JP2010203892A - Substrate inspecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate inspecting method for detecting whether the defect of the substrate is a backside defect produced in the front stage of the inspection process or the backside defect produced during inspection. <P>SOLUTION: The substrate inspection method is configured to inspect the defect formed to the backside of a wafer having a plurality of patterns formed on the surface thereof and defect of the surface other than the backside of the wafer and includes a first backside defect detecting step S201 of detecting the presence and position of the defect in the backside of the wafer, another surface defect detecting steps S202-204 of detecting the presence and position of the defect in the surface other than the backside of the wafer and a second backside defect detecting step S205 of again detecting the presence and position of the defect in the backside of the wafer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate inspection method for inspecting defects on a back surface and a surface other than the back surface of a substrate to be tested such as a semiconductor wafer.

  A semiconductor wafer (hereinafter also referred to as a wafer) is subjected to various manufacturing processes to form a plurality of circuit patterns on the surface, and finally divided into circuit patterns to produce semiconductor chips (IC chips or the like). At this time, if there is a defect on the surface in each manufacturing process, the expected performance of the semiconductor chip made of a circuit pattern may not be obtained, so surface defect inspection in the wafer manufacturing process is very important. . In recent years, as the degree of integration of circuit patterns formed on the wafer surface has increased, if there is an edge defect such as dust at or near the edge of the wafer, the edge defect will be removed in the subsequent manufacturing process. Since there is a case in which the above-mentioned adverse effects are caused by going around the surface side, it is also important to inspect the wafer edge for defects.

  In addition, the occurrence of surface defects in the wafer manufacturing process, such as line width defects in the circuit pattern in the exposure process, is often considered to be related to back surface defects such as scratches and dust attached to the back surface of the wafer. Inspection of defects on the backside of wafers is also becoming important. As described above, the defect inspection of the wafer in the wafer manufacturing process is mainly performed by performing a defect inspection on the entire surface of the wafer through a plurality of inspection processes including a front surface inspection, an edge inspection, and a back surface inspection. Such a defect inspection on the entire surface of the wafer is performed by a conventionally known surface inspection apparatus (see, for example, Patent Document 1), edge inspection apparatus (see, Patent Document 2), and back surface inspection apparatus (for example, Patent Document 3). For example).

JP 2008-281502 A JP 2008-45964 A Japanese Patent Laid-Open No. 10-9287

  By the way, in an apparatus that performs surface inspection and edge inspection of a wafer, the inspection is generally performed in a state where the wafer is placed and held on the holder, that is, in a state where the wafer back surface is in contact with the upper surface of the holder. For this reason, if dust or the like adheres to the upper surface of the holder, the dust or the like may adhere to the back surface of the wafer and cause a back surface defect. As described above, the defect generated on the back surface of the wafer at the time of inspection is detected by performing the back surface inspection of the wafer later. This defect is a defect generated at the time of the previous inspection or occurred in the previous stage of the inspection process. It cannot be detected whether it is a defect. Therefore, conventionally, there has been a problem that when a back surface defect occurs at the time of inspection, it is not possible to quickly take measures to remove the cause.

  The present invention has been made in view of such circumstances, and provides a substrate inspection method capable of detecting whether a back surface defect has occurred in the previous stage of the inspection process or a back surface defect that has occurred during inspection. Objective.

  In order to achieve such an object, a substrate inspection method according to the present invention is a substrate inspection method for inspecting defects on a surface other than a back surface and a back surface of a test substrate on which a plurality of patterns are formed, A first back surface defect detecting step for detecting the presence and position of a defect on the back surface of the substrate to be tested; a second surface defect detecting step for detecting the presence and position of a defect on a surface other than the back surface of the substrate to be tested; A second back surface defect detection step for detecting again the presence and position of the defect on the back surface of the substrate to be tested.

  The substrate inspection method preferably includes a detection result comparison step of dividing the back surface of the test substrate and a surface other than the back surface into arbitrary regions and comparing the defect detection results for each region.

  Further, in the substrate inspection method, the other surface defect inspection step includes a surface defect detection step for detecting the presence and position of a defect on the surface of the substrate to be tested, and a presence of a defect at the outer peripheral edge of the substrate to be tested. And an end defect detecting step for detecting the position thereof.

  Moreover, in the said board | substrate inspection method, it is preferable that surfaces other than the said back surface include at least one of the said surface or the surface between the said surface and the said back surface.

  According to the present invention, since a defect is detected on the back surface of the substrate to be tested at the beginning and end of the inspection process, it is detected whether the defect is a back surface defect that occurred in the previous stage of the inspection process or a back surface defect that occurred during the inspection process. be able to.

It is a flowchart which shows the content of the inspection method which concerns on this invention. It is a figure which shows the whole structure of the test | inspection apparatus to which this invention is applied. It is a figure which shows the structure of the back surface inspection stage which comprises the said inspection apparatus. It is a figure which shows the structure of the edge part inspection stage which comprises the said inspection apparatus. It is a figure which shows the structure of the 1st surface inspection stage which comprises the said inspection apparatus. It is a figure which shows the structure of the 2nd surface inspection stage which comprises the said inspection apparatus. It is a schematic diagram of the database which shows the test result by each said test | inspection stage.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 2 shows the overall configuration of the inspection apparatus to which the present invention is applied, and FIGS. 3 to 6 show the configurations of the inspection stages constituting the inspection apparatus 1. First, the inspection apparatus 1 is described with reference to these drawings. A schematic configuration will be described.

  As shown in FIG. 2, the inspection apparatus 1 includes a back surface inspection stage ST <b> 1 that images the back surface of a semiconductor wafer W (hereinafter simply referred to as a wafer W) that is a substrate to be tested, and an end that images the outer peripheral edge of the wafer W. Partial inspection stage ST2, first surface inspection stage ST3 that receives scattered light from the surface of the wafer W on which a large number of circuit patterns are formed, and images the wafer surface; specularly reflected light or diffracted light from the surface of the wafer W Receiving the second surface inspection stage ST4 for imaging the wafer surface, the wafer transfer device 10 for transferring the wafer W to each inspection stage, and an image for performing defect inspection based on the image of the wafer W imaged at each inspection stage. And a processing inspection unit 50.

  The wafer W is formed in a thin disk shape, and although not shown in particular, in order to form a circuit pattern corresponding to a plurality of semiconductor chips (chip regions) taken out from the wafer W, an insulating film, Thin films such as electrode wiring films and semiconductor films are formed over multiple layers. On the other hand, the circuit pattern or the like is not formed on the back surface of the wafer W, and the back surface of the wafer W is mirror-like (that is, no circuit pattern or the like is formed). Further, the outer peripheral edge of the wafer W connects the upper bevel formed in a ring shape on the outer peripheral portion on the front surface side, the lower bevel formed symmetrically with the upper bevel on the outer peripheral portion on the rear surface side, and the upper bevel and the lower bevel. It has a shape having an apex (wafer end face).

  As shown in FIG. 2, the wafer transfer apparatus 10 includes a guide rail 11 fixed on the inspection table T, a base portion 12 that is movably attached along the guide rail 11, and a base portion 12. The bending arm 13 includes a bending arm 13 and a transfer arm 15 capable of holding the wafer W by means such as vacuum suction. The base portion 12 is movable along the guide rail 11 by an operation of an electric motor (not shown). The bending arm 13 has one end connected to the base portion 12 and the other end connected to the transfer arm 15, and performs an operation including bending and extending operations in a horizontal plane by the operation of an electric motor (not shown). 15 can be moved freely in a horizontal posture. The wafer transfer apparatus 10 includes a wafer cassette 5 that stores a plurality of wafers W by moving the wafer W held on the transfer arm 15 along the guide rail 11 of the base portion 12 and bending / extending operation of the bending / extending arm 13 and the like. It can be freely transported to and from the inspection stage.

  As shown in FIG. 3, the back surface inspection stage ST1 includes a back surface inspection holder 20 that holds the wafer W with the back surface exposed downward, and is transferred by the wafer transfer device 10 (see FIG. 2). The wafer W is held by the back surface inspection holder 20 with the back surface exposed downward. At this time, the wafer W is aligned with reference to a notch (not shown) formed at the edge of the wafer. The back surface inspection holder 20 is constituted by, for example, a support member that supports only the peripheral portion of the wafer W or a transparent support member that supports the entire back surface of the wafer W, and is held with the back surface of the wafer W exposed downward. It is possible to do.

  The back surface inspection stage ST1 further irradiates inspection illumination light Li (hereinafter referred to as illumination light Li) at a shallow (small) angle with respect to the back surface of the wafer W held by the back surface inspection holder 20. And back-side imaging in which the regular reflection light Lo (1) from the back surface of the wafer W that has been irradiated with the illumination light Li is disposed at a dark field position where no incident light is incident, and the back surface of the wafer W is imaged using dark-field illumination. The apparatus 40 is comprised. The back surface imaging device 40 includes an imaging device 42 and an imaging optical system (not shown). The imaging device 42 converts an image of the back surface of the wafer W formed on the imaging surface into an image signal and supplies the image signal to the image processing inspection unit 50. Output.

  When the illumination light Li is irradiated to the back surface of the wafer W by the back surface illumination device 30, the back surface of the wafer W is mirror-like, so that it is regularly reflected on the back surface of the wafer and the regular reflection light Lo (1) is as shown in FIG. To exit. When the back surface of the wafer W is imaged by the back surface imaging device 40, the back surface imaging device 40 is disposed in the dark field position (the regular reflection light Lo (1) does not enter the back surface imaging device 40). If the wafer W is a normal wafer W with no foreign matter attached or scratched on the back surface, a black image of the wafer back surface is obtained as an image generated by the image processing inspection unit 50 based on the image signal from the image sensor 42. Only.

  However, when a defect d (such as adhesion or scratching of foreign matter) exists on the back surface of the wafer W, the illumination light Li irradiated on the back surface of the wafer is irregularly reflected by the defect d, and scattered light Lo ( A part of 2) also enters the back imaging device 40. For this reason, a bright spot indicating a defect d (a portion having a brightness brighter than a predetermined brightness) appears in the image on the back surface of the wafer generated by the image processing inspection unit 50 based on the image signal from the image sensor 42. Thus, the presence of the defect d on the back surface of the wafer W can be detected.

  As shown in FIG. 4, the end inspection stage ST2 includes an end inspection holder 60 that rotatably holds the wafer W, and the wafer W transferred by the wafer transfer apparatus 10 (see FIG. 2) is this. It is rotatably held on the end inspection holder 60 by vacuum suction or the like. At this time, the wafer W is aligned with reference to the notch at the edge of the wafer, as in the case of the back surface inspection stage ST1.

  The edge inspection stage ST2 further illuminates the outer peripheral edge of the wafer W held by the edge inspection holder 60 with epi-illumination (not shown), and the outer peripheral edge of the illuminated wafer W (the upper and lower ends described above). An end imaging device 70 for imaging a bevel and apex) is provided. The edge imaging device 70 is disposed so as to face the outer peripheral end surface (apex) of the wafer W, and images the apex over the entire circumference of the wafer W by rotating the wafer W by the edge inspection holder 60. it can. The edge imaging device 70 can be moved to positions facing the upper and lower bevels of the wafer W by a moving mechanism (not shown), and can also image the upper and lower bevels over the entire circumference of the wafer W. The image sensor 72 of the edge imaging device 70 converts the image of the outer peripheral edge of the wafer W formed on the imaging surface into an image signal and outputs the image signal to the image processing inspection unit 50.

  As shown in FIG. 5, the first surface inspection stage ST3 includes a first surface inspection holder 80 for mounting and holding the wafer W with the surface facing upward, and the wafer transfer apparatus 10 (see FIG. 2). The wafer W transferred by the above is placed on the first surface inspection holder 80 and fixed and held by means such as vacuum suction. At this time, the wafer W is aligned with reference to the notch at the end of the wafer, similarly to the inspection stages ST1 and ST2.

  The first surface inspection stage ST3 further emits inspection illumination light Li ′ (hereinafter referred to as illumination light Li ′) at a shallow (small) angle with respect to the surface of the wafer W held by the first surface inspection holder 80. The first surface illumination device 90 that irradiates and the regular reflection light Lo ′ (1) and the diffracted light Lo ′ (3) from the surface of the wafer W that has been irradiated with the illumination light Li ′ are arranged in a dark field position where they do not enter. And a first surface imaging device 100 that images the surface of the wafer W using dark field illumination. The image sensor 102 of the first surface imaging device 100 converts an image of the surface of the wafer W formed on the imaging surface into an image signal and outputs the image signal to the image processing inspection unit 50.

  When the surface of the wafer W is irradiated with the illumination light Li ′ by the first surface illumination device 90, it is regularly reflected on the wafer surface and the regular reflection light Lo ′ (1) is emitted as shown in FIG. Further, as described above, a circuit pattern is formed on the surface of the wafer W, and the diffracted light Lo ′ (3) in a direction corresponding to the repetitive pitch of the wiring forming the circuit pattern and the wavelength of the illumination light Li ′. Is emitted as shown in FIG.

  When the surface of the wafer W is imaged by the first surface imaging device 100, the first surface imaging device 100 is disposed in the dark field position (the first surface imaging device 100 has specularly reflected light Lo ′ (1) and diffraction). Since the light Lo ′ (3) is not incident), if the wafer W is a normal wafer W with no foreign matter attached or scratched on the surface of the wafer W, it is generated by the image processing inspection unit 50 based on the image signal from the image sensor 102. As an image to be obtained, only a black image of the back surface of the wafer is obtained. However, when a defect d ′ (attachment of foreign matter, scratches, etc.) exists on the surface of the wafer W, the illumination light Li ′ irradiated on the wafer surface is irregularly reflected by the defect d ′, and the irregular reflection light is scattered. A part of the light Lo ′ (2) also enters the first surface imaging device 100. For this reason, in the image on the back surface of the wafer generated by the image processing inspection unit 50 based on the image signal from the image sensor 102, a bright spot indicating a defect d ′ (part having a brightness brighter than a predetermined brightness) appears. Thereby, the presence of the defect d ′ on the surface of the wafer W can be detected.

  As shown in FIG. 6, the second surface inspection stage ST4 includes a second surface inspection holder 110 for mounting and holding the wafer W with the surface facing upward, and a wafer transfer apparatus 10 (see FIG. 2). The wafer W transferred by the above is placed on the second surface inspection holder 110 and fixed and held by means such as vacuum suction. At this time, the wafer W is aligned with reference to the notch at the end of the wafer, similarly to the inspection stages ST1, ST2, ST3.

  The second surface inspection holder 110 passes through the center of the wafer W fixed and held in this way (the center of the second surface inspection holder 110) and rotates an axis AX (hereinafter referred to as the vertical axis AX) perpendicular to the wafer surface. The wafer W is held so as to be rotatable (rotation within the surface of the wafer W) as an axis. Further, the second surface inspection holder 110 can adjust the incident angle θi of the inspection illumination light with respect to the wafer surface by tilting the wafer W about an axis passing through the wafer surface.

  The second surface inspection stage ST4 further includes an illumination optical system 120 that irradiates inspection illumination light (hereinafter referred to as illumination light) onto the surface of the wafer W fixedly held by the second surface inspection holder 110, and an illumination optical system. And an imaging optical system 130 that images the surface of the wafer W irradiated with illumination light by 120.

  The illumination optical system 120 has a light source such as a mercury lamp to emit illumination light, and an illumination system concave mirror 122 that reflects the illumination light emitted from the surface illumination device 121 toward the surface of the wafer W. It is mainly composed. The surface illumination device 121 includes a wavelength selection filter (not shown) and can emit illumination light having a specific wavelength corresponding to a circuit pattern formed on the wafer surface. The illumination light emitted from the surface illumination device 121 spreads (diverges) around the optical axis of the illumination optical system 120 and is emitted to the illumination system concave mirror 122, but the exit end of the surface illumination device 121 is the illumination system concave mirror 122. Therefore, the illumination system concave mirror 122 converts the light into a substantially parallel light beam and irradiates the surface of the wafer W held by the second surface inspection holder 110.

  The imaging optical system 130 receives an inspection system concave mirror 131 that collects inspection light (regular reflection light or diffracted light) from the surface of the wafer W, and inspection light collected by the imaging system concave mirror 131. The second surface imaging device 135 that forms the image is mainly configured. When the imaging system concave mirror 131 performs inspection using specularly reflected light as inspection light, the illumination light irradiated onto the surface of the wafer W at the incident angle θi is adjusted by tilt adjustment of the second surface inspection holder 110. It is arranged at a position to receive specular reflection inspection light that is specularly reflected on the surface and emitted with an outgoing angle θr (= incident angle θi), and reflects and converges the specular reflection inspection light from the surface of the wafer W. It is converted (condensed) into a luminous flux. When performing inspection using diffracted light as inspection light, the illumination light applied to the surface of the wafer W at the incident angle θi is reflected by the surface of the wafer W by adjusting the tilt of the second surface inspection holder 110. It is arranged at a position to receive the diffracted light emitted with an exit angle θr (diffraction angle), and reflects (condenses) inspection light, which is diffracted light from the surface of the wafer W, into a convergent light beam.

  The inspection light collected by the imaging system concave mirror 131 in this way passes through the imaging lens 136 of the second surface imaging device 135 and reaches the imaging device 137, and an image of the surface of the wafer W (an image by regular reflection light or An image by diffracted light) is formed on the imaging surface of the image sensor 137. The image sensor 137 of the second surface imaging device 135 photoelectrically converts an image of the wafer surface formed on the imaging surface to generate an image signal, and outputs the image signal to the image processing inspection unit 50.

  The image processing inspection unit 50 generates a digital image of the wafer W based on the image signal of the wafer W input from the imaging device at each inspection stage, and inspects the defect on the wafer W based on this image. The image processing inspection unit 50 is electrically connected to a database unit 51 in which images of non-defective wafers (inspection reference images) and the like are stored in advance, and an image display device 52 that displays inspection results and the like. The inspection result by the image processing inspection unit 50 and the image of the wafer W at that time are stored in the database unit 51 and output and displayed on the image display device 52.

  A wafer W defect inspection method using the inspection apparatus 1 configured as described above will be described below with reference to the flowchart shown in FIG. In the defect inspection of the wafer W in the wafer manufacturing process, first, the defect inspection of the wafer back surface is performed in the back surface inspection stage ST1 (step S201). The wafer W transferred to the back surface inspection stage ST1 by the wafer transfer device 10 is held by the back surface inspection holder 20 with the back surface exposed downward. Then, the back surface illumination device 30 irradiates the back surface of the wafer W with illumination light Li.

  When the irradiation light Li is irradiated on the back surface of the wafer W, if the wafer W is a normal wafer W with no foreign matter attached or scratched on the back surface of the mirror-like wafer W, only regular reflection light is generated from the wafer back surface. On the other hand, when a defect (such as adhesion or scratching of foreign matter) exists on the back surface of the wafer W, the illumination light Li is irregularly reflected by this defect, and scattered light (diffuse reflected light) is also generated from the back surface of the wafer W.

  The back surface imaging device 40 is provided at a position where the regular reflection light Lo (1) emitted from the back surface of the wafer is not incident, and captures a dark field image of the back surface of the wafer W. However, when there is a defect on the back surface of the wafer W and the scattered light is emitted when the defect hits the illumination light Li, a part of the scattered light is captured by the imaging element 42 of the back surface imaging device 40. Image on top. At this time, the imaging element 42 of the back surface imaging device 40 captures the back surface of the wafer by the scattered light, photoelectrically converts the back surface image of the wafer W formed on the imaging surface, and generates an image signal. The signal is output to the image processing inspection unit 50.

  Then, the image processing inspection unit 50 generates a digital image of the back surface of the wafer W based on the image signal of the back surface of the wafer input from the back surface imaging device 40, and inspects a defect on the back surface of the wafer W based on this image. Specifically, the signal intensity (corresponding to the luminance value) in the image on the back surface of the wafer is measured, and when the signal intensity exceeds a threshold value preset in the database unit 51, it is determined that there is a defect, and the wafer The presence / absence of a defect and the defect position on the back surface of W are inspected.

  When the defect inspection on the back surface of the wafer is completed, the defect inspection is performed on the outer peripheral edge of the wafer W in the edge inspection stage ST2 (step S202). The wafer W transferred from the back surface inspection stage ST1 to the edge inspection stage ST2 by the wafer transfer device 10 is rotatably held by the edge inspection holder 60 in a state where the center of the wafer W and the rotation center are aligned. The edge imaging device 70 images the outer peripheral edge (upper and lower bevels, apex) of the wafer W every time the wafer W is rotated by a predetermined angle by the edge inspection holder 60. At this time, the imaging element 72 of the edge imaging device 70 images the outer peripheral edge of the entire circumference of the wafer W, photoelectrically converts the image of the outer peripheral edge of the wafer W formed on the imaging surface, and outputs an image signal. The image signal is generated and output to the image processing inspection unit 50.

  Then, the image processing inspection unit 50 generates a digital image of the outer peripheral edge of the wafer W based on the image signal input from the edge imaging device 70, and inspects the defect at the outer peripheral edge of the wafer W based on this image. To do. Specifically, the image of the outer peripheral edge of the wafer W is compared with an image of a non-defective wafer (inspection reference image) stored in the database unit 51, and the presence / absence and position of the difference from the inspection reference image are determined. To detect. For example, when there is a defect such as adhesion of a foreign substance or a flaw on the outer peripheral edge of the wafer W, a difference in brightness from the inspection reference image is detected in that part, so that the presence of the defect is detected.

  When the defect inspection at the outer peripheral edge of the wafer is completed, the defect inspection of the wafer surface based on the scattered light is then performed at the first surface inspection stage ST3 (step S203). The wafer W transferred from the end inspection stage ST2 to the first surface inspection stage ST3 by the wafer transfer apparatus 10 is placed and held on the upper surface of the first surface inspection holder 80. Then, the first surface illumination device 90 irradiates the surface of the wafer W with illumination light Li ′. When the surface of the wafer W is irradiated with the irradiation light Li ′, if the surface of the wafer W is normal and has no foreign matter attached or scratched, regular reflection light and diffracted light are generated from the wafer surface. On the other hand, when there is a defect (such as adhesion or scratching of foreign matter) on the surface of the wafer W, the illumination light Li ′ is irregularly reflected by this defect, and scattered light (diffuse reflected light) is also generated from the surface of the wafer W.

  The first surface imaging device 100 is provided at a position where regular reflection light and diffracted light emitted from the wafer surface do not enter, and captures a dark field image of the surface of the wafer W. However, when a defect exists on the surface of the wafer W and the scattered light is emitted when the defect is irradiated with the illumination light Li ′, a part of the scattered light is captured by the imaging element 102 of the first surface imaging device 100. The image is formed on the imaging surface. At this time, the imaging element 102 of the first surface imaging device 100 performs imaging of the wafer surface with the scattered light, photoelectrically converts an image of the surface of the wafer W formed on the imaging surface, and generates an image signal. The image signal is output to the image processing inspection unit 50.

  Then, the image processing inspection unit 50 generates a digital image of the surface of the wafer W based on the image signal of the wafer surface input from the first surface imaging device 100, and inspects defects on the surface of the wafer W based on this image. To do. Specifically, the signal intensity (corresponding to the luminance value) in the image of the wafer surface is measured, and when the signal intensity exceeds a threshold set in advance in the database unit 51, it is determined that there is a defect, and the wafer The presence or absence of a defect and the defect position on the surface of W are inspected.

  When the defect inspection of the wafer surface based on the scattered light is finished, the defect inspection of the wafer surface (circuit pattern) based on the specularly reflected light or diffracted light is then performed in the second surface inspection stage ST4 (step S204). The wafer W transferred from the first surface inspection stage ST3 to the second surface inspection stage ST4 by the wafer transfer device 10 is placed and held on the upper surface of the second surface inspection holder 110. The illumination optical system 120 irradiates the surface of the wafer W with illumination light having a specific wavelength. At this time, the wavelength of the illumination light corresponding to the circuit pattern formed on the wafer surface is set by the wavelength selection filter of the surface illumination device 121.

  Then, the second surface inspection holder 110 is rotated so that desired inspection light (regular reflection light or diffracted light) is taken into the imaging system concave mirror 131 from the surface of the wafer W irradiated with illumination light by the illumination optical system 120. And tilt. The inspection light emitted from the surface of the wafer W is collected by the imaging system concave mirror 131 and forms an image on the imaging surface of the imaging element 137 through the imaging lens 136 of the second surface imaging device 135. At this time, the imaging element 137 of the second surface imaging device 135 generates an image signal by photoelectrically converting an image of the surface of the wafer W (an image by specular reflection light or an image by diffraction light) on the imaging surface, The image signal is output to the image processing inspection unit 50.

  Then, the image processing inspection unit 50 generates a digital image of the surface of the wafer W based on the image signal of the wafer surface input from the second surface imaging device 135, and the image (digital image) and the database unit 51 have this image (digital image). A non-defective wafer image (inspection reference image) is compared to detect the presence of a difference from the inspection reference image and its position. Specifically, the signal intensity (corresponding to the luminance value) in the wafer surface image is compared with the signal intensity in the non-defective wafer image, and when the amount of change in the signal intensity exceeds a preset threshold, there is a defect. Is determined. For example, if there is a defect such as a pattern shape abnormality due to defocus, film thickness unevenness, adhesion of foreign matter, or scratches on the surface of the wafer W, a difference in brightness from the inspection reference image is detected in that portion. The presence of a defect is detected.

  When the defect inspection on the wafer surface (circuit pattern) based on the specularly reflected light or diffracted light is completed, the defect inspection on the wafer back surface is performed again at the back surface inspection stage ST1 (step S205). The wafer W transferred from the second surface inspection stage ST4 to the back surface inspection stage ST1 by the wafer transfer device 10 is held by the back surface inspection holder 20 with the back surface exposed downward. Then, as in step S201, the presence / absence of a defect and the defect position on the back surface of the wafer W are inspected.

  In the above method, the defect inspection of the wafer outer peripheral portion in step S202, the defect inspection of the wafer surface based on the scattered light in step S203, and the defect inspection of the wafer surface based on the specularly reflected light or diffracted light in step S204 The inspection order can be changed. For example, the defect inspection of the outer peripheral edge of the wafer in step S203 may be performed after step S203 or step S204.

  The inspection results by the image processing inspection unit 50 in steps S201 to S205 and the images of the wafer back surface, the wafer outer peripheral edge, and the wafer surface at that time are stored in the database unit 51 and output and displayed on the image display device 52. The state of W can also be visually confirmed. As shown in FIG. 7, the database unit 51 divides the front surface, outer peripheral edge, and back surface of the wafer W into corresponding arbitrary regions, and stores defect information (inspection results) for each region. In the database unit 51, the inspection results of a plurality of wafers W are stored in the order of slots for storing the wafers W provided in the wafer cassette 5 ((N + 1) slots are arranged above the N slots). It is databased.

  By comparing these inspection results, the relevance of each defect can be estimated. For example, when a defect is concentrated on the same divided area when a back surface defect inspection result and a surface pattern inspection result are compared on a certain wafer W, the defect on the back surface of the wafer causes a pattern defect on the wafer surface in the relation of the front and back. It is estimated that Alternatively, when the edge inspection result is compared with the surface and back surface inspection results in a certain wafer W and defects are concentrated in the same divided area, the defects at the wafer edge cause defects on the wafer surface and the wafer back surface. It is estimated that Alternatively, the back surface inspection result of the wafer W in the (N + 1) slot is compared with the surface inspection result of the wafer W in the (N) slot. If defects are concentrated in the same divided area, the wafer W in the (N + 1) slot is It is estimated that a back surface defect (foreign matter or the like) may have dropped and adhered to the surface of the wafer in the (N) slot stored below in the wafer cassette 5. Or, it is not always necessary to specialize in comparing inspection results on one wafer or between wafers in the front and rear slots. If there is a tendency that defects are concentrated on the wafer W in a specific slot in the lot, specify It is estimated that the defect may be caused by a limited apparatus in the process.

  In the above, an example in which the back surface of the wafer W is inspected using scattered light has been shown, but instead, defects are detected by inspection using specular reflection light similar to the front surface inspection of the wafer W. May be. However, since the circuit pattern is not formed on the back surface of the wafer W and is in a mirror surface state, the inspection using the diffracted light cannot be performed.

  As described above, in the defect inspection method for the wafer W according to the present embodiment, the defect inspection on the wafer back surface is performed at the back surface inspection stage ST1 at the beginning and the end of the inspection process. Therefore, it is possible to determine that the defect detected in the back surface defect inspection of the wafer W performed at the beginning of the inspection process is the back surface defect generated in the previous stage of the inspection process. Further, among the defects detected in the back surface defect inspection of the wafer W performed at the end of the inspection process, defects other than the defects detected in the previous back surface defect inspection are generated during the inspection (in any of the inspection processes). It can be judged as a defect. Thereby, when the back surface defect which arises at the time of a test | inspection is remarkable, the countermeasure (cleaning etc. of the wafer support surface of each test holder) which removes the cause can be taken rapidly. In addition, by using the defect inspection results on the front surface, outer peripheral edge, and back surface of the wafer W as described above, the wafer W is divided into arbitrary regions and the defect tendency is compared from a macro viewpoint. Relevance can be found.

ST1 Back surface inspection stage ST2 Edge inspection stage ST3 First surface inspection stage ST4 Second surface inspection stage W Wafer (substrate to be tested) 1 Inspection apparatus 10 Wafer transfer apparatus 50 Image processing inspection section 51 Database section

Claims (4)

A substrate inspection method for inspecting defects on a surface other than the back surface and the back surface of a substrate to be tested on which a plurality of patterns are formed,
A first back surface defect detection step for detecting the presence and position of defects on the back surface of the test substrate;
Other surface defect detection step for detecting the presence and position of defects on the surface other than the back surface of the test substrate,
A substrate inspection method comprising: a second back surface defect detection step for detecting again the presence and position of a defect on the back surface of the substrate to be tested.   2. The substrate inspection method according to claim 1, further comprising a detection result comparison step of dividing the back surface of the test substrate and a surface other than the back surface into arbitrary regions and comparing the defect detection results for each region. . The other surface defect inspection step includes:
A surface defect detection step for detecting the presence and position of defects on the surface of the substrate to be tested;
3. The substrate inspection method according to claim 1, further comprising an edge defect detection step of detecting the presence and position of a defect at an outer peripheral edge of the substrate to be tested.   4. The substrate inspection method according to claim 1, wherein the surface other than the back surface includes at least one of the front surface or a surface between the front surface and the back surface. 5. .

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