JP6760820B2 - Scratch detection method - Google Patents

Description

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 ground with a grinding device, a saw mark is formed as a grinding mark on the surface to be ground of the wafer. Saw marks are formed radially from the center of the wafer toward the outer circumference. Among the saw marks, so-called scratches may occur in which abrasive grains that have fallen off from the grinding wheel during processing come into contact with the surface to be ground of the wafer and cause scratches. 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 device that detects scratches on a wafer after grinding has been proposed (see, for example, Patent Document 1). In Patent Document 1, the surface to be ground of the processed wafer is irradiated with a light beam, and the presence or absence of scratches is determined based on the amount of the reflected light.

JP-A-2009-95903

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

In this case, when scratch detection is performed by the grinding apparatus of Patent Document 1, not only scratches but also dividing lines are detected. Therefore, it is assumed that the scratch and the dividing line cannot be distinguished and the scratch cannot be detected properly.

The present invention has been made in view of the above points, and one of the objects of the present invention is to provide a scratch detection method capable of appropriately detecting scratches by distinguishing between a dividing line and scratches.

In the scratch detection method of one aspect of the present invention, a dividing groove having a depth that does not completely cut along the planned division line is formed from the front surface side on the wafer in which the device is formed by being partitioned by the planned division line on the front surface, and then the back surface is ground. In the division of the wafer, which divides the wafer by exposing the dividing groove to the back surface side, the surface to be ground on the back surface of the wafer ground by the grinding wheel is imaged by an imaging means to detect the presence or absence of scratches. The imaging means includes a line sensor extending in the radial direction of the wafer to image the surface to be ground and a light extending parallel to the line sensor to illuminate the surface to be ground. Positioning the extending direction parallel to the radial direction within the radius of the wafer, the holding table that holds the wafer is rotated around the center of the wafer, and the imaging means images the surface to be ground in a ring shape with the dividing groove and scratch. An imaging step of acquiring an image captured by scattered light in which the light of the light is scattered, a removing step of removing a grid-like straight line corresponding to a dividing groove from the captured image captured in the imaging step, and a predetermined width in the image after the removing step. It is provided with a determination step of determining that a scratch has occurred when there is the above arc or straight line.

According to this configuration, the holding table is rotated while the line sensor images the radial portion of the wafer, so that an image of the surface to be ground of the wafer can be acquired. Since the radial portion of the wafer is illuminated by the light during imaging, a grid-like straight line (division line) corresponding to a scratch and a division groove can be recognized from the brightness and darkness of the captured image. In particular, by editing the captured image into a strip-shaped image, scratches can be displayed as regular straight lines. On the other hand, the dividing line is displayed on the strip-shaped image as a line (for example, a curve) different from the scratch. Therefore, it is possible to distinguish between scratches and dividing lines. Then, by determining the presence or absence of scratches based on the strip-shaped image from which the dividing line has been removed, scratches can be appropriately detected.

Further, in the above-mentioned 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 wheel are not captured by the imaging means.

According to the present invention, scratches can be appropriately detected by distinguishing between a dividing line and scratches.

It is a schematic diagram which shows an example of the machined groove forming process which concerns on this embodiment. It is a schematic diagram which shows an example of the grinding process which concerns on this Embodiment. It is a schematic diagram which shows an example of the imaging process which concerns on this Embodiment. It is a schematic diagram which shows an example of the editing process which concerns on this Embodiment. It is a schematic diagram which shows an example of the removal process which concerns on this Embodiment. It is a schematic diagram which shows an example of the determination process which concerns on this Embodiment.

Conventionally, when a wafer is in-feed ground with a grinding device, grinding marks (saw marks) including scratches may be formed on the surface to be ground of the wafer. Examples of scratches include arc-shaped patterns (grinding marks) that are regularly formed from the center of the wafer toward the outer circumference. In addition, the abrasive grains that have fallen off from the grinding wheel during processing may come into contact with the surface to be ground of the wafer, causing scratches. Since this scratch affects the device formed on the wafer, it is less preferable that the scratch is formed.

For example, by supplying a large amount of grinding water to the upper surface of the wafer and performing the grinding process, it is conceivable to remove the fallen abrasive grains from the surface to be ground of the wafer and make it difficult to form scratches. However, increasing the supply amount of grinding water is uneconomical, and further, due to a large amount of grinding water, the force with which the grinding wheel is caught on the wafer, that is, the biting of the abrasive grains is weakened. As a result, the grinding efficiency may deteriorate.

In this way, it is possible to suppress the occurrence of scratches by increasing the amount of grinding water, but it is difficult to achieve both grinding efficiency. Therefore, it is necessary to confirm the presence or absence of scratches at the end of grinding. Therefore, conventionally, a grinding device provided with a scratch detecting means for irradiating a surface to be ground of a wafer after processing with a light beam and determining the presence or absence of scratches based on the amount of reflected light has been proposed.

By the way, as one of the processing methods for wafers, there is a DBG (Dicing Before Grinding) process. In the DBG process, a half cut is made from the surface side of the wafer along the planned division line, and a division groove having a depth corresponding to the finished thickness of the device is formed in the wafer. Then, grinding is performed from the back surface side of the wafer, the dividing groove is exposed from the back surface side, the dividing groove is penetrated in the thickness direction, and the wafer is divided into individual devices.

When scratch detection is performed on a wafer ground by such a DBG process by the scratch detecting means described above, not only scratches but also dividing lines (dividing grooves) are detected. That is, the dividing line is erroneously recognized as a scratch. As described above, the conventional scratch detecting means cannot distinguish between the scratch and the dividing line, and there is a possibility that the scratch cannot be detected appropriately.

Therefore, the present inventor has conceived to distinguish between the dividing line and the scratch and appropriately detect the scratch in the DBG process.

Hereinafter, the scratch detection method according to the present embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a schematic view showing an example of a machined groove forming step according to the present embodiment. FIG. 2 is a schematic view showing an example of the grinding process according to the present embodiment. FIG. 2A shows a state before grinding, and FIG. 2B shows a state during grinding. FIG. 3 is a schematic view showing an example of the 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 in the direction of arrow A in FIG. 3A. FIG. 3C is a top view of the wafer after grinding, and FIG. 3D is a captured image. FIG. 4 is a schematic diagram showing an example of the editing process according to the present embodiment. FIG. 5 is a schematic view showing an example of the removal step according to the present embodiment. FIG. 6 is a schematic diagram showing an example of the determination process according to the present embodiment. In addition, each of the following steps may be carried out by an independent processing apparatus, or all the steps may be carried out by a single processing apparatus.

The scratch detection method according to the present embodiment includes a machining groove forming step (see FIG. 1) for forming a machining groove (split groove) on the front surface of the wafer and a grinding step for grinding the wafer from the back surface to expose the machining groove. (See FIG. 2), an imaging step (see FIG. 3) of imaging the surface to be ground (back surface) of the waiha after grinding, and an editing process of converting the image of the waiha into a strip-shaped image (see FIG. 4). ), A removal step of removing the line corresponding to the dividing groove from the strip-shaped image (see FIG. 5), and a determination step of determining the presence or absence of scratches based on the strip-shaped image after removal (see FIG. 6). ..

As shown in FIG. 1, the wafer W has a protective tape T1 (for example, dicing tape) attached to the back surface side, and the back surface side is placed on a holding table 10 of a cutting device (not shown) via the protective tape T1. It is sucked and held. The wafer W is formed in a substantially disk shape, and is divided into a plurality of regions by grid-like (for example, X-direction and Y-direction) division schedule lines (not shown) formed on the surface. A device (not shown) is formed in each region. The wafer W may be a semiconductor wafer in which devices such as ICs and LSIs are formed on a semiconductor substrate such as silicon or gallium arsenide, or an optical device such as an LED is formed on a ceramic, glass, or sapphire-based inorganic material substrate. It may be an optical device wafer. The holding table 10 is configured to be rotatable about a central axis in the vertical direction by a rotating means (not shown) and to be moved (cutting feed) in the horizontal direction by the cutting feed means 11.

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

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

Then, the holding table 10 is cut and fed in the horizontal direction relative to the cutting blade 12 that rotates at high speed. As a result, the surface of the wafer W is cut along the planned division line, and a division groove V having a depth corresponding to the finished thickness of the device is formed. When the cutting of one line is completed, the cutting blade 12 is indexed and fed in the direction of the rotation axis, and the dividing groove V is formed again along the adjacent division scheduled line.

In this way, after the division groove V is formed along all the division schedule lines in one direction of the wafer W, the holding table 10 is rotated by 90 degrees. Then, the holding table 10 is cut and fed to the cutting blade 12 again, so that a new dividing groove V is formed along another division scheduled line orthogonal to the previously cut dividing groove V. As described above, a grid-like dividing groove V is formed on the surface of the wafer W.

When the processing groove forming step is completed, the protective tape T1 attached to the back surface side of the wafer W is peeled off, and this time, a new protective tape T2 (for example, back grind tape) is attached to the front surface side (dividing groove V side) of the wafer W. (See Fig. 2)) is attached. The peeling of the protective tape T1 and the sticking of the protective tape T2 may be carried out manually by an operator, or may be carried out by a predetermined peeling (or sticking) device (not shown).

Next, the grinding process is carried out. As shown in FIG. 2, in the grinding process, the back surface side of the wafer W is in-feed ground by the grinding means 30, and the previously formed dividing groove V is exposed on the back surface side, so that the wafer W is divided into individual chips. Will be done.

Specifically, as shown in FIG. 2A, the wafer W is conveyed from the cutting device to the grinding device (not shown), and is placed on the holding table 20 with the surface side to which the protective tape T2 is attached facing down. It will be placed. The holding table 20 is composed of a porous chuck in which a disk-shaped porous plate 21 is attached to a frame body 22 as a body. A holding surface 21a for sucking and holding the wafer W is formed on the upper surface of the porous plate 21.

The holding surface 21a has an inclined surface whose apex is the center of rotation of the holding table 20 (center of the holding surface 21a) and whose outer circumference is slightly lowered. When the wafer W is sucked and held by the holding surface 21a that is inclined in a conical shape, the wafer W is deformed into a gently inclined conical shape along the shape of the holding surface 21a.

Further, the holding table 20 is connected to the table rotating means 23, and is configured to be rotatable around the center of the wafer W by driving the table rotating means 23. Further, the holding table 10 is configured so that its inclination can be adjusted by an inclination adjusting means (not shown).

The grinding means 30 is configured to rotate the grinding wheel 32 around the central axis by the 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 wheels 34 are arranged at intervals in an annular shape. The grinding wheel 34 is formed by, for example, bonding diamond abrasive grains having a predetermined grain size with a vitrified bond. The grinding wheel 34 is not limited to this, and the diamond abrasive grains may be formed by solidifying with a binder such as a metal bond or a resin bond. Further, the grinding means 30 is configured to be able to move up and down in the vertical direction by the grinding feeding means 35.

The holding table 20 that sucks and holds the surface side of the wafer W is positioned below the grinding means 30. At this time, the rotation axis of the holding table 20 is positioned at a position eccentric from the rotation axis of the grinding wheel 34. Further, the inclination of the rotating shaft of the holding table 20 is adjusted by the inclination adjusting means so that the grinding surface 34a and the holding surface 21a of the grinding wheel 34 are parallel to each other.

Then, while the holding table 20 is rotated, the grinding means 30 is lowered (grinding feed) toward the holding surface 21a by the grinding feed means 35 while rotating the grinding wheel 32 (grinding grindstone 34) by the spindle 31. .. The grinding surface 34a of the grinding wheel 34 is brought into contact with the radial portion from the center of the wafer W to the outer periphery in an arc shape.

In this way, the grinding means 30 grinds the portion to be ground of the arc of the wafer W in the radial area between the center of the wafer W and the outer circumference of the grinding wheel 34 passing through the center of the wafer W. By gradually grinding and feeding the wafer W in the Z-axis direction while rotating the grinding wheel 34 and the wafer W in rotational contact, the wafer W is ground in the thickness direction and thinned.

As shown in FIG. 2B, when the wafer W is thinned to a desired thickness, that is, the finished thickness of the device, the dividing groove V is exposed from the back surface side of the wafer W, and the grinding process is completed. As a result, the dividing groove V along the planned division line penetrates in the thickness direction of the wafer W, and the wafer W is divided into individual devices (chips). Since each device is fixed by the protective tape T2, the circular shape of the wafer W is maintained as a whole. The grid-like straight line formed on the wafer W by penetrating the dividing groove V is referred to as a "dividing line". Also, the "dividing line" may be called a calf.

Next, an imaging step is performed. In the imaging step, 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 detecting means 40 for detecting the scratch formed on the surface to be ground of the wafer W will be described. In the present embodiment, the case where the scratch detecting means 40 is provided in the grinding apparatus will be described, but the present invention is not limited to this configuration. The scratch detecting means 40 may be provided in an independent device.

As shown in FIGS. 3A and 3B, the scratch detecting means 40 includes an imaging means 41 that images the surface to be ground of the wafer W and a determining means 42 that determines the presence or absence of scratches based on the captured image captured by the imaging means 41. And have. The imaging means 41 is composed of a line sensor 43 that images the surface to be ground of the wafer W from above, and a light 44 that is arranged along the line sensor 43.

The line sensor 43 is composed of, 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 apparatus, and includes an editorial unit 45 that edits the captured image and a determination unit 46 that determines the presence or absence of scratches based on the edited captured image. Have.

In the imaging step, the wafer W after grinding is positioned below the imaging means 41 while being sucked and held by the holding table 20. Further, the inclination of the rotation axis of the holding table 20 is adjusted by the inclination adjusting 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 to each other. ..

As shown in FIGS. 3A and 3B, the imaging region of the line sensor 43 corresponds to a part of the radius of the wafer W directly below the line sensor 43. The light 44 irradiates light toward the imaging region of the line sensor 43. The imaging means 41 images the surface to be ground of the wafer W by rotating the wafer W on the holding table 20 once while imaging a part of the radius of the wafer W irradiated with the light of the light 44 by the line sensor 43. To do. The light emitted from the light 44 has a wavelength that is reflected on the surface of the wafer W, and light having a wavelength that is transparent to the wafer W is not used.

As shown in FIG. 3C, innumerable grid-like dividing lines L and innumerable arc-shaped scratches S from the center of the wafer W toward the outer circumference are formed on the surface to be ground of the wafer W after grinding. .. When the surface to be ground of the wafer W is imaged, a ring-shaped image can be acquired as shown in FIG. 3D.

In the captured image shown in FIG. 3D, light and darkness is generated by scattered light in which the light of the light 44 is scattered at the dividing line L (dividing groove) and the scratch S. Specifically, since the reflected light of the imaging light is weakened (scattered) by the fine irregularities formed on the wafer W, it is possible to recognize the scratch S and the dividing line L from the contrast between light and dark.

In particular, in the present embodiment, since the captured image includes the division line L, the amount of data in the captured image may increase accordingly. Therefore, the imaging means 41 is made shorter than the radius of the wafer W to reduce the imaging range. As a result, the ring-shaped captured image shown in FIG. 3D can be obtained, and the amount of data in the captured image can be reduced as compared with the case where the entire surface of the wafer W is imaged. As a result, it is possible to reduce the processing load of the determination means 42 in the subsequent process.

Further, by arranging the imaging means 41 along the radial direction of the wafer W and rotating the holding table 20 for holding the wafer W once to image the surface to be ground of the wafer W, the degree of light hitting the scratch can be determined. It can always be uniform. As a result, it is possible to acquire an appropriate captured image of the wafer W without shifting the center of the wafer W.

Next, the editing process is carried out. In the editing step, the captured image obtained in the imaging step is coordinate-converted and edited into a strip-shaped image shown in FIG. Specifically, the editorial unit 45 (see FIG. 3) has the radial direction (from the center of the wafer to the outer periphery of the wafer) of the captured image (see FIG. 3D) as the vertical axis, and the circumferential direction (0 ° to 360 °) of the captured image as the horizontal axis. Perform coordinate conversion as an axis. As shown in FIG. 4, the edited image obtained by the coordinate conversion is represented by a rectangular image (strip-shaped image) long in the circumferential direction.

For example, the division line L and scratch S shown in Figure 3D, the band-like image in FIG. 4, respectively by a curve L _A and a straight line S _A. The strip-shaped image of FIG. 4 is shown by extracting a part of the radial direction and the circumferential direction of FIG. 3D. For convenience of description, FIG. 4 shows a curve L _A that correspond to the dividing line by a broken line. Further, in FIG. 4, among the plurality of straight lines S _A, it is assumed that the straight line S _B of a relatively thick width appearing on the strip image.

In this way, the actual captured image, the scratch S whereas indicated by arcuate curve, the belt-shaped image after editing, the scratch S is indicated by a straight line S _A having regularity. This makes it easier for the determination unit 46 to determine the presence or absence of scratches in the subsequent determination step. On the other hand, in the captured image in FIG. 3D, the division line L whereas indicated by grid lines, the strip-shaped edited image, the division line L is represented by the arcuate curve L _A. In particular, the curve L _A, or intersect, the trend is a straight line S _A having regularity is represented by different curves (curves having no regularity) with respect to the straight line S _A. Therefore, the scratch S (linear _{S A)} and dividing lines L and (curve _{L A)} is coded to.

Next, a removal step is carried out. In the removing step, a grid-like straight line (divided line L) corresponding to the dividing groove is removed from the captured image captured in the imaging step. Specifically, the belt-shaped image edited, trend linearly S _A different curve L _A is removed. Editing section 45, after editing the captured image in a strip image, differentiate between dividing line L and a scratch S, removes no regularity curve L _{A (the} parting line L) of a strip-shaped images. In this case, the straight line S _B, because they are formed by the position and direction have the same regularity as the straight line S _A having regularity, the editing unit 45 does not remove the linear S _B from the band image. As a result, the strip-shaped image shown in FIG. 5 is obtained.

Next, the determination process is carried out. In the determination step, the presence or absence of scratches is determined based on the strip-shaped image obtained in the removal step. For example, the determination unit 46 (see FIG. 3) determines that scratches have occurred when the strip-shaped image after the removal step has an arc or a straight line having a predetermined width or more. Specifically, in the strip-shaped image shown in FIG. 5, if the width of the regular straight line is larger than the preset width, the determination unit 46 determines that there is scratch, and the width of the regular straight line is preset. If it is less than the width, it is judged that there is no scratch. Further, the determination unit 46 also determines that there is a scratch when there is a line other than a regular straight line in the strip-shaped image.

As shown in FIG. 6, the belt-shaped image after the removal step, consider the case where relatively thick linear S _B is shown along a straight line S _A having regularity. Determination unit 46 detects the width D of the straight line S _B from the band image is compared with the straight line width as a preset scratch existence criterion. As a result, if the direction of the width of the linear S _B is greater recognizes the straight line S _B as a scratch S _B. That is, the determination unit 46 determines that there is a scratch. The determination unit 46 also detects the width of the linear S _A, as the width is smaller than the predetermined straight line width, not recognized as a scratch to be removed linearly S _A.

As described above, in the present embodiment, even when a scratch having regularity such as a grinding mark is shown in the captured image, a relatively large scratch or a scratch having no regularity is obtained from the strip-shaped image after the removal step. Can be detected. That is, it is possible to select and judge scratches that may affect the subsequent process and the device formed on the wafer W.

As described above, according to the present embodiment, the holding table 20 is rotated while the line sensor 43 images the radial portion of the wafer W to acquire an image of the surface to be ground of the wafer W. Can be done. Since the radial portion of the wafer W is illuminated by the light 44 during imaging, a grid-like straight line (division line L) corresponding to the scratch S and the division groove V can be recognized from the brightness and darkness of the captured image. In particular, by editing the captured image in a strip image can be displayed scratch S in a straight line S _A having regularity. On the other hand, the division line L, on the strip image is displayed in a different line (e.g. curve L _A) from the scratch. Therefore, it is possible to distinguish between the scratch S and the dividing line L. Then, by determining the presence or absence of scratches based on the strip-shaped image from which the dividing line L has been removed, scratches can be appropriately detected.

In the present embodiment, the holding table 20 is rotated once to image the surface to be ground of the wafer W, but the configuration is not limited to this. For example, the imaging means 41 may be rotated around the center of the wafer W.

Further, in the present embodiment, the imaging means 41 is configured to extend with a length corresponding to a part of the radius of the wafer W, but the present invention is not limited to this configuration. The imaging means 41 (line sensor 43 and light 44) may have a length corresponding to a radial 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.

Further, in the present embodiment, each of the above steps may be carried out by an independent processing device, or all the steps may be carried out by a single processing device. For example, it is possible to carry out the process from the grinding process to the determination process with a single grinding device. As a result, it is possible to save the trouble of transporting the wafer W to another device for scratch detection and scratch removal.

Further, in the present embodiment, the appearance of the grinding marks in the captured image may be adjusted by adjusting the brightness of the light 44 during the imaging process. For example, the brightness of the light 44 is preferably adjusted to a brightness at which grinding marks are not imaged (not displayed in the captured image). Innumerable grinding marks are formed between the arcuate scratch S having regularity and the adjacent scratch S, but if all of them are imaged, not only the amount of data in the captured image becomes large, but also the amount of data in the captured image becomes large. It may be difficult to determine the presence or absence of scratches.

Therefore, by adjusting the brightness of the light 44 and thinning out the number of grinding marks displayed in the captured image, it is possible to reduce the amount of data in the captured image and make it easier to determine the presence or absence of scratches. .. Specifically, since the amount of scattered light is reduced by making the light 44 relatively dark (reducing the amount of light), it is possible to thin out the number of grinding marks or not to display the grinding marks in the captured image. On the other hand, when the light 44 is made relatively bright (increasing the amount of light), the amount of scattered light becomes large, so that grinding marks are likely to appear in the captured image.

Further, by adjusting the brightness of the light 44 during the imaging process, not only the appearance of the grinding marks in the captured image may be adjusted, but also the distance between the imaging means 41 and the wafer W may be adjusted.

Moreover, although the present embodiment and the modified example have been described, as another embodiment of the present invention, the above-described embodiment and the modified example may be combined in whole or in part.

Further, the embodiment of the present invention is not limited to the above-described embodiment, and may be variously modified, replaced, or modified without departing from the spirit of the technical idea of the present invention. Furthermore, if the technical idea of the present invention can be realized in another way by the advancement of the technology or another technology derived from the technology, the method may be used. Therefore, the scope of claims covers 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 scratches can be appropriately detected by distinguishing between a dividing line and scratches, and is particularly useful for a scratch detection method applied to a DBG process.

20 Holding table 21a Holding surface 23 Table rotating means 30 Grinding means 31 Spindle 32 Grinding wheel 33 Mount 34 Grinding whetstone 40 Scratch detecting means 41 Imaging means 42 Judging means 43 Line sensor 44 Light 45 Editing part 46 Judging part W Wafer V Dividing groove ( Dividing line)
L division line L _A curve S scratch S _{A, S B} line (scratch)
D width

Claims (2)

A dividing groove having a depth that does not completely cut along the planned division line is formed on the front surface of the wafer, which is partitioned by the planned division line and the device is formed. This is a scratch detection method for detecting the presence or absence of scratches by imaging the surface to be ground on the back surface of the wafer ground with the grinding wheel with an imaging means in the division of the wafer to be exposed to the surface and divide the wafer.
The imaging means includes a line sensor extending in the radial direction of the wafer to image the surface to be ground, and a light extending parallel to the line sensor to illuminate the surface to be ground.
The imaging means is positioned in the extending direction parallel to the radial direction within the radius of the wafer, the holding table for holding the wafer is rotated around the center of the wafer, and the imaging means images the surface to be ground in a ring shape. Then, an imaging step of acquiring an image captured by scattered light in which the light of the light is scattered by the dividing groove and the scratch,
A removal step of removing grid-like straight lines corresponding to the dividing grooves from the captured image captured in the imaging step, and
A scratch detection method including a determination step of determining that a scratch has occurred when an arc or a straight line having a predetermined width or more is present in the image after the removal step. The scratch detection method according to claim 1, wherein the brightness of the light is adjusted so that the imaging means does not image the grinding marks formed on the wafer by the grinding wheel.

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