JP2010096596A - Evaluation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation device identifying causes of abnormality in a repetition pattern. <P>SOLUTION: The evaluation device 1 is provided with: an illumination system 30 for applying linear polarized light L1 onto the surface of a wafer 10 having a prescribed repetition pattern; a light reception system 40 for detecting the polarized light state of elliptic polarized light L2, namely regular reflection light from the repetition pattern irradiated with the linear polarized light L1; and an image processing section 50 for evaluating the shape of the repetition pattern from the polarized light state of the elliptic polarized light L2 detected by the light reception system 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an evaluation apparatus for evaluating a pattern formed on the surface of a semiconductor wafer, a liquid crystal substrate, or the like.

As a device for inspecting the surface of a substrate on which a fine repetitive pattern is formed in a semiconductor device manufacturing process, for example, based on the amount of light leaked from a crossed Nicols optical system, which is a change in polarization state due to structural birefringence of the pattern A method of detecting an abnormality in a pattern has been proposed (see, for example, Patent Document 1). According to this method, even if the pattern has a fine period that does not generate diffracted light with respect to the illumination wavelength, abnormalities in the pattern can be detected by capturing changes in the polarization state of specularly reflected light (0th order diffracted light). Therefore, it is possible to detect a pattern abnormality without shortening the wavelength of light used for inspection.
JP 2006-135211 A

  However, since the pattern abnormality is detected by comparing the amount of light leakage from the crossed Nicols system, the cause of the abnormality cannot be identified.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an evaluation apparatus capable of specifying the cause of a repetitive pattern abnormality.

  In order to achieve such an object, the evaluation apparatus according to the present invention includes an illumination unit that irradiates polarized light on the surface of a substrate having a predetermined repetitive pattern, and polarization of specularly reflected light from the repetitive pattern irradiated with the polarized light. A polarization state detection unit that detects a state, and an evaluation unit that evaluates the shape of the repeated pattern based on the polarization state detected by the polarization state detection unit.

  In the above-described invention, it is preferable that the illumination unit irradiates the surface of the substrate with linearly polarized light.

  In the above invention, the repetitive pattern is formed using an exposure apparatus, the polarization state of the regular reflection light is elliptical polarization, and the evaluation unit is the elliptical polarization detected by the polarization state detection unit. Based on the shape characteristics of the exposure apparatus, the shape error of the repetitive pattern caused by a deviation from an appropriate value of the exposure amount in the exposure apparatus and the shape error of the repetitive pattern caused by a deviation from an appropriate focus position are determined. It is preferable to detect.

  In the invention described above, the repeating pattern is a line-and-space pattern, and the evaluation unit determines the volume of lines and spaces of the pattern based on the shape characteristic of the elliptically polarized light detected by the polarization state detection unit. It is preferable to detect by detecting the defect of the ratio and the defect of the line edge roughness.

  In the above-described invention, the polarization state detection unit includes a condensing optical system including a wave plate and a polarizing plate that are rotatably arranged and a detector, and detects the polarization state by a rotation phase shifter method. It is preferable to do.

  In the above-described invention, the polarization state detection unit includes a condensing optical system including a polarizing plate rotatably arranged and a detector, and detects the polarization state by a rotation analyzer method. Also good.

  In the above-described invention, the illumination unit may include a phase modulation element, and the polarization state detection unit may detect the polarization state by a phase modulation method.

  According to the present invention, it is possible to identify the cause of a repetitive pattern abnormality.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the evaluation apparatus 1 of this embodiment includes a stage 20 that supports a semiconductor wafer 10 (hereinafter referred to as a wafer 10), an alignment system 25, an illumination system 30, and a light receiving system 40. Configured. In addition, the evaluation apparatus 1 includes an image processing unit 50 that performs image processing of an image captured by the light receiving system 40, and a monitor 55 that displays an image captured by the light receiving system 40 and an image processing result by the image processing unit 50. I have. After exposure / development of the uppermost resist film, the wafer 10 is carried from a wafer cassette (not shown) or a developing device by a conveyance system (not shown), and is sucked and held on the stage 20.

  On the surface of the wafer 10, as shown in FIG. 2, a plurality of chip regions 11 (shots) are arranged in the XY direction, and a predetermined repetitive pattern 12 is formed in each chip region. As shown in FIG. 3, the repetitive pattern 12 is a resist pattern in which a plurality of line portions 2A are arranged at a constant pitch P along the short direction (X direction) (for example, a wiring pattern that is a line and space pattern). ). Between adjacent line parts 2A is a space part 2B. The arrangement direction (X direction) of the line portions 2A is referred to as “repeating direction of the repeating pattern 12”. A pattern having such a structure has different refractive indexes in the X direction and the Y direction, and has so-called structural birefringence. In the present embodiment, the structural birefringence is positively used to specify the pattern shape, and as a result, it is possible to discriminate between an exposure amount defect and a focus defect.

Here, the design value of the line width D _A of the line portion 2A in the repetitive pattern 12 and 1/2 of the pitch P. If repeated pattern 12 is formed as the design value, the line width D _B of the line width D _A and the space portion 2B of the line portion 2A are equal, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: 1 In contrast, when the exposure dose for forming the repeating pattern 12 deviates from a proper value, the pitch P does not change, with the line width D _A of the line portion 2A becomes different from a design value, the space portion 2B becomes different and the line width D _B also, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: off the 1, changes the amount of form birefringence pattern. Further, when the focus is deviated from an appropriate value, the line edge shape is not changed and the so-called line edge roughness (Line Edge Roughness) is maintained without changing the average line width of the line portion as in the repeated pattern 12 'shown in FIG. : Hereinafter referred to as LER) may occur greatly. Also in this case, the amount of structural birefringence of the pattern changes. Note that FIG. 6 is exaggerated than the actual one. LER is a value representing the size of the irregularities formed on the pattern wall.

  The evaluation apparatus 1 of the present embodiment performs shape evaluation (defect detection) of the repetitive pattern 12 using the change in the volume ratio between the line portion 2A and the space portion 2B in the repetitive pattern 12 as described above. . In order to simplify the explanation, the ideal volume ratio (design value) is 1: 1. The change in the volume ratio is caused by the deviation of the exposure dose from the appropriate state, and appears for each shot area of the wafer 10. The volume ratio can also be referred to as the area ratio of the cross-sectional shape.

  In the present embodiment, it is assumed that the pitch P of the repeating pattern 12 is sufficiently small compared to the wavelength of illumination light (described later) for the repeating pattern 12. For this reason, diffracted light is not generated from the repetitive pattern 12, and the shape of the repetitive pattern 12 cannot be evaluated by the diffracted light.

  The stage 20 of the evaluation apparatus 1 supports the wafer 10 on the upper surface and fixes and holds it by, for example, vacuum suction. Further, the stage 20 is rotatable about the normal A1 at the center of the upper surface as a central axis. By this rotation mechanism, the repeating direction of the repeating pattern 12 on the wafer 10 (the X direction in FIGS. 2 and 3) can be rotated within the surface of the wafer 10. The stage 20 has a horizontal upper surface, and can always keep the wafer 10 in a horizontal state.

  The alignment system 25 illuminates the outer edge of the wafer 10 while the stage 20 is rotating, detects the position in the rotation direction of an external reference (for example, a notch) provided on the outer edge, and the stage 20 at a predetermined position. Stop. As a result, the repetitive direction (X direction in FIGS. 2 and 3) of the repetitive pattern 12 on the wafer 10 is set to be inclined at an angle of 45 degrees with respect to an illumination light incident surface A2 (see FIG. 4) described later. can do. The angle is not limited to 45 degrees, and can be set in an arbitrary angle direction such as 22.5 degrees or 67.5 degrees.

  The illumination system 30 is a decentered optical system that includes a light source 31, a polarizer 32, and an illumination lens 33. The illumination system 30 converts the repetitive pattern 12 of the wafer 10 on the stage 20 into linearly polarized light L1 (first linear line L1). Illuminate with polarized light. This linearly polarized light L1 is illumination light for the repeated pattern 12. The linearly polarized light L1 is irradiated on the entire surface of the wafer 10.

  The traveling direction of the linearly polarized light L1 (the direction of the principal ray of the linearly polarized light L1 reaching an arbitrary point on the surface of the wafer 10) passes through the center of the stage 20 and is a predetermined angle θ with respect to the normal A1 of the stage 20. Tilted. Incidentally, a plane including the traveling direction of the linearly polarized light L1 and parallel to the normal A1 of the stage 20 is an incident surface of the linearly polarized light L1. An incident surface A <b> 2 in FIG. 4 is an incident surface at the center of the wafer 10.

  In the present embodiment, the linearly polarized light L1 is p-polarized light. The vibration plane (direction) of the linearly polarized light L <b> 1 is defined by the transmission axis of the polarizer 32.

  The light source 31 of the illumination system 30 is an inexpensive discharge light source or LED. The polarizer 32 is disposed in the vicinity of the emission end of the light source 31, and its transmission axis is set to a predetermined direction, and the light from the light source 31 is converted into linearly polarized light L1 according to the transmission axis. The illumination lens 33 is disposed so that it substantially coincides with the emission end of the light source 31 and the rear focal point substantially coincides with the surface of the wafer 10, and guides light from the polarizer 32 to the surface of the wafer 10. That is, the illumination system 30 is an optical system telecentric with respect to the wafer 10 side.

  In the illumination system 30, the light from the light source 31 becomes p-polarized linearly polarized light L <b> 1 through the polarizer 32 and the illumination lens 33 and enters the entire surface of the wafer 10. The incident angle of the linearly polarized light L1 at each point of the wafer 10 is the same because of the parallel light flux, and corresponds to the angle θ formed by the optical axis and the normal line A1.

  In this embodiment, since the linearly polarized light L1 incident on the wafer 10 is p-polarized light, as shown in FIG. 4, the repeating direction (X direction) of the repeated pattern 12 is the incident surface A2 of the linearly polarized light L1 (the surface of the wafer 10). Is set to an angle of 45 degrees with respect to the linearly polarized light L1 traveling direction), the direction of the vibrating surface of the linearly polarized light L1 on the surface of the wafer 10 (the V direction in FIG. 5) and the repeating direction of the repeating pattern 12 (X The angle formed by (direction) is also set to 45 degrees.

  In other words, the linearly polarized light L1 is repeated with the vibration plane direction (V direction in FIG. 5) of the linearly polarized light L1 on the surface of the wafer 10 inclined by 45 degrees with respect to the repeating direction (X direction) of the repeating pattern 12. The light repeatedly enters the pattern 12 so as to cross the pattern 12 diagonally.

  The angle state between the linearly polarized light L1 and the repeated pattern 12 is uniform over the entire surface of the wafer 10. The reason why the angle formed by the vibration surface direction (V direction) and the repeat direction (X direction) in FIG. 5 is set to 45 degrees is to maximize the change in the polarization state due to the repeat pattern 12.

  When the linear pattern L1 is used to illuminate the repetitive pattern 12, the elliptically polarized light L2 is generated as specularly reflected light due to the influence of the reflectance difference on the structural birefringence of the repetitive pattern 12 and the vibration of light in the XY directions. . Note that linearly polarized light and circularly polarized light are special cases of elliptically polarized light, and when expressed as elliptically polarized light in the present embodiment, it is specified that linearly polarized light and circularly polarized light are also included. At this time, if there is any defect in the pattern, the state of elliptically polarized light (for example, S0, S1, S2, S3 in terms of Stokes parameters) changes compared to when there is no defect. In the present embodiment, the defect of the pattern is detected based on the difference in the polarization state, and the cause of the defect is specified.

  As shown in FIG. 1, the light receiving system 40 includes a light receiving lens 41, a phase shifter 42, an analyzer 43, and a two-dimensional imaging camera 44. Measure state. The light receiving system 40 is disposed such that its optical axis passes through the center of the stage 20 and is inclined by an angle θ with respect to the normal A1 of the stage 20. The light receiving lens 41 condenses the elliptically polarized light L <b> 2 on the imaging surface of the two-dimensional imaging camera 44.

  The phase shifter 42 is a quarter-wave plate and is configured to be rotatable around the optical axis of the light receiving system 40 using a rotation driving device (not shown). In the rotational phase shifter method, even if the phase shifter deviates from a quarter wavelength, it can be corrected by calculation if the value is known.

  The two-dimensional imaging camera 44 is a CCD camera having a CCD imaging device (not shown), photoelectrically converts a regular reflection image of the wafer 10 formed on the imaging surface, and outputs an image signal to the image processing unit 50. The two-dimensional imaging camera 44 incorporates a lens (not shown), and can cooperate with the light receiving lens 41 to capture an entire image or a partial image (regular reflection image) of the wafer 10. . At this time, when a plurality of images are taken while the phase shifter 42 is rotated, the brightness of the image of the wafer 10 changes with the rotation of the phase shifter 42.

  Here, the principle of measuring the polarization state by the rotational phase shifter method will be described. FIG. 7 (a) schematically shows the measurement principle of the rotational phase shifter method. As shown in FIG. 7A, when the phase shifter 42 arranged in front of the analyzer 43 is rotated while the polarizer 32 and the analyzer 43 are fixed, the detector (two-dimensional imaging camera 44) And the shape of elliptically polarized light can be specified from the waveform. The Stokes parameter measurement by the Rotational Transition Phase Method has been introduced in various books and magazines. For example, “Method by Rotating λ / 4 Plate” on page 233 of “Applied Optics II-Baifukan” by Tatsuta Tatsuo It is introduced as. Specifically, when the waveform of the signal intensity due to the rotation of the phase shifter 42 is expanded in Fourier series, S0 in the Stokes parameter is a bias component and a cos4θ component, S1 is a cos4θ component, S2 is a sin4θ component, and S3 is a sin2θ component. Therefore, the Stokes parameters can be obtained from these Fourier series.

  In the present embodiment, since the imaging camera 44 is two-dimensional, the polarization state can be collectively measured for the entire surface or a part of the wafer 10. FIG. 7B shows a waveform of a signal obtained by the rotational phase shifter method, which is a plot of a signal from one pixel of the two-dimensional imaging camera 44. In practice, waveform data for the number of pixels of the camera can be acquired at a time.

  The image processing unit 50 converts the image of the wafer 10 (regular reflection image) into a digital image of a predetermined bit (for example, 8 bits) based on the image signal of the wafer 10 input from the two-dimensional imaging camera 44. Further, the image processing unit 50 performs predetermined signal processing to obtain the shape of the elliptically polarized light L2, and evaluates the shape of the repeated pattern 12. The evaluation result of the repeated pattern 12 by the image processing unit 50 and the image of the wafer 10 at that time are output and displayed on the monitor 55.

  In the evaluation apparatus 1 configured as described above, in order to evaluate the repeated pattern 12, first, the wafer 10 to be evaluated is transferred to the stage 20. After the wafer 10 is transferred, alignment is performed so that the repeating direction of the repeating pattern 12 is inclined by 45 degrees with respect to the illumination direction (the traveling direction of the linearly polarized light L1 on the surface of the wafer 10). The alignment angle is not limited to 45 degrees, and may be 67.5 degrees or 22.5 degrees.

  After carrying and aligning the wafer 10, the surface of the wafer 10 is irradiated with linearly polarized light L 1, and the specularly reflected light (elliptical polarized light L 2) reflected on the surface of the wafer 10 is passed through the phase shifter 42 and the analyzer 43. The two-dimensional imaging camera 44 detects and images. At this time, light from the light source 31 becomes linearly polarized light L <b> 1 through the polarizer 32 and the illumination lens 33 and is irradiated on the surface of the wafer 10. Then, the specularly reflected light (elliptical polarized light L2) reflected from the surface of the wafer 10 is collected by the light receiving lens 41, the second linearly polarized light L3 is extracted by the phase shifter 42 and the analyzer 43, and the two-dimensional imaging camera 44 is extracted. The two-dimensional imaging camera 44 is imaged on the imaging surface of the wafer 10 to generate an image signal by photoelectrically converting the regular reflection image of the wafer 10 by the second linearly polarized light L3 formed on the imaging surface. The image is output to the image processing unit 50. At this time, the two-dimensional imaging camera 44 captures a plurality of regular reflection images of the wafer 10 while rotating the phase shifter 42.

  When the image signal of the wafer 10 by the second linearly polarized light L3 is input to the image processing unit 50, the image processing unit 50 performs Stokes of the elliptically polarized light L2 by the rotational phase shift method in units of pixels of the two-dimensional imaging camera 44. Find parameters. When the Stokes parameter is obtained, the average value of the Stokes parameter is calculated for each shot, and the change amount from the appropriate value of the dose amount (exposure amount) is obtained for each shot from the calculated average value. Further, for each shot, the amount of change from the appropriate focus value is obtained separately from the amount of change in dose from the calculated average value of the Stokes parameters. The dose amount or focus change amount obtained in this way is displayed on the monitor 55 together with the image of the wafer 10, and if the dose amount or focus change amount exceeds a predetermined threshold, it is determined as a dose failure or a focus failure. This is notified. At this time, the image processing unit 50 compares the dose amount change amount and the focus change amount with the Stokes parameter (that is, the shape of elliptically polarized light), for example, by comparing with a previously obtained data table. The change amount of the amount and the change amount of the focus are determined and obtained.

  Here, an actual example in which the evaluation apparatus 1 according to the present embodiment is actually created and the polarization state is measured is shown in FIG. 8 (a) and 8 (b) show a focus shift and a shot that intentionally gives an excess or deficiency in exposure amount with respect to a wafer (conditional wafer) in which a plurality of exposure shots are arranged as shown in FIG. The result of measuring the polarization state of the reflected light from the shot is shown. Since the figure of this elliptically polarized light L2 is drawn with Stokes parameters whose light quantity is not standardized so that S0 = 1, the size of the ellipse also changes reflecting the reflectance from each shot.

The reason why it is possible to distinguish and detect a dose defect and a focus defect will be described with reference to FIG. Each shot in FIG. 8A intentionally has an excess or deficiency in the exposure amount (dose amount). The appropriate exposure amount is in the vicinity of the center of FIG. 8A, and the left side of FIG. Is a shot in which the exposure amount is insufficient as it goes to the left, and the right side of FIG. 8A is a polarization state in which the exposure amount is excessive as it goes to the right. When a pattern having structural birefringence is illuminated by linearly polarized light L1 as shown in FIG. 8C, the reflected light generally becomes elliptically polarized light L2 having an inclination. From FIG. 8A, when the exposure amount is changed, the thickness of the ellipse changes (corresponding to S3), and the major axis angle and size (length) of the ellipse change (size). (S0, the major axis angle is calculated by ψ = tan ⁻¹ (S2 / S1) / 2, where the horizontal axis is 0 degree). Each shot in FIG. 8B is obtained by intentionally changing the focus. The focus in the vicinity of the center in FIG. 8B is a normal focus, and the left side in FIG. 8B is focused toward the left. The right side of FIG. 8B shows the polarization state of a shot that becomes negative as the focus becomes positive as it goes to the right. From FIG. 8B, when the focus is changed, the thickness of the ellipse changes (corresponding to S3), but the angle and size (length) of the major axis of the ellipse hardly change ( It can be seen that the magnitude is S0, and the major axis angle is calculated as ψ = tan ⁻¹ (S2 / S1) / 2, where the horizontal is 0 degrees.

  From these facts, in the case of the pattern used in this experiment, the size of the ellipse and the inclination of the major axis do not change so much, and those whose oval thickness changes are poor focus, the major axis angle of the ellipse and It can be seen that the change in size is a dose failure (exposure dose failure). In this way, according to the present embodiment, it is possible to determine and detect a dose defect and a focus defect, and it is possible to specify the cause of the abnormality of the repeated pattern 12.

  At this time, by using the linearly polarized light L1 as the illumination light, it is possible to evaluate the repetitive pattern 12 using structural birefringence with a simple configuration.

  Further, by detecting the polarization state by the rotational phase shifter method, it is possible to accurately detect and detect the dose failure and the focus failure from the elliptical shape of the elliptically polarized light L2.

  In the present embodiment, by making the wavelength of illumination light (linearly polarized light L1) selectable, it is possible to perform highly sensitive measurement by selecting a wavelength with a large change in elliptically polarized light L2.

  In the above-described embodiment, the amount of change in dose (exposure amount) and the amount of change in focus are determined and determined, but the present invention is not limited to this. For example, a change in the line width of the repetitive pattern 12 caused by a change in dose amount and an increase in LER caused by a change in focus may be detected and detected. Note that, depending on the pattern to be evaluated, the method of changing the elliptical polarization L2 of the dose defect and the focus defect may be different from the present embodiment, but as described above, the repetition pattern 12 due to the dose defect is different. The shape change is mainly a phenomenon in which the ratio of the line portion 2A and the space portion 2B changes, whereas the shape change of the repeated pattern 12 due to a focus failure is a LER change, and the way of changing the elliptically polarized light L2 is different. Therefore, it is effective to evaluate the shape of the pattern only by using different judgment algorithms.

  In this embodiment, the Stokes parameter is used as an index representing the polarization state, but the present invention is not limited to this. As an index indicating the polarization state, for example, a method of expressing the polarization state using the major axis azimuth angle and ellipticity angle or the major axis azimuth angle and ellipticity when the polarization state is represented by an ellipse, or the polarization state represented by a Jones vector. There are a method of expressing using a complex amplitude amplitude term and a phase term, a method of expressing a polarization state using a Jones amplitude vector and a complex amplitude real term and an imaginary term, and the like. These represent the shape of the ellipse of elliptically polarized light and the direction of rotation in the end, even if the form of expression is different. Therefore, although the Stokes parameters are obtained in the present embodiment, any measurement using another expression format may be used as long as it can represent the shape of the ellipse and the direction of rotation.

  In the above-described embodiment, the polarization state is detected by the rotational phase shifter method. However, the present invention is not limited to this, and various methods such as the rotational analyzer method and the phase modulation method are known. Any method can be used as long as it can measure the polarization state.

  In order to detect the polarization state by the rotation analyzer method, for example, as shown in FIG. 9, the light receiving system 140 includes a light receiving lens 41, an analyzer 143, a rotation driving device 144, and an imaging camera 44. Composed. That is, instead of the phase shifter 42 described above, the analyzer 143 is configured to be able to rotate the azimuth (polarization direction) of the transmission axis around the optical axis of the light receiving system 140 using the rotation drive device 144. The two-dimensional imaging camera 44 captures a plurality of regular reflection images of the wafer 10 by the second linearly polarized light L3 formed on the imaging surface. Then, the Stokes parameter can be obtained by Fourier transforming the signal intensity obtained by the two-dimensional imaging camera 44. However, with this method, it is impossible to distinguish between clockwise polarized light and counterclockwise polarized light. That is, the code of S3 cannot be specified.

  In order to detect the polarization state by the phase modulation method, for example, as shown in FIG. 10, the illumination system 230 includes a laser light source 231, a polarizer 232, and a photoelastic modulator 233 that is a phase modulation element. The light receiving system 240 includes an analyzer 241 and a photodetector 242. That is, the laser light emitted from the laser light source 231 is transmitted through the polarizer 232 and the photoelastic modulator 233 to be polarized and irradiated on the surface of the wafer 10, and the specularly reflected light reflected on the surface of the wafer 10 is The light is transmitted through the analyzer 241 and detected by the photodetector 242. Here, the photoelastic modulator 233 continuously changes the phase difference of light transmitted through the photoelastic modulator 233, and (linear) polarized light obtained by transmitting through the polarizer 232 is converted into linearly polarized light, It can be changed to either elliptically polarized light or circularly polarized light. Then, the signal intensity obtained by the photodetector 242 is detected by detecting the light by the photodetector 242 while rotating the wafer 10 by the stage 20 and changing the polarization phase difference by the photoelastic modulator 233. Thus, it is possible to determine the polarization state of light obtained by structural birefringence.

  In this embodiment, the illumination light is p-polarized light. However, the present invention is not limited to this. For example, s-polarized light, elliptically polarized light, circularly polarized light, etc., except for linearly polarized light that is perpendicular or horizontal to the pattern repeat direction. Any polarization state may be used.

  In the above-described embodiment, the repeated pattern 12 formed on the surface of the wafer 10 is evaluated. However, the present invention is not limited to this. For example, a pattern formed on a glass substrate can be evaluated. It is.

It is a figure which shows the whole structure of an evaluation apparatus. It is an external view of the surface of a semiconductor wafer. It is a perspective view explaining the uneven structure of a repeating pattern. It is a figure explaining the inclination state of the entrance plane of a linearly polarized light and the repeating direction of a repeating pattern. It is a figure explaining the inclination state of the direction of the vibration surface of linearly polarized light, and the repeating direction of a repeating pattern. It is a schematic diagram which shows line edge roughness. (A) is the figure which showed typically the measurement principle of the rotation phase shifter method, (b) is a figure which shows the waveform of the signal obtained by the rotation phase shifter method. (A) And (b) is a figure which shows the polarization state of the elliptically polarized light reflected from each shot of a condition wafer, (c) is a figure which shows the polarization state of a linearly polarized light. It is a figure which shows the 1st modification of an evaluation apparatus. It is a figure which shows the 2nd modification of an evaluation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Evaluation apparatus 10 Wafer (substrate) 12 Repeat pattern 30 Illumination system (illumination part)
40 Light receiving system (polarization state detector) 42 Phase shifter (wave plate)
43 Analyzer (polarizing plate) 44 Two-dimensional imaging camera (detector)
50 Image processing unit (evaluation unit)
140 Light Receiving System (Modification) 143 Analyzer (Polarizing Plate)
230 Illumination System (Modification) 233 Photoelastic Modulator (Phase Modulation Element)
L1 First linearly polarized light L2 Elliptical polarized light L3 Second linearly polarized light

Claims (7)

An illumination unit that irradiates polarized light onto the surface of the substrate having a predetermined repeating pattern;
A polarization state detector that detects a polarization state of specularly reflected light from the repetitive pattern irradiated with the polarized light;
An evaluation apparatus comprising: an evaluation unit that evaluates the shape of the repetitive pattern based on the polarization state detected by the polarization state detection unit.   The evaluation apparatus according to claim 1, wherein the illumination unit irradiates the surface of the substrate with linearly polarized light. The repeating pattern is formed using an exposure apparatus,
The polarization state of the regular reflection light is elliptically polarized light,
Based on the shape characteristics of the elliptically polarized light detected by the polarization state detection unit, the evaluation unit determines from the shape error of the repetitive pattern caused by the deviation from the appropriate value of the exposure amount in the exposure apparatus and the appropriate focus position. The evaluation apparatus according to claim 1, wherein the evaluation apparatus discriminates and detects a shape error of the repetitive pattern caused by a deviation of the pattern. The repeating pattern is a line and space pattern,
The evaluation unit discriminates and detects a defect in the volume ratio of the line and space of the pattern and a defect in line edge roughness based on the shape characteristic of the elliptically polarized light detected by the polarization state detection unit. The evaluation apparatus according to any one of claims 1 to 3.   The polarization state detection unit includes a condensing optical system including a wave plate and a polarizing plate that are rotatably arranged and a detector, and detects the polarization state by a rotational phase shifter method. Item 5. The evaluation device according to any one of Items 1 to 4.   5. The polarization state detection unit includes a condensing optical system including a polarizing plate rotatably disposed and a detector, and detects the polarization state by a rotation analyzer method. The evaluation apparatus according to any one of the above.   5. The evaluation apparatus according to claim 1, wherein the illumination unit includes a phase modulation element, and the polarization state detection unit detects the polarization state by a phase modulation method. 6.

Images