JP2010134036A - Differential interference type inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily adjust a shear amount over a comparatively wide range at low cost. <P>SOLUTION: The differential interference type inspection device 1 includes: a light source 7 which emits light to irradiate a sample 3; an illumination optical system 10 which branches the light from the light source 7 to two optical paths so as to irradiate different places of the sample 3 with the light; and a photographic optical system 20 which combines reflected light being the light made to irradiate the sample 3 by the illumination optical system 10 and performs photographing with obtained interference light. The illumination optical system 10 includes an optical path-branching part 16 which branches the light from the light source 7 to two optical paths, and reflects first polarized light 15A and transmits second polarized light 15B; a first mirror 17 which reflects the second polarized light 15B transmitted through the optical path-branching part 16 in a direction in parallel with the first polarized light 15A reflected by the optical path-branching part 16; and an interval adjusting mechanism which adjusts a relative distance between the first mirror 17 and the optical path-branching part 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a differential interference inspection apparatus.

  2. Description of the Related Art Conventionally, in semiconductor wafer inspection, with the miniaturization of patterns and the increase in size of wafers, there is an increasing demand for macro inspection apparatuses that automatically inspect all wafers for relatively large defects (for example, patents) Reference 1).

  The surface defect inspection apparatus of Patent Literature 1 acquires a two-dimensional observation image by relatively moving the line illumination unit, the line sensor, and the substrate in a direction intersecting the longitudinal direction of the line-shaped illumination region. It is like that. However, in such a conventional inspection apparatus, it is difficult to distinguish between irregularities such as scratches and foreign matters on a flat surface with a pattern and the pattern of the pattern, and it is difficult to observe only the irregularities with high contrast.

  Here, in principle, a differential interference microscope that obtains an epi-illuminated differential interference image is known as an observation method that is highly sensitive to the unevenness of the sample surface (see, for example, Patent Document 2). The differential interference microscope described in Patent Document 2 enables high-accuracy differential interference observation by changing the lateral shift amount (so-called shear amount) of two rays, which is a heavy parameter that determines the contrast and resolution of the differential interference image. Can be done.

JP-A-9-61365 Japanese Patent Laid-Open No. 10-161031

  However, the differential interference microscope described in Patent Document 2 moves one of the crystal plates in a direction orthogonal to the optical axis direction of the illumination optical system with respect to linearly polarized light passing through a pair of wedge-shaped crystal plates. There is a problem in that the amount of shear is changed by changing the thickness of the plate in the optical axis direction, and the amount of shear can only be finely adjusted. In addition, if a Nomarski prism is used as a configuration for finely adjusting the amount of shear, there is an inconvenience that it is expensive.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a differential interference inspection apparatus capable of adjusting the amount of shear over a relatively wide range in a simple and inexpensive manner.

In order to solve the above problems, the present invention employs the following means.
The present invention includes a light source that emits light to irradiate a sample, an illumination optical system that divides the light from the light source into two optical paths and irradiates different locations on the sample, and irradiates the sample with the illumination optical system. A photographing optical system for photographing the interference light obtained by synthesizing the reflected light of the light, and the illumination optical system splits the light from the light source into the two light paths and emits one light. An optical path branching member that reflects the other light and reflects the other light that has passed through the optical path branching member in a direction parallel to the one light reflected by the optical path branching member And a differential interference inspection apparatus comprising a distance adjusting mechanism for adjusting a relative distance between the parallel reflection member and the optical path branching member.

  According to the present invention, the distance in the direction perpendicular to the optical axis of the two optical paths branched by the optical path branching member and the parallel reflecting member by the photographing optical system, that is, the lateral shift amount (hereinafter referred to as “shear amount”). A differential interference image in which minute steps of the sample are visualized in a three-dimensional manner is obtained with a corresponding contrast and resolution.

  In this case, with respect to one light reflected by the optical path branching member, the other light that has passed through the optical path branching member is reflected in a parallel direction by the parallel reflecting member, so that the amount of shear is split between the parallel reflecting member and the optical path. It can be determined according to the distance to the member. Moreover, the amount of shear can be changed by adjusting the relative distance between the parallel reflecting member and the optical path branching member by the distance adjusting mechanism. Therefore, the amount of shear can be adjusted over a relatively wide range simply and inexpensively without using an expensive Nomarski prism.

In the above invention, the imaging optical system may include a reduction optical system.
With this configuration, macro observation can be performed. For example, in the inspection of a circuit board, a relatively wide inspection range can be reduced by a reduction optical system and observed macroscopically.

  In addition, when a predetermined pattern is repeated on the circuit board, the distance adjustment mechanism secures an amount of shear that matches an integer multiple of the pattern repetition period, thereby suppressing the occurrence of pattern interference images. Only defects such as scratches and foreign matter existing inside can be highlighted. Therefore, even when a pattern exists on the circuit board, the contrast between the pattern and the defect is improved, and the defect can be detected well.

In the above invention, the optical path branching member may be a beam splitter, and the parallel reflecting member may be a mirror.
By comprising in this way, the light emitted from the light source is decomposed into two optical paths arranged in parallel with a relatively wide range in the direction orthogonal to the optical axis with a simple and inexpensive construction. be able to.

In the above invention, the optical path branching member may be a polarization beam splitter.
By comprising in this way, the light emitted from the light source can be branched into two polarized lights having polarization planes orthogonal to each other, and interference can be efficiently performed.

  In the above invention, the illumination optical system may include a phase difference adjustment mechanism that adjusts the phase of the light branched into the two optical paths.

  With this configuration, the light branched into the two optical paths can be set to a phase difference suitable for the shape of the sample. Therefore, for example, in the inspection of a circuit board, the S / N ratio (signal noise) of a defect is set by setting a phase difference so that a differential interference image of a normal pattern having no defect becomes relatively dark by a phase difference adjustment mechanism. Ratio) can be improved.

In the above invention, the photographing optical system may be provided with an optical path length adjusting mechanism that adjusts optical path lengths of the two optical paths.
By correcting the optical path length difference on the photographing optical system side, which slightly occurs according to the relative distance between the parallel reflecting member and the optical path branching member, it is possible to connect the images of the reflected light of the two optical paths to the same focus position. Therefore, a clear differential interference image can be acquired.

  In the above invention, the illumination optical system includes a beam shaping optical system that shapes the cross-sectional shape of the light branched into the two optical paths into a line shape, and the sample, the illumination optical system, and the imaging optical A moving mechanism that relatively moves the system in the direction intersecting the line-shaped light may be provided.

  With this configuration, a two-dimensional differential interference image can be acquired. Therefore, for example, in the inspection of the circuit board, the differential interference image of the entire surface of the circuit board can be acquired by one photographing, and the inspection efficiency can be improved.

  According to the present invention, there is an effect that the amount of shear can be easily and inexpensively adjusted over a relatively wide range.

[First Embodiment]
Hereinafter, a differential interference inspection apparatus 1 according to a first embodiment of the present invention will be described with reference to the drawings.
The differential interference inspection apparatus 1 according to this embodiment is for inspecting defects such as scratches and foreign matters attached to a pattern having a repeated structure of a sample such as a semiconductor substrate or an FPD (flat panel display). .

  As shown in FIGS. 1 and 2, the differential interference inspection apparatus 1 includes a uniaxial stage 5 on which the sample 3 is arranged, a light source 7 that emits light to irradiate the sample 3, and two lights emitted from the light source 7. An illumination optical system 10 that diverges into an optical path and irradiates a different location of the sample 3; and an imaging optical system 20 that captures light obtained by synthesizing the reflected light of the light irradiated on the sample 3 by the illumination optical system 10; And a control mechanism 9 for controlling the operations of the uniaxial stage 5, the illumination optical system 10, and the photographing optical system 20.

  The uniaxial stage 5 includes a moving mechanism (not shown) and is arranged so as to be movable in one direction (the arrow Y direction in FIG. 1). The uniaxial stage 5 is connected to an image input unit 35 and an image processing unit 37.

  The illumination optical system 10 includes a projection lens 11 into which light emitted from the light source 7 is incident, a polarizing plate 13 that converts light transmitted through the projection lens 11 into linearly polarized light, and a phase difference of ¼ wavelength with respect to linearly polarized light. A quarter-wave plate 14 for generating light, an optical path branching part (optical path branching member, polarization beam splitter) 16 for splitting linearly polarized light into two optical paths, and a first light reflecting the light transmitted through the optical path branching part 16 A mirror (parallel reflection member) 17 and a first collimating lens 19 are provided.

The light source 7 generates light having a pure monochromatic wavelength, for example.
The projection lens 11 shapes the light from the light source 7 into a rectangular shape extending in a direction orthogonal to the moving direction of the uniaxial stage 5 and enlarges and projects the light onto the sample 3.

  The polarizing plate 13 has a property of transmitting only light oscillating in a certain direction. In addition, the polarizing plate 13 has, for example, a disk shape and is disposed so as to be rotatable about the optical axis of the light transmitted through the projection lens 11. The polarizing plate 13 and the quarter-wave plate 14 change the change state of the transmitted light and change the phase difference of the light incident on the optical path branching portion 16 between 0 and λ.

  The optical path branching unit 16 is, for example, a cube-type PBS (polarizing beam splitter), and branches incident linearly polarized light into two polarized lights having polarization planes orthogonal to each other. The optical path branching unit 16 is arranged so that linearly polarized light transmitted through the quarter-wave plate 14 is incident at an angle of about 45 ° with respect to the incident surface, and light that vibrates in a direction perpendicular to the incident surface. (Hereinafter referred to as “first polarized light”) 15A is reflected substantially at a right angle, and light having a vibration direction within the incident plane (hereinafter referred to as “second polarized light”) 15B is transmitted. .

  The first mirror 17 has a reflecting surface arranged in parallel to the reflecting surface of the optical path branching unit 16, and the second polarized light 15B transmitted through the optical path branching unit 16 is about 45 ° with respect to the incident surface. It is arrange | positioned so that it may inject with the angle of. The first mirror 17 is arranged to be movable in a direction approaching and moving away from the optical path branching section 16 while maintaining a state parallel to the optical path branching section 16.

  The first mirror 17 reflects the second polarized light 15B in a direction parallel to the first polarized light 15A reflected by the optical path branching unit 16. The second polarized light 15 </ b> B reflected by the first mirror 17 is at an interval t between the optical path branching unit 16 and the first mirror 17 with respect to the first polarized light 15 </ b> A reflected by the optical path branching unit 16. They are arranged at intervals in the direction perpendicular to the optical axis direction by a distance that depends on the distance. Hereinafter, the distance in the direction orthogonal to the optical axis between the optical path of the first polarized light 15A and the optical path of the second polarized light 15B, that is, the lateral shift amount is referred to as the shear amount.

The first collimating lens 19 constitutes a beam shaping optical system that shapes the cross-sectional shapes of the first polarized light 15A and the second polarized light 15B into a line shape by the action of the projection lens 11. The polarized light 15A and the second polarized light 15B are irradiated onto the sample 3 as substantially parallel light. Note that the amount of lateral deviation between the first polarized light 15A and the second polarized light 15B irradiated to the sample 3 is denoted by δ.
Hereinafter, the reflected light of the first polarized light 15A reflected by the sample 3 is referred to as first reflected light 25A, and the reflected light of the second polarized light 15B is referred to as second reflected light 25B.

  The imaging optical system 20 includes a second collimating lens 21 on which the first reflected light 25 </ b> A and the second reflected light 25 </ b> B reflected from the sample 3 are incident, and the second reflected light that has passed through the second collimating lens 21. From the second mirror 24 that reflects the light 25B, the polarization combining unit (polarization beam splitter) 23 that combines the first reflected light 25A and the second reflected light 25B, and the light combined by the polarization combining unit 23 An analyzer 26 that extracts an interference signal, an imaging lens 27, and a line sensor 29 that captures light transmitted through the imaging lens 27 are provided.

  An optical path length correction element 69 that corrects the optical path length between the sample 3 and the imaging lens 27 is provided on the optical path of the first reflected light 25A between the second collimating lens 21 and the polarization combining unit 23. Has been placed. The optical path length correction element 69 is, for example, a glass plate.

  The polarization combining unit 23 is, for example, a cube-type PBS (polarization beam splitter). The polarization combining unit 23 is provided on the optical path of the first reflected light 25A and the second reflected light 25B, and the first reflected light 25A and the second reflected light 25B are about 45 ° with respect to the incident surface. It arrange | positions so that it may inject at an angle. In addition, the polarization combining unit 23 reflects the first reflected light 25A that vibrates in the direction perpendicular to the incident surface, and transmits the second reflected light 25B having the vibration direction on the incident surface.

  The second mirror 24 has a reflection surface arranged in parallel to the reflection surface of the polarization beam combiner 23, and the second reflected light 25B transmitted through the polarization beam combiner 23 is about 45 ° with respect to the incident surface. It is arrange | positioned so that it may inject with the angle of. The second mirror 24 is arranged so as to be movable in a direction approaching and moving away from the polarization combining unit 23 while maintaining a state parallel to the polarization combining unit 23.

  The second mirror 24 reflects the second reflected light 25B in parallel with the first reflected light 25A on the optical path of the first reflected light 25A reflected by the polarization beam combiner 23. The second reflected light 25 </ b> B reflected by the second mirror 24 is combined with the first reflected light 25 </ b> A and emitted when passing through the polarization beam combiner 23 again.

  The imaging lens 27 constitutes a reduction optical system that reduces and projects the rectangular irradiation area of the sample 3 by the action of the second collimating lens 21. In addition, the imaging lens 27 forms a differential interference image of the sample 3 on the line sensor 29 based on the interference signal extracted by the analyzer 26.

  The line sensor 29 is disposed so as to be movable in the optical axis direction of the light transmitted through the imaging lens 27. The line sensor 29 is connected to the image input unit 35 and the image processing unit 37.

  The control mechanism 9 includes a storage unit 31 that stores inspection conditions suitable for the shapes of various samples, an interval t between the first mirror 17 and the optical path branching unit 16, and an interval t between the second mirror 24 and the polarization combining unit 23. , An interval adjustment mechanism 41 that adjusts the phase difference, a phase difference adjustment mechanism 51 that adjusts the phase difference between the first polarized light 15A and the second polarized light 15B, and optical path length correction between the sample 3 and the imaging lens 27. And an optical path length correction mechanism 61 for adjusting the optical path length correction mechanism 61, a distance adjustment mechanism 41, a phase difference adjustment mechanism 51, an optical path length correction mechanism 61, a line sensor 29, and a control unit 33 for controlling the uniaxial stage 5. .

  In the storage unit 31, for example, a cycle of a repetitive pattern for each sample is stored as an inspection condition. Based on the inspection conditions, by operating each adjustment mechanism to ensure the amount of shear that matches an integer multiple of the pattern repetition period, the generation of differential interference images of the pattern is suppressed, and only defects present in the pattern are detected. Can stand out,

  The interval adjustment mechanism (distance adjustment mechanism) 41 includes a first mirror driving unit 43 that moves the first mirror 17, a second mirror driving unit 45 that moves the second mirror 24, the first mirror 17, and the first mirror 17. And an interval setting unit 47 for setting the position of the second mirror 24.

  By reflecting the second polarized light 15B in the parallel direction by the first mirror 17 with respect to the first polarized light 15A reflected by the optical path branching section 16, the shear amount is different from that of the first mirror 17 and the optical path. It is determined according to the distance t with the branching section 16. Further, the amount of shear is changed by adjusting the interval between the first mirror 17 and the optical path branching unit 16 by the interval adjusting mechanism 41. The interval setting unit 47 operates the first mirror driving unit 43 and the second mirror driving unit 45 in conjunction with each other.

  The phase difference adjusting mechanism 51 includes a polarizing plate rotation driving unit 53 that rotates the polarizing plate 13 around the optical axis, and a phase difference setting unit that sets a phase difference between the first polarized light 15A and the second polarized light 15B. 57. The phase difference setting unit 57 rotates the polarizing plate 13 via the polarizing plate rotation driving unit 53.

  The optical path length correction mechanism 61 includes an optical path length correction element insertion / removal drive unit 63 that inserts an optical path length correction element 69 on the optical path of the first reflected light 25A, and a line sensor drive unit that moves the line sensor 29 in the optical axis direction. 65, and an optical path length correction amount setting unit 67 that sets an optical path length correction amount between the sample 3 and the imaging lens 27.

  The optical path length correction amount setting unit 67 selects an appropriate thickness from a plurality of optical path length correction elements 69 having different thicknesses via the optical path length correction element insertion / removal driving unit 63, and selects the selected optical path length correction element. 69 is inserted into the optical path of the first reflected light 25A. The optical path length correction amount setting unit 67 moves the line sensor 29 in the optical axis direction via the line sensor driving unit 65.

The operation of the differential interference inspection apparatus 1 according to the present embodiment configured as described above will be described.
In order to inspect the surface of the sample 3 by the differential interference inspection apparatus 1 according to the present embodiment, first, the sample 3 is placed on the uniaxial stage 5 and an inspection start signal is input to the control unit 33. In the control unit 33, inspection conditions suitable for the sample 3 are read from the storage unit 31, and the inspection conditions are output to the interval adjustment mechanism 41, the phase difference adjustment mechanism 57, and the optical path length correction mechanism 61.

  In the interval adjusting mechanism 41, the interval setting unit 47 drives the first mirror driving unit 43 and the second mirror driving unit 45 based on the input inspection conditions. As a result, the first mirror 17 and the second mirror 24 move so as to obtain an appropriate amount of shear, the interval t between the first mirror 17 and the optical path branching unit 16, and the second mirror 24 and the polarization combining unit 23. The intervals t are adjusted respectively.

  In the phase difference adjusting mechanism 57, the polarizing plate rotation driving unit 53 is driven by the phase difference setting unit 57 based on the input inspection conditions. Accordingly, the polarizing plate 13 rotates so that the phase difference between the first polarized light 15A and the second polarized light 15B becomes an appropriate phase amount.

  In the optical path length correction mechanism 61, the optical path length correction amount setting unit 67 drives the optical path length correction element insertion / removal drive unit 63 and the line sensor drive unit 65 based on the input inspection conditions. An optical path length correction element 69 having an appropriate thickness is selected by the optical path length correction element insertion / removal drive unit 63 and inserted into the optical path of the first reflected light 25A. In addition, the line sensor driving unit 65 moves the line sensor 29 by a set amount in the optical axis direction.

  When the adjustment by the interval adjustment mechanism 41, the phase difference adjustment mechanism 57, and the optical path length correction mechanism 61 is completed, the control unit 33 outputs an imaging start instruction to the line sensor 29 and an investigation start instruction to the uniaxial stage 5. In addition, the control unit 33 inputs a capture start signal for the uniaxial stage 5 to the image input unit 35.

  The light emitted from the light source 7 passes through the projection lens 11 and then sequentially passes through the polarizing plate 13 and the quarter wavelength plate 14. By rotating the polarizing plate 13 by the polarizing plate rotation driving unit 53, the phase difference between the two polarized light beams (the first polarized light 15A and the second polarized light 15B) that have passed through the polarizing plate 13 is adjusted. The For example, the S / N ratio (signal / noise ratio) of the defect can be improved by setting the phase difference so that the differential interference image becomes relatively dark in a normal pattern having no defect.

  The linearly polarized light that has passed through the polarizing plate 13 and the quarter-wave plate 14 reaches the optical path separation unit 16 and is branched into two polarized lights that are orthogonal to each other. Specifically, the first polarized light 15 </ b> A is reflected by the optical path separation unit 16, and the second polarized light 15 </ b> B is transmitted through the optical path separation unit 16 and then parallel to the first polarized light 15 </ b> A by the first mirror 17. It is reflected in the direction.

  In this case, the second polarized light 15 </ b> B is a distance t that depends on the distance t between the optical path branching unit 16 and the first mirror 17 with respect to the first polarized light 15 </ b> A reflected by the optical path branching unit 16. It arrange | positions at intervals in the direction orthogonal to an optical axis direction.

  The first polarized light 15 </ b> A and the second polarized light 15 </ b> B pass through the first collimating lens 19 and become line-shaped substantially parallel light orthogonal to the moving direction of the uniaxial stage 5, and are orthogonal to the optical axis on the sample 3. Irradiation is performed with an interval of a lateral displacement amount δ in the direction of movement.

In this case, the relationship between the distance t between the optical path branching section 16 and the first mirror 17 and the lateral deviation amount δ on the sample 3 of the first polarized light 15A and the second polarized light 15B is
(Expression 1) δ≈t / sin (45 deg) ≈1.4 t
It is represented by (Equation 1) is when the incident angle of linearly polarized light from the light source 7 to the optical path separating unit 16 is 45 °, and the incident angles of the first polarized light 15A and the second polarized light 15B to the sample 3 are close to 0 °. Is illustrated. From (Equation 1), it is derived that the lateral shift amount δ of the first polarized light 15A and the second polarized light 15B on the sample 3 changes according to the interval t.

  The first reflected light 25A and the second reflected light 25B reflected at the respective positions of the sample 3 pass through the second collimating lens 21, respectively, and only the first reflected light 25A passes through the optical path length correction element 69. Thus, each reaches the polarization beam combining unit 23.

  By passing the first reflected light 25A through the optical path length correcting element 69, the optical path length difference on the imaging optical system side generated according to the interval t is corrected, and the first reflected light 25A and the second reflected light 25B are corrected. Can be connected to the same focus position.

  The first reflected light 25A is reflected by the polarization combining unit 23, and the second reflected light 25B is transmitted through the polarization combining unit 23, and then the first reflected light 25A is reflected on the optical path of the first reflected light 25A by the second mirror 24. Reflected so as to be parallel to the reflected light 25A. Thus, in the polarization combining unit 23, the first reflected light 25A and the second reflected light 25B are combined and emitted on the same optical path.

  Interference signals are extracted from the light combined by the polarization beam combiner 23 in the analyzer 26, pass through the imaging lens 27, and form an image of the sample on the line sensor 29. This image is, for example, a differential interference image between adjacent chips separated by a distance δ on the sample 3. Accordingly, the line sensor 29 acquires a differential interference image in which the minute steps of the sample 3 are stereoscopically visualized with the contrast and resolution corresponding to the shear amount.

  Then, the image input unit 35 acquires line data from the line sensor 29 and constructs a two-dimensional image. The two-dimensional image constructed by the image input unit 35 is sent to the image processing unit 37 where defect detection is performed, and a determination result of the presence / absence of a defect is output.

  As described above, according to the differential interference microscope 1 according to the present embodiment, macroscopic observation in which a relatively wide inspection range of the sample 3 is reduced can be performed by 100% inspection. Further, the amount of shear of the first polarized light 15 </ b> A and the second polarized light 15 </ b> B irradiated to the sample 3 is determined according to the distance t between the first mirror 17 and the optical path branching unit 16. The amount of shear can be changed by adjusting the distance to the optical path branching section 16. Therefore, the shear amount can be adjusted over a relatively wide range according to the shape of the sample 3 easily and inexpensively without using an expensive Nomarski prism. For example, the amount of shear may be changed, and a differential interference image may be acquired in a pattern unit including a plurality of chips and observed macroscopically.

In the present embodiment, the line sensor 29 or the line sensor 29 and the imaging lens 27 may be set so as to be movable in the optical axis direction by the change in the optical path length. By doing in this way, the change of the lateral magnification for every sample 3 which generate | occur | produces slightly according to the space | interval t can be prevented, and the dispersion | variation in defect coordinates, etc. can be eliminated.
In the present embodiment, the cube-type PBS is exemplified as the optical path separating unit 16 and the polarization combining unit 23. However, instead of this, for example, a cube-type PBS may be modified. Alternatively, a wire grid type PBS may be adopted. Since the wire grid type PBS is a thin glass substrate, it is effective when the shear amount is set to a small amount of 1 mm or less.

  In the present embodiment, the light emitted from the light source 7 is polarized and separated by the optical path separation unit 16. However, for example, a beam splitter or a half mirror may be used instead of the optical path separation unit 16. Good. In this case, for example, a differential interference image can be acquired simply by shifting the position of light to two optical paths using a half mirror. Second-order and third-order reflected light is generated, so that a differential interference image with a relatively large amount of shear can be obtained with a cheaper structure by removing excess light appropriately by coating a half mirror or a diaphragm. It becomes possible to do.

  In the present embodiment, the light source 7 generates light having a pure monochromatic wavelength, but may generate light having a white wavelength. In the present embodiment, the phase difference adjustment mechanism 57 has been described as an example of the means for adjusting the phase amount of the first polarized light 15A and the second polarized light 15B. However, instead of this, the light source 7 It is also possible to respond by changing the wavelength used. Further, for example, when a semiconductor wafer is used as the sample 3, there may be no adjacent chip at a laterally shifted position of the first polarized light 15A and the second polarized light 15B. In this case, instead of the uniaxial stage 5, a rotary stage may be employed, and all the chips on the sample 3 may be inspected by rotating the sample 3 by 45 ° or 90 ° and photographing.

  In addition, for example, a diaphragm may be provided in the polarization combining unit 23 so that only light that contributes to an effective differential interference image reaches the imaging lens 27. In this way, the first reflected light 25A and the second reflected light 25B receive the polarization characteristics of the sample 3 and become elliptically polarized light, which corresponds to the case where the reflected light is generated from other places of the polarization beam combiner 23. be able to. The distance adjusting mechanism 41 may be any mechanism that adjusts the relative distances between the first mirror 17 and the optical path branching unit 16 and the second mirror 24 and the polarization combining unit 23. The combining unit 23 may be moved.

  Further, although the description has been given by exemplifying that the imaging lens 27 and the second collimating lens 21 constitute the reduction optical system and perform the macro observation, the magnification optical system may be configured instead. Further, the first mirror 17 and the second mirror 24 may be constituted by a micromirror array. In addition, liquid crystal for phase difference adjustment or the like may be employed for optical path length correction and phase difference adjustment. Further, instead of the line sensor 29, a two-dimensional photographing means such as a CCD may be adopted.

1 is a schematic configuration diagram of a differential interference microscope according to an embodiment of the present invention. It is a block diagram which shows the control mechanism of the differential interference type | mold microscope of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Differential interference type | mold inspection apparatus 3 Sample 7 Light source 10 Illumination optical system 15A 1st polarized light 15B 2nd polarized light 16 Optical path branching part (optical path branching member)
17 1st mirror (parallel reflection member)
20 Shooting optical system

Claims (7)

A light source that emits light to irradiate the sample;
An illumination optical system that divides the light from the light source into two optical paths and irradiates different positions of the sample;
A photographing optical system for photographing interference light obtained by synthesizing the reflected light of the light irradiated on the sample by the illumination optical system;
The illumination optical system branches the light from the light source into the two optical paths, reflects one light and transmits the other light, and transmits the other light transmitted through the optical path branching member. Differential interference comprising: a parallel reflection member that reflects in a direction parallel to the one light reflected by the optical path branching member; and a distance adjustment mechanism that adjusts a relative distance between the parallel reflection member and the optical path branching member. Type inspection device.   The differential interference inspection apparatus according to claim 1, wherein the imaging optical system includes a reduction optical system.   The differential interference inspection apparatus according to claim 1, wherein the optical path branching member is a beam splitter, and the parallel reflection member is a mirror.   The differential interference inspection apparatus according to claim 3, wherein the optical path branching member is a polarization beam splitter.   The differential interference inspection apparatus according to claim 1, wherein the illumination optical system includes a phase difference adjustment mechanism that adjusts a phase of the light branched into the two optical paths.   The differential interference inspection apparatus according to claim 1, wherein the photographing optical system includes an optical path length adjustment mechanism that adjusts an optical path length of the two optical paths. The illumination optical system includes a beam shaping optical system that shapes the cross-sectional shape of the light branched into the two optical paths into a line shape,
The differential interference inspection according to any one of claims 1 to 6, further comprising a moving mechanism that relatively moves the sample, the illumination optical system, and the imaging optical system in a direction intersecting the line-shaped light. apparatus.

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