KR102257264B1 - Scratch detecting method - Google Patents

Abstract

It is an object of the present invention to appropriately detect a scratch by discriminating between a segmentation line and a scratch.
The scratch detection method of the present invention includes a processing groove forming step of forming a divided groove V on the surface of a wafer W, a grinding step of grinding the wafer from the back surface to expose the processing groove, and grinding the wafer after grinding. An imaging process for capturing a surface, an editing process for coordinate conversion of a captured image of a wafer to edit into a strip image, a removal process for removing a line corresponding to a division line from a strip image, and a scratch based on the strip image after removal. It includes a judgment process to determine the presence or absence.

Description

Scratch detection method {SCRATCH DETECTING METHOD}

The present invention relates to a scratch detection method for detecting scratches formed on the surface of a wafer after grinding.

When the wafer is in-feed grinding with a grinding device, saw marks are formed as grinding marks on the surface to be ground of the wafer. The small mark is formed radially from the center of the wafer toward the outer periphery. Among the small marks, in particular, a so-called scratch may occur in which abrasive grains removed from the grinding grindstone during processing come into contact with the surface to be ground of the wafer and become scratched. Since this scratch affects the device formed on the wafer, it is necessary to confirm the presence or absence of the scratch at the end of grinding.

Therefore, a grinding apparatus for detecting scratches on a wafer after grinding has been proposed (see, for example, Patent Document 1). In Patent Document 1, a light beam is irradiated onto the surface to be ground of a wafer after processing, and the presence or absence of a scratch is determined based on the amount of reflected light.

Japanese Patent Publication No. 2009-95903

By the way, in the DBG (Dicing Before Grinding) process in which the wafer is half-cut along the line to be divided before the grinding process, the wafer is divided into individual chips by performing the grinding process. Therefore, not only the above-described scratches but also division lines are exposed on the surface to be ground of the wafer after grinding.

In this case, when scratch detection is performed with the grinding device of Patent Document 1, not only the scratch but also the divided line is detected. For this reason, it is assumed that the scratch and the divided line cannot be distinguished, and the scratch cannot be properly detected.

The present invention has been made in view of these points, and an object of the present invention is to provide a scratch detection method capable of appropriately detecting a scratch by discriminating between a division line and a scratch.

In the scratch detection method of one aspect of the present invention, a dividing groove of a depth that is not completely cut along the dividing line is formed on a wafer in which the device is formed by being divided by a dividing line on the surface from the surface side, and then the rear surface is ground A scratch detection method for detecting the presence or absence of a scratch by photographing the surface to be ground on the back surface of the wafer ground with a grinding grindstone in the segmentation of the wafer to divide the wafer by grinding with an image on the back surface of the wafer, The imaging means includes a line sensor extending in a radial direction of the wafer to image a surface to be polished, and a light extending parallel to the line sensor to illuminate the surface to be polished, and the imaging means is provided in a radial direction within a radius of the wafer. It is placed in the extension direction in parallel, and the holding table holding the wafer is rotated around the center of the wafer, and the imaging means captures the surface to be polished in a ring shape, and the light of the light is scattered from the divided grooves and scratches. An imaging process for acquiring an image, a removal process for removing a lattice-like straight line corresponding to a division groove from a captured image captured in the imaging process, and a scratch when there is an arc or straight line of a predetermined width or more in the image after the removal process. It includes a judgment process for determining that has occurred.

According to this configuration, the holding table is rotated while the line sensor captures the radial portion of the wafer, so that a captured image of the surface to be ground of the wafer can be acquired. During imaging, since the radial portion of the wafer is illuminated by the light, it is possible to recognize a grid-like straight line (dividing line) corresponding to scratches and division grooves from the brightness of the captured image. In particular, by editing the captured image into a strip image, scratches can be displayed in a regular straight line. On the other hand, the dividing line is displayed as a line (eg, a curve) different from the scratch on the band-shaped image. For this reason, it is possible to distinguish between a scratch and a dividing line. Then, it is possible to appropriately detect the scratch by determining the presence or absence of the scratch based on the strip-shaped image from which the divided lines have been removed.

Further, in the above scratch detection method of one aspect of the present invention, the brightness of the light is adjusted to a brightness at which the grinding marks formed on the wafer by the grinding grindstone are not captured by the imaging means.

According to the present invention, it is possible to appropriately detect the scratch by distinguishing the division line from the scratch.

1 is a schematic diagram showing an example of a process of forming a machining groove according to this embodiment.
2 is a schematic diagram showing an example of a grinding process according to the present embodiment.
3 is a schematic diagram showing an example of an imaging process according to the present embodiment.
4 is a schematic diagram showing an example of an editing process according to the present embodiment.
5 is a schematic diagram showing an example of a removal process according to the present embodiment.
6 is a schematic diagram showing an example of a determination process according to the present embodiment.

Conventionally, when a wafer is in-feed grinding with a grinding device, grinding marks (small marks) including scratches may be formed on the surface to be ground of the wafer. An example of the scratch is an arc shape (grinding mark) that is regularly formed from the center of the wafer toward the outer circumference. In addition, there may be a case where the abrasive grains removed from the grinding grindstone during processing come into contact with the surface to be ground of the wafer, resulting in scratches that become scratches. Since this scratch affects the device formed on the wafer, it is not so preferable that the scratch is formed.

For example, by supplying a large amount of grinding water to the upper surface of the wafer to perform grinding, it is conceivable that the removed abrasive grains are removed from the surface to be ground of the wafer, making it difficult to form scratches. However, if the supply amount of grinding water is increased, it is uneconomical, and consequently, a large amount of grinding water becomes a factor, and the force exerted by the grinding grindstone on the wafer, that is, the bite of the abrasive grains is weakened. As a result, there is a fear that the grinding efficiency may deteriorate.

As described above, it is possible to suppress the occurrence of scratches by increasing the number of grinding, but it is difficult to achieve compatibility with grinding efficiency. For this reason, it is necessary to confirm the presence or absence of a scratch at the end of grinding. Therefore, conventionally, a grinding apparatus having a scratch detection means has been proposed that irradiates a light beam onto a surface to be ground of a wafer after processing and determines the presence or absence of a scratch based on the amount of the reflected light.

By the way, as one of the wafer processing methods, there is what is called a DBG (Dicing Before Grinding) process. In the DBG process, a half-cut is performed along a line to be divided from the surface side of the wafer, and division grooves having a depth corresponding to the finished thickness of the device are formed in the wafer. Then, the wafer is ground from the rear surface side, the divided groove is exposed from the rear surface, the divided groove is penetrated in the thickness direction, and the wafer is divided into individual devices.

When scratches are detected by the above-described scratch detection means on the wafers ground by such a DBG process, not only the scratches but also the division lines (divided grooves) are detected. In other words, the division line is misrecognized as a scratch. As described above, in the conventional scratch detection means, the scratch and the divided line cannot be distinguished, and there is a fear that the scratch cannot be properly detected.

Therefore, the inventor of the present invention conceived of appropriately detecting the scratch by discriminating the division line and the scratch in the DBG process.

Hereinafter, a scratch detection method according to the present embodiment will be described with reference to FIGS. 1 to 6. 1 is a schematic diagram showing an example of a process of forming a machining groove according to the present embodiment. 2 is a schematic diagram showing an example of a grinding process according to the present embodiment. Fig. 2A shows a state before grinding, and Fig. 2B shows a state during grinding. 3 is a schematic diagram showing an example of an imaging process according to the present embodiment. Fig. 3A is a side view of the holding table as viewed from a predetermined direction, and Fig. 3B is a side view of the holding table as viewed from the direction of arrow A in Fig. 3A. 3C is a plan view of the wafer after grinding, and FIG. 3D is a captured image. 4 is a schematic diagram showing an example of an editing process according to the present embodiment. 5 is a schematic diagram showing an example of a removal process according to the present embodiment. 6 is a schematic diagram showing an example of a determination process according to the present embodiment. In addition, each of the following steps may be performed by an independent processing device, or all steps may be performed by a single processing device.

The scratch detection method according to the present embodiment includes a processing groove forming step (see Fig. 1) of forming a processing groove (divided groove) on the surface of a wafer, and a grinding step of grinding the wafer from the back surface to expose the processing groove (Fig. 2). Reference), an imaging process (refer to FIG. 3) for imaging the surface (rear surface) of the wafer after grinding, an editing process (refer to FIG. 4) for editing the captured image of the wafer into a strip image by coordinate conversion (see FIG. 4), and a strip image It is carried out by a removal process (refer to FIG. 5) of removing the line corresponding to the divided groove from the and a judgment process (refer to FIG. 6) of judging the presence or absence of a scratch based on the strip-shaped image after removal.

As shown in Fig. 1, the wafer W has a protective tape T1 (for example, a dicing tape) adhered to the back side, and the back side is a cutting device (not shown) through the protective tape T1. ) Is suction-held on the holding table 10. The wafer W is formed in a substantially disk shape, and is divided into a plurality of regions by a grid-like (for example, X-direction and Y-direction) line to be divided (not shown) formed on the surface. Devices (not shown) are formed in each region. In addition, the wafer W may be a semiconductor wafer in which devices such as IC and LSI are formed on a semiconductor substrate such as silicon or gallium arsenide, or an optical device in which an optical device such as LED is formed on a ceramic, glass, or sapphire inorganic material substrate. It may be a wafer. The holding table 10 is configured to be rotatable about a central axis in the vertical direction by a rotation means (not shown), and to be moved in the horizontal direction (cutting transfer) by the cutting transfer means 11.

In the processing groove forming step, the surface of the wafer W is half-cut along the line to be divided by the cutting blade 12. That is, on the surface of the wafer W, a dividing groove V having a depth that is not completely cut along the line to be divided is formed.

Specifically, the wafer W is suction-held by the holding table 10 with the device surface facing upward, and the cutting blade 12 is positioned at a predetermined height along the line to be divided in the vicinity of the outer periphery of the wafer W. It is done. At this time, the height of the cutting blade 12 is positioned so that the lower end of the cutting blade 12 does not completely cut the wafer W in the thickness direction.

In addition, the holding table 10 is relatively cut and conveyed in the horizontal direction with respect to the cutting blade 12 rotating at high speed. Accordingly, the surface of the wafer W is cut along the line to be divided, and a division groove V having a depth corresponding to the finished thickness of the device is formed. When the cutting process of one line is completed, the cutting blade 12 is indexed and conveyed in the direction of the rotation axis, and a division groove V is formed again along the adjacent division scheduled line.

In this way, after the division grooves V are formed along all the division scheduled lines in one direction of the wafer W, the holding table 10 is rotated 90 degrees. Then, by cutting and feeding the holding table 10 with respect to the cutting blade 12 again, a new division groove V is formed along a separate division scheduled line orthogonal to the division groove V previously cut. As described above, the lattice-shaped dividing groove V is formed on the surface of the wafer W.

When the processing groove formation process is completed, the protective tape T1 adhered to the back side of the wafer W is peeled off, and this time, a new protective tape ( T2) (e.g., a back grind tape (see Fig. 2)) is adhered. In addition, peeling of the protective tape T1 and adhesion of the protective tape T2 may be performed manually by an operator, or may be performed by a predetermined peeling (or bonding) device (not shown).

Next, a grinding process is performed. As shown in FIG. 2, in the grinding process, the back side of the wafer W is in-feed grinding by the grinding means 30, and the previously formed divided groove V is exposed on the back side, thereby forming the wafer W. It is divided into individual chips.

Specifically, as shown in Fig. 2A, the wafer W is conveyed from the cutting device to the grinding device (not shown), and the holding table is in a state with the surface side to which the protective tape T2 is adhered face down. It is placed on top of (20). The holding table 20 is composed of a porous chuck in which a disk-shaped porous plate 21 is attached to a main frame 22. On the upper surface of the porous plate 21, a holding surface 21a for attracting and holding the wafer W is formed.

The holding surface 21a has an inclined surface in which the outer periphery is slightly low and inclined with the rotation center of the holding table 20 (the center of the holding surface 21a) as a vertex. When the wafer W is suction-held by the holding surface 21a inclined in a conical shape, the wafer W is deformed into a conical shape of a mild slope along the shape of the holding surface 21a.

Further, the holding table 20 is connected to the table rotation means 23, and is configured to be rotatable about the center of the wafer W by the drive of the table rotation means 23. Moreover, the holding table 20 is comprised so that its inclination can be adjusted by the inclination adjustment means (not shown).

The grinding means 30 is configured to rotate the grinding wheel 32 around a central axis with a spindle 31. A grinding wheel 32 is attached to the shaft end (lower end) of the spindle 31 via a mount 33. On the lower surface side of the grinding wheel 32, a plurality of grinding grindstones 34 are annularly arranged at intervals. The grinding grindstone 34 is constituted by, for example, bonding diamond abrasive grains having a predetermined abrasive grain diameter by vitrified bonds. Further, the grinding grindstone 34 is not limited to this, and may be formed by hardening diamond abrasive grains with a binder such as a metal bond or a resin bond. In addition, the grinding means 30 is configured to be able to move up and down in the vertical direction by the grinding transfer means 35.

The holding table 20 which sucked and held the surface side of the wafer W is located under the grinding means 30. At this time, the rotation shaft of the holding table 20 is located at a position eccentric from the rotation shaft of the grinding grindstone 34. Further, in the holding table 20, the inclination of the rotation axis is adjusted by the tilt adjustment means so that the grinding surface 34a of the grinding grindstone 34 and the holding surface 21a become parallel.

And, while the holding table 20 is rotated, the grinding means 30 rotates the grinding wheel 32 (grinding grindstone 34) by the spindle 31, while the holding surface by the grinding transfer means 35 It descends toward (21a) (grinding and feeding). The grinding surface 34a of the grinding grindstone 34 is in circular arc contact with a radial portion extending from the center of the wafer W to the outer periphery.

In this way, the grinding means 30, the grinding grindstone 34 passes through the center of the wafer W, and in the radial region between the center of the wafer W and the outer circumference, the circular arc portion of the wafer W To grind. The wafer W is ground in the thickness direction and thinned by gradually grinding and transferring in the Z-axis direction while rotating the grinding grindstone 34 and the wafer W in rotational contact.

As shown in Fig. 2B, when the wafer W is thinned to a desired thickness, that is, the finished thickness of the device, the divided groove V is exposed from the back side of the wafer W, and the grinding process is finished. Accordingly, the dividing groove V along the line to be divided passes in the thickness direction of the wafer W, and the wafer W is divided into individual devices (chips). In addition, since each device is fixed by the protective tape T2, the circular shape of the wafer W is maintained as a whole. In addition, a lattice-like straight line formed on the wafer W by passing the dividing groove V will be referred to as a "dividing line". In addition, the "dividing line" may be called a kerf.

Next, an imaging process is performed. In the imaging process, as shown in FIG. 3, the back surface (surface to be ground) of the wafer W is imaged by the imaging means 41. Here, the configuration of the scratch detection means 40 for detecting scratches formed on the surface to be ground of the wafer W will be described. In the present embodiment, a case where the scratch detection means 40 is provided in the grinding device is described, but is not limited to this configuration. The scratch detection means 40 may be provided in an independent device.

3A and 3B, the scratch detection means 40 is based on an imaging means 41 that captures a surface to be ground of the wafer W, and a captured image captured by the imaging means 41. And a determination means 42 for determining the presence or absence of a scratch. The imaging means 41 is constituted by a line sensor 43 for imaging a surface to be ground of the wafer W from above, and a light 44 disposed along the line sensor 43.

The line sensor 43 is constituted by, for example, an image sensor. The line sensor 43 extends in the radial direction of the wafer W and has a length shorter than the radial portion. The line sensor 43 can image a region corresponding to a part of the radius of the wafer W. The light 44 extends in the same direction (parallel) and the same length as the line sensor 43, and irradiates light toward the surface to be ground of the wafer W. Specifically, the light 44 illuminates the surface to be ground of the wafer W so as to brighten the imaging range of the line sensor 43.

The determination means 42 is incorporated in a control device that collectively controls the operation of the grinding device, an editing unit 45 for editing a captured image, and a determination unit 46 for determining the presence or absence of a scratch based on the edited captured image. ).

In the imaging process, the wafer W after grinding is placed under the imaging means 41 while being sucked and held by the holding table 20. In addition, the holding table 20 is rotated by the tilt adjustment means so that the extending direction of the imaging means 41 (line sensor 43) and the surface to be ground (holding surface 21a) of the wafer W are parallel. The slope of is adjusted.

As shown in FIGS. 3A and 3B, the imaging area of the line sensor 43 corresponds to a part of the radius of the wafer W immediately below the line sensor 43. The light 44 irradiates light toward the imaging area of the line sensor 43. The imaging means 41 rotates the wafer W on the holding table 20 once while imaging a part of the radius of the wafer W to which the light of the light 44 is irradiated with the line sensor 43. The surface to be ground of W) is imaged. Further, the light irradiated from the light 44 has a wavelength reflected from the surface of the wafer W, and light having a wavelength having transmittance to the wafer W is not used.

As shown in FIG. 3C, on the surface to be ground of the wafer W after grinding, a grid-shaped division line L and a regular arc-shaped scratch S from the center of the wafer W toward the outer periphery are formed. It is formed innumerable. When the surface to be ground of the wafer W is captured, as shown in Fig. 3D, a ring-shaped captured image can be obtained.

In the picked-up image shown in Fig. 3D, in the dividing line L (dividing groove) and the scratch S, the light from the light 44 is scattered, resulting in contrast due to the scattered light. Specifically, since the reflected light of the picked-up light is weakened (scattered) due to fine irregularities formed on the wafer W, the scratch S and the division line L can be recognized from the contrast of the contrast.

In particular, in the present embodiment, since the divided line L is included in the captured image, there is a possibility that the amount of data of the captured image increases by that amount. Therefore, the imaging means 41 is made shorter than the radius of the wafer W to reduce the imaging range. Accordingly, it is possible to obtain the ring-shaped captured image shown in Fig. 3D, and it is possible to reduce the amount of data of the captured image compared to the case of capturing the entire surface of the wafer W. As a result, it is possible to reduce the processing burden of the judgment means 42 in subsequent steps.

Further, by arranging the imaging means 41 along the radial direction of the wafer W and rotating the holding table 20 holding the wafer W by one rotation, the surface to be ground of the wafer W is imaged. It is always possible to make the situation where the light hits the scratch evenly. As a result, it is possible to acquire an appropriate captured image of the wafer W so that the center of the wafer W is not shifted.

Next, the editing process is carried out. In the editing process, the captured image obtained in the imaging process is transformed into coordinates and edited into a strip-shaped image shown in FIG. 4. Specifically, the editing unit 45 (see Fig. 3A) has the radial direction (from the center of the wafer to the outer circumference of the wafer) of the captured image (see Fig. 3D) as the vertical axis, and the circumferential direction of the captured image (0° to 360°) as the horizontal axis. Then, the coordinates are converted. The edited image obtained by coordinate transformation is displayed as a rectangular image (band-shaped image) long in the circumferential direction, as shown in FIG. 4.

For example, the dividing line L and the scratch S shown in FIG. 3D are respectively represented by a curve L _A and a straight line S _{A in} the band-shaped image of FIG. 4. In addition, the strip-shaped image of FIG. 4 is shown by extracting a part of the radial direction and the circumferential direction of FIG. 3D. In addition, in FIG. 4, for convenience of explanation, the curve L _A corresponding to the dividing line is indicated by a broken line. In addition, in FIG. 4, _{it is assumed that among the plurality of straight lines S A} , a relatively thick straight line S _B is exposed on the strip-shaped image.

As described above, in the actual captured image, the scratch S is indicated by an arc-shaped curve, whereas in the edited strip-shaped image, the scratch S is indicated by a regular straight line S _A. This makes it easy for the determination unit 46 to determine the presence or absence of a scratch in a subsequent determination process. On the other hand, in the captured image of Fig. 3D, the dividing line L is indicated by a grid-shaped straight line, whereas in the edited strip-shaped image, the dividing line L is indicated by an _{arc-shaped curve L A.} . In particular, curve (L _A) is a straight line is indicated by (curve having no regularity) tend to be different and the cross curve, or with respect to the (S _A), the straight line (S _A) with a regularity. For this reason, it becomes easy to distinguish between the scratch S (straight line S _A ) and the split line L (curve L _{A ).}

Next, a removal process is performed. In the removal process, a lattice-shaped straight line (dividing line L) corresponding to the division groove is removed from the captured image captured in the imaging process. Specifically, in the edited strip-shaped image, the _{curve L A} having a tendency different from that of the _{straight line S A} is removed. After editing the captured image into a strip image, the editing unit 45 separates the scratch (S) and the dividing line (L), and _{removes the curve L A} (dividing line L) that does not have regularity from the strip-shaped image. do. In this case, since the straight line S _B is formed by the position and direction having the same regularity as the regular straight line S _{A , the editing unit 45 uses the straight line S B} as a strip image. Do not remove from As a result of these, a band-shaped image shown in Fig. 5 can be obtained.

Next, a judgment process is carried out. In the judgment process, the presence or absence of a scratch is judged based on the strip-shaped image obtained in the removal process. For example, the determination unit 46 (refer to Fig. 3A) determines that a scratch has occurred when there is an arc or a straight line of a predetermined width or more in the strip-shaped image after the removal process. Specifically, in the band-shaped image shown in FIG. 5, the determination unit 46 judges that there is a scratch if the width of the regular straight line is larger than the preset width, and the width of the regular straight line is If it is less than the set width, it is determined that there is no scratch. Further, the determination unit 46 determines that there is a scratch even when there is a line other than a straight line with regularity in the band-shaped image.

As shown in Fig. 6, a case where a relatively thick straight line S _{B is displayed along a regular straight line S A} in the strip-shaped image after the removal step is considered. The determination unit 46 detects the width D of the straight line SB from the strip-shaped image _{, and compares the width D of the straight line S B} to a preset standard for determining the presence or absence of a scratch. If the result is larger width of the straight line (S _B), the straight line (S _B) is recognized as a scratch (S _B). That is, the determination unit 46 determines that there is a scratch. In addition, the determination unit 46, by detecting the width of the straight road (S _A), is smaller than the line width of the predetermined range, and do not recognized as a scratch can be removed in a straight line (S _A).

As described above, in the present embodiment, even when scratches having regularity such as grinding marks are displayed in the captured image, it is possible to detect relatively large scratches or scratches without regularity from the strip-shaped image after the removal step. That is, it is possible to select and determine the scratches that may have an influence on the subsequent processes or the devices formed on the wafer W.

As described above, according to the present embodiment, the holding table 20 rotates while the line sensor 43 photographs the radial portion of the wafer W, thereby obtaining a captured image of the surface to be ground of the wafer W. I can. During imaging, since the radial portion of the wafer W is irradiated by the light 44, a grid-like straight line (dividing line L) corresponding to the scratch S and the split groove V is obtained from the contrast of the captured image. I can recognize it. In particular, by editing the captured image into a strip image, the scratch S can be displayed _{as a regular straight line S A.} On the other hand, the dividing line L is displayed as a line different from the scratch (for example, a curve L _{A) in a band-shaped image.} For this reason, it is possible to distinguish between the scratch S and the dividing line L. Then, by determining the presence or absence of a scratch on the basis of the strip-shaped image from which the division line L has been removed, it is possible to appropriately detect the scratch.

In the present embodiment, although the holding table 20 is rotated by one rotation to capture an image of the surface to be ground of the wafer W, it is not limited to this configuration. For example, the imaging means 41 may be rotated around the center of the wafer W.

In addition, in this embodiment, although the imaging means 41 is made into a structure extending to a length corresponding to a part of the radius of the wafer W, it is not limited to this structure. The imaging means 41 (line sensor 43 and light 44) may have a length corresponding to the radius portion of the wafer W, or may be longer than that. By setting the imaging means 41 to a length corresponding to the radial portion of the wafer W, it is possible to image the entire surface of the wafer W.

In addition, in the present embodiment, each of the above-described steps may be performed by an independent processing device, or all steps may be performed by a single processing device. For example, it is also possible to perform from the grinding process to the judgment process with a single grinding device. Accordingly, time for transporting the wafer W to a separate device for scratch detection or scratch removal can be omitted.

In addition, in the present embodiment, by adjusting the brightness of the light 44 during the imaging process, the state of reflection of the grinding marks in the captured image may be adjusted. For example, the brightness of the light 44 is preferably adjusted to a brightness in which no grinding marks are captured (not displayed in a captured image). Grinding marks are formed innumerably between the circular arc-shaped scratches S having regularity and the adjacent scratches S, but if all of them are captured, not only the amount of data in the captured image increases, but also the determination of the presence or absence of scratches becomes difficult. There is a concern.

Thus, by adjusting the brightness of the light 44 and selectively extracting the number of grinding marks displayed in the captured image, it is possible to reduce the amount of data in the captured image and to easily determine the presence or absence of a scratch. Specifically, since the light amount of the scattered light is reduced by making the light 44 relatively dark (reducing the amount of light), it is possible to selectively extract the number of grinding marks in the captured image or not to display the grinding marks. On the other hand, when the light 44 is relatively bright (increasing the amount of light), the amount of scattered light increases, so that the grinding marks are more likely to be exposed in the captured image.

In addition, by adjusting the brightness of the light 44 during the imaging process, not only the reflection state of the grinding mark in the captured image may be adjusted, but also the distance between the imaging means 41 and the wafer W may be adjusted.

In addition, although this embodiment and a modified example have been described, as another embodiment of the present invention, a combination of the above embodiment and modified example may be used in whole or in part.

In addition, the embodiment of the present invention is not limited to the above-described embodiment, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea of the present invention. Furthermore, as long as the technical idea of the present invention can be realized by a separate method, it may be implemented using that method. Accordingly, the claims cover all embodiments that may be included within the scope of the technical idea of the present invention.

As described above, the present invention has an effect that it is possible to appropriately detect a scratch by discriminating between a division line and a scratch, and is particularly useful for a scratch detection method applied to a DBG process.

20: holding table 21a: holding surface
23: table rotation means 30: grinding means
31: spindle 32: grinding wheel
33: mount 34: grinding wheel
40: scratch detection means 41: imaging means
42: judging means 43: line sensor
44: light 45: editorial department
46: judging unit W: wafer
V: Divided groove (divided line) L: Divided line
L _A : Curve S: Scratch
S _A , S _B : Straight (scratch) D: Width

Claims (2)

Dividing grooves of a depth that are not completely cut along the division-planned line are formed from the front side of the wafer on which the device is formed by being divided by the dividing line on the surface, and then the rear surface is ground with a grinding grindstone, and the dividing groove is placed on the rear side. A scratch detection method for detecting the presence or absence of a scratch by imaging the surface to be ground on the back surface of the wafer ground with the grinding grindstone in the wafer segmentation by which the wafer is expressed, comprising:
The imaging means includes a line sensor extending in a radial direction of the wafer to capture a predetermined area of a surface to be polished, and a light extending parallel to the line sensor to illuminate the predetermined area of the surface to be polished,
The imaging means is positioned so that its extension direction is parallel to the radial direction within the radius of the wafer, and the holding table for holding the wafer is rotated about the center of the wafer, and the imaging means rotates the surface to be polished in a ring shape. An imaging step of capturing an image and acquiring a captured image by scattered light from which light of the light is scattered from the divided groove and the scratch;
A removal step of removing a lattice-shaped straight line corresponding to the divided groove from the captured image captured in the imaging step; and
A judgment process of determining that a scratch has occurred when there is an arc or a straight line of a predetermined width or more in the image after the removal process
Including,
The removal process,
An editing process of editing the captured image to form a strip image,
In the band-shaped image, a determination process of determining a curve of an arc as the divided groove
Scratch detection method comprising a. The scratch detection method according to claim 1, wherein the brightness of the light is adjusted to a brightness at which the grinding marks formed on the wafer by the grinding grindstone are not captured by the imaging means.

Images