JP2012013614A - Specular inspection method and specular inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a specular inspection device that can quantitatively detect irregularity of a surface with high sensitivity.SOLUTION: A specular inspection method includes the steps of orienting an illumination light irradiated from a light source substantially parallel to be irradiated onto a sample having a specular surface, condensing a light reflected by the sample to which the illumination light is irradiated by a condensation lens, passing the reflection light condensed by the condensation lens from the sample through a pin hole to shield lights except for the reflection light, detecting the reflection light from the sample through the pin hole by a detector arranged at a position offset from a focus position of the condensation lens, and processing a signal detected by the detector. The detector detects the reflection light from the sample through the pin hole under a plurality of conditions and detects a distribution of local irregularity on the sample using a detection signal of the reflection light detected by the detector under the plurality of conditions.

Description

  The present invention relates to a mirror inspection method and apparatus for detecting minute irregularities on a mirror-like sample.

  Small irregularities on the surface of flat, mirror-like members, such as silicon wafers, rolled metal, and hard disk substrates, cause malfunctions in devices that use them, and aesthetic problems. It is required to detect with sensitivity. On the other hand, Patent Document 1 discloses a method of performing inspection using a phenomenon called magic mirror. The magic mirror phenomenon is a phenomenon in which when a sample is irradiated with parallel light and this reflected light is detected by an image sensor, it becomes darker or brighter depending on the surface irregularities. In particular, unevenness whose depth or height ratio is very small with respect to the spread of unevenness is difficult to obtain sensitivity by other methods such as detection by scattered light and the method using a height profile measuring instrument. It is a defect that is suitable for use.

JP 2006-84255 A

  The conventional surface irregularity inspection system using the magic mirror phenomenon detects only the brightness of the image, so if the image becomes dark or dark for reasons other than the surface roughness, for example, if the reflectance of the surface varies depending on the location. It is impossible to tell whether the image is due to unevenness in the brightness of the image. In addition, a sample having a fine surface roughness causes scattering (diffuse reflection) due to this, hiding the bright and dark components of the image due to specular reflection, and there is a problem that the detection sensitivity of the unevenness cannot be obtained. In addition, due to the same reasons as above, there is a problem that quantitative measurement cannot be performed with respect to the size of the unevenness. In addition, in order to improve the sensitivity to unevenness, there is a problem that it is necessary to largely shift the focus of the detector at the expense of resolution.

  By acquiring multiple signals or images with different detection conditions and calculating the difference between them or by synchronous detection of the signals, the disturbance and offset on the signal or image are removed, and the surface state is restored. Regardless of this, highly sensitive micro unevenness detection is realized. The detection conditions can be changed by placing a pinhole in the focal plane of the detection lens and shifting the pinhole in the direction of the optical axis, resulting in a brighter image when the sample surface curvature is positive, and a negative curvature. In this case, an image is taken under two conditions of a bright image. As another method, by shifting the pinhole in the direction perpendicular to the optical axis, the image becomes brighter on the surface inclined in the same direction as the direction in which the pinhole is shifted. And take a picture. As another method, when an image is acquired by changing the position in the optical axis direction of the image sensor at the conjugate position with the sample while the pinhole is placed on the focal plane of the detection lens, the image sensor If the image sensor is moved away from the sample, the image will be brighter with respect to the concave surface. If the image sensor is moved closer to the sample, the image will be brighter with respect to the convex surface. Acquire images in two cases.

  In addition to the above, by providing a lens system and a detector or an image sensor for detecting scattered light, it is possible to detect foreign matters, scratches, etc. on the sample in addition to thin irregularities.

  That is, in order to achieve the above object, in the present invention, the specular inspection apparatus irradiates a sample having a specular surface with a light source that emits illumination light and illumination light emitted from the light source as substantially parallel light. Illumination light irradiation means, condensing means for condensing the reflected light from the sample irradiated with the illumination light by the illumination light irradiation means, and reflected light from the sample collected by the condensing means through the reflected light A pinhole means for blocking light other than the light, a detection means for detecting light passing through the pinhole means disposed at a position shifted from the focal position of the light collection means on the optical axis of the light collection means, and a detection means A signal processing means for processing a signal obtained by detecting the light transmitted through the condensing means, the detection means detects light that has passed through the pinhole means under a plurality of different conditions, and the signal processing means is a plurality of different detection means. Passed through pinhole means detected by condition It constituted by using the detection signals to detect the distribution of the local asperity on the sample.

  In order to achieve the above object, according to the present invention, the specular inspection method is performed by irradiating a sample having a specular surface with illumination light emitted from a light source being substantially parallel light and irradiating the sample with illumination light. Reflected light from the sample is collected by the condenser lens, and the reflected light from the sample collected by the condenser lens is passed through the pinhole to block light other than the reflected light, and reflected from the sample that has passed through the pinhole. The light is detected by a detector arranged at a position shifted from the focal position of the condenser lens, and the signal detected by the detector is processed, and the detector differs in the reflected light from the sample that has passed through the pinhole. Detection was performed under a plurality of conditions, and a local unevenness distribution on the sample was detected using a detection signal of reflected light detected by a detector under a plurality of different conditions.

  According to the present invention, a flat, mirror-like member is canceled while canceling the influence of the difference in the surface roughness and reflectivity of a sample of a mirror-like sample such as a silicon wafer, a rolled metal, and a hard disk substrate. It is possible to detect minute irregularities on the surface of the surface with high sensitivity. Further, according to the present invention, it is possible to detect defects such as scratches and foreign matters at the same time.

1 is a block diagram showing a schematic configuration of a specular inspection apparatus according to a first embodiment of the present invention. It is a block diagram which shows the structure of the outline of the mirror surface inspection apparatus which concerns on the modification of 1st Example of this invention. It is a block diagram which shows the structure of the outline of the mirror surface inspection apparatus which concerns on 2nd Example of this invention. It is a graph which shows the result of having carried out synchronous detection with the waveform signal detected by vibrating a pinhole back and forth along an optical axis, and the drive signal of a pinhole. It is a block diagram which shows the structure of the outline of the mirror surface inspection apparatus which concerns on 3rd Example of this invention. It is a block diagram which shows the schematic structure of the mirror surface inspection apparatus which concerns on the modification of the 3rd Example of this invention. It is a block diagram which shows the structure of the outline of the mirror surface inspection apparatus which concerns on the 4th Example of this invention. It is a front view of the optical system which shows the detection principle of the 1st, 2nd, 4th Example. It is a front view of the optical system which shows the detection principle of the modification of a 1st Example. It is a front view of the optical system which shows the detection principle of a 3rd Example. It is a front view of the optical system which shows the detection principle of the modification of a 3rd Example. It is a front view of the optical system which shows the principle of a magic mirror.

  First, the principle of the magic mirror will be described with reference to FIG. The light emitted from the light source 101 is once condensed by the lens 102, passes through the pinhole 103, converted to parallel light by the collimating lens 104, and then irradiated to the sample 1 by the half mirror 120. The light specularly reflected by the sample 1 passes through the half mirror 120, passes through the lenses 105 and 108, and then forms an image of the sample 1 on the image sensor 109. At this time, if the image sensor 109 is placed at a position deviated from the conjugate (imaging) plane 110 of the sample 1, light and dark according to the unevenness of the sample 1 appears in the image detected by the image sensor by the magic mirror principle. Specifically, when the concave surface 330 exists on the sample 1, the light beam is bent inward and deviates from a dotted line of the light beams 160 and 161 to a locus like a solid line. Then, the light rays 160 and 161 bent by the imaging lens 108 intersect with the light rays 160 ′ and 161 ′ represented by dotted lines when not bent by the concave surface portion 330 at the conjugate plane 110, and then deviate.

  When the image sensor 109 is placed at a position deviated from the conjugate (imaging) plane 110 of the sample 1 as shown in FIG. 11A, the light reflected from the concave surface portion 330 is an image region 330 corresponding to the concave surface portion. Since they gather inside ', a bright image is obtained at the center of the image region 330 ′ corresponding to the concave surface as shown in FIG. On the contrary, in the case of the 330-surface convex surface on the sample 1, since the light beam diverges after passing through the conjugate surface 110, the image region 330 'becomes dark. On the other hand, if there is a portion with a different reflectance (a dark portion in the figure) on the sample 1 as indicated by 331 in FIG. 11A, the brightness of the corresponding image region 331 ′ changes even if there is no unevenness ( It will be dark in the example in the figure). It was difficult to know whether this was due to unevenness or due to the difference in reflectance depending on the location on the sample 1. In addition, due to subtle differences in brightness, it was difficult to quantitatively measure the size of irregularities and detect them with high sensitivity. In addition, when the sample is not a perfect mirror surface and includes a certain amount of scattered reflection components, this component reaches the image sensor 109 and becomes noise, resulting in a problem that the detection sensitivity of the unevenness is lowered. There is also a problem that it is difficult to detect defects such as scratches and foreign objects other than the specular unevenness.

  Therefore, in the present invention, as shown in FIG. 9, the positional relationship between the image sensor 109 and the sample conjugate surface 110 is changed, and images are taken at a plurality of image sensor positions such as 109 and 109 '. Here, the position of 109 ′ is shifted closer to the lens 108 with respect to the conjugate plane 110. Then, since the specularly reflected light rays 160 and 161 from the concave surface portion 330 on the sample 1 are detected by the image sensor 109 ′ before crossing again with the light rays 160 ′ and 161 ′ when the conjugate surface 110 has no specular surface, As a result, the image is detected in a state where it is wider than the original image, and as shown in FIG. 9C, an image in which the center of the image region 330 ′ with respect to the concave surface portion 330 becomes dark is obtained. On the contrary, the image obtained in 109 is an image in which the center of the image region 330 ′ with respect to the surface portion 330 becomes bright.

  Therefore, by calculating the image 1-image 2 from the image 2 of FIG. 9C placed at a position close to the image 1 of FIG. 9B where the image sensor is placed far from the conjugate position 109, The offset of brightness can be canceled to improve the detection sensitivity, and at the same time, the influence of a region such as 331 having a different reflection surface can be canceled. Further, by dividing this by the average brightness of image 1 and image 2 and calculating (image 1-image 2) / (image 1 + image 2), as shown in FIG. The size of the unevenness can be quantitatively evaluated without being influenced by the difference in general reflectance. Further, it is possible to simultaneously detect the reflectance distribution of the sample 1 using the image 1 + image 2.

  Furthermore, by placing the stop 107 at the rear focal plane of the lens 105, it is possible to block scattered light that is not a specular reflection component generated in the sample 1 and prevent the scattered light from overlapping the detection image as noise.

  Next, referring to FIG. 1, an embodiment of a specific apparatus embodying the invention will be described. The mirror surface inspection apparatus shown in FIG. 1 includes an illumination / detection optical system 100, a signal processing / control system 200, and a stage system 300.

  The illumination / detection optical system 100 includes a light source 101 that emits illumination light, a lens 102 that collects light emitted from the light source 101, and a pinhole 103 that has an opening for allowing the light collected by the lens 102 to pass therethrough. The collimating lens 104 that irradiates the sample 1 with the light that has passed through the opening of the pinhole 103 as parallel light or substantially parallel light, the lens 105 that collects the light reflected by the sample 1, and part of the light that has passed through the lens 105 Mirror 106 for reflecting the light and transmitting the remaining light, pin hole 107 a provided with an opening for passing the light transmitted through half mirror 106, sensor 109 a for detecting the light passing through pin hole 107 a, and reflection by half mirror 106 Pinhole 107b provided with an opening for allowing the transmitted light to pass, and sensor 10 for detecting the light that has passed through pinhole 107b b. The specularly reflected light of the light reflected from the sample 1 which is provided with an elliptical hole at the central part and irradiated with parallel light or substantially parallel light is passed through the hole provided at the central part and scattered around the periphery. A mirror 130 for reflecting light, a condensing lens 131 for condensing scattered light from the sample 1 reflected by the mirror 130, and a detector 132 for detecting scattered light from the sample 1 collected by the condensing lens 131. It is prepared for.

  The signal processing / control system 200 includes an image acquisition unit 201a that processes a signal in which specular reflection light from the sample 1 is detected by the sensor 109a, and an image acquisition unit that processes a signal in which the specular reflection light from the sample 1 is detected by the sensor 109b. 201b, an unevenness detection means 202 for detecting unevenness on the surface of the sample 1 using the images acquired by the image acquisition means 201a and 201b, and an image acquisition means for processing a signal in which scattered light from the sample 1 is detected by the detector 132. 240, a defect detection unit 203 that detects a defect on the sample 1 by processing signals output from the unevenness detection unit 202 and the image acquisition unit 240, and outputs information on the defect detected by the defect detection unit 203 on the screen. The display unit 204, the storage unit 205 that stores information about the defects detected by the defect detection unit 203, and the stage system 300 are controlled. Stage control means 250 which includes a general control unit 210 for controlling the whole.

  The stage system 300 includes an X stage 301 that can move in the X direction and a Y stage 302 that can move in the Y direction perpendicular to the X direction.

  Next, the operation of the mirror inspection apparatus having the above-described configuration will be described. The light emitted from the light source 101 is once condensed by the lens 102, passes through the pinhole 103, converted to parallel light 100 by the collimating lens 104, and then irradiated to the sample 1 by the half mirror 120. When a laser is used as the light source 101, parallel light or substantially parallel light can be generated without necessarily using the condensing lens 102 and the pinhole 103, and a configuration without these two or either is also conceivable. .

  The light specularly reflected by the sample 1 passes through the lens 105, is divided into two by the half mirror 106, passes through the pinholes 107a and 107b, and is detected by the sensors 109a and 109b. When the position of the pinhole is placed on the focal plane of the detection lens 105, when the sample 1 is flat, the illumination light reflected from the sample 1 at this position is collected. At this time, the pinholes 107 a and 107 b are placed at positions shifted from the focal plane of the detection lens 105.

  In this figure, the pinhole 107a is far from the lens 105 (away from the focal point 115a of the lens 105), and the pinhole 107b is nearer to the lens 105 (closer to the focal point 115b of the lens 105). At this time, when the illumination light hits the convex portion on the sample 1, the condensing position moves in a direction away from the lens 105, so that the detection light amount of the detector 109a increases and the detection light amount of the detector 109b increases. Decrease. On the other hand, when the illumination light hits a concave portion on the sample 1, the condensing position approaches the lens 105, so that the detected light amount of the detector 109b increases and the detected light amount of the detector 109a decreases.

  The change of the light beam in the case of the concave surface is shown in FIG. When the illumination light 100 is irradiated onto the concave surface portion 330 on the sample 1 in this way, the amount of light reaching the detector 109b is changed by changing the optical path of the reflected light from the sample 1 from the dotted line state to the solid line state. Increases, and the amount of light reaching the detector 109a decreases. With the above configuration, similar to the principle described with reference to FIG. 9, the size of the unevenness is quantified by calculating from the detected light amounts of the detector 109a and the detector 109b without being influenced by the difference in local reflectance of the sample 1. Can be evaluated.

  Further, a mirror 130 having an elliptical central portion surrounding the optical path through which the specular reflection light from the sample 1 passes is placed, and thereby diffuse reflection light or scattered light from the sample 1 is reflected and condensed by the lens 131. By detecting with the detector 132, a defect such as a foreign matter or a scratch on the sample 1 can be detected. This is because a tall defect, such as a foreign object or a flaw, easily scatters light compared to a shallow mirror surface. Here, the sample 1 is placed on the stage 302, and the stage is controlled by the stage control unit 250, and the X stage 301 and the Y stage 302 are controlled so that the illumination light scans the sample 1. The position signal at this time is sent to the image acquisition means 201a, 201b, 240, and the image (image) is acquired by taking in the data of the light quantity detected by the detectors 109a, 109b in synchronization with the position.

  The X stage 301 and the Y stage 302 are driven in the orthogonal X and Y directions. The stage unit 300 may be a stage driven in the polar coordinate R-Θ direction instead of the XY stage. From the image 1 (image acquired by the image acquisition unit 201a) and the image 2 (image acquired by the image acquisition unit 201b) thus obtained, the unevenness detection unit 202 calculates the degree of unevenness = (image 1-image 2) / (Image 1 + Image 2) is calculated, and a positive portion of this value is a convex portion and a negative portion is a concave portion. Further, the defect detection unit 203 detects the defect location on the sample 1 together with the information of the image 3 (image acquired by the image acquisition unit 240) indicating the distribution of the size of the scattered light.

  That is, it is determined that a convexity defect is positive when it is larger than the threshold value and is larger than the threshold value, a concave defect when it is larger than the negative value, and a defect where the image 3 is larger than the threshold value is a defect such as foreign matter or scratch. These results and the detected image that is the reference for determination are stored in the storage unit 205 and simultaneously displayed on the display unit 204. These operations are controlled by the overall control means. As the detectors 109a, 109b, and 132, photoelectric detectors such as photodiodes and photomultipliers may be used.

[Modification of Example 1]
A modification of the first embodiment is shown in FIG. In this modification, the configurations of the illumination / detection optical system 2100 and the signal processing / control system 2200 are different from the configuration of FIG. 1 described in the first embodiment.

  First, in the illumination / detection optical system 2100, the point where the pinholes 117a and 117b are both arranged at the back focal position of the lens 105, the point where the imaging lenses 108a and 108b are provided, and the image sensors 119a and 119b, respectively. This embodiment differs from the first embodiment shown in FIG. 1 in that the imaging lenses 108a and 108b are installed with their positions shifted from each other and that there is no optical system for detecting scattered light.

  Further, the signal processing / control system 2200 is different from that of the first embodiment in that it does not include the image acquisition unit 240 that processes the signal that detects the scattered light from the sample 1 described in the configuration of FIG.

  The configuration shown in FIG. 2 is the same as that of the first embodiment described with reference to FIG. 1 until the reflected light from the sample 1 passes through the lens 105 and is divided into two by the half mirror 106. The holes 117a and 117b are placed at the back focal position of the lens 105 and block scattered light components from the sample 1. At this time, the pinholes 117a and 117b for allowing the specularly reflected light from the sample 1 collected by the lens 105 to pass are not blocked by the pinholes 117a and 117b with the degree of change in the optical path due to the unevenness on the sample 1. Keep the opening large. The light that has passed through the pinholes 117a and 117b is imaged on the image planes 110a and 110b by the imaging lenses 108a and 108b, respectively. At this time, the image sensor 119a is shifted forward from the image plane 110a (direction approaching the lens 108a), and the image sensor 119b is shifted backward from the image plane 110b. Then, as shown in the diagram of the optical path shown in FIG. 8, the light hitting the concave surface on the sample 1 advances as shown by the solid line compared to the optical path shown by the dotted line of the light hitting the flat surface, and the lens After passing through 108a and 108b, it advances while converging toward the image planes 110a and 110b. Therefore, the image is bright on the surface of the image sensor 119a, and the image is dark on the surface of the image sensor 119b.

  The change of the light beam in the case of the concave surface is shown in FIG. When the illumination light emitted from the light source 101 is irradiated onto the concave portion on the sample 1 in this way, the optical path of the reflected light from the sample 1 changes from the dotted line state to the solid line state, thereby detecting the detector ( It can be read that the illuminance on the linear image sensor 119b increases and the illuminance on the detector (linear image sensor) 119a decreases.

  At this time, if the image sensors 119a and 119b are line image sensors in which pixels are arranged in a direction perpendicular to the paper surface, and the illumination light is also long slit light in the direction perpendicular to the paper surface, the line in the direction perpendicular to the paper surface on the sample 1 is used. The top / bottom data can be acquired at once. At this time, the X stage 301 is scanned by the stage control means 250 in the direction (X direction) indicated by the arrow in FIG. When the data is taken in by the image acquisition means 211a and 211b, planar light and dark distribution data is obtained. The subsequent configuration and processing are the same as those in the embodiment shown in FIG. As a result, two-dimensional image data can be obtained only by scanning the X stage 301 in one dimension (in the right direction in the figure) without swinging the stage in two dimensions of XY or R-Θ. In this embodiment diagram, the configuration of 130, 131, 132, and 240 in FIG. 1 for detecting scattered light is not written, but this is added in the embodiment of FIG. Inspection can also be performed. The sensor 132 when added to this embodiment is a one-dimensional image sensor.

  Next, a second mode of realization different from that of the first embodiment shown in FIG. 1 will be described with reference to FIG. The configuration of the illumination / detection optical system 3100 and the signal processing / control system 3200 is different from the configuration of the first embodiment described in FIG. The illumination / detection optical system 3100 includes a pinhole 3170 provided with a driving unit 3211 and a detector 3111. The signal processing / control system 3200 synchronously detects a pinhole drive control unit 3212 that controls the drive unit 3211 and a signal detected by the detector 3111 with a signal that drives the pinhole 3170 by the pinhole drive control unit 3212. A circuit portion 3210 is provided.

  Below, based on the structure shown in FIG. 3, the operation | movement in an Example is demonstrated. First, the configuration of the optical path to the lens 105 is the same as that of the first embodiment described with reference to FIG. There is no subsequent half mirror 106, and a pinhole 3107 placed near the back focal plane of the lens 105 and a detector 3111 are placed behind each pinhole 3107. Here, the pinhole 3107 is vibrated back and forth along the optical axis by driving means 3112 configured using a piezoelectric element, a voice coil motor, or the like. The synchronous detection means 3210 synchronously detects the light amount signal received by the detector 3111 with the drive signal indicating the position of the pinhole 3107 at this time.

  The signal waveform is shown with time taken on the horizontal axis of FIG. As shown in this figure, when the detection light emitted from the light source 101 hits the convex surface on the sample 1, the amount of transmitted light increases when the pinhole 3107 moves away from the lens 105, so the signal of the detector 3111 is growing. When the detection light hits a flat surface, the signal of the detector 3111 increases when the pinhole 3107 is at an intermediate position, and the signal output from the detector 3111 increases, and the pinhole 3107 moves away from the lens 105. When the case approaches, the signal of the detector 3111 becomes small. When the detection light strikes the concave surface 330 on the sample 1, the amount of transmitted light increases when the pinhole 3107 approaches the lens 105, so the signal of the detector 3111 increases.

  For the signal of the detector 3111 having such behavior, the synchronous detection means 3210 removes the direct current component, and then the result of synchronous detection by the drive signal indicating the pinhole position from the pinhole drive control unit 3212 is obtained. This is shown in the right half of FIG. A solid curve indicates a product waveform of the pinhole drive signal oscillated from the pinhole drive control unit 3212 and the signal of the detector 3111. A dotted straight line indicates a time average value of the product waveform. By performing synchronous detection in this way, a signal proportional to the degree of unevenness can be obtained.

  By acquiring the output signal of the synchronous detection means 3210 in synchronization with the position signal from the stage control means 3250, the image acquisition means 3201 obtains a signal as a result of the synchronous detection necessary for detecting the unevenness. Further, by detecting the maximum value of the signal of the detector 3111 before removing the DC signal by the synchronous detection means 3210, a brightness signal corresponding to the reflectance of the scanning position on the sample 1 can also be obtained. The unevenness of the surface of the sample 1 is detected by calculating the unevenness level = synchronous detection result signal / brightness signal by the unevenness detecting means 3202. The subsequent processing is the same as that described in the first embodiment with reference to FIG.

  A third embodiment for realizing the principle of the present invention described in FIG. 9 will be described with reference to FIG. In this embodiment, the optical system is the same as that described in FIG. The configuration of the illumination / detection optical system 4100 and the signal processing / control system 4200 is different from the configuration of the first embodiment described in FIG. Unlike the first and second embodiments, the illumination / detection optical system 4100 illuminates the sample 1 with illumination light emitted from the light source 4101 from directly above. For this purpose, the configuration shown in FIG. 4 includes a half mirror 4120. Further, in the present embodiment, an imaging lens 4108 for imaging the reflected light that has passed through the slit 4107 on the detection side is provided, as in the modification of the first embodiment described with reference to FIG. Further, a driving unit 4112 for vibrating the image sensor 4109 along the optical axis direction is provided.

  On the other hand, the signal processing / control system 4200 includes a drive control unit 4212 for controlling the drive unit 4112, and an image acquisition unit 4201 that acquires an image from the detection signal from the image sensor 4109 using the drive signal of the drive control unit 4112. It has.

  In the above configuration, the light emitted from the light source 4101, collected by the lens 4102, and passed through the slit 4103 is collimated by the collimator lens 4104 and then enters the half mirror 4120, and a part thereof is the sample 1. Reflected in the direction. The light incident on the sample 1 and reflected by the surface of the sample 1 is incident on the half mirror 4120 again, and part of the light is transmitted through the half mirror 4120 and incident on the lens 4105 to be condensed on the rear focal plane of the lens 4105. The A pinhole 4107 is provided on the rear focal plane, and only the light condensed on the rear focal plane passes through the opening provided in the pinhole 4107 and enters the imaging lens 4108 to be on the sample conjugate plane 4110. Imaged.

  In this embodiment, the image sensor 4109 is a two-dimensional image sensor such as a CCD sensor. As means for changing the positional relationship between the image sensor 4109 and the sample conjugate surface 4110, the drive means 4112 moves the position of the image sensor 4109 up and down in the optical axis direction. At this time, the image acquisition unit 4201 acquires an image 1 when the image sensor 4109 is at the uppermost position and an image 2 when the image sensor 4109 is at the lowermost position. By calculating the image 1-image 2 using the unevenness calculating means 4202, the brightness offset is canceled and the detection sensitivity is improved. At the same time, the influence of the region 331 having a different reflection surface is also canceled. Can do. Furthermore, by dividing this by the average brightness of image 1 and image 2 and calculating (image 1-image 2) / (image 1 + image 2), it does not depend on the difference in local reflectance of the sample. Thus, the size of the unevenness can be quantitatively evaluated. Further, it is possible to simultaneously detect the reflectance distribution of the sample 1 using the image 1 + image 2. The operation of other parts is the same as that of the embodiment described in FIGS.

[Modification of Example 3]
Next, a modification of the third embodiment described with reference to FIG. 4 will be described with reference to FIG. In this modification, as shown in FIG. 5, the illumination / detection optical system 5100 from the light source 5101 to the image sensor 5109 is the same as the optical system configuration from the light source 4101 to the image sensor 4109 shown in FIG. Instead of moving the image sensor 5109, the pinhole 5107 is rotated around the optical axis by the driving means 5112 instead. As shown in FIG. 5, when the opening 51071 of the pinhole 5107 is shifted from the center of the optical axis in the horizontal direction in the figure, only the light component inclined from the sample 1 by a certain distance is selected from the reflected light from the sample 1. An image can be obtained.

  That is, the focal length of the lens 5105 (the distance between the lens 5105 and the pinhole 5107 in FIG. 5A) is f, and the angle deviation in the x and y directions from the vertical direction of the reflected light from the sample 1 is (Θx, Θy). Then, the condensing position at the position of the pinhole 5107 is shifted from the optical axis center by (f · Θx, f · Θy). Therefore, the X stage 301 is moved in the horizontal direction while the pinhole 5107 is rotated while the opening 51071 of the pinhole 5107 is shifted from the rotation center of the pinhole 5107, and each image is captured by the image sensor 5109.

While the pinhole 5107 is driven by the driving means 5112 and rotated, the X stage 301 and the Y stage 302 are driven two-dimensionally by the stage controller 5250 of the signal processing / control system 5200 and the image sensor 5109 detects the image. Then, the position of the pinhole that is brightest at each position in the image is determined by the unevenness detecting means 5202, and the surface angle distribution of the sample 1 can be calculated by dividing this position by f. When the brightest data is selected at each position in the image, the surface reflectance distribution of the sample 1 is also obtained. The amount by which the opening 51071 of the pinhole 5107 is displaced from the rotation center of the pinhole 5107 may be set to about ((f · Θx) ² + (f · Θy) ² ) ^1/2 .

  Alternatively, the pinhole 5107 is rotated in an eccentric state, and the unevenness detecting means 5202 obtains the direction α in which the brightness is maximum at each position in the image, and further, the brightness at the angle α and the angle − When the brightness difference at α is obtained, the direction and magnitude of the surface tilt of the sample 1 can be obtained. The state of the light beam at this time will be supplementarily described with reference to FIG. In this way, among the light rays that hit the concave surface 330 on the sample 1, the light that hits the right slope 3301 of the concave surface 330 moves leftward from a light ray 5160 ′ indicated by a dotted line to a light ray 5160 indicated by a solid line. It shifts and passes through the opening 51071 of the pinhole 5107 eccentric to the left and reaches the image sensor 5109. On the contrary, the light hitting the left slope 3302 of the concave surface 330 is shifted from the light ray 5161 ′ indicated by the dotted line to the right as shown by the light ray 5161 indicated by the solid line, thereby causing the pinhole 5107 eccentric to the left to enter the pinhole 5107. Since the image does not pass through, the corresponding image on the image sensor 5109 becomes dark.

  A fourth embodiment according to the present invention will be described with reference to FIG. The configuration is characterized in that the detection light is scanned on the sample 1. In the first embodiment shown in FIG. 1, the stage portion 300 is scanned in the XY two-dimensional direction so that the illumination light is scanned over the entire surface of the sample 1. However, in the fourth embodiment shown in FIG. By scanning the stage in the direction perpendicular to the paper surface while scanning in the horizontal direction, high-speed two-dimensional scanning of the sample 1 is realized.

  The mirror surface inspection apparatus shown in FIG. 6 includes an illumination / detection optical system 6100, a signal processing / control system 6200, and a stage system 6300.

  The illumination / detection optical system 6100 includes a light source 101 that emits illumination light, a lens 102 that collects light emitted from the light source 101, and a pinhole 6103 provided with an opening for allowing the light collected by the lens 102 to pass therethrough. , A collimating lens 6104 for converting the light passing through the pinhole 6103 into parallel light or substantially parallel light, a beam splitter (half mirror) 6120 for branching the optical path of the parallel light, a lens 6151 for condensing the branched parallel light, A polygon mirror 6150 for reflecting the illumination light collected by the lens 6151 in the direction of the substrate 1, a lens 6152 for converting the illumination light reflected by the polygon mirror 6150 into parallel light or substantially parallel light, and illumination light are irradiated. Reflecting from the sample 1, the lens 6152, the polygon mirror 6150, the lens 6151, and the beam splitter 612 are reflected. Of the reflected light that has passed through the lens 6130, the lens 6105 that collects the reflected light that has passed through the elliptical hole provided at the center of the mirror 6130, and a part of the reflected light that has passed through the lens 6105 is reflected and the rest is transmitted. Reflected by the half mirror 6106, a sensor 6109a that detects reflected light that has passed through the pinhole 6107a, a pinhole 6107a provided at a position farther than the focal position of the lens 6105 on the optical path of the light transmitted through the half mirror 6106, and the half mirror 6106 The pinhole 6107b provided at a position closer to the focal position of the lens 6105 on the optical path of the reflected light, the sensor 6109b for detecting the reflected light passing through the pinhole 6107b, and the scattered light from the sample 1 reflected by the mirror 6130 are collected. Scattering from the sample 1 collected by the condenser lens 6131 and the condenser lens 6131 that emit light Includes a detector 6132 for detecting is configured to.

  The signal processing / control system 6200 is an image acquisition unit 6201a that processes a signal in which specular reflection light from the sample 1 is detected by the sensor 6109a, and an image acquisition unit that processes a signal in which the specular reflection light from the sample 1 is detected by the sensor 6109b. 6201b, an unevenness detection means 6202 for detecting unevenness on the surface of the sample 1 using the images acquired by the image acquisition means 6201a and 6201b, and an image acquisition means for processing a signal in which scattered light from the sample 1 is detected by the detector 6132. 6240, a defect detection unit 6203 that detects a defect on the sample 1 by processing signals output from the unevenness detection unit 6202 and the image acquisition unit 6240, and outputs information on the defect detected by the defect detection unit 6203 on the screen. Storage for storing information on defects detected by the display means 6204 and the defect detection unit 6203 Stage 6205, stage control unit 6250 for controlling the stage system 6300, an overall control section 6210 for controlling the polygon mirror control unit 6220, and the overall controls the Porigonmira 6150.

  The stage system 6300 includes an X stage 6301 that can move in the X direction and a Y stage 6302 that can move in the Y direction perpendicular to the X direction.

Next, the operation of each unit will be described.
The light emitted from the light source 6101 is once condensed by the lens 6102, passes through the opening of the pinhole 6103, converted into parallel light by the collimator lens 6104, and then leftward in the figure by the beam splitter (half mirror) 6120. After being condensed by the lens 6151, the angle is changed by a polygon mirror 6150 (or a galvano mirror is also possible), and then the light is changed to parallel light or substantially parallel light by a lens 6152 and then irradiated to the sample 1. Note that when a laser is used as the light source 6101, parallel light or substantially parallel light can be generated without necessarily using the condenser lens 6102 and the pinhole 6103, and a configuration without these two or either is also conceivable. . The light that is specularly reflected by the sample 1 returns again through the same optical path, passes through the lens 6152, and is then reflected by the polygon mirror 6150 toward the lens 6151.

  The light passes through a beam splitter (half mirror) 6120, is collected by a lens 6105, passes through openings provided in pinholes 6107a and b, and then detected by sensors 6109a and 6109b. When the position of the pinhole is placed on the focal plane of the lens system including the lenses 6152, 6151, and 6105, when the sample 1 is flat, the illumination light reflected from the sample 1 at this position is collected. At this time, the pinholes 6107a and 6107b are placed at positions shifted from the focal plane of the lens system including the lenses 6152, 6151 and 6105. In this figure, the pinhole 6107a is located away from the lens 6105, and the pinhole 6107a is located closer to the lens 6105.

  The output of these sensors 6109a and 6109b can be used to quantitatively evaluate the size of the unevenness without being influenced by the difference in local reflectance of the sample. The operation is exactly the same as that of the embodiment shown in FIG. The polygon mirror 6150 is controlled by the polygon mirror control means 6304, and the stage control means 6250 operates in conjunction with this, so that a two-dimensional image can be obtained by synchronizing the stage and the mirror.

  Further, the diffused reflected light or scattered light from the sample 1 is reflected by the mirror 6130 having an elliptical center part surrounding the optical path through which the specular reflected light from the sample 1 passes, and is collected by the lens 6131 to be detected. By detecting at 6132, defects such as foreign matter or scratches on the sample 1 can be detected. Also in this regard, the subsequent configuration and operation are the same as those of the first embodiment shown in FIG.

  In the general description of the embodiments of the present invention, the illumination light for illuminating the sample 1 is assumed to be parallel light. However, the illumination light may be substantially parallel, and the condensing position on the back side of the lens 6105 and the pinhole. It is supplemented that if the positional relationship with 6107 or the positional relationship between the conjugate position of sample 1 and detectors 6109a and 6109b is satisfied, the same effect can be obtained even if the illumination light deviates from parallel.

101, 4101, 5101, 6101 ... Light source 102, 4102, 5102, 6102 ... Lens 103, 4103, 5103, 6103 ... Pinhole 104, 4104, 5104, 6104 ... Collimating lens 105, 4105 5105, 6105 ... Condensing lenses 106, 6106 ... Half mirrors 107a, 107b, 117a, 117b, 3107, 4107, 5107, 6107a, 6107b ... Detection pinholes 108, 108a, 108b, 4108, 5108 ..Image forming lenses 109, 109a, 109b, 119a, 119b, 311, 4109, 5109, 6109a, 6109b... Detectors 3112, 4112, 5112... Driving means 130, 6130. L, 131, 6131 ... Condensing lens 132, 6132 ... Detector 6150 ... Polygon mirror 6151 ... Lens 6152 ... Lens 201a, 201b, 240, 211a, 211b, 3201, 4201, 5201, 6201a, 6201b, 6240 ... Image capturing means 202, 212, 3202, 4202, 5202, 6202 ... Concavity and convexity detection means 203, 213, 3202, 4203, 5203, 6203 ... Defect detection means 3210 ... Synchronization Detection means 3212 ... Driving means 4212 ... Driving means 5212 ... Driving means 6220 ... Mirror control means.

Claims (16)

A light source that emits illumination light;
Illumination light irradiating means for irradiating a sample having a mirror-like surface with illumination light emitted from the light source as substantially parallel light;
Condensing means for condensing the reflected light from the sample irradiated with the illumination light by the illumination light irradiating means;
Pinhole means for passing reflected light from the sample collected by the light collecting means and blocking light other than the reflected light; and
A detecting means for detecting the light passing through the pinhole means arranged at a position shifted from the focal position of the light collecting means on the optical axis of the light collecting means;
Signal processing means for processing a signal obtained by detecting light transmitted through the light collecting means by the detection means;
The detection means detects light passing through the pinhole means under a plurality of different conditions,
The mirror is characterized in that the signal processing means detects a local unevenness distribution on the sample by using a detection signal of light passing through the pinhole means detected by the detection means under a plurality of different conditions. Inspection device. The signal processing means is a difference signal obtained by subtracting the sum signal information obtained by adding the detection signals of the light passing through the pinhole means detected by the detection means under a plurality of different conditions and the detection signals detected by the plurality of conditions. The specular inspection apparatus according to claim 1, wherein a local unevenness distribution on the sample is detected using the information of the mirror.   An optical path branching unit that splits the reflected light from the sample collected by the condensing unit into two optical paths; the pinhole unit and the detection unit are reflected from the sample branched by the branching unit; The mirror surface inspection apparatus according to claim 1, wherein the mirror surface inspection apparatus is disposed in each of optical paths of light.   Of the pinhole means arranged in each of the optical paths of the reflected light from the sample branched by the branching means, one is arranged closer to the light collecting means than the focal position of the light collecting means, and the other 4. The specular inspection apparatus according to claim 3, wherein is disposed on a side farther from the light collecting means than a focal position of the light collecting means.   An imaging means is provided between the pinhole means and the detection means on each optical path of the reflected light from the sample branched by the branch means, and the detection is performed on one optical path on each of the optical paths. Means is disposed closer to the image forming means than the image forming surface of the image forming means, and the detecting means is arranged on the other optical path on the respective optical paths to form the image on the image forming surface of the image forming means. 5. The specular inspection apparatus according to claim 4, wherein the specular inspection apparatus is disposed on a side away from the means.   The signal processing means further includes driving means for vibrating the pinhole means along the optical axis of the light collecting means, and the signal processing means reflects the reflected light from the sample that has passed through the pinhole being vibrated by the driving means. Of the detection signals obtained by detection by the detection means, the detection signal obtained by detection by the detection means when the pinhole approaches the light collection means side along the optical axis and the pinhole The local unevenness distribution on the sample is detected using a detection signal obtained by detection by the detection means when moving away from the light collection means along the optical axis. Item 3. The mirror inspection apparatus according to Item 1 or 2. An image forming means between the pinhole means and the detection means, and a drive means for vibrating the detection means along the optical axis of the image forming means are further provided, and the signal processing means is vibrated by the drive means. The detection means that is detected by the detection means when the detection means is closer to the imaging means side than the imaging plane of the imaging means and the imaging plane of the imaging means. 3. A local unevenness distribution on the sample is detected using a detection signal obtained by detection by the detection means when the imaging means is moved away from the imaging means side. Specular surface inspection device described in 1.   It further comprises a pinhole rotation driving means for rotating the pinhole means, and the pinhole means is condensed by the light condensing means at a position deviated from a rotation center for rotating the pinhole means by the pinhole rotation driving means. 3. The specular inspection apparatus according to claim 1, further comprising an opening through which reflected light passes. Irradiate a sample having a mirror-like surface with illumination light emitted from a light source as substantially parallel light,
The reflected light from the sample irradiated with the illumination light is collected by a condenser lens,
The reflected light from the sample collected by the condenser lens is passed through a pinhole to block light other than the reflected light,
The reflected light from the sample that has passed through the pinhole is detected by a detector disposed at a position shifted from the focal position of the condenser lens,
A method of processing a signal detected by the detector,
The detector detects reflected light from the sample that has passed through the pinhole under a plurality of different conditions,
A specular inspection method, wherein a local unevenness distribution on the sample is detected using detection signals of the reflected light detected under a plurality of different conditions by the detector. Using the information of the sum signal obtained by adding the detection signals of the reflected light detected under a plurality of different conditions by the detector and the information of the difference signal obtained by subtracting the detection signals detected under the plurality of conditions on the sample The specular inspection method according to claim 9, wherein a local unevenness distribution is detected.   The reflected light from the sample collected by the condenser lens is branched in two optical paths, and the branched reflected light is detected by a first detector through a first pinhole, and the branched The other reflected light is detected by the second detector through the second pinhole, detected by the first detector, and detected by the second detector. The specular inspection method according to claim 9 or 10, wherein a local unevenness distribution on the sample is detected using the detected signal.   The first detector detects reflected light from the sample that has passed through a pinhole disposed on the side of the condenser lens with respect to the focal position of the condenser lens, and the second detector detects the condenser. The reflected light from the sample that has passed through the pinhole disposed on the side away from the condenser lens with respect to the focal position of the optical lens is detected, and the signal obtained by detecting with the first detector and the first 12. The specular inspection method according to claim 11, wherein a local unevenness distribution on the sample is detected using a signal obtained by detecting with the detector of No. 2.   The first detector detects reflected light from the sample that has passed through the pinhole at a position closer to the imaging lens than an image plane formed by the imaging lens, and the second detector The reflected light from the sample that has passed through the pinhole is detected at a position farther from the imaging lens than the image plane imaged by the imaging lens, and the signal obtained by the detection by the first detector and the first 12. The specular inspection method according to claim 11, wherein a local unevenness distribution on the sample is detected using a signal obtained by detecting with the detector of No. 2.   Of the detection signals obtained by vibrating the pinhole along the optical axis of the condenser lens and detecting reflected light from the sample that has passed through the vibrating pinhole, the pinhole is A detection signal obtained by detecting when approaching the condenser lens side along the optical axis and a detection signal obtained by detecting when the pinhole moves away from the condenser lens along the optical axis The specular surface inspection method according to claim 9 or 10, wherein a local unevenness distribution on the sample is detected by using.   The reflected light from the sample that has passed through the pinhole is imaged by an imaging lens, and the image of the reflected light that has been imaged is detected while vibrating the detector along the optical axis of the imaging lens. The signal detected when the detector approaches the imaging lens among the signals of the reflected light image detected while vibrating the detector and the detector moved away from the imaging lens The specular inspection method according to claim 9 or 10, wherein a local unevenness distribution on the sample is detected using the detected signal.     Of the reflected light from the sample collected by the condenser lens, the reflected light that has passed through the opening is detected by the detector when a pinhole having an opening is rotated at a position shifted from the center of rotation. The specular inspection method according to claim 9 or 10, wherein a local unevenness distribution on the sample is detected using a detection signal of the reflected light detected by the detector.

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