JP2012177650A - Pattern inspection device and pattern inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern inspection device capable of inspection with laser light of which an optical axis has been adjusted more accurately.SOLUTION: A pattern inspection device 100 includes: a noise direction specifying circuit 128 which uses the amount of laser light received by a photo diode array 212 receiving light by surfaces in the first to fourth quadrants independently of one another, to specify a generation direction of noise component light generated together with the laser light; a noise light amount calculation circuit 130 which uses the amount of laser light to calculate the amount of noise component light; mirror controllers 121 and 122 which control positions of reflecting surfaces of mirrors 202 and 204 so that an absolute value of a centroid value in the generation direction of noise component light is equal to a value obtained by dividing the amount of noise component light by a total amount of laser light and a centroid value in a direction orthogonal to the generation direction of noise component light is 0; an optical image acquisition unit 150 which uses laser light having the optical axis adjusted, to acquire an optical image of a pattern of a sample to be inspected; and a comparison circuit 108 which receives a reference image and compares the optical image with the reference image.

Description

  The present invention relates to a pattern inspection apparatus and a pattern inspection method, for example, a pattern inspection in which an optical axis of a laser beam from a light source is adjusted and a pattern defect of an object serving as a sample used for semiconductor manufacture is inspected with the adjusted laser beam. The present invention relates to an apparatus and a method thereof.

  In recent years, the circuit line width required for a semiconductor element has been increasingly narrowed as a large scale integrated circuit (LSI) is highly integrated and has a large capacity. These semiconductor elements use an original pattern pattern (also referred to as a mask or a reticle, hereinafter referred to as a mask) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. It is manufactured by forming a circuit. Therefore, a pattern drawing apparatus capable of drawing a fine circuit pattern is used for manufacturing a mask for transferring such a fine circuit pattern onto a wafer. A pattern circuit may be directly drawn on a wafer using such a pattern drawing apparatus. For example, drawing is performed using an electron beam or a laser beam.

  In addition, improvement in yield is indispensable for manufacturing an LSI that requires a large amount of manufacturing cost. However, as represented by a 1 gigabit class DRAM (Random Access Memory), the pattern constituting the LSI is about to be in the order of submicron to nanometer. One of the major factors that reduce the yield is a pattern defect of a mask used when an ultrafine pattern is exposed and transferred onto a semiconductor wafer by a photolithography technique. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. Therefore, it is necessary to improve the accuracy of a pattern inspection apparatus that inspects defects in a transfer mask used in LSI manufacturing.

  On the other hand, with the development of multimedia, LCDs (Liquid Crystal Display) are increasing in size of the liquid crystal substrate to 500 mm × 600 mm or more, and TFTs (Thin Film Transistors) formed on the liquid crystal substrate. : Thin film transistors) and the like are being miniaturized. Therefore, it is required to inspect a very small pattern defect over a wide range. For this reason, it has become an urgent task to develop a pattern inspection apparatus for efficiently inspecting defects of a photomask used in manufacturing such a large area LCD pattern and a large area LCD in a short time.

  With the miniaturization and high integration of the mask pattern, the inspection apparatus is required to have a high resolution, and the wavelength of illumination light of the inspection apparatus is also short. For example, deep ultraviolet light of 266 nm or less is used. And the laser beam used as this illumination light is oscillated from the laser light source device. The optical axis of the laser beam is adjusted to illuminate the inside of the inspection apparatus. For example, a method has been devised in which laser light is received by a surface light receiving element, the shape of the laser light is determined, and the optical axis is adjusted using the symmetry of the shape of the laser light (see, for example, Patent Document 1). ).

  However, in addition to the main laser beam that is originally intended to be used, noise component light may be generated together with the laser light generated from such a laser light source, and the optical axis of the original laser beam that is desired to be used by such noise component light. There was a problem that an error occurred in the adjustment.

JP 2005-259833 A

  As described above, there has conventionally been a problem that an error occurs in the adjustment of the optical axis of the original laser beam to be used due to the noise component light generated together with the laser beam generated from the laser light source.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern inspection apparatus and method that can overcome the above-described problems and can be inspected with a laser beam whose optical axis is adjusted with higher accuracy.

The pattern inspection apparatus according to one aspect of the present invention includes:
A light source that generates laser light;
First and second mirrors that sequentially reflect the laser light and adjust the optical axis of the laser light, each capable of changing the position of the reflecting surface;
A half mirror for branching a part of the laser light reflected by the first and second mirrors;
An illumination optical system that illuminates the inspected sample on which the pattern is formed with the remaining laser light that has not been split by the half mirror;
A first light receiving unit that is arranged at a position conjugate with the illumination optical system and that receives a part of the laser beam branched by the half mirror independently on the first to fourth quadrants;
A second light receiving unit that is disposed at a position conjugate with the second mirror and that receives a part of the laser beam branched by the half mirror independently on the surfaces of the first to fourth quadrants;
A noise component direction specifying unit for specifying a generation direction of noise component light generated together with the laser light from the light source, using the amount of laser light received by at least one of the first and second light receiving units;
A noise component light amount calculation unit for calculating the light amount of the noise component light using the light amount of the laser light received by at least one of the first and second light receiving units;
A centroid calculating unit for calculating the centroid of each laser beam received by the first and second light receiving units,
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the first light receiving unit, and in the direction orthogonal to the noise component light generation direction. A first mirror control unit that controls the position of the reflecting surface of the first mirror so that the center of gravity value becomes 0;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the second light receiving unit, and in the direction orthogonal to the noise component light generation direction. A second mirror control unit that controls the position of the reflecting surface of the second mirror so that the center of gravity value becomes 0;
An optical image acquisition unit that acquires an optical image of a pattern of a sample to be inspected using laser light having an optical axis adjusted by the first and second mirrors;
A comparison unit that inputs a reference image and compares the optical image with the reference image;
It is provided with.

The center of gravity of the laser beam in the x direction is obtained by subtracting the sum of the amounts of light received by the second and third quadrants from the sum of the amounts of light received by the first and fourth quadrants. It is defined by the value divided by the total light quantity of each light quantity received in the quadrant plane,
The center of gravity of the laser beam in the y direction is obtained by subtracting the sum of the respective light amounts received by the first and second quadrant surfaces from the sum of the respective light amounts received by the third and fourth quadrant surfaces. It is preferable that the value is defined by a value obtained by dividing the total amount of light received at 1.

  In addition, the noise component direction specifying unit determines the generation direction of the noise component light by using the change in the amount of laser light in the moving direction obtained by moving at least one of the first and second mirrors to a plurality of positions. It is preferable that the configuration is specified.

  The noise component direction specifying unit calculates the light amount of the noise component light using the change in the light amount of the laser light in the moving direction obtained by moving at least one of the first and second mirrors to a plurality of positions. It is preferable.

The pattern inspection method of one embodiment of the present invention includes:
Generating laser light from a light source;
An object to be inspected in which a laser beam is sequentially reflected by the first and second mirrors while moving at least one of the first and second mirrors, each of which can change the position of the reflecting surface, to a plurality of positions. A part of the laser beam reflected by the first and second mirrors is independently produced in the first to fourth quadrant planes by the first light receiving unit arranged at a position conjugate with the illumination optical system for illuminating the sample. Receiving light; and
A second light receiving element disposed at a position conjugate with the second mirror by sequentially reflecting the laser light by the first and second mirrors while moving at least one of the first and second mirrors to a plurality of positions. A step of independently receiving a part of the laser light reflected by the first and second mirrors on the surfaces of the first to fourth quadrants,
Identifying the generation direction of the noise component light generated together with the laser light from the light source using the light amount of the laser light received by at least one of the first and second light receiving units;
Calculating the amount of noise component light using the amount of laser light received by at least one of the first and second light receiving units;
Calculating the center of gravity of each laser beam received by the first and second light receiving units;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the first light receiving unit, and in the direction orthogonal to the noise component light generation direction. Controlling the position of the reflecting surface of the first mirror so that the centroid value becomes 0;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the second light receiving unit, and in the direction orthogonal to the noise component light generation direction. Controlling the position of the reflecting surface of the second mirror so that the centroid value becomes 0;
A step of acquiring an optical image of a pattern of a sample to be inspected using the laser light whose optical axis is adjusted by the first and second mirrors;
Inputting a reference image and comparing the optical image with the reference image;
It is provided with.

  According to the present invention, it is possible to adjust the optical axis of laser light by removing noise component light. Therefore, high-precision inspection can be performed by performing pattern inspection using the laser light with the optical axis adjusted as illumination light.

1 is a conceptual diagram illustrating a partial configuration of a pattern inspection apparatus according to Embodiment 1. FIG. FIG. 3 is a conceptual diagram showing the remaining configuration of the pattern inspection apparatus in the first embodiment. 6 is a diagram showing an example of a beam profile of laser light in the first embodiment. FIG. FIG. 4 is a flowchart showing main steps of the pattern inspection method in the first embodiment. FIG. 3 is a conceptual diagram illustrating an example of an image on a photodiode array when the laser beam in the first embodiment is scanned in the y direction. FIG. 3 is a conceptual diagram showing an example of an image on a photodiode array when the laser beam in the first embodiment is scanned in the x direction. 6 is a diagram showing an example of a beam profile indicated by a total light amount measured by the photodiode array in Embodiment 1. FIG. FIG. 7 is a conceptual diagram showing another example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the x direction. FIG. 7 is a conceptual diagram showing another example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the y direction. 6 is a diagram for explaining an optical image acquisition procedure according to Embodiment 1. FIG. It is a figure for demonstrating another optical image acquisition method.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating a partial configuration of the pattern inspection apparatus according to the first embodiment. FIG. 2 is a conceptual diagram showing the remaining configuration of the pattern inspection apparatus according to the first embodiment. 1 and 2, a pattern inspection apparatus 100 that inspects a defect of such a sample using a substrate such as a mask as a sample includes a light source 103, an optical axis adjustment unit 172, an illumination optical system 170, an optical image acquisition unit 150, and a control circuit 160. It has. The optical axis adjustment unit 172 includes mirrors 202 and 204, half mirrors 230 and 232, a mirror 234, drive mechanisms 222 and 224, and photodiode arrays 212 and 214. The optical image acquisition unit 150 includes an XYθ table 102, an enlargement optical system 104, a photodiode array 105, a sensor circuit 106, a laser length measurement system 122, and an autoloader 130. In the control circuit 160, the control computer 110 serving as a computer transmits a position circuit 107, a comparison circuit 108 serving as an example of a comparison unit, a development circuit 111, a reference circuit 112, and an autoloader control circuit 113 via a bus 120 serving as a data transmission path. , Table control circuit 114, magnetic disk device 109 as an example of a storage device, magnetic tape device 115, flexible disk device (FD) 116, CRT 117, pattern monitor 118, printer 119, mirror control circuits 121 and 122, measurement circuit 124, 126, a magnetic disk device 140 as an example of a storage device, a noise direction specifying circuit 128, a noise light amount calculation circuit 130, a centroid calculation circuit 132, a determination circuit 134, and an optical axis adjustment circuit 136.

  Further, the incident surface of the photodiode array 212 is disposed at a position having a conjugate relationship with the incident surface to the illumination optical system 170. The incident surface of the photodiode array 214 is disposed at a position having a conjugate relationship with the reflecting surface of the mirror 204. Specifically, the laser light generated from the laser light source 103 is reflected by the mirror 202 and subsequently reflected by the mirror 204. A part of the reflected laser light is branched by the half mirror 230, and the rest is incident on the illumination optical system 170. A part of the light beam of the laser beam branched by the half mirror 230 is further branched by the half mirror 232, and a part of the light beam is received by the photodiode array 214. The remaining light beam that has passed through the half mirror 232 is reflected by the mirror 234 and received by the photodiode array 212. Further, the reflecting surface of the mirror 202 is configured to be moved in, for example, a biaxial direction by a drive mechanism 222 using a servo motor or the like. Similarly, the reflecting surface of the mirror 204 is configured to be moved in, for example, two axial directions by a driving mechanism 224 using a servo motor or the like. By controlling the positions of the reflecting surfaces of the mirrors 202 and 204, adjustment is made so that the optical axis of the laser light incident on the illumination optical system 170 is not shifted.

  The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor. In FIGS. 1 and 2, constituent parts necessary for explaining the first embodiment are described. It goes without saying that the pattern inspection apparatus 100 may normally include other necessary configurations.

  FIG. 3 is a diagram illustrating an example of a beam profile of laser light in the first embodiment. In FIG. 3, the vertical axis indicates the light intensity, and the horizontal axis indicates the position. In addition to the main laser beam 20 originally intended to be used, the noise component beam 10 may be generated together with the laser beam generated from the light source 103. Attempting to adjust the optical axis without distinguishing between the laser beam 20 and the noise component light 10 results in the center of gravity of the combined light of the laser beam 20 and the noise component light 10 being aligned with the optical axis. For this reason, the center of gravity of the laser beam 20 that is originally intended to be used is deviated from the optical axis, and a part of the laser beam 20 is not used for illumination when it enters the subsequent optical system. Say). As a result, a light amount loss occurs. Therefore, in the first embodiment, the generation direction and the light amount of the noise component light 10 are specified, and the center of gravity of the laser light 20 originally intended to be used excluding the noise component light 10 is adjusted to the optical axis.

  FIG. 4 is a flowchart showing main steps of the pattern inspection method according to the first embodiment. In FIG. 4, a y-direction scanning (scanning) step (S102), a light amount measuring step (S104), an x-direction scanning (scanning) step (S106), a light amount measuring step (S108), and a noise light direction specifying step ( S114), a noise light amount calculation step (S116), a center of gravity calculation step (S118), a determination step (S120), an optical axis adjustment step (S122), and a pattern inspection step (S130). . In FIG. 4, after a set of the y-direction scanning (scanning) step (S102) and the light amount measuring step (S104) is performed, a set of the x-direction scanning (scanning) step (S106) and the light amount measuring step (S108) is performed. However, it is not limited to this. Either the y-direction scanning (scanning) step (S102) and the light quantity measurement step (S104) or the x-direction scanning (scanning) process (S106) and the light quantity measurement step (S108) may be performed first. Absent. In addition, the order of the noise light direction specifying step (S114) and the noise light amount calculation step (S116) may be first.

  As a y-direction scanning (scanning) step (S102), laser light is generated from the light source 103. Then, the optical axis adjustment circuit 136 sequentially reflects the laser light by the mirrors 202 and 204 while moving at least one of the mirrors 202 and 204 that can change the position of the reflecting surface to a plurality of positions in the y direction. The laser light is scanned on the light receiving surfaces of the photodiode arrays 212 and 214.

  FIG. 5 is a conceptual diagram showing an example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the y direction. For example, FIG. 5 shows a case where the noise component light 10 is generated in the y direction with respect to the laser light 20. Here, the photodiode array 212 (an example of the first light receiving unit) is configured such that four light receiving elements 30, 32, 34, and 36 are arranged in a 2 × 2 arrangement. The four light receiving elements 30, 32, 34, and 36 independently receive light on the surfaces in the first to fourth quadrants. The light receiving element 30 sets the center of the photodiode array 212 as the reference position (x, y = 0), and the light incident on the surface of the positive region (second quadrant: region indicated by A) of −x, + y. Receives light. The light receiving element 32 receives the amount of light incident on the surface of the positive region of −x, −y (third quadrant: region indicated by B). The light receiving element 34 receives the amount of light incident on the surface of the positive area (first quadrant: area indicated by C) of + x and + y. The light receiving element 36 receives the amount of light incident on the surface of the positive region of + x, −y (fourth quadrant: region indicated by D). Similarly, the photodiode array 214 (an example of a second light receiving unit) is configured so that four light receiving elements 40, 42, 44, and 46 are arranged in a 2 × 2 arrangement. The four light receiving elements 40, 42, 44, and 46 receive light independently in the first to fourth quadrant surfaces. The light receiving element 40 uses the center of the photodiode array 212 as the reference position (x, y = 0), and the light incident on the surface of the positive region (second quadrant: region indicated by A) of −x, + y. Receives light. The light receiving element 42 receives the amount of light incident on the surface of the positive region of −x, −y (third quadrant: region indicated by B). The light receiving element 44 receives the amount of light incident on the surface of the positive regions of + x and + y (first quadrant: region indicated by C). The light receiving element 46 receives the amount of light incident on the surface of the positive region of + x, −y (fourth quadrant: region indicated by D).

  Here, in the photodiode array 212, four photodiodes are combined as the light receiving elements 30, 32, 34, and 36. However, the present invention is not limited to this, and the light amount can be measured independently in a region where the light receiving surface is divided into four. Any light receiving mechanism may be used. The same applies to the photodiode array 214.

  For example, the optical axis adjustment circuit 136 controls the mirror control circuit 121 to cause the drive mechanism 224 to move the position of the reflection surface of the mirror 204. At that time, first, light (both laser light 20 and noise component light 10) generated from the light source 103 cannot be detected by, for example, the photodiode array 212 at all. The light moves in the y direction sequentially from the position in the y direction. Scan to. Or you may scan so that light may move toward -y direction sequentially from the position of + y direction. For example, scanning is performed so as to step-feed to a plurality of positions in the y direction. Thereby, only the noise component light 10 is received by the light receiving elements 32 and 36 (B, D) in order from the position where the light generated from the light source 103 (both the laser light 20 and the noise component light 10) is not detected at all. Detected. Subsequently, the light amounts of both the noise component light 10 and the laser light 20 are detected by the light receiving elements 32 and 36 (B, D). Subsequently, only the noise component light 10 is detected by the light receiving elements 30, 34 (A, C), and only the laser light 20 is detected by the light receiving elements 32, 36 (B, D). Subsequently, a part of the noise component light 10 and the laser beam 20 is detected by the light receiving elements 30 and 34 (A, C), and the remaining part of the laser beam 20 is detected by the light receiving elements 32 and 36 (B, D). Detected. Subsequently, the light amounts of both the noise component light 10 and the laser light 20 are detected by the light receiving elements 30 and 34 (A, C). Subsequently, the light amount of only the laser beam 20 is detected by the light receiving elements 30 and 34 (A, C). Finally, both the laser light 20 and the noise component light 10 are not detected at all. The same applies to the photodiode array 214 instead of the photodiode array 212.

  In the light quantity measurement step (S104), the measurement circuit 126 measures the light quantity at each position scanned in the y direction using the light receiving elements 30, 32, 34, and 36. Specifically, the light receiving elements 30, 32, 34, and 36 each receive light at each position scanned in the y direction, photoelectrically convert the received light amount, and output it to the measurement circuit 126. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuit 126 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202. Similarly, the measurement circuit 124 measures the amount of light at each position scanned in the y direction using the light receiving elements 40, 42, 44, 46. Specifically, the light receiving elements 40, 42, 44, 46 respectively receive light at each position scanned in the y direction, photoelectrically convert the received light amount, and output it to the measurement circuit 124. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuit 124 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202.

  Next, as an x-direction scanning (scanning) step (S106), the optical axis adjustment circuit 136 moves at least one of the mirrors 202 and 204 that can change the position of the reflecting surface to a plurality of positions in the x-direction. Then, the laser beams are sequentially reflected by the mirrors 202 and 204, and the laser beams are scanned on the light receiving surfaces of the photodiode arrays 212 and 214.

  FIG. 6 is a conceptual diagram showing an example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the x direction. FIG. 6 shows the case where the noise component light 10 is generated in the y direction with respect to the laser light 20, for example, as in FIG.

  For example, the optical axis adjustment circuit 136 controls the mirror control circuit 121 to cause the drive mechanism 224 to move the position of the reflection surface of the mirror 204. At this time, first, light (both laser light 20 and noise component light 10) generated from the light source 103 cannot be detected by the photodiode array 212 at all, for example, so that the light moves in the x direction sequentially from the position in the -x direction. Scan to. Or you may scan so that light may move toward the-x direction sequentially from the position of + x direction. For example, scanning is performed so as to step-feed to a plurality of positions in the x direction. Thereby, both the laser light 20 and the noise component light 10 are sequentially received by the light receiving elements 30 and 32 (A, A, from the position where the light generated from the light source 103 (both the laser light 20 and the noise component light 10) is not detected at all. In B), the amount of light is detected. Alternatively, both a part of the laser light 20 and the noise component light 10 are detected by the light receiving element 30, and the remaining part of the laser light 20 is detected by the light receiving element 32. Subsequently, the light amounts of both the laser beam 20 and the noise component light 10 are detected by the light receiving elements 30, 32, 34, and 36 (A, B, C, and D). Alternatively, both a part of the laser beam 20 and the noise component beam 10 are detected by the light receiving elements 32 and 36, and the remainder of the laser beam 20 is detected by the light receiving elements 32 and 36. Subsequently, the light amounts of both the laser beam 20 and the noise component light 10 are detected by the light receiving elements 33 and 36 (C, D). Alternatively, both a part of the laser light 20 and the noise component light 10 are detected by the light receiving element 34, and the remaining part of the laser light 20 is detected by the light receiving element 36. Finally, both the laser light 20 and the noise component light 10 are not detected at all. The same applies to the photodiode array 214 instead of the photodiode array 212.

  In the light quantity measurement step (S108), the measurement circuit 126 measures the light quantity at each position scanned in the x direction using the light receiving elements 30, 32, 34, and 36. Specifically, the light receiving elements 30, 32, 34, and 36 each receive light at each position scanned in the x direction, photoelectrically convert the received light amount, and output it to the measurement circuit 126. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuit 126 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202. Similarly, the measurement circuit 124 measures the amount of light at each position scanned in the x direction using the light receiving elements 40, 42, 44, 46. Specifically, the light receiving elements 40, 42, 44, 46 respectively receive light at each position scanned in the x direction, photoelectrically convert the received light amount, and output it to the measurement circuit 124. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuit 124 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202.

  As described above, the amount of light received by the photodiode arrays 212 and 214 when scanned in the x and y directions is stored in the storage device 140 relative to the position of the reflection surface of the mirror 202.

  Here, the position of the reflecting surface of the mirror 202 is moved, but the present invention is not limited to this. Instead of the mirror 202, the position of the reflecting surface of the mirror 204 may be moved to perform the same measurement. Alternatively, the positions of both reflecting surfaces of the mirrors 202 and 204 may be moved to perform the same measurement. In addition, the measurement data when scanning in the x and y directions was measured by both the photodiode arrays 212 and 214, but the present invention is not limited to this. Only one of the photodiode arrays 212 and 214 may be measured.

  FIG. 7 is a diagram showing an example of a beam profile indicated by the total light amount measured by the photodiode array in the first embodiment. FIG. 7 shows an example of a beam profile when the light component is scanned in the y direction when the noise component light 10 is generated in the y direction with respect to the laser light 20. The vertical axis represents the amount of light, and the horizontal axis represents the position in the y direction. As shown in FIG. 7, with the movement of the y position, first, the light amount of the noise component light 10 is measured, and then the light amount of the laser light 20 is added to the light amount of the noise component light 10. And it becomes the sum total of the light quantity of both the laser beam 20 and the noise component light 10, and the light quantity of the noise component light 10 decreases. Finally, the amount of laser light 20 decreases.

  FIG. 8 is a conceptual diagram showing another example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the x direction. For example, FIG. 8 shows a case where the noise component light 10 is generated in the x direction with respect to the laser light 20.

  FIG. 9 is a conceptual diagram showing another example of an image on the photodiode array when the laser beam in the first embodiment is scanned in the y direction. FIG. 8 shows a case where the noise component light 10 is generated in the x direction with respect to the laser light 20, for example, as in FIG.

  As shown in FIGS. 8 and 9, when the noise component light 10 is generated in the x direction, the scanning is performed in the x direction as follows. In such a case, as shown in FIG. 8, only the noise component light 10 is received in order from the position where the light generated from the light source 103 (both the laser light 20 and the noise component light 10) is not detected at all. The light quantity is detected at 32 (A, B). Subsequently, the light amounts of both the noise component light 10 and the laser light 20 are detected by the light receiving elements 30 and 32 (A, B). Subsequently, only the noise component light 10 is detected by the light receiving elements 34 and 36 (C, D), and only the laser light 20 is detected by the light receiving elements 30 and 32 (A, B). Subsequently, the light amounts of the noise component light 10 and the laser light 20 are detected by the light receiving elements 34 and 36 (C, D), and the remainder of the laser light 20 is detected by the light receiving elements 30 and 32 (A, B). Detected. Subsequently, the light amounts of both the noise component light 10 and the laser light 20 are detected by the light receiving elements 34 and 36 (C, D). Subsequently, the light amount of only the laser beam 20 is detected by the light receiving elements 34 and 36 (C, D). Finally, both the laser light 20 and the noise component light 10 are not detected at all. The same applies to the photodiode array 214 instead of the photodiode array 212. Similarly, the measurement circuit 126 measures the amount of light at each position scanned in the x direction using the light receiving elements 30, 32, 34, and 36. The measurement circuit 124 measures the amount of light at each position scanned in the x direction using the light receiving elements 40, 42, 44, 46. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuits 124 and 126 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202.

  As shown in FIGS. 8 and 9, when the noise component light 10 is generated in the x direction, the scanning is performed in the y direction as follows. In such a case, as shown in FIG. 9, both the laser light 20 and the noise component light 10 are sequentially arranged from the position where the light generated from the light source 103 (both the laser light 20 and the noise component light 10) is not detected at all. However, the light quantity is detected by the light receiving elements 32 and 36 (B, D). Alternatively, both a part of the laser light 20 and the noise component light 10 are detected by the light receiving element 36, and the remaining part of the laser light 20 is detected by the light receiving element 32. Subsequently, the light amounts of both the laser beam 20 and the noise component light 10 are detected by the light receiving elements 30, 32, 34, and 36 (A, B, C, and D). Alternatively, both a part of the laser light 20 and the noise component light 10 are detected by 34 and 36, and the remaining part of the laser light 20 is detected by the light receiving elements 30 and 32. Subsequently, the light amounts of both the laser light 20 and the noise component light 10 are detected by the light receiving elements 30 and 34 (A, C). Alternatively, both a part of the laser light 20 and the noise component light 10 are detected by the light receiving element 34, and the remaining part of the laser light 20 is detected by the light receiving element 30. Finally, both the laser light 20 and the noise component light 10 are not detected at all. The same applies to the photodiode array 214 instead of the photodiode array 212. Similarly, the measurement circuit 126 measures the amount of light at each position scanned in the x direction using the light receiving elements 30, 32, 34, and 36. The measurement circuit 124 measures the amount of light at each position scanned in the x direction using the light receiving elements 40, 42, 44, 46. Then, the optical axis adjustment circuit 136 stores the amount of light at each position measured by the measurement circuits 124 and 126 in the storage device 140 so as to be relative to the position of the reflection surface of the mirror 202.

  As the noise light direction specifying step (S114), the noise direction specifying circuit 128 reads the measurement data in the x and y directions stored in the storage device 140, and the amount of laser light received by at least one of the photodiode arrays 212 and 214. The generation direction of the noise component light 10 generated from the light source 103 together with the laser light 20 is specified. Specifically, the noise direction specifying circuit 128 is an example of a noise component direction specifying unit. The noise direction specifying circuit 128 specifies the generation direction of the noise component light by using the change in the amount of laser light in the moving direction obtained by moving at least one of the mirrors 202 and 204 to a plurality of positions. More specifically, for example, when noise component light 10 is generated in the y direction, a beam profile as shown in FIG. 7 is obtained from the measurement data. For example, when the noise component light 10 is generated in the x direction, a beam profile in which the horizontal axis in FIG. 7 is read as the x position is obtained. For example, when the noise component light 10 is generated in the −y direction, a beam profile obtained by horizontally inverting the beam profile as shown in FIG. 7 is obtained. Further, for example, when the noise component light 10 is generated in the −x direction, a beam profile obtained by reversing the beam profile obtained by replacing the horizontal axis in FIG. 7 with the x position is obtained. Thus, the generation direction of the noise component light 10 can be specified from the change in the light amount of the beam profile obtained from the measurement data. Specifically, in the example of FIG. 7, first, the amount of noise component light 10 is measured with the movement of the y position, and then the amount of laser light 20 is added to the amount of noise component light 10. Go. Therefore, it can be seen that the noise component light 10 is located in the y direction with respect to the laser light 20. Therefore, it can be specified that the noise component light 10 is generated in the y direction. Conversely, as the y position moves, the light amount of the noise component light 10 decreases from the sum of the light amounts of both the laser light 20 and the noise component light 10, and then the light amount of the laser light 20 decreases. For example, it can be seen that the noise component light 10 is located in the −y direction with respect to the laser light 20. Therefore, it can be specified that the generation direction of the noise component light 10 is the -y direction.

  Similarly, with the movement of the x position, first, the light amount of the noise component light 10 is measured, and then, when the light amount of the laser light 20 is added to the light amount of the noise component light 10, the noise component light 10 is It can be seen that it is located in the x direction with respect to the laser beam 20. Therefore, it can be specified that the noise component light 10 is generated in the x direction. Conversely, as the x position moves, the light amount of the noise component light 10 decreases from the sum of the light amounts of both the laser light 20 and the noise component light 10, and then the light amount of the laser light 20 decreases. For example, it can be seen that the noise component light 10 is located in the −x direction with respect to the laser light 20. Therefore, it can be specified that the noise component light 10 is generated in the −x direction.

  As the noise light amount calculation step (S116), the noise light amount calculation circuit 130 calculates the light amount of the noise component light 10 using the light amount of the laser light received by at least one of the photodiode arrays 212 and 214. The noise light amount calculation circuit 130 is an example of a noise component light amount calculation unit. Specifically, the noise light amount calculation circuit 130 calculates the light amount of the noise component light 10 using the change in the light amount of the laser light in the moving direction obtained by moving at least one of the mirrors 202 and 204 to a plurality of positions. Calculate. More specifically, when the generation direction of the noise component light 10 is the y direction, as shown in FIG. 7, the total amount of light received by the photodiode array 212 is set, and first, the light amount ΔL0 of the noise component light 10 is Detected. Therefore, what is necessary is just to obtain | require this light quantity (DELTA) L0. Alternatively, the light amount ΔL0 can also be calculated because the light amount ΔL0 of the noise component light 10 decreases from the total light amount L1 of both the laser light 20 and the noise component light 10 as the y position moves.

  As described above, the generation direction and light amount of the noise component light 10 can be acquired. In the first embodiment, the optical axis adjustment of the laser light 20 excluding the influence of the noise component light 10 is performed using such information.

As the center of gravity calculation step (S118), the center of gravity calculation circuit 132 calculates the center of gravity of each laser beam received by the photodiode arrays 212 and 214, respectively. The center-of-gravity calculation circuit 132 is an example of a center-of-gravity calculation unit. Specifically, the centroid in the x direction and the centroid in the y direction are calculated. The center of gravity Gx in the x direction of the laser beam is the sum of the amounts of light received at the second and third quadrant surfaces (A, B) from the sum of the amounts of light received at the first and fourth quadrant surfaces (C, D). The subtracted value is defined by a value obtained by dividing the subtracted value by the total amount of light received by the first to fourth quadrant planes (A, B, C, D), and can be expressed by the following Expression 1. The center of gravity Gy in the y direction of the laser light is the sum of the amounts of light received at the first and second quadrant surfaces (C, A) from the sum of the amounts of light received at the third and fourth quadrant surfaces (B, D). The subtracted value is defined by a value obtained by dividing the subtracted value by the total amount of light received by the first to fourth quadrant planes (A, B, C, D), and can be expressed by the following Expression 2.
(1) Gx = {(Lc + Ld)-(La + Lb)} / (La + Lb + Lc + Ld)
(2) Gy = {(Lb + Ld)-(La + Lc)} / (La + Lb + Lc + Ld)

  La, Lb, Lc, and Ld respectively indicate the light quantity in the second quadrant (A), the light quantity in the third quadrant (B), the light quantity in the first quadrant (C), and the light quantity in the fourth quadrant (D). Here, if the positions of the reflecting surfaces of the mirrors 202 and 204 are controlled so that Gx = 0 and Gy = 0, it is likely that the center of gravity of the beam shape of the laser light 20 can be adjusted to the optical axis. However, in actuality, as described above, the noise component light 10 is also generated at the same time. Therefore, such a position is a position affected by the noise component light 10. Therefore, the center of gravity of the beam shape of the laser light 20 is shifted from the optical axis. Therefore, in the first embodiment, the centroid value in the generation direction of the noise component light 10 is an absolute value of a value obtained by dividing the light amount of the noise component light 10 by the total light amount of the laser light, and is orthogonal to the generation direction of the noise component light 10. The positions of the reflecting surfaces of the mirrors 202 and 204 are controlled so that the centroid value in the direction to go is zero. Specifically, it operates as follows.

  As a determination step (S120), the determination circuit 134 inputs the calculated gravity center values Gx and Gy in the x and y directions, and the absolute value of the gravity center value in the generation direction of the noise component light 10 is ΔL0 / (La + Lb + Lc + Ld). Yes, it is determined whether or not the centroid value in the direction orthogonal to the generation direction of the noise component light 10 is zero. For example, if the noise component light 10 is generated in the x direction, it is determined whether Gx = ΔL0 / (La + Lb + Lc + Ld) and Gy = 0. For example, when the generation direction of the noise component light 10 is the y direction, it is determined whether Gx = 0 and Gy = ΔL0 / (La + Lb + Lc + Ld). Such determination determines whether both of the photodiode arrays 212 and 214 satisfy such a condition. If not, the process proceeds to S122. If these conditions are satisfied, the optical axis adjustment is completed.

  As the optical axis adjustment step (S122), the optical axis adjustment circuit 136 controls the mirror control circuit 121 to move the position of the reflection surface of the mirror 204 to the drive mechanism 224, for example. Alternatively, for example, the mirror control circuit 122 is controlled to move the position of the reflection surface of the mirror 202 to the drive mechanism 222. Alternatively, for example, the mirror control circuits 121 and 122 are controlled to move the positions of the reflecting surfaces of the mirrors 202 and 204 to the drive mechanisms 222 and 224. Then, the process returns to the center of gravity calculation step (S118), and the steps from the center of gravity calculation step (S118) to the optical axis adjustment step (S122) are repeated until the conditions described above in the determination step (S120) are satisfied.

  Specifically, in the mirror control circuit 122, the absolute value of the barycentric value in the generation direction of the noise component light 10 is a value obtained by dividing the light amount of the noise component light 10 by the total light amount of the laser light received by the photodiode array 212. The position of the reflecting surface of the mirror 202 is controlled so that the centroid value in the direction orthogonal to the generation direction of the noise component light 10 becomes zero. The mirror control circuit 121 is an example of a first mirror control unit. Similarly, in the mirror control circuit 122, the absolute value of the barycentric value in the generation direction of the noise component light 10 becomes a value obtained by dividing the light amount of the noise component light 10 by the total light amount of the laser light received by the photodiode array 214. The position of the reflection surface of the mirror 204 is controlled so that the centroid value in the direction orthogonal to the generation direction of the component light 10 becomes zero. The mirror control circuit 121 is an example of a second mirror control unit.

  As the pattern inspection step (S130), the optical image acquisition unit 150 acquires an optical image of the pattern of the sample to be inspected using the laser light 20 whose optical axis is adjusted by the mirrors 202 and 204. The comparison circuit 108 receives the reference image and compares the optical image with the reference image. This will be specifically described below.

  Prior to the start of inspection, first, the photomask 101, which is a pattern-formed inspected sample, is provided by the autoloader 130 controlled by the autoloader control circuit 113 so that it can be moved in the horizontal and rotational directions by the motors of the XYθ axes. Is loaded on the XYθ table 102 and placed on the XYθ table 102. Also, design pattern information (design pattern data) used when forming the pattern of the photomask 101 is input to the pattern inspection apparatus 100 from the outside of the apparatus and stored in the magnetic disk device 109 as an example of a storage device (storage unit). The

  The XYθ table 102 is driven by the table control circuit 114 under the control of the control computer 110. It can be moved by a drive system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. For example, step motors can be used as these X motor, Y motor, and θ motor. The movement position of the XYθ table 102 is measured by the laser length measurement system 122 and supplied to the position circuit 107. The photomask 101 on the XYθ table 102 is automatically conveyed from the autoloader 130 driven by the autoloader control circuit 113, and is automatically discharged after the inspection is completed. The magnifying optical system 104 is driven by, for example, a piezoelectric conversion element, and the image is focused on the photodiode array 105.

  FIG. 10 is a diagram for explaining an optical image acquisition procedure according to the first embodiment. As shown in FIG. 10, the inspected region is virtually divided into a plurality of strip-shaped inspection stripes having a scan width W, for example, in the Y direction. Then, the operation of the XYθ table 102 is controlled so that each of the divided inspection stripes is continuously scanned, and an optical image is acquired while moving in the X direction. In the photodiode array 105, images having a scan width W as shown in FIG. 10 are continuously input. Then, after acquiring the image of the first inspection stripe, the image of the scan width W is continuously input in the same manner while moving the image of the second inspection stripe in the opposite direction. When an image in the third inspection stripe is acquired, the image moves while moving in the direction opposite to the direction in which the image in the second inspection stripe is acquired, that is, in the direction in which the image in the first inspection stripe is acquired. To get. In this way, it is possible to shorten a useless processing time by continuously acquiring images. Although the forward (FWD) -backward (BWD) method is used here, the present invention is not limited to this, and a forward (FWD) -forward (FWD) method may be used.

  The pattern formed on the photomask 101 is irradiated with light by the above-described light source 103 disposed above the XYθ table 102. The laser light 20 emitted from the light source 103 irradiates the photomask 101 via the illumination optical system 170 described above. Light that has passed through the photomask 101 due to illumination forms an optical image on the photodiode array 105 via the magnifying optical system 104 and is incident thereon. The pattern image formed on the photodiode array 105 is photoelectrically converted by the photodiode array 105 and further A / D (analog-digital) converted by the sensor circuit 106. The photodiode array 105 is provided with a sensor such as a TDI (Time Delay Integrator) sensor. As described above, the optical image acquisition unit 150 acquires optical image data (stripe data) for each inspection stripe of the sample to be inspected.

  The measurement data (optical image data) of each inspection stripe output from the sensor circuit 106 is sequentially compared with data indicating the position of the photomask 101 on the XYθ table 102 output from the position circuit 107 for each inspection stripe. Is output. The measurement data is, for example, 8-bit unsigned data for each pixel, and the brightness gradation of each pixel is expressed by, for example, 0 to 255. These light source 103, illumination optical system 170, magnifying optical system 104, photodiode array 105, and sensor circuit 106 constitute a high-magnification inspection optical system.

  The development circuit 111 (an example of a reference image creation unit) reads design pattern data from the magnetic disk device 109 through the control computer 110 for each predetermined region, and the read design pattern data of the photomask 101 is binary or multiple. Conversion (development processing) into design image data (reference image data) which is image data of values. The predetermined region may be an image region (area) corresponding to the optical image to be compared.

  The figure constituting the pattern defined in the design pattern data is a basic figure such as a rectangle or a triangle. The design pattern data includes, for example, coordinates (x, y) at the reference position of the figure, side length, rectangle Stored is graphic data that defines the shape, size, position, etc. of each pattern graphic with information such as a graphic code that is an identifier for distinguishing graphic types such as triangles and triangles.

When such graphic data is input to the design image creation circuit 112, the graphic data is expanded to data for each graphic, and a graphic code, a graphic dimension, and the like indicating the graphic shape of the graphic data are interpreted. Then, binary or multivalued image data is developed as a pattern arranged in a grid having a grid with a predetermined quantization size as a unit. The developed image data (developed image data) is stored in a pattern memory (not shown) in the circuit or in the magnetic disk device 109. In other words, the design pattern data is read and the occupancy rate of the figure in the design pattern is calculated for each cell formed by virtually dividing the inspection area as a cell with a predetermined dimension as a unit, and n-bit occupancy data Is output to a pattern memory (not shown) or a magnetic disk device 109. For example, it is preferable to set one square as one pixel. If a resolution of 1/2 ⁸ (= 1/256) is given to one pixel, 1/256 small areas are allocated by the figure area arranged in the pixel, and the occupation ratio in the pixel is set. Calculate. The developed image data is stored in the pattern memory or the magnetic disk device 109 as area-unit image data defined by 8-bit occupancy data for each pixel.

  The reference circuit 112 performs data processing (image processing) on the developed image data, and performs appropriate filter processing. The optical image data (measurement data) is in a state in which a filter is activated by the resolution characteristics of the magnifying optical system 104, the aperture effect of the photodiode array 105, or the like, in other words, in an analog state that continuously changes. For this reason, the developed image data, which is the image data on the design side of which the image intensity (shading value) is a digital value, can also be matched to the measurement data by performing a filtering process according to a predetermined model. For example, filter processing such as resizing processing for performing enlargement or reduction processing, corner rounding processing, or blurring processing is performed. In this way, a reference image to be compared with the optical image is created. The predetermined region may be an image region (area) corresponding to the optical image to be compared. The created reference image data is output to the comparison circuit 108.

  Then, in the comparison circuit 108 (comparison unit), the optical image data for each stripe is read out, and the optical image data is cut out so that the optical image data becomes an image of an area having the same size as the reference data. Then, the comparison circuit 108 compares the corresponding optical image data with the reference data for each pixel under a predetermined determination condition. Such an inspection technique is a die-to-database inspection. Then, the comparison result is output. The comparison result may be output from the magnetic disk device 109, the magnetic tape device 115, the flexible disk device (FD) 116, the CRT 117, the pattern monitor 118, or the printer 119.

  Alternatively, the die-to-die inspection may be performed using the photomask 101 in which a plurality of pattern regions (inspected regions) drawn with the same design pattern are formed. In such a case, for example, the whole of the two pattern regions is virtually divided into a plurality of inspection stripes shown in FIG. Then, the optical image acquisition unit 150 acquires optical image data (measurement data) for each inspection stripe. Therefore, the measurement data of one inspection stripe includes both images of the two pattern areas. Then, the die-to-die inspection may be performed using one image of the two regions as an inspection target image and the other as a reference image.

  Moreover, it is preferable that each process from the gravity center calculation process (S118) to the optical axis adjustment process (S122) is performed in real time in parallel with the pattern inspection process even after the pattern inspection process is started.

  As described above, in the first embodiment, the optical axis of the laser light can be adjusted by removing the noise component light. Therefore, the loss of the light quantity of the laser beam 20 can be reduced. As a result, a highly accurate inspection can be performed by performing a pattern inspection using the laser light with the adjusted optical axis as illumination light.

Embodiment 2. FIG.
In the first embodiment, the detection sensitivity of the photodiode arrays 212 and 214 is set to a sensitivity that can also detect the noise component light 10 (for example, the sensitivity that can detect the light quantity H0 shown in FIG. 3). Absent. For example, the detection sensitivity of the photodiode arrays 212 and 214 may be lowered to a sensitivity at which the noise component light 10 cannot be detected (sensitivity at which, for example, the light amount H1 shown in FIG. 3 can be detected). Thereby, the optical axis of the laser beam can be adjusted by removing noise component light. In such a case, the steps from the y-direction scanning (scan) step (S102) to the noise light amount calculation step (S116) and the determination step (S120) in FIG. 4 can be eliminated. In the optical axis adjustment step (S122), the mirror control circuit 122 controls the position of the reflecting surface of the collar 202 so that the center of gravity value becomes 0 in both the x and y directions. What is necessary is just to control the position of the reflective surface of the collar 204 so that the value becomes 0 in both the x and y directions.

  FIG. 11 is a diagram for explaining another optical image acquisition method. In the configuration of FIG. 2 and the like, the photodiode array 105 that simultaneously enters the number of pixels of the scan width W is used. However, the present invention is not limited to this, and as shown in FIG. Each time a constant pitch movement is detected by the laser interferometer, the laser beam is scanned in the Y direction by a laser scanning optical device (not shown) in the Y direction, and transmitted light or reflected light is detected to a predetermined size. A method of acquiring a two-dimensional image for each area may be used.

  In the above description, what is described as “to part”, “to circuit”, or “to process” can be configured by a computer-operable program. Or you may make it implement by not only the program used as software but the combination of hardware and software. Alternatively, a combination with firmware may be used. When configured by a program, the program is recorded on a recording medium such as the magnetic disk device 109, the magnetic tape device 115, the FD 116, or a ROM (Read Only Memory). For example, position circuit 107, comparison circuit 108, expansion circuit 111, reference circuit 112, autoloader control circuit 113, table control circuit 114, mirror control circuits 121 and 122, measurement circuits 124 and 126, noise direction specifying circuit 128, noise light quantity calculation The circuit 130, the center-of-gravity calculation circuit 132, the determination circuit 134, the optical axis adjustment circuit 136, and the like may be configured as electrical circuits or may be realized as software that can be processed by the control computer 110. . Moreover, you may implement | achieve with the combination of an electrical circuit and software.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, in the embodiment, a transmissive optical system using transmitted light is used, but a configuration in which reflected light or transmitted light and reflected light are used simultaneously may be employed.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used.

  In addition, all pattern inspection apparatuses or pattern inspection methods that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Noise component light 20 Laser light 30,32,34,36,40,42,44,46 Light receiving element 100 Pattern inspection apparatus 101 Photomask 102 XY (theta) table 103 Light source 104 Expansion optical system 105 Photodiode array 106 Sensor circuit 107 Position circuit 108 Comparison circuit 109, 140 Magnetic disk device 110 Control computer 112 Design image creation circuit 115 Magnetic tape device 120 Bus 121, 122 Mirror control circuit 124, 126 Measurement circuit 128 Noise direction specifying circuit 130 Noise light amount calculation circuit 132 Center of gravity calculation circuit 134 Determination Circuit 136 Optical axis adjustment circuit 150 Optical image acquisition unit 160 Control circuit 170 Illumination optical system 172 Optical axis adjustment unit 202, 204 Mirror 230, 232 Half mirror 234 Mirror 222, 224 Drive mechanism 212, 214 Photodiode array

Claims (5)

A light source that generates laser light;
First and second mirrors that sequentially reflect the laser light and adjust the optical axis of the laser light, each capable of changing the position of the reflecting surface;
A half mirror for branching a part of the laser beam reflected by the first and second mirrors;
An illumination optical system that illuminates the sample to be inspected on which the pattern is formed, with the remaining laser light not branched by the half mirror;
A first light receiving unit that is arranged at a position conjugate with the illumination optical system and that receives a part of the laser beam branched by the half mirror independently from the first to fourth quadrants;
A second light receiving unit, which is disposed at a position conjugate with the second mirror and receives a part of the laser beam branched by the half mirror independently on the first to fourth quadrant surfaces;
A noise component direction specifying unit that specifies a generation direction of noise component light generated together with the laser light from the light source, using a light amount of laser light received by at least one of the first and second light receiving units;
A noise component light amount calculation unit for calculating a light amount of the noise component light using a light amount of laser light received by at least one of the first and second light receiving units;
A centroid calculating unit for calculating the centroid of each laser beam received by the first and second light receiving units;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the first light receiving unit, and is orthogonal to the noise component light generation direction. A first mirror controller that controls the position of the reflecting surface of the first mirror so that the center of gravity value in the direction of
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the second light receiving unit, and is orthogonal to the noise component light generation direction. A second mirror control unit for controlling the position of the reflecting surface of the second mirror so that the center of gravity value in the direction to be
An optical image acquisition unit that acquires an optical image of a pattern of the sample to be inspected by using the laser light whose optical axis is adjusted by the first and second mirrors;
A comparison unit that inputs a reference image and compares the optical image with the reference image;
A pattern inspection apparatus comprising: The center of gravity of the laser beam in the x direction is obtained by subtracting the sum of the respective light amounts received by the second and third quadrant surfaces from the sum of the respective light amounts received by the first and fourth quadrant surfaces. Defined by the value divided by the total amount of light received at
The center of gravity of the laser beam in the y direction is obtained by subtracting the sum of the respective light amounts received by the first and second quadrant surfaces from the sum of the respective light amounts received by the third and fourth quadrant surfaces. The pattern inspection apparatus according to claim 1, wherein the pattern inspection apparatus is defined by a value obtained by dividing the total light quantity of each light quantity received in step 1.   The noise component direction specifying unit determines a generation direction of the noise component light by using a change in the amount of laser light in a moving direction obtained by moving at least one of the first and second mirrors to a plurality of positions. 3. The pattern inspection apparatus according to claim 1, wherein the pattern inspection apparatus is specified.   The noise component direction specifying unit uses the change in the light amount of the laser light in the moving direction obtained by moving at least one of the first and second mirrors to a plurality of positions. The pattern inspection apparatus according to claim 1, wherein the pattern inspection apparatus performs calculation. Generating laser light from a light source;
The laser beam is sequentially reflected by the first and second mirrors while moving at least one of the first and second mirrors, each of which can change the position of the reflecting surface, to a plurality of positions. A part of the laser beam reflected by the first and second mirrors is converted into a surface in the first to fourth quadrants by a first light receiving unit disposed at a position conjugate with an illumination optical system that illuminates the inspection sample. A process of receiving light independently,
A laser beam is sequentially reflected by the first and second mirrors while moving at least one of the first and second mirrors to a plurality of positions, and is arranged at a position conjugate with the second mirror. A step of independently receiving a part of the laser light reflected by the first and second mirrors on the surfaces of the first to fourth quadrants by two light receiving units;
Identifying a generation direction of noise component light generated together with the laser light from the light source using a light amount of laser light received by at least one of the first and second light receiving units;
Calculating the amount of noise component light using the amount of laser light received by at least one of the first and second light receiving units;
Calculating the center of gravity of each laser beam received by the first and second light receiving units;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the first light receiving unit, and is orthogonal to the noise component light generation direction. Controlling the position of the reflecting surface of the first mirror so that the center of gravity value in the direction to go to 0;
The absolute value of the barycentric value in the noise component light generation direction is a value obtained by dividing the light amount of the noise component light by the total light amount of the laser light received by the second light receiving unit, and is orthogonal to the noise component light generation direction. Controlling the position of the reflecting surface of the second mirror so that the center of gravity value in the direction to be
Obtaining an optical image of the pattern of the sample to be inspected using the laser light whose optical axis is adjusted by the first and second mirrors;
Inputting a reference image and comparing the optical image with the reference image;
A pattern inspection method comprising:

Images