JP5254539B2 - Wafer grinding equipment - Google Patents

Description

  The present invention relates to a wafer grinding apparatus for grinding a wafer such as a semiconductor wafer to a predetermined thickness by back grinding, and in particular, a wafer suitable for grinding only a device forming region inside the outer peripheral portion while leaving the outer peripheral portion. The present invention relates to a grinding apparatus.

  A semiconductor chip of a device used for various electronic devices generally has a rectangular rectangular area defined by dividing lines called streets on the surface of a disk-shaped semiconductor wafer, and an electronic circuit is formed on the surface of these areas. Then, it is manufactured by a method in which the back surface is ground and thinned and divided along the street. By the way, downsizing and thinning of electronic devices in recent years are remarkable, and accordingly, a semiconductor chip is required to be thinner, which means that it is necessary to make the semiconductor wafer thinner than before.

  However, when the semiconductor wafer is thinned, the rigidity is lowered, so that there is a problem that handling in the subsequent process becomes difficult or breakage is likely to occur. Therefore, at the time of back surface grinding, only the portion corresponding to the circular device formation region on which the semiconductor chip is formed on the surface is ground and thinned to the required thickness, and at the same time, the surrounding annular peripheral region is relatively By leaving it as a thick reinforcing portion, the above-mentioned problem due to thinning is prevented from occurring. Techniques for forming the recesses on the back surface with the outer peripheral portion being thick are disclosed in, for example, Patent Documents 1 and 2.

JP 2004-281551 A JP 2005-123425 A

  As a method of forming a recess on the back surface of the wafer, a wafer is sucked and held concentrically on a rotatable chuck table such as a vacuum chuck type while the back surface is exposed. There is a method of pressing a cup-shaped grindstone wheel in which grindstones are arranged in an annular shape against a surface to be ground. In this method, the diameter of the grindstone wheel is approximately equal to the radius of the wafer, and the outer edge is left behind by facing the wafer so that the cutting edge passes through the rotation center of the wafer and the inner periphery of the outer circumference. Only the portion corresponding to the formation region is ground.

  By the way, there are various sizes of semiconductor wafers, that is, diameters, for example, 150 mm and 125 mm are used in addition to the mainstream 200 mm. When performing the above-mentioned back grinding for semiconductor wafers of different sizes, the grinding wheel is changed according to the wafer size, and the position of the grinding wheel facing the wafer is rotated as described above. It is necessary to adjust to a position that passes through the center and the inner peripheral edge of the outer peripheral portion, and this position adjustment is possible by horizontally moving either one of the grindstone wheel or the chuck table.

  If the grinding shaft for rotating the grinding wheel is one simple grinding device, it is relatively easy to provide a mechanism for horizontally moving the chuck table or the grinding shaft. However, in a multi-axis type grinding machine that has a plurality of grinding axes for rough grinding and finish grinding, and sequentially performs rough grinding and finishing grinding on wafers on a plurality of chuck tables by rotating a turntable. However, there is no provision of a mechanism that can adjust the position of the grindstone wheel facing the wafer.

  Therefore, according to the present invention, in a multi-axis wafer grinding apparatus having a plurality of grinding axes, a grinding wheel that is exchanged according to the size of the wafer can be formed with a recess in which the cutting edge passes through the rotation center of the wafer and the inner peripheral edge of the outer circumference. An object of the present invention is to provide a wafer grinding apparatus which can be adjusted to a position and can smoothly proceed with an operation of forming recesses on the back surface while supporting a plurality of wafer sizes with a single apparatus.

The present invention is a wafer grinding apparatus for grinding at least one surface of a disk-shaped wafer inside the outer peripheral portion leaving the outer peripheral portion, the wafer holding formed so as to be inclined in an umbrella shape with the rotation center as a vertex A self-rotating chuck table having a surface, a wafer attaching / detaching position for supporting the chuck table so as to rotate and attaching / detaching the wafer to / from the chuck table, a first grinding position for rough grinding the wafer, A turntable for positioning the chuck table at three positions of a second grinding position for finish-grinding the wafer, an annular grinding wheel that passes through the rotation center of the wafer held by the chuck table and the inner peripheral edge of the outer periphery, A first grinding means for roughly grinding a wafer positioned at a first grinding position, and a rotational drive source for rotating the grinding wheel. Passes through the inner circumferential edge of the rotation center and the peripheral portion of the wafer held on the chuck table, and an annular grinding wheel having parallel contact surfaces against grinded wafer by first grinding means, a whetstone wheel A rotation driving source for rotating, a second grinding means for finish-grinding the wafer positioned at the second grinding position, and a direction perpendicular to the wafer holding surface of the chuck table. A first vertical movement means for moving the first vertical movement means, a first grinding means and a chuck table relative to the wafer holding surface of the chuck table in a direction parallel to the wafer holding surface; A second vertical movement means for moving the second grinding means in a direction perpendicular to the wafer holding surface of the chuck table; a second grinding means; and the chuck table. And a second parallel direction moving means for relatively moving in a direction parallel to the wafer holding surface of Kkuteburu, the wafer each grinding wheel is held on the chuck table of the first ground unit and the second grinding means The arcuate machining points pressed in contact with each other are characterized by being the same when viewed on the chuck table.

  In the wafer grinding apparatus of the present invention, the wafer is held on the chuck table positioned at the wafer attaching / detaching position, and then the turntable is rotated to position the wafer at the first grinding position. One side is rough ground. The portion to be ground is the inside of the outer peripheral portion leaving the outer peripheral portion on one side, and a concave portion is formed on one side. Next, the turntable is rotated and the wafer is positioned at the second grinding position, and the rough ground surface is finish ground by the second grinding means. Thereafter, the wafer is returned to the wafer attaching / detaching position and carried out of the apparatus, and a new wafer to be processed next is moved to the chuck table and held, and the above grinding operation is repeated.

  In the present invention, the chuck table corresponds to at least the three positions of the turntable from the viewpoint of efficiently performing a series of steps of holding the wafer on the chuck table and then carrying out the wafer through rough grinding and finish grinding. A configuration is preferable in which a total of three are provided, one at each position, and the wafer is processed at each position.

  The first and second grinding means are configured to rotate an annular grinding wheel with a rotational drive source. These grinding means are moved in the chuck table direction by the first and second vertical movement means, respectively, so that the grinding wheel is pressed against the wafer. The wafer is ground by pressing the grindstone wheel against the wafer while rotating the wafer by the chuck table. A wheel with a diameter approximately equal to the radius of the wafer is used, and the position where the cutting edge faces the wafer so as to pass through the rotation center of the wafer and the inner peripheral edge of the outer periphery (hereinafter referred to as a recess-forming position) Is pressed against the wafer, the inside of the outer peripheral portion is ground on one side of the wafer leaving the outer peripheral portion, and a recess is formed.

  As described above, the grinding wheel for forming the recesses has a diameter approximately equal to the radius of the wafer. When grinding wafers with different diameters, it is necessary to replace the grinding wheel according to the size of the wafer, and at the same time, the cutting edge of the grinding wheel passes through the rotation center of the wafer and the inner periphery of the outer periphery. It is necessary to adjust the position of the grinding wheel relative to the wafer.

  For this purpose, in the first grinding means for rough grinding, the first parallel movement means relatively moves the first grinding means and the chuck table in a direction parallel to the wafer holding surface of the chuck table. Let In the second grinding means, the second parallel movement means moves the second grinding means and the chuck table relative to each other in a direction parallel to the wafer holding surface of the chuck table.

  Examples of the direction of the relative movement include an inter-axis direction along a line connecting the rotation center of the chuck table positioned at each grinding position and the rotation center of the turntable. In this case, when the chuck table is positioned at the first grinding position, the first parallel movement means moves the chuck table and the first grinding means between the rotation center of the chuck table and the rotation of the turntable. The distance between the two axes is varied by relative movement in the inter-axis direction along a line connecting the center, and the second parallel-direction moving means is configured so that the chuck table is positioned when the chuck table is positioned at the second grinding position. The table and the second grinding means are moved relative to each other in the inter-axis direction along the line connecting the rotation center of the chuck table and the rotation center of the turn table, so that the distance between the axes is variable.

As described above, in any of the first grinding position and the second grinding position, the direction of relative movement between the chuck table and the respective grinding means is determined based on the rotation center of the chuck table and the rotation center of the turntable. By using the inter-axis direction along the line connecting the two, there is the following advantage. That is, the arc-shaped machining point at which the grinding wheel of each grinding means is pressed against the wafer is the same at the first grinding position and the second grinding position when viewed on the chuck table. For this reason, when the finish grinding is first performed by the second grinding means at the second grinding position with respect to the processing point of the wafer that has been coarsely ground by the first grinding means at the first grinding position, the grindstone is applied to the wafer. The contact surfaces of the wheels are parallel, and the amount of finish grinding is uniform over the radial direction. Therefore, uneven contact of the grinding wheel during finish grinding does not occur. This effect is for wafer holding surface Ji Yakkuteburu arises because of the slightly inclined like an umbrella rotation center as the vertex.

  The relative movement by each of the parallel direction moving means is performed by moving either one of the grinding means or the chuck table in the inter-axis direction. That is, the first parallel direction moving means moves the first grinding means in the direction between the axes, and the second parallel direction moving means moves the second grinding means in the direction between the axes, or the first parallel direction. The direction moving means and the second parallel direction moving means have a specific form in which the chuck table is moved in the inter-axis direction.

  Further, the position of the grindstone wheel can be adjusted to the position where the recess can be formed by rotating the turntable to a position where the chuck table is slightly shifted from the three positions. That is, in this case, the turntable becomes the first parallel direction moving means and the second parallel direction moving means.

  According to the present invention, in a multi-axis wafer grinding apparatus provided with a plurality of grinding shafts, a grinding wheel that has been exchanged according to the size of the wafer is formed with a recess whose blade edge passes through the rotation center of the wafer and the inner peripheral edge of the outer periphery. It is possible to adjust the position to a possible position, and there is an effect that it is possible to smoothly advance the operation of forming the concave portion on the back surface while supporting a plurality of wafer sizes with one apparatus.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Semiconductor Wafer Reference numeral 1 in FIG. 1 indicates a disk-shaped semiconductor wafer (hereinafter abbreviated as a wafer) in which a recess is formed on the back surface by the wafer grinding apparatus of one embodiment. The wafer 1 is a silicon wafer or the like, and the thickness before processing is, for example, about 600 to 700 μm. A plurality of rectangular semiconductor chips 3 are defined on the surface of the wafer 1 by grid-like division lines 2, and electronic circuits (not shown) such as ICs and LSIs are formed on the surface of the semiconductor chips 3. Has been.

  The plurality of semiconductor chips 3 are formed in a substantially circular device formation region 4 concentric with the wafer 1. The device forming region 4 occupies most of the wafer 1, and the outer peripheral portion of the wafer around the device forming region 4 is an annular outer peripheral region 5 in which the semiconductor chip 3 is not formed. A V-shaped notch 6 indicating the crystal orientation of the semiconductor is formed at a predetermined location on the peripheral surface of the wafer 1. The notch 6 is formed in the outer peripheral surplus region 5. The wafer 1 is finally cut and divided along the planned division line 2 and separated into a plurality of semiconductor chips 3. In the wafer grinding apparatus according to the present embodiment, a region corresponding to the device formation region 4 on the back surface of the wafer 1 is thinned by grinding to a target thickness before the semiconductor chip 3 is singulated, and a recess is formed on the back surface. It is a device to do.

  When the wafer 1 is ground on the back surface, a protective tape 7 is attached to the surface on which the electronic circuit is formed as shown in FIG. 1 for the purpose of protecting the electronic circuit. As the protective tape 7, for example, one having a configuration in which an adhesive of about 10 μm is applied to one side of a polyethylene or polyolefin sheet having a thickness of about 100 to 200 μm is used.

[2] Configuration of Wafer Grinding Device Next, the wafer grinding device of this embodiment will be described.
FIG. 2 shows the entire wafer grinding apparatus 10, and this wafer grinding apparatus 10 includes a rectangular parallelepiped base 11 whose upper surface is horizontal. In FIG. 2, the longitudinal direction of the base 11, the horizontal width direction perpendicular to the longitudinal direction, and the vertical direction are indicated by a Y direction, an X direction, and a Z direction, respectively. At one end in the Y direction of the base 11, a pair of columns 12 and 13 are erected in the X direction (here, the left and right direction). On the base 11, a processing area 11A for grinding the wafer 1 is provided on the side of the columns 12 and 13 in the Y direction, and the unprocessed wafer 1 is supplied to the processing area 11A on the side opposite to the columns 12 and 13. In addition, a detachable area 11B for collecting the processed wafer 1 is provided.

  In the processing area 11A, a disk-shaped turntable 20 whose rotation axis is parallel to the Z direction and whose upper surface is horizontal is rotatably provided. The turntable 20 is rotated in the direction of arrow R by a rotation drive mechanism (not shown). A plurality of (in this case, three) disk-shaped chuck tables 30 whose rotation axis is parallel to the Z direction and whose upper surface (wafer holding surface) 30a is horizontal are arranged on the outer periphery of the turntable 20 in the circumferential direction. Are arranged so as to be rotatable at regular intervals.

  These chuck tables 30 are of a generally known vacuum chuck type, and suck and hold the wafer 1 placed on the upper surface 30a. Each chuck table 30 is independently rotated or rotated in one direction or both directions by a rotation drive mechanism (not shown) provided in the turntable 20, and revolves when the turntable 20 rotates. It becomes a state.

  As shown in FIG. 2, in a state where two chuck tables 30 are arranged in the X direction on the columns 12 and 13 side, a rough grinding unit ( A first grinding means (40A) and a finish grinding unit (second grinding means) 40B are provided. Each chuck table 30 is intermittently rotated by the turntable 20 so that the rough grinding position below the rough grinding unit 40A, the finish grinding position below the finish grinding unit 40B, and the attachment / detachment closest to the attachment / detachment area 11B. It can be positioned at three positions.

  The rough grinding unit 40A and the finish grinding unit 40B are respectively attached to columns (rough grinding side column 12 and finish grinding side column 13). The mounting structures of the rough grinding unit 40A and the finish grinding unit 40B with respect to the columns 12 and 13 are the same and are symmetrical in the X direction. Therefore, the mounting structure will be described with reference to FIG.

  The front surface 13a facing the processing area 11A of the finish grinding side column 13 is a vertical surface with respect to the upper surface of the base 11, but as it goes from the center in the X direction to the end portion (on the side opposite to the detachable area 11B) ) Is formed on a tapered surface that recedes obliquely at a predetermined angle. The horizontal direction of the taper surface 13a (the taper surface 12a in the rough grinding column 12), that is, the taper direction, is relative to the line connecting the rotation center of the chuck table 30 and the rotation center of the turntable 20 positioned at the finish grinding position. Are set to be parallel. An X-axis slider 55 is attached to the taper surface 13a via an X-axis feed mechanism (second parallel movement means) 50. Further, a Z-axis feed mechanism (second vertical direction) is attached to the X-axis slider 55. A Z-axis slider 65 is attached via a moving means) 60.

  The X-axis feed mechanism 50 includes a pair of upper and lower guide rails 51 fixed to the tapered surface 13a (12a), and a screw (not shown) that is disposed between the guide rails 51 and is screwed into and penetrates the X-axis slider 55. It is comprised from the rod and the motor 53 which rotates this screw rod forward / reversely. Both the guide rail 51 and the threaded rod extend in parallel with the taper direction of the tapered surface 13a (12a), and the X-axis slider 55 is slidably mounted on the guide rail 51. The X-axis slider 55 is adapted to reciprocate along the guide rail 51 as the power of the screw rod rotated by the motor 53 is transmitted. The reciprocating direction of the X-axis slider 55 is parallel to the direction in which the guide rail 51 extends, that is, the taper direction of the taper surface 13a (12a).

  The front surface of the X-axis slider 55 is a surface along the X / Z direction, and a Z-axis feed mechanism 60 is provided on the front surface. The Z-axis feed mechanism 60 has a configuration in which the feed direction of the X-axis feed mechanism 50 is changed to the Z direction, and is a pair of left and right (one on the right side in FIG. Only one guide rail 61, a screw rod 62 extending between the guide rails 61 and extending in the Z direction threadedly engaged with the Z-axis slider 65 and rotating the screw rod 62 forward and backward. And a motor 63. The Z-axis slider 65 is slidably mounted on the guide rail 61 and is moved up and down along the guide rail 61 by the power of the screw rod 62 rotated by the motor 63.

  The front surface 12a facing the processing area 11A of the rough grinding side column 12 is formed in a tapered surface that is inclined backward at a predetermined angle from the center in the X direction toward the end, symmetrically to the finish grinding side column 13. An X-axis slider 55 is attached to the taper surface 12a via an X-axis feed mechanism (first parallel movement means) 50. Further, a Z-axis feed mechanism (first vertical movement) is attached to the X-axis slider 55. Means) A Z-axis slider 65 is attached via 60. The taper direction of the tapered surface 12a of the rough grinding column 12 is set to be parallel to a line connecting the rotation center of the chuck table 30 and the rotation center of the turntable 20 positioned at the rough grinding position.

  The rough grinding unit 40A and the finish grinding unit 40B are fixed to the Z-axis sliders 65 attached to the rough grinding side column 12 and the finish grinding side column 13, respectively. These units 40A and 40B will be described below, but since they have the same configuration, common reference numerals will be given.

  As shown in FIG. 3, each of the grinding units 40A and 40B includes a cylindrical spindle housing 41 whose axial direction extends in the Z direction, a spindle 42 that is coaxially and rotatably supported in the spindle housing 41, A motor (rotation drive source) 43 that is fixed to the upper end portion of the spindle housing 41 and rotationally drives the spindle 42 and a disk-like flange 44 that is coaxially fixed to the lower end of the spindle 42 are provided. A grindstone wheel 45 is detachably attached to the flange 44 by means such as screwing.

  The grindstone wheel 45 is formed by affixing a plurality of grindstones 47 arranged in a ring shape and fixed to the lower end surface of a frame 46 having a disc shape and a conical lower portion. As the grindstone 47, for example, a vitreous sintered material called vitrified mixed with diamond abrasive grains and fired is used. As the grindstone wheel 45, a wheel whose outer diameter is ground by the grindstone 47, that is, a diameter of the outer peripheral edge of the plurality of grindstones 47 is approximately equal to the radius of the wafer 1 is used. This corresponds to the device formation region 4 with the cutting edge of the grindstone 47 passing through the rotation center of the wafer 1 and the inner peripheral edge of the outer peripheral surplus region 5 while leaving the thickness of the outer peripheral surplus region 5 during the back surface grinding of the wafer 1. This is a dimension setting for enabling only the region to be ground to be ground.

  The grindstone 47 of the grindstone wheel 45 is used for grinding a silicon wafer, in which abrasive grains having a particle size of about # 280 to # 8000 are mixed. Further, as the grindstone 47 used in the coarse grinding unit 40A, For example, those containing # 280 to # 600 abrasive grains are suitable, and as the grindstone 47 used in the finish grinding unit 40B, for example, those containing # 2000 to # 8000 abrasive grains are suitable.

  In the rough grinding unit 40A, the rotation center of the grindstone wheel 45 (axial center of the spindle 42) exists immediately above the line connecting the rotation center of the chuck table 30 positioned at the rough grinding position and the rotation center of the turntable 20. The position is set as follows. The coarse grinding unit 40A reciprocates along the taper direction of the tapered surface 12a of the column 12 as the Z-axis slider 65 reciprocates. Therefore, at the time of the reciprocal movement, the rotation center of the grindstone wheel 45 is reciprocated just above the line connecting the rotation center of the chuck table 30 positioned at the rough grinding position and the rotation center of the turntable 20. It has become. Since this reciprocating direction is the direction between the axes of the chuck table 30 and the turntable 20, it will be abbreviated as “inter-axis direction” hereinafter.

  The position setting is the same on the finish grinding unit 40B side, and the center of rotation of the grinding wheel 45 of the finish grinding unit 40B (the center of the spindle 42) is the same as the center of rotation of the chuck table 30 positioned at the finish grinding position. When the finish grinding unit 40B reciprocates along the taper direction of the taper surface 13a of the column 13 together with the Z-axis slider 65 and the X-axis slider 55, it exists immediately above the line connecting the rotation center of the table 20. The rotation center of the grinding wheel 45 is reciprocated along the direction of the line, that is, the direction between the axes, directly above the line connecting the rotation center of the chuck table 30 and the rotation center of the turntable 20 positioned at the finish grinding position. It is supposed to be.

The above is the configuration related to the processing area 11A on the base 11, and the detachable area 11B will be described with reference to FIG.
In the center of the detachable area 11B, a two-bar link pickup robot 70 that moves up and down is installed. Around the pickup robot 70, a supply cassette 71, an alignment table 72, a supply arm 73, a recovery arm 74, a spinner type cleaning device 75, and a recovery cassette 76 are arranged counterclockwise as viewed from above. ing.

  The cassette 71, the alignment table 72, and the supply arm 73 are means for supplying the wafer 1 to the chuck table 30. The collection arm 74, the cleaning device 75, and the cassette 76 collect the wafer 1 from which the back surface grinding has been completed from the chuck table 30. Thus, it is means for moving to the next step. The cassettes 71 and 76 accommodate the plurality of wafers 1 in a horizontal posture and in a stacked state at regular intervals in the vertical direction, and are set at predetermined positions on the base 11.

  When one wafer 1 is taken out from the supply cassette 71 by the pick-up robot 70, the wafer 1 is placed on the alignment table 72 with the back side to which the protective tape 7 is not attached facing up, Here, it is determined at a certain position. Next, the wafer 1 is picked up from the alignment table 72 by the supply arm 73 and placed on the chuck table 30 waiting at the attachment / detachment position.

  On the other hand, the back surface is ground by each of the grinding units 40A and 40B, and the wafer 1 on the chuck table 30 positioned at the attachment / detachment position is taken up by the recovery arm 74, transferred to the cleaning device 75, washed with water and dried. The wafer 1 cleaned by the cleaning device 75 is transferred and accommodated in the collection cassette 76 by the pickup robot 70.

[3] Operation of Wafer Grinding Device The configuration of the wafer grinding device 10 has been described above. Next, the operation of grinding the back surface of the wafer 1 by the wafer grinding device 10 to form a recess will be described.
First, the wafer 1 accommodated in the supply cassette 71 is moved to the alignment table 72 and positioned by the pickup robot 70, and then the supply arm 73 waits at the attachment / detachment position and is vacuum operated. The wafer 1 is placed on the chuck table 30 with the back side facing up. The wafer 1 is placed concentrically with the chuck table 30 by being positioned by the alignment table 72. In the wafer 1, the protective tape 7 on the front surface side is in close contact with the upper surface 30 a of the chuck table 30, and is attracted and held on the upper surface 30 a with the back surface exposed.

  Next, the turntable 20 rotates in the direction of the arrow R in FIG. 2, and the chuck table 30 holding the wafer 1 stops at the rough grinding position below the rough grinding unit 40A. At this time, the next chuck table 30 is positioned at the attachment / detachment position, and the wafer 1 to be ground next is set on the chuck table 30 as described above.

  The rough grinding unit 40A above the wafer 1 positioned at the rough grinding position is appropriately moved in the inter-axis direction by the X-axis feed mechanism 50, and the rough grinding unit 40A is moved with respect to the back surface of the wafer 1 as shown in FIG. The grindstone wheel 45 is positioned at a recess formable position where the cutting edge of the grindstone 47 passes through the rotation center O of the wafer 1 and the inner peripheral edge of the outer peripheral surplus region 5. In this case, the position where the recess can be formed is on the outer peripheral side of the turntable 20 with respect to the rotation center of the wafer 1. Next, the wafer 1 is rotated in one direction by rotating the chuck table 30 and the grindstone wheel 45 is rotated at a high speed so that the rough grinding unit 40A is lowered by the Z-axis feed mechanism 60, and the grindstone 47 of the grindstone wheel 45 is moved to the wafer. Press against the back of 1.

  As a result, only the region corresponding to the device forming region 5 is ground on the back surface of the wafer 1, and the ground region becomes the concave portion 1A as shown in FIG. 5, and the original thickness remains on the outer peripheral portion around the concave portion 1A. An annular convex portion 5A is formed. In the rough grinding, the device formation region 4 is thinned to, for example, about 200 to 100 μm or about 50 μm, but in any case, the device forming region 4 is ground to a thickness of about several μm thicker than the finished thickness.

  When the device formation region 4 reaches the target thickness in rough grinding, the lowering of the grinding wheel 45 by the Z-axis feed mechanism 60 is stopped, and the grinding wheel 45 is rotated as it is for a certain period of time, and then the rough grinding unit 40A is raised. Finish rough grinding. In the wafer 1 after rough grinding, as shown in FIG. 5 (a), grinding striations 9 having a shape in which a large number of arcs are radially drawn from the center remain on the bottom surface 4a of the recess 1A. The grinding striation 9 is a trajectory of crushing processing by abrasive grains in the grindstone 47 and is a mechanical damage layer including microcracks and the like. This mechanical damage layer is removed by the next finish grinding.

  The wafer 1 that has been subjected to the rough grinding is transferred to a finish grinding position below the finish grinding unit 40B by rotating the turntable 20 in the R direction. The wafer 1 previously held on the chuck table 30 at the attachment / detachment position is transferred to the rough grinding position, and the wafer 1 is subjected to the rough grinding in parallel with the preceding finish grinding. Further, the wafer 1 to be processed next is set on the chuck table 30 moved to the attachment / detachment position.

  When the wafer 1 is positioned at the finish grinding position, the finish grinding unit 40B is appropriately moved in the inter-axis direction by the X-axis feed mechanism 50, the grindstone wheel 45 enters the recess 1A, and the cutting edge of the grindstone 47 rotates the wafer 1. The center and the inner peripheral edge of the annular convex portion 5A are positioned at a position where a concave portion can be formed. Also here, the position where the recess can be formed is on the outer peripheral side of the turntable 20 with respect to the rotation center of the wafer 1. Next, the wafer 1 is rotated in one direction by rotating the chuck table 30 and the grinding wheel 45 of the finish grinding unit 40B is rotated at a high speed. The grindstone 47 is pressed against the bottom surface 4 a of the recess 1 </ b> A formed on the back surface of the wafer 1.

  Thereby, the bottom surface 4a of the recess 1A is ground by the grindstone 47 for finish grinding. The amount of finish grinding is until the device formation region 4 reaches the target thickness of the semiconductor chip 3, and when the grinding is performed to the thickness, the lowering of the grinding wheel 45 by the Z-axis feed mechanism 60 is stopped and left for a certain time. After the grinding wheel 45 is rotated, the finish grinding unit 40B is raised to finish the finish grinding. By the finish grinding, the mechanical damage layer due to the grinding striations 9 shown in FIG. 5A is removed, and the bottom surface 4a of the recess 1A is finished to a mirror surface.

  Here, examples of suitable operating conditions for rough grinding and finish grinding will be given. In both the rough grinding unit 40A and the finish grinding unit 40B, the rotational speed of the grinding wheel 45 is 3000 to 5000 RPM, and the rotational speed of the chuck table 30 is 100 to 300 RPM. The lowering speed, which is the processing feed rate of the rough grinding unit 40A, is 3 to 5 μm / second, and the lowering speed of the finish grinding unit 40B is 0.3 to 1 μm / second.

  When both finish grinding and rough grinding, which have been performed in parallel, are completed, the turntable 20 is rotated in the R direction, and the wafer 1 after finish grinding is transferred to the attachment / detachment position. As a result, the subsequent wafer 1 is transferred to the rough grinding position and the finish grinding position, respectively. The wafer 1 on the chuck table 30 positioned at the attachment / detachment position is transferred to the cleaning device 75 by the recovery arm 74, and is washed and dried. The wafer 1 cleaned by the cleaning device 75 is transferred and accommodated in the collection cassette 76 by the pickup robot 70.

  The above is the cycle in which the recess 1A is formed on the back surface of one wafer 1 and only the device forming region 4 on the back surface side is thinned to the thickness of the semiconductor chip 3. According to the wafer grinding apparatus 10 of the present embodiment, while the turntable 20 is intermittently rotated as described above, rough grinding is performed on the wafer 1 at the rough grinding position, and finish grinding is performed at the finish grinding position in parallel. As a result, the plurality of wafers 1 are efficiently ground.

  In the wafer grinding apparatus 10 of the present embodiment, a grindstone wheel 45 that forms the recess 1A on the back surface of the wafer 1 has a diameter substantially equal to the radius of the wafer 1. Therefore, when grinding a wafer having a different size (diameter), the wheel is replaced with a grinding wheel 45 having a size corresponding to the wafer. The exchange of the grinding wheel 45 is performed for both the rough grinding unit 40A and the finish grinding unit 40B.

  After the grinding wheel 45 is replaced, the grinding units 40A and 40B are appropriately moved in the inter-axis direction by the X-axis feed mechanism 50, and the grinding wheel 45 can be formed with a recess that can form the recess 1A on the back surface of the wafer 1. Position to position. By moving the grindstone wheel 45 according to the size of the wafer 1 in this way, the cutting edge of the grindstone 47 of the grindstone wheel 45 is a position where it passes through the center of rotation of the wafer 1 and the inner peripheral edge of the outer peripheral surplus region 5. In grinding, only the region corresponding to the device forming region 5 is ground to form the recess 1A, and in finish grinding, the bottom surface 4a of the recess 1A is finish-ground.

  FIG. 6 shows a state in which the wafer 1B having a smaller diameter than the wafer 1 shown in FIG. 4 is subjected to back grinding, and the grinding wheel 45B has a diameter substantially equal to the radius of the wafer 1B and corresponds to the wafer 1B. Smaller ones are used. Then, the grindstone wheel 45B (rough grinding unit 40A) is moved closer to the rotation center of the turntable 20 than in the case of FIG. 4, and is positioned at a position where a recess can be formed with respect to the wafer 1B.

  The wafer grinding apparatus 10 of the present embodiment includes two grinding units for rough grinding and finish grinding, but each grinding unit 40A, 40B can be moved in the inter-axis direction by the X-axis feed mechanism 50. By configuring, it is possible to adjust the position of the replaced grinding wheel 45 (45B...) According to the size of the wafer 1 (1B...) To a position where a recess can be formed. The operation of forming the recess 1A on the back surface can be smoothly advanced while correspondingly.

[4] Other Embodiments of Means for Moving in Inter-axis Direction Instead of moving the rough grinding unit 40A and the finish grinding unit 40B in the inter-axis direction, the chuck tables 30 positioned at the rough grinding position and the finish grinding position are Even if it is moved in the direction between the axes, the position of the grindstone wheel in the horizontal direction relative to the wafer can be adjusted and positioned at the position where the recess can be formed. FIG. 7 shows a wafer grinding apparatus 10B in which the chuck table 30 is moved and the grinding units 40A and 40B are moved so as not to move in the horizontal direction. It is attached.

  First, the rough grinding unit 40A and the finish grinding unit 40B in this case move only in the Z direction and do not move in the horizontal direction along the surfaces in the X and Y directions. That is, the Z-axis slider 65 to which the grinding units 40A and 40B are fixed is rotated by the guide rail 61 and the motor 63 on the front surfaces 12a and 13a of the columns 12 and 13 formed on the surfaces along the X and Z directions. It is attached so as to be movable in the Z direction via a Z-axis feed mechanism 60 composed of a screw rod 62 that performs the above operation. Each of the grinding units 40A and 40B is moved up and down in the Z direction by the Z-axis feed mechanism 60, the grindstone wheel 45 is lowered in a rotating state, and is pressed against the back surface of the wafer 1, whereby the back surface of the wafer 1 is ground.

  The horizontal positions of the grinding units 40A and 40B are such that, in the rough grinding unit 40A, the rotation center of the grindstone wheel 45 is the rotation center of the chuck table 30 positioned at the rough grinding position and the rotation center of the turntable 20. In the finish grinding unit 40B, the center of rotation of the grinding wheel 45 is directly above the line connecting the center of rotation of the chuck table 30 and the center of rotation of the turntable 20 in the finish grinding position. Each is fixed at an existing position.

Next, a mechanism for moving the chuck table 30 in the inter-axis direction will be described with reference to FIGS.
The turntable 20 includes a disk-shaped table base 21 that is rotatably attached to the base 11 and a cover 22 that covers the upper side of the table base 21. On the table base 21, a chuck table slider 31 is movably attached along the radial direction of the table base 21 via a pair of guide rails 23. The chuck table slider 31 is parallel to the guide rail 23 and is threaded through a screw rod 33 that is rotated by a chuck table moving motor 32. The chuck table slider 31 is reciprocated along the radial direction of the turntable 20 when the screw rod 33 is rotated by the chuck table moving motor 32.

  The chuck table 30 is fixed to the upper end of a cylindrical chuck table base 34 that is rotatably supported by the chuck table slider 31. The chuck table base 34 has a rotation axis parallel to the rotation axis of the turntable 20 and penetrates the chuck table slider 31. The chuck table 30 is rotated with respect to the rotation center of the turntable 20 along the radial direction of the turntable 20 via the chuck table base 34 when the screw rod 33 is rotated by the chuck table moving motor 32. Reciprocates in the direction of separation. A long hole 22 a is formed in the movement region of the cover 22 in the chuck table 30 along the moving direction. The chuck table 30 protrudes above the cover 22 from the long hole 22 a.

  A chuck table rotation motor 35 is fixed to the chuck table slider 31. A pinion 35 a of the motor 35 is parallel to the chuck table base 34 and protrudes below the chuck table slider 31. The timing belt 36 is wound around the pinion 35a and the lower protruding end 34a of the chuck table base 34. When the chuck table rotation motor 35 is operated, the power is supplied to the timing belt 36, the chuck table. It is transmitted to the chuck table 30 via the base 34, and the chuck table 30 rotates.

  Thus, according to the embodiment in which the chuck table 30 moves in the radial direction of the turntable 20, the turntable 20 is rotated to position the wafer 1 at the rough grinding position and the finish grinding position, and then the chuck table 30 is moved to the chuck table. By appropriately moving the turntable 20 in the radial direction by the moving motor 32, the grindstone wheel 45 mounted on each grinding unit can be positioned at a position where a recess can be formed according to the size of the wafer 1. The radial direction of the turntable 20 coincides with the inter-axis direction connecting the rotation center of the chuck table 30 and the rotation center of the turntable 20 positioned at the rough grinding position and the finish grinding position, respectively.

  FIG. 10A shows a state in which the wafer is relatively small in diameter and the rotation center of the wafer is shifted to the outer peripheral side of the turntable 20, and FIG. 10B shows that the chuck table 30 is moved from the position of FIG. A state in which the wafer is moved to the inner peripheral side and is made to correspond to a relatively large diameter wafer is shown.

  When grinding the back surface of the wafer 1, the wafer is ground while measuring the wafer thickness with the measurement reference surface as the upper surface 30a of the chuck table 30, but before the grinding, the upper surface 30a of the chuck table 30 is ground by the grindstone wheel 45. Is done. Grinding called self-grinding uses a grinding wheel having a diameter equal to or larger than the radius of the chuck table. However, in the configuration in which the grinding wheel 45 and the chuck table 30 are relatively moved in the axial direction as in the above embodiments, In order to make the moving range of the grinding wheel 45 or the chuck table 30 as small as possible to improve the space efficiency, the grinding wheel for self-grinding may have a diameter slightly larger than the radius of the chuck table.

[5] Other Embodiments of Parallel Direction Moving Means In each of the above embodiments, the grindstone wheel 45 of the grinding units 40A and 40B and the chuck table 30 are moved relative to each other in the inter-axis direction to move the grindstone wheel 45 in the horizontal direction relative to the wafer 1. It is a form which adjusts the position of. In the present invention, the target position adjustment can be performed as long as the grinding wheel 45 and the chuck table 30 are separated from each other, not limited to the inter-axis direction.

  Further, the grindstone wheel 45 can be positioned at the position where the recess can be formed by slightly rotating the turntable 20 without providing the grinding units 40A and 40B and the chuck table 30 with a moving mechanism in the horizontal direction. FIG. 11 shows a wafer grinding apparatus 10 </ b> C in which the position of the grinding wheel can be adjusted by rotating the turntable 20 in the wafer grinding apparatus 10 </ b> B shown in FIG. 7. The turntable 20 is rotated in the L direction. The chuck table 30 is moved from the position of the broken line to the position of the solid line.

  Specifically, first, a wafer 1 having a relatively large diameter (for example, 200 mm diameter) shown in FIG. 12A is held by the chuck table 30 and corresponds to the wafer 1 (the diameter is about the radius of the wafer 1). The grindstone wheel 45 is positioned at a position where the concave portion can be formed corresponding to the wafer 1. When the grinding process for the wafer 1 is finished and then the wafer 1B having a small diameter (for example, 150 mm diameter) indicated by the solid line in FIG. 12B is held on the chuck table 30, the grinding wheel 45B for the wafer 1B is ground. By attaching the units 40A and 40B and slightly rotating the turntable 20 in the direction of the arrow L, the grindstone wheel 1B can be positioned at a position where a recess can be formed corresponding to the wafer 1B.

  Thus, in the case of replacement from a large diameter wafer to a small diameter wafer, the turntable 20 is rotated in the direction of the arrow L. Conversely, in the case of replacement from a small diameter wafer to a large diameter wafer, the turntable 20 is rotated. Is rotated in the direction of arrow R to adjust the position.

It is the (a) perspective view and (b) side view of the wafer which are ground with the wafer grinding device concerning one embodiment of the present invention. It is a perspective view of the wafer grinding device concerning one embodiment of the present invention. It is the (a) perspective view and (b) side view of the grinding unit which a wafer grinding device comprises. It is the (a) side view and (b) top view which show the state which grinds the back surface of a wafer with the grindstone wheel located in the recessed part formation possible position. It is the (a) perspective view and (b) sectional view of a wafer in which a crevice was formed in the back. It is the (a) side view and (b) top view which show the state which grinds the back surface of a wafer with the grindstone wheel located in the position which can form a recessed part corresponding to the wafer (small diameter) from which size differs. It is a perspective view of the wafer grinding device concerning other embodiments of the present invention. It is a perspective view which shows the chuck table moving mechanism of the wafer grinding apparatus which concerns on other embodiment. FIG. 9 is a partial cross-sectional view taken along arrow IX in FIG. 8. FIGS. 9A and 9B are partial cross-sectional views taken along the arrow X in FIG. 8, in which FIG. 8A shows a state where the chuck table is in a position corresponding to a small diameter wafer / small diameter grinding wheel, and FIG. 8B shows a chuck table having a large diameter wafer / large diameter grinding wheel. The state in the position corresponding to is shown. It is a perspective view of the wafer grinding device concerning other embodiments of the present invention. 11A is a plan view showing a state in which the grinding wheel for a large diameter wafer is positioned at a position where a recess can be formed with respect to the large diameter wafer in the wafer grinding apparatus shown in FIG. 11, and FIG. It is a top view which shows the state by which the grindstone wheel for small diameter wafers was located in the recessed part formation position with respect to a small diameter wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer 1A ... Recessed part 3 ... Semiconductor chip (device)
4 ... Device formation region 5 ... Peripheral surplus region (outer periphery)
5A ... annular convex part (outer peripheral part)
10, 10B, 10C ... Wafer grinding device 20 ... Turn table 30 ... Chuck table 30a ... Upper surface (wafer holding surface)
40A: Coarse grinding unit (first grinding means)
40B: Finish grinding unit (second grinding means)
43 ... Motor (rotary drive source)
45 ... Whetstone wheel 47 ... Whetstone 50 ... X-axis feed mechanism (first parallel direction moving means, second parallel direction moving means)
60... Z-axis feed mechanism (first vertical direction moving means, second vertical direction moving means)

Claims (6)

A wafer grinding device that grinds at least one side of a disk-shaped wafer, leaving the outer periphery, and the inside of the outer periphery,
A self-rotating chuck table having a wafer holding surface formed so as to be inclined in an umbrella shape with the rotation center as a vertex ;
A wafer attachment / detachment position for supporting the chuck table so as to be rotatable and attaching / detaching the wafer to / from the chuck table, a first grinding position for rough grinding the wafer, and a second grinding position for finish grinding the wafer after rough grinding A turntable for positioning the chuck table at three positions;
An annular grinding wheel that passes through the rotation center of the wafer held by the chuck table, the inner peripheral edge of the outer peripheral portion, and a rotational drive source that rotates the grinding wheel, and is positioned at the first grinding position. First grinding means for rough grinding the wafer;
An annular grinding wheel having a contact surface passing through the rotation center of the wafer held by the chuck table and the inner periphery of the outer peripheral portion and parallel to the wafer ground by the first grinding means ; A second driving means for finishing grinding the wafer positioned at the second grinding position, and a rotational drive source for rotating the grinding wheel;
First vertical movement means for moving the first grinding means in a direction perpendicular to the wafer holding surface of the chuck table;
First parallel direction moving means for relatively moving the first grinding means and the chuck table in a direction parallel to the wafer holding surface of the chuck table;
Second vertical movement means for moving the second grinding means in a direction perpendicular to the wafer holding surface of the chuck table;
A second parallel direction moving means for relatively moving the second grinding means and the chuck table in a direction parallel to the wafer holding surface of the chuck table;
The arc-shaped machining points at which the grinding wheel wheels of the first grinding means and the second grinding means are pressed against the wafer held on the chuck table are the same when viewed on the chuck table. A wafer grinding apparatus characterized by being provided.   2. The wafer grinding apparatus according to claim 1, wherein a total of three chuck tables are provided, one at a position corresponding to the three positions of the turntable. The first parallel movement means moves the chuck table and the first grinding means between the rotation center of the chuck table and the rotation of the turntable when the chuck table is positioned at the first grinding position. Relative movement in the direction of the axis along the line connecting the center, the distance between the axes is variable,
The second parallel movement means moves the chuck table and the second grinding means between the rotation center of the chuck table and the rotation of the turntable when the chuck table is positioned at the second grinding position. 3. The wafer grinding apparatus according to claim 1, wherein the distance between the two axes is varied by relative movement in a direction between the axes along a line connecting the centers.   The first parallel direction moving means moves the first grinding means in the inter-axis direction, and the second parallel direction moving means moves the second grinding means in the inter-axis direction. The wafer grinding apparatus according to claim 3.   4. The wafer grinding apparatus according to claim 3, wherein the first parallel direction moving means and the second parallel direction moving means move the chuck table in the inter-axis direction.   2. The wafer grinding apparatus according to claim 1, wherein the first parallel direction moving means and the second parallel direction moving means are the turntable.

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