specify the position of the bright line of the 1st interference fringe IF1 and the 2nd interference fringe IF2 based on the image from the image sensor 32. FIG. For example, since the amounts of light L1 and L2 passing through the slits 23a and 23b are different from the amounts of light L3 and L4 passing through the slits 23c and 23d, the first interference fringe IF1 and the first The intensity of the bright lines of the orders corresponding to the two interference fringes IF2 are different. Which of the bright lines of the first interference fringe IF1 and the second interference fringe IF2 is large is determined in advance depending on the shape of the slit mask 23. In general, in one interference fringe, the intensity of bright lines decreases as the degree increases. In other words, in one interference fringe, the intensity of light of order 0 is higher than the intensity of light of other order.

For example, the control part 50 determines whether each peak value of the pixel value (in other words, the intensity of light) in an image represents the bright line of the 1st interference fringe IF1 and the 2nd interference fringe IF2. Judgment is made based on the peak value. For example, when the intensity of the bright line of the second interference fringe IF2 is higher than that of the bright line of the first interference fringe IF1, the controller 50 has the highest intensity in the image from the image sensor 32. The high position may be determined as the position of the 0th order bright line of the second interference fringe IF2. The pitch between the bright lines of the second interference fringes IF2 is predetermined 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 0th bright line of the interference fringe IF2 is determined, the position of the bright line of another order can be estimated. For example, the control part 50 estimates the position which added the predetermined pitch to the position of a 0 degree bright line as a position of a primary bright line. The control part 50 specifies the position where intensity takes a peak value in the vicinity of the position estimated as the position of a primary bright line as the position of the primary bright line. The control part 50 can also specify the position of the bright line of another order similarly.

The 0th order bright line of the 1st interference fringe IF1 is located between the 0th order bright line of the 2nd interference fringe IF2, and the 1st (or -1st order) bright line. Thus, the control unit 50 determines the position where the intensity takes the peak value between the 0th order bright line of the specific second interference fringe IF2 and the 1st order (or -1st order) bright line. Identifies as the location of the 0th bright line. Since the pitch between bright lines of the first interference fringe IF1 is also determined in advance, the control unit 50 can specify the position of the bright line of the mth order of the first interference fringe IF1 in the same manner as the second interference fringe IF2. Can be.

As mentioned above, the control part 50 can specify the position of the bright line of the 1st interference fringe IF1, and the bright line of the 2nd interference fringe IF2. The control part 50 calculates the displacement amount x0 of the bright line corresponding to each other of the 1st interference fringe IF1 and the 2nd interference fringe IF2. Thereby, the displacement amount x0 which reflects a phase difference with high precision can be obtained.

Moreover, the control part 50 may move an optical system to the reference position P [0], and may specify the position of the bright line of the 1st reference interference fringe IF10 and the 2nd reference interference fringe IF20 in the same manner to the above. And the control part 50 moves an optical system to the measurement position P [k], and specifies the position of the bright line of the 1st interference fringe IF1 and the 2nd interference fringe IF2 similarly to the above. The control part 50 is based on the 1st interference fringe IF1, the 2nd interference fringe IF2, the 1st reference interference fringe IF10, and the 2nd reference interference fringe IF20, as mentioned above, and the displacement amount x0 ) Thereby, the displacement amount x0 which reflects a phase difference with higher precision can be obtained.

In addition, although the phase shift mask 80 is illustrated as the measurement object 8 in the example mentioned above, it is not necessarily limited to this. In short, the phase difference measuring apparatus 1 can measure the phase difference of the light which permeate | transmitted the different refractive index area with respect to the measurement object 8 which has refractive index distribution. As another example of the measurement object 8, a mineral etc. are illustrated.

As mentioned above, although the board | substrate holding apparatus and the substrate processing apparatus were demonstrated in detail, the said description is an illustration in all aspects, This indication is not limited to it. In addition, the various modifications mentioned above can be applied in combination unless they are mutually inconsistent. And, it is understood that many modifications which are not illustrated can be assumed without departing from the scope of this disclosure.

1: phase difference measuring device
8: measuring object
8a: first refractive index region
8b: second refractive index region
10: investigation means (irradiation unit)
23: slit mask
23a: first slit (slit)
23b: second slit (slit)
23c: third slit (slit)
23d: fourth slit (slit)
30: detection means (detection unit)
31: Fourier Transform Lens
32: image sensor
40: moving mechanism
50: arithmetic processing means (control unit)
60: isolation element
IF1: first interference pattern (interference pattern)
IF2: second interference pattern (interference pattern)
IF10: first reference interference pattern (reference interference pattern)
IF20: second reference interference pattern (reference interference pattern)
P [0]: reference position
P [k]: measuring position

Claims (10)

A phase difference measuring apparatus for measuring a 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,
Irradiation means for irradiating light to the measurement object;
A first slit disposed on a path of light passing through the first refractive index region, a second slit disposed on a path of light passing through a second refractive index region and adjacent to the first slit at intervals; A slit mask disposed on the path of light passing through the second index of refraction region and having a neighboring third slit and a fourth slit, the slit mask being separate from the measurement object,
Detecting means for detecting a first interference fringe by interference of light passing through the first slit and the second slit, and a second interference fringe by interference of light passing through the third slit and the fourth slit, respectively; Equipped,
The length in the longitudinal direction of a said 1st slit and a said 2nd slit is a phase difference measuring apparatus longer than both of the length along the longitudinal direction of a said 3rd slit and a 4th slit. The method of claim 1,
And an arithmetic processing means for obtaining a displacement amount of a position of the bright line of the predetermined order of the first interference fringe with respect to a position of the bright line of the predetermined order of the second interference fringe. The method of claim 2,
And said predetermined order is zero order. The method of claim 1,
Arithmetic processing means,
Further provided with a moving means for moving the irradiation means, the slit mask and the detection means,
Said moving means moves said set of said irradiation means, said slit mask and said detection means to each of a reference position and a measurement position,
The reference position is a position at which light passing through the second refractive index region from the irradiation means passes through the first to fourth slits,
The measurement position is that the light passing through the first refractive index region from the irradiation means passes through the first slit, and the light passing through the second refractive index region from the irradiation means passes through the second to fourth slits. Position through
The detection means is a first reference interference pattern due to interference of light passing through the first slit and the second slit at the reference position, and by interference of light passing through the third slit and the fourth slit. Detect a second reference interference fringe,
The arithmetic processing means is configured to perform the second interference fringe 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 phase difference measuring apparatus which subtracts the 2nd displacement amount of the position of the bright line of the. The method according to any one of claims 1 to 4,
And a pitch between the third slit and the fourth slit is narrower than a pitch between the first slit and the second slit. The method according to any one of claims 1 to 4,
The first slit and the second slit are adjacent in the first direction, the third slit and the fourth slit are adjacent in the first direction, and the third slit is the second slit and the The phase difference measuring apparatus which adjoins in the 2nd direction orthogonal to a 1st direction. The method according to any one of claims 1 to 4,
And a separation element for separating the light passing through the first slit and the second slit, respectively, and the light passing through the third slit and the fourth slit, respectively. The method according to any one of claims 1 to 4,
With an image sensor,
A Fourier transform lens for forming light from the slit mask into the image sensor;
A phase difference comprising calculation processing means for specifying, based on the peak value, each peak value of the intensity of light detected by the image sensor indicates which of the bright lines of the first interference fringe and the second interference fringe is represented. Measuring device. A phase difference measuring apparatus having at least a slit mask, comprising: a 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; As a phase difference measuring method to measure,
Irradiating light to the measurement object;
A first interference fringe caused by interference of the first light passing through the first refractive index region and the first slit of the slit mask, the second light passing through the second refractive index region and the second slit of the slit mask, and Detecting a second interference fringe by interference of a third light passing through a second refractive index region and a third slit of the slit mask and a fourth light passing through the second refractive index region and a fourth slit of the slit mask And
The length along the longitudinal direction of a said 1st slit and a said 2nd slit is a phase difference measuring method longer than both of the length along the longitudinal direction of a said 3rd slit and a said 4th slit. delete

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