JP2019169608A - Grinding device - Google Patents

Abstract

When a cross line is found on a wafer after grinding, an operator can immediately grasp the adhering substance adhering position corresponding to the position where the cross line on the table holding surface is formed on the wafer, and remove the adhering substance. Prevents generation of cross cracks in wafer grinding. The apparatus includes a table having a holding surface, a means for rotating the table, a means for grinding a held wafer, and a means for notifying an operator of information. Means 40 for illuminating the ground surface Wb of the wafer W with the illumination 400 and imaging the ground surface Wb, means 91 for detecting a cross line in the captured image, and X-axis and Y-axis coordinates of the intersection of the detected cross line Means 90 for storing the position, a spotlight 41 for illuminating the holding surface 300a at the stored X-axis and Y-axis coordinate positions, and control for notifying the notifying means 17 of the detection of the cross line and stopping the grinding operation of the apparatus. A grinding device 1 comprising means 9. [Selection] Figure 2

Description

  The present invention relates to a grinding apparatus for grinding a workpiece such as a semiconductor wafer.

A grinding apparatus for grinding a wafer grinds a wafer held by a holding surface made of a porous material of a holding table with a grinding surface of a rotating grinding wheel positioned parallel to the holding surface.
When a wafer held on the holding surface is sandwiched between the holding surface of the holding table and the lower surface of the wafer with an adhering substance such as grinding dust or abrasive grains, the wafer to be ground directly above the adhering substance is ground. A cross-shaped crack is formed on the surface. And in order not to form a cross crack in a wafer, the holding surface before sucking and holding the wafer is cleaned by a cleaning device as described in Patent Document 1 or 2.

Japanese Patent No. 4079289 Japanese Patent No. 5538971

  However, if deposits remain on the holding surface after cleaning using the cleaning device, a cross crack is formed. Therefore, before the wafer is sucked and held by the holding surface of the holding table, it is necessary to check the presence or absence of deposits on the holding surface. Therefore, although the holding surface is imaged by an imaging camera, there is a problem that it is difficult for the operator to determine whether the pattern is a porous ceramic pattern or a deposit from the formed captured image.

  Therefore, in the grinding apparatus, when a cross-crack is found in the ground wafer, the position of the holding surface of the holding table corresponding to the position where the cross-crack is formed on the wafer (the adhering matter is attached to the holding surface). There is a problem that the operator can immediately grasp the position) and remove the deposits to prevent the occurrence of cross cracks in the wafer during subsequent wafer grinding.

  In order to solve the above problems, the present invention provides a holding table provided with a porous plate having a holding surface for holding a wafer, holding table rotating means for rotating the center of the holding table as an axis, and holding by the holding surface. A grinding apparatus comprising a grinding means for grinding a wafer with a grinding wheel and a notifying means for notifying an operator of various types of information, wherein the surface to be ground of the wafer held by the holding surface and ground by the grinding wheel is illuminated. An imaging means for illuminating and imaging the surface to be ground, a detecting means for detecting a cross line in an image captured by the imaging means, and an X-axis and Y-axis coordinate position of the intersection of the cross lines detected by the detecting means are stored. A storage unit, a spotlight that illuminates the holding surface at the X-axis and Y-axis coordinate positions stored in the storage unit, and a notification unit that notifies the operator that the detection unit has detected a cross line. And a control means for stopping the grinding operation of the apparatus with a grinding apparatus.

  A grinding apparatus according to the present invention includes a holding table provided with a porous plate having a holding surface for holding a wafer, holding table rotating means for rotating about the center of the holding table, and a wafer held on the holding surface by a grinding wheel. An imaging means comprising a grinding means for grinding and a notifying means for notifying an operator of various kinds of information, illuminating a surface to be ground of a wafer held by a holding surface and ground by a grinding wheel with illumination, and imaging Detecting means for detecting a cross line in the image captured by the means, storage means for storing the X-axis and Y-axis coordinate position of the intersection of the cross lines detected by the detecting means, and X-axis and Y-axis coordinates stored by the storing means A spotlight that illuminates the holding surface at a position, and a control means that causes the notification means to notify the operator that the detection means has detected a cross line and to stop the grinding operation of the apparatus. Therefore, if a cross crack occurs in the ground wafer, the holding surface directly under the cross crack can be illuminated with a spotlight. After the wafer is removed from the holding surface, the operator removes grinding debris and abrasives on the holding surface. It becomes possible to immediately grasp the position where the particles are attached. Then, when the operator removes the adhering matter at the spot on the illuminated holding surface, the adhering matter causing the cross crack can be immediately removed from the holding surface.

It is a perspective view which shows an example of a grinding device. It is sectional drawing which shows an example of a holding table, a washing | cleaning means, and an imaging means. It is sectional drawing which shows the state currently imaged with the imaging means, illuminating the to-be-ground surface of the wafer hold | maintained with the holding surface and ground with the grinding wheel with illumination. It is a top view which shows the state currently imaged with the imaging means, illuminating the to-be-ground surface of the wafer hold | maintained with the holding surface, and was ground with the grinding wheel. It is explanatory drawing explaining the case where a detection means detects the cross line in the image which the imaging means imaged.

A grinding apparatus 1 shown in FIG. 1 is an apparatus that performs grinding on a wafer W sucked and held by a holding table 30.
The wafer W shown in FIG. 1 is, for example, a circular plate-shaped semiconductor wafer made of a silicon base material, and a plurality of devices are formed on the surface Wa of the wafer W facing downward in FIG. T is attached and protected. The back surface Wb of the wafer W facing upward is a surface to be ground on which grinding is performed.
On the outer peripheral edge of the wafer W, a notch N, which is a mark indicating the crystal orientation, is formed in a state of being recessed radially inward toward the center of the wafer W.

  On the front side (−X direction side) of the base 10 of the grinding apparatus 1, an input means 19 for an operator to input processing conditions and the like to the grinding apparatus 1 is disposed. Further, on the front side on the base 10, a first cassette 331 that accommodates a wafer W before grinding and a second cassette 332 that accommodates a ground wafer W are disposed. Between the first cassette 331 and the second cassette 332, an articulated arm that carries the wafer W before grinding from the first cassette 331 and carries the ground wafer W into the second cassette 332 A robot 330 is provided.

  In the movable range of the robot 330, a temporary placement table 333a for temporarily placing the unprocessed wafer W is provided, and the temporary placement table 333a is provided with positioning means 333b. The alignment means 333b aligns (centers) the wafer W, which is unloaded from the first cassette 331 and placed on the temporary placement table 333a, at a predetermined position with an alignment pin that reduces the diameter.

  A detection unit 333c for detecting the notch N of the wafer W is disposed on the side of the temporary placement table 333a. The detection unit 333c is constituted by, for example, a light reflection type or transmission type optical sensor, and the outer periphery of the wafer W is detected by the detection unit 333c as the temporary placement table 333a holding the centered wafer W rotates. By passing (below), the notch N formed on the outer peripheral edge of the wafer W can be detected. The detection unit 333c may be configured by a camera or the like, and the notch N on the outer peripheral edge of the wafer W may be detected by the detection unit 333c performing image processing on a captured image captured by the camera.

  A cleaning means 334 for cleaning the ground wafer W is disposed in the movable range of the robot 330. The cleaning means 334 is, for example, a single wafer type spinner cleaning apparatus.

  A first transport unit 335 is disposed in the vicinity of the alignment unit 333b, and a second transport unit 336 is disposed in the vicinity of the cleaning unit 334. The first transfer means 335 transfers the unground wafer W placed on the temporary placement table 333a and centered to one of the holding tables 30 shown in FIG. 1, and the second transfer means 336 The ground wafer W held on the holding table 30 is transferred to the cleaning means 334.

  A turntable 34 is disposed on the rear side of the first conveying means 335 on the base 10. For example, four holding tables 30 (only two are shown) are arranged on the upper surface of the turntable 34 in the circumferential direction. They are arranged at equal intervals. The turntable 34 can rotate about the axis in the Z-axis direction on the base 10. One of the holding tables 30 is positioned in the vicinity of the first transport unit 335 and the second transport unit 336 by the rotation of the turntable 34.

  As shown in FIG. 2, the holding table 30 has, for example, a circular outer shape, and includes a porous plate 300 that sucks the wafer W and a frame body 301 that supports the porous plate 300. The porous plate 300 communicates with a suction source 39 such as a vacuum generator, and the suction force generated by the suction of the suction source 39 is transmitted to the holding surface 300a that is the exposed surface of the porous plate 300, thereby holding the porous plate 300. The table 30 sucks and holds the wafer W on the holding surface 300a. The holding surface 300a is formed in a conical surface having a very gentle inclination with the rotation center as a vertex.

A holding table rotating means 37 is connected to the lower surface side of the holding table 30, and the holding table 30 can be rotated around the axis in the Z-axis direction by the holding table rotating means 37 on the turntable 34 shown in FIG. It has become.
Further, an inclination adjusting mechanism 38 is disposed below the holding table 30 via a coupling or the like. The tilt adjusting mechanism 38 can adjust the tilt of the holding surface 300a of the holding table 30 with respect to the horizontal plane.

For example, the holding table rotating means 37 rotates the holding table 30 about the spindle 370 whose axial direction is the Z-axis direction and whose upper end is connected to the lower surface of the frame 301 of the holding table 30 and the center of the holding table 30 as an axis. It is a pulley mechanism provided with a motor 371 as a driving source to be driven. A main driving pulley 372 is attached to the shaft of the motor 371, and an endless belt 373 is wound around the main driving pulley 372. A driven pulley 374 is attached to the spindle 370, and the endless belt 373 is also wound around the driven pulley 374. When the motor 371 rotates the main driving pulley 372, the endless belt 373 rotates with the rotation of the main driving pulley 372, and when the endless belt 373 rotates, the driven pulley 374 and the spindle 370 rotate.
For example, a rotary encoder 379 that detects the rotation angle of the motor 371, that is, the rotation angle of the holding table 30 is connected to the motor 371.

  As shown in FIG. 1, a column 11 is erected on the rear side (+ X direction side) on the base 10, and a wafer W in which rough grinding means 31 is held by a holding table 30 on the front surface of the column 11. The coarse grinding feed means 35 for grinding and feeding to the wafer W and the finish grinding feed means 36 for grinding and feeding the finish grinding means 32 to the wafer W held by the holding table 30 are arranged side by side.

  The rough grinding feed means 35 includes a ball screw (not shown) having a vertical (Z-axis direction) axis, a pair of guide rails 351 arranged in parallel to the ball screw, and a motor 352 connected to the ball screw and rotating the ball screw. And an elevating part 353 whose inner side is screwed to the ball screw and whose side part is in sliding contact with the guide rail 351, and the elevating part 353 that supports the rough grinding means 31 as the motor 352 rotates the ball screw. It is guided by the guide rail 351 and moves up and down.

  The finish grinding feed means 36 includes a ball screw (not shown) having a vertical axis, a pair of guide rails 361 arranged parallel to the ball screw, a motor 362 connected to the ball screw and rotating the ball screw, and an internal nut. And an elevating part 363 whose side part is in sliding contact with the guide rail 361. The elevating part 363 that supports the finish grinding means 32 as the motor 362 rotates the ball screw guides the guide rail 361. Lifted up and down.

  The rough grinding means 31 is attached to a rotary shaft 310 whose axial direction is a vertical direction, a housing 311 that rotatably supports the rotary shaft 310, a motor 312 that rotationally drives the rotary shaft 310, and a lower end of the rotary shaft 310. And a grinding wheel 314 detachably connected to the mount 313. On the bottom surface of the grinding wheel 314, a plurality of rough grinding wheels 314a having a substantially rectangular parallelepiped shape are annularly arranged. The rough grinding wheel 314a is formed by fixing diamond abrasive grains or the like with a predetermined bonding agent. The rough grinding wheel 314a is, for example, a grindstone having relatively large abrasive grains contained in the grindstone.

  For example, a flow path (not shown) that communicates with a grinding water supply source and serves as a path for grinding water is formed inside the rotary shaft 310 so as to penetrate in the axial direction of the rotary shaft 310, and the flow path is formed by the grinding wheel 314. Is opened so that the grinding water can be ejected toward the rough grinding wheel 314a.

  The finish grinding means 32 can perform finish grinding that improves flatness on the wafer W thinned by rough grinding. That is, the finish grinding means 32 further grinds the back surface Wb of the wafer W ground by the rough grinding means 31 with a grinding wheel 314 provided with a finish grinding wheel 324a and rotatably mounted. The abrasive grains contained in the finish grinding wheel 324a are abrasive grains having a smaller particle diameter than the abrasive grains contained in the coarse grinding wheel 314a. The configuration of the finish grinding means 32 other than the finish grinding wheel 324 a is the same as that of the rough grinding means 31.

  Cleaning means 8 for cleaning the holding surface 300a of the holding table 30 is disposed above the movement path of the holding table 30. As shown in FIG. 2, the cleaning means 8 includes a rotary shaft 80 having a vertical axis, a housing 81 that rotatably supports the rotary shaft 80, and a cleaning grindstone disposed at the lower end of the rotary shaft 80. 82 and lifting / lowering means 83 that lifts and lowers the housing 81. The cleaning means 8 can be reciprocated in the Y-axis direction by the Y-axis moving means 89 shown in FIG.

  The Y-axis moving means 89 shown in FIG. 1 includes, for example, a ball screw 890 having an axis in the Y-axis direction, a bridge portion 891 that supports the ball screw 890, and an internal nut screwed into the ball screw 890. A movable portion 892 that reciprocates in the axial direction and a motor (not shown) that is connected to one end of the ball screw 890 and rotates the ball screw 890 are provided. Cleaning means 8 is disposed on the front surface of the movable portion 892.

The cleaning grindstone 82 is formed, for example, from a resin bond grindstone, a resin material or a ceramic material in a circular plate shape, and scrapes off contaminants such as grinding scraps adhering to the holding surface 300 a of the holding table 30. The cleaning means 8 may include a cleaning brush instead of the cleaning grindstone 82.
The elevating means 83 includes a rail 830 on which the housing 81 slides and a motor or the like provided inside the housing 81, for example, and can elevate the housing 81.

  The grinding apparatus 1 illuminates the surface to be ground Wb of the wafer W held by the holding surface 300a of the holding table 30 and ground by the finish grinding wheel 324a with illumination 400 (see FIG. 2), and images the ground surface Wb. And a spotlight 41 that illuminates the holding surface 300 a of the holding table 30.

  The imaging unit 40 is, for example, a line sensor camera, and is disposed on the side surface of the housing 81 of the cleaning unit 8, and can move together with the cleaning unit 8 in the Y-axis direction and the Z-axis direction. As illustrated in FIG. 2, the imaging unit 40 includes, for example, a rectangular parallelepiped housing 401 that shields external light, and an illumination 400 that illuminates the wafer W from above the wafer W is provided on a side surface of the housing 401. It is attached. The illumination 400 is, for example, an LED or a xenon lamp, and light generated by the illumination 400 is propagated into the housing 401 by a transmission optical system such as an optical fiber (not shown). The amount of light emitted by the illumination 400 can be adjusted by an adjuster (not shown).

  The imaging means 40 is disposed in the housing 401 and reflects the light emitted from the illumination 400 downward to change the direction, and the half mirror 402 in the housing 401 is disposed below the half mirror 402. An objective lens (not shown) that receives light reflected by the mirror 402 and an imaging unit 403 that is arranged above the half mirror 402 and that is reflected by the wafer W and captured by the objective lens is photoelectrically converted and output as image information. And.

  The imaging unit 403 includes, for example, a plurality of light receiving elements such as CCDs arranged in a horizontal row in the X-axis direction. The imaging unit 403 has an imaging region whose length in the longitudinal direction (X-axis direction) is substantially the same as the radius of the holding surface 300a of the holding table 30 and has a length equal to or greater than the radius of the wafer W. . The data transmitted by each pixel of the light receiving element according to the intensity of reflected light is expressed by, for example, 256 kinds of brightness values of 8-bit gradation, that is, 0 to 255.

  The spotlight 41 is, for example, an LED light or the like that can illuminate the holding surface 300a of the holding table 30 from above, and is near the imaging means 40, that is, the housing 81 of the cleaning means 8 in this embodiment. It is attached to the side. In addition, the incident angle of the spot light by the spotlight 41 can be adjusted by, for example, an adjusting unit (not shown), and the spot light diameter can be reduced to a desired value. Further, the location of the spotlight 41 is not limited to the example shown in FIGS.

  As shown in FIGS. 1 and 2, the grinding apparatus 1 includes a control unit 9 that is configured by a storage unit 90 such as a CPU and a memory and controls the entire apparatus. The control means 9 is electrically connected to the finish grinding feed means 36, the Y-axis moving means 89, the holding table rotating means 37 and the like by wiring not shown, and the finish grinding feed is controlled under the control of the control means 9. The movement operation of the finish grinding means 32 in the Z-axis direction by the means 36, the positioning action of the imaging means 40 in the Y-axis direction by the Y-axis movement means 89, and the rotation operation of the holding table 30 by the holding table rotating means 37 are controlled. The

  The grinding apparatus 1 includes a notification unit 17 that notifies the operator of various information. The notification means 17 displays notification information on a monitor (not shown) or issues an alarm.

The operation of the grinding apparatus 1 when the wafer W is ground by the grinding apparatus 1 shown in FIG. 1 will be described below.
First, as the turntable 34 shown in FIG. 1 rotates, the holding table 30 on which the wafer W is not placed revolves, and the holding table 30 moves to the vicinity of the first transfer means 335. The robot 330 pulls out one wafer W from the first cassette 331 and moves the wafer W to the temporary placement table 333a.

  After the wafer W is centered on the temporary placement table 333a by the alignment means 333b, the notch N formed on the outer peripheral edge of the wafer W is detected by the detection unit 333c. Then, the wafer W is rotated by the temporary placement table 333a, and the notch N is positioned at a predetermined position in the circumferential direction. Next, the first transfer means 335 moves the wafer W, which is centered and the notch N is positioned at a predetermined position in the circumferential direction, onto the holding table 30 so as not to shift the grasped circumferential position of the notch N.

  For example, the holding table 30 may be formed with a notch alignment portion (alignment mark) (not shown) for aligning with the notch N when the wafer W is placed. In the holding table 30, the notch N of the wafer W and the notch alignment portion of the holding table 30 are aligned. That is, the position of the notch N when the first transfer means 335 holds the wafer W is determined when holding and unloading the wafer W from the temporary placement table 333a, so that the holding table 30 is rotated by a predetermined angle, Positioning is performed such that the position of the notch N of the wafer W held by the temporary placement table 333a coincides with the notch alignment portion of the holding table 30. Then, the wafer W is placed on the holding surface 300a with the back surface Wb facing up so that the center of the holding table 30 and the center of the wafer W substantially coincide.

Then, the suction force generated by the operation of the suction source 39 (see FIG. 2) is transmitted to the holding surface 300a of the porous plate 300, whereby the holding table 30 sucks and holds the wafer W on the holding surface 300a. . Further, the position of the notch N of the wafer W that is sucked and held is grasped by the control means 9.
The position of the notch N of the wafer W sucked and held on the holding table 30 is always grasped at least until the wafer W is unloaded from the holding table 30 by the second transfer means 336 described later. . That is, the rotary encoder 379 of the holding table rotating means 37 shown in FIG. 2 outputs an encoder signal (the number of rotations of the motor 371) to the control means 9 when the holding table 30 is rotated by the holding table rotating means 37. To do. The control means 9 can feedback-control the rotation speed of the holding table 30 by the holding table rotating means 37 based on the received encoder signal, and can sequentially grasp the position of the notch N of the rotating wafer W.

  Note that the position of the notch N of the wafer W on the holding table 30 may be grasped together with the edge alignment when the edge alignment of the wafer W using the imaging unit 40 is performed. In edge alignment, the holding table 30 rotates, and the outer peripheral edge of the wafer W held on the holding table 30 is imaged at a plurality of locations by the imaging means 40. Then, for example, the coordinates of three points separated from the outer peripheral edge are detected, and the accurate center coordinates of the wafer W on the holding table 30 are obtained by geometric calculation processing based on the coordinates of the three points. Further, the coordinate position of the notch N is grasped from the formed captured image.

  After the holding table 30 sucks and holds the wafer W, the turntable 34 shown in FIG. 1 rotates in the clockwise direction when viewed from the + Z direction. Then, the holding table 30 holding the wafer W revolves, the rotation center of the rough grinding wheel 314a of the rough grinding means 31 is shifted in the horizontal direction by a predetermined distance from the rotation center of the wafer W, and the rotation locus of the rough grinding wheel 314a. The wafer W is positioned so that passes through the center of rotation of the wafer W. Further, the inclination of the holding table 30 is adjusted by the inclination adjusting mechanism 38 (see FIG. 2) so that the holding surface 300a which is a gentle conical surface is parallel to the grinding surface (lower surface) of the rough grinding wheel 314a. The back surface Wb of the wafer W sucked and held following the holding surface 300a is parallel to the grinding surface of the rough grinding wheel 314a.

  The rough grinding means 31 is sent in the −Z direction by the rough grinding feed means 35, and the rotating rough grinding wheel 314 a comes into contact with the back surface Wb of the wafer W held by the holding table 30, so that rough grinding is performed. Further, as the holding table rotating means 37 rotates the holding table 30 at a predetermined rotation speed, the wafer W on the holding surface 300a also rotates, so that the rough grinding wheel 314a performs rough grinding on the entire back surface Wb of the wafer W. Do. During grinding, the grinding water is supplied to the contact portion between the rough grinding wheel 314a and the back surface Wb of the wafer W, and the contact portion is cooled and cleaned.

After the wafer W is roughly ground before the finish thickness, the coarse grinding feed means 35 raises the coarse grinding means 31 and separates it from the wafer W.
Next, the turntable 34 rotates in the clockwise direction when viewed from the + Z direction, and the holding table 30 that sucks and holds the wafer W moves to below the finish grinding means 32. After the positioning of the finish grinding wheel 324a and the wafer W is performed, the finish grinding means 32 is sent downward by the finish grinding feed means 36, and the rotating finish grinding wheel 324a contacts the back surface Wb of the wafer W, Further, as the holding table 30 rotates, the entire back surface Wb of the wafer W is finish-ground.

After the finish grinding means 32 is separated from the wafer W ground to the finished thickness and the flatness of the back surface Wb is increased, the turntable 34 rotates in the clockwise direction when viewed from the + Z direction, so that the wafer W becomes the second one. It moves to the vicinity of the conveying means 336. Then, the second transfer unit 336 transfers the wafer W on the holding table 30 to the cleaning unit 334.
After the wafer W is cleaned in the cleaning unit 334, the robot 330 unloads the wafer W from the cleaning unit 334 and loads the wafer W into the second cassette 332. In the grinding apparatus 1, such a series of grinding operations are repeatedly performed, and a plurality of wafers W are ground.

  When the wafer W is ground as described above, grinding scraps and deagglomerated abrasive grains enter between the holding surface 300a of the holding table 30 shown in FIG. 1 and the protective tape T attached to the wafer W, and the grinding is performed. Waste and abrasive grains may adhere to the holding surface 300a. When the wafer W is ground in this state, a cross-shaped crack (cross line) is generated in the wafer W. Further, when the next wafer W is sucked and held on the holding surface 300a while the deposit remains on the holding surface 300a and the back surface Wb of the next wafer W is ground, the next wafer W is cross-shaped. Shape cracks occur.

  Therefore, the cleaning unit 8 is moved in the Y-axis direction by the Y-axis moving unit 89, and the cleaning grindstone 82 is positioned above the holding surface 300a of the holding table 30 from which the wafer W is unloaded. Then, the holding table rotating unit 37 rotates the holding table 30, and the cleaning grindstone 82 rotated by the lifting / lowering unit 83 is lowered to press the cleaning grindstone 82 against the holding surface 300a. If it does so, the grinding | polishing waste etc. which protruded upwards from the holding surface 300a will be scraped off, and the holding surface 300a will be wash | cleaned.

For example, after performing cleaning by the cleaning unit 8 in the case where a plurality of wafers W are ground continuously while holding the holding surface 300a cleaning of the holding table 30 using the cleaning unit 8 at an appropriate timing, etc. In this case, a cross line is formed on the back surface Wb of the wafer W held by the holding surface 300a by grinding.
Therefore, it is necessary to prevent a plurality of wafers W from being ground in a state where a cross line is formed on the wafer W, and the grinding apparatus 1 according to the present invention performs an operation as described below.

  For example, a predetermined plurality of wafers W are ground to a finish thickness by finish grinding, and after the finish grinding means 32 shown in FIG. 1 is separated from the wafer W, the turntable 34 rotates in the clockwise direction when viewed from the + Z direction. Further, the wafer W and the imaging means are arranged so that the Y-axis moving means 89 moves the imaging means 40 in the Y-axis direction so that the imaging means 40 can take an image of the back surface Wb of the wafer W sucked and held by the holding table 30. 40 is aligned. That is, as shown in FIGS. 3 and 4, the imaging unit 403 is aligned so as to straddle a line from above the center Wc of the wafer W to above the outer peripheral edge. 3 and 4, the configuration other than the imaging unit 403 of the imaging unit 40 is omitted.

Next, the holding table rotating unit 37 rotates the holding table 30 by a predetermined angle under the control of the control unit 9, for example, as shown in FIG. 4, an imaginary line L 1 passing through the center Wc and the notch N of the wafer W. Are parallel to the X-axis direction, and the notch N is positioned at a position on the + X direction side (0 degree position which is an imaging start position).
Further, the imaging means 40 is operated, and an objective lens (not shown) is focused by the vertical movement of the imaging means 40 by the elevating means 83 shown in FIG. When the objective lens is focused on the back surface Wb of the wafer W, the elevating means 83 stops the vertical movement of the imaging means 40.

  In this state, as shown in FIGS. 3 and 4, the holding table rotating means 37 rotates the holding table 30, for example, counterclockwise when viewed from the + Z direction side at a predetermined rotational speed. Further, the illumination 400 (see FIG. 2) of the imaging means 40 irradiates the back surface Wb of the wafer W through the half mirror 402, and the reflected light from the back surface Wb of the wafer W is captured by an objective lens (not shown). It is incident on the light receiving element 403. Then, the back surface Wb of the wafer W that rotates relative to the imaging means 40 is continuously imaged line by line from the center Wc of the wafer W to the outer periphery thereof by the imaging means 40.

The imaging unit 403 sequentially transmits captured images in units of lines to the control unit 9 illustrated in FIGS. The line-by-line captured images are sequentially stored in the storage unit 90 of the control unit 9 so that a captured image in which the entire back surface Wb of the wafer W is captured can be configured. In addition, the control means 9 uses the encoder signal received from the rotary encoder 379 (see FIG. 2) of the holding table rotating means 37 for rotating the holding table 30, and the captured image showing one line for the back surface Wb of the wafer W, The rotation angle of the holding table 30 from the imaging start position (0-degree position) when the captured image indicating one line is captured is linked and stored in the storage unit 90 in order.
Then, when the holding table rotating means 37 rotates the holding table 30 360 degrees and the imaging means 40 passes over the upper surface of the back surface Wb of the wafer W (the notch N returns to the imaging start position), the entire back surface Wb of the wafer W is A captured image is formed, and the rotation of the holding table 30 is stopped.

The amount of reflected light (the amount of received light) incident on each light receiving element of the imaging unit 403 differs when there is a cross line on the back surface Wb of the wafer W. That is, in each light receiving element of the image pickup unit 403, a portion where the cross line on the back surface Wb of the wafer W is present increases in the amount of received light, the brightness value approaches 255 and approaches white, and there is no cross line on the back surface Wb of the wafer W. In the region, the amount of received light decreases, and the luminance value approaches 0 and approaches black. Accordingly, in the captured image G showing the entire back surface Wb of the wafer W displayed on the virtual output screen having a predetermined resolution shown in FIG. 5, the cross line C on the back surface Wb of the wafer W is shown in white, for example. The back surface Wb of the surrounding wafer W is shown in gray.
Note that binarization processing may be performed on the captured image G so that the cross line C and its surroundings can be more clearly distinguished.

  As shown in FIGS. 1 and 2, the grinding apparatus 1 includes a detection unit 91 that detects a cross line C in a captured image G captured by the imaging unit 40. The detection unit 91 is, for example, a control unit 9. Built in. The detection means 91 counts the sum in the Y-axis direction of white pixels and the sum in the X-axis direction of white pixels in the back surface Wb (in the gray region) of the wafer W shown in the captured image G shown in FIG. The line C is detected and the size of the cross line C is calculated. Also, the pixel at the intersection of the cross line C is specified.

Next, the X-axis and Y-axis coordinate positions of the detected intersection pixel of the cross line C are determined by the detection unit 91. A coordinate position of the center Wc of the wafer W that substantially matches the rotation center of the holding table 30 is defined as, for example, an origin coordinate (0, 0), and a pixel indicating an intersection of the identified cross line C with the origin coordinate (0, 0) An imaginary line L2 is drawn. The angle θ1 between the imaginary line L1 and the imaginary line L2 is the same as the angle at which the holding table 30 is rotated from the imaging start position when the captured image of the line unit including the cross line C is captured. 90 is a known value stored in 90.
Further, the length of the virtual line L2 is calculated by the pixel count from the origin coordinates (0, 0) to the pixel at the intersection of the cross line C (for example, the calculated value is r). Then, the X-axis and Y-axis coordinate position (x, y) of the detected pixel at the intersection of the cross line C is determined to be (r cos θ1, −r sin θ1). The X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) of the intersection of the cross line C is stored in the storage unit 90.

  Note that the determination of the X-axis and Y-axis coordinate position (x, y) of the pixel at the intersection of the detected cross line C is not limited to the above example. For example, a virtual line L3 (not shown in FIG. 5) orthogonal to the virtual line L1 is drawn from the pixel at the intersection of the cross line C, and the X-axis coordinate of the intersection of the virtual line L1 and the virtual line L3 is the origin coordinate. It is determined by the pixel count from (0, 0) to the intersection of the virtual line L1 and the virtual line L3. The pixel count from the intersection of the virtual line L1 and the virtual line L3 to the intersection of the cross line C is further performed to determine the intersection Y-axis coordinate position of the cross line C, and the X axis of the pixel at the intersection of the cross line C The Y-axis coordinate position (x, y) may be finally determined.

  When the X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) of the intersection of the cross line C is stored in the storage unit 90, the stored X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) of the back surface Wb of the wafer W is stored. Are illuminated by a spotlight 41 shown in FIGS. That is, under the control of the control means 9, the movement of the spotlight 41 in the Y-axis direction by the Y-axis movement means 89, the movement of the spotlight 41 in the Z-axis direction by the elevating means 83, and / or the spot by the adjustment means (not shown). By adjusting the incident angle of the spot light irradiated by the light 41, the spot light 41 has the predetermined spot diameter and the stored X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) of the back surface Wb of the wafer W. Illuminate. In addition, the spot diameter of the spotlight of the spotlight 41 is, for example, a diameter that is large in the length and width of the cross line C.

As described above, when the detection unit 91 detects the cross line C, a control signal is transmitted from the control unit 9 to the notification unit 17, and the notification unit 17 notifies the operator that the cross line C has been detected on the wafer W. To do. In addition, under the control of the control unit 9, a grinding operation, that is, the transfer of the wafer W to the holding table 30 other than the holding table 30 holding the wafer W on which the cross line C is formed by the first transfer unit 335, Rough grinding (finish grinding) on the wafer W held by another holding table 30, transfer of the wafer W on which the cross line C is formed from the holding table 30 to the cleaning means 334 by the second transfer means 336, and The rotation of the turntable 34 is stopped. As a result, the grinding apparatus 1 is in a state in which the operator can remove the wafer W on which the cross line C is formed from the holding table 30 and then remove the deposit on the holding surface 300a of the holding table 30.
If the cross line C is not detected on the wafer W, the wafer W is moved to the vicinity of the second transfer means 336 by the rotation of the turntable 34 as described above, and the second transfer is performed. The means 336 transports the wafer W on the holding table 30 to the cleaning means 334.

  After the grinding operation of the grinding apparatus 1 is stopped as described above, the wafer W in which the cross line C is detected is regarded as a wafer that is not suitable for a product wafer by the operator after the suction holding of the wafer W by the holding table 30 is released. It is unloaded from the holding table 30. Therefore, the spotlight 41 (see FIG. 2) illuminating the stored X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) of the back surface Wb of the wafer W with a predetermined spot diameter has a cross line C on the wafer W. The holding surface 300a immediately below the formed X-axis Y-axis coordinate position (r cos θ1, −rsin θ1) is illuminated with spot light. That is, the deposit on the holding surface 300 a that causes the cross line C to be formed on the wafer W is in a state of being pinpointed by the spotlight 41.

  The operator can immediately grasp the position on the holding surface 300a where deposits such as grinding scraps and abrasive grains are attached by the spotlight of the spotlight 41. Therefore, the operator can immediately remove the deposits causing the cross line C from the holding surface 300a using, for example, a deposit removal tool (for example, a scraper or a cleaning brush).

  After the operator removes the deposits on the holding surface 300a as described above, the grinding device 1 is set by the operator so that the grinding operation of the grinding device 1 can be started again. Then, the wafer W is held on the holding table 30 that has become the holding surface 300a in a state where the cross line C is not formed, and the grinding is performed.

The grinding device 1 according to the present invention is not limited to the above embodiment, and the configuration of each device illustrated in the accompanying drawings is not limited to this, and the effects of the present invention are exhibited. It can be changed as appropriate within a possible range.
For example, in the spotlight 41, after the operator unloads the wafer W from which the cross line C is detected from the holding table 30, the X-axis Y-axis coordinate position (r cos θ1) of the intersection of the cross line C stored in the storage unit 90 is stored. , -Rsin θ1) may begin to illuminate.

1: Grinding device 10: Base 11: Column 17: Notification means 30: Holding table 300: Porous plate 300a: Holding surface 301: Frame body 31: Coarse grinding means 310: Rotating shaft 311: Housing 312: Motor 314: Grinding wheel 314a : Coarse grinding wheel 32: finish grinding means 324a: finish grinding wheel 330: robot 331: first cassette 332: second cassette 333a: temporary placement table 333b: positioning means 333c: notch detection unit 334: cleaning means 335: First transport means 336: Second transport means 34: Turntable 35: Coarse grinding feed means 350: Ball screw 351: Guide rail 352: Motor 353: Lifting unit 36: Finish grinding feed means 360: Ball screw 361: Guide rail 362 : Motor 363: Lifting part
37: Holding table rotating means 370: Spindle 371: Motor 372: Main driving pulley 373: Endless belt 374: Driven pulley 379: Rotary encoder 38: Tilt adjusting mechanism 39: Suction source 8: Cleaning means 80: Rotating shaft 81: Housing 82: Cleaning grindstone 83: Lifting means 89: Y-axis moving means 40: Imaging means 400: Illumination 401: Housing 402: Half mirror 403: Imaging unit 41: Spotlight 9: Control means 90: Storage means 91: Detection means W: Wafer Wa: Wafer surface Wb: Wafer surface to be ground (back surface) T: Protective tape N: Notch C: Cross line

Claims (1)

A holding table provided with a porous plate having a holding surface for holding a wafer, a holding table rotating means for rotating around the center of the holding table, a grinding means for grinding the wafer held on the holding surface with a grinding wheel, A grinding device comprising notification means for notifying an operator of various information,
Imaging means for illuminating the surface to be ground of the wafer held by the holding surface and ground by the grinding wheel with illumination, and imaging the surface to be ground;
Detecting means for detecting a cross line in the image captured by the imaging means;
Storage means for storing the X-axis and Y-axis coordinate position of the intersection of the cross lines detected by the detection means;
A spotlight that illuminates the holding surface at an X-axis Y-axis coordinate position stored in the storage means;
And a control means for causing the notification means to notify the operator that the detection means has detected a cross line and to stop the grinding operation of the apparatus.