JP7247397B2 - Wafer chamfering device and wafer chamfering method - Google Patents

Description

As a semiconductor substrate, the present invention is a process for removing an unbonded portion that inevitably remains on the outer periphery of the upper surface layer side of a bonded wafer or a wafer with a film layer, that is, a process for forming a terrace shape, or the outer periphery of the wafer ( The present invention relates to a wafer chamfering apparatus and a wafer chamfering method suitable for processing an end face edge portion.

Since it has advantages such as high-speed operation and low power consumption, as a bonded wafer, one silicon wafer on which an oxide film (insulating film) is formed is bonded to another silicon wafer, and this bonding is performed. One of the combined silicon wafers is ground and polished to form an SOI layer, and after implanting oxygen ions into the silicon wafer, high temperature annealing is performed to form a buried oxide film inside the silicon wafer, After forming an ion-implanted layer by implanting hydrogen ions or the like into the surface layer portion of a silicon wafer (active layer side wafer) serving as the SOI layer on the upper portion of the oxide film (active layer side wafer), the silicon wafer for the support substrate. and the like are known.

In addition, as a wafer with a film layer, a thin film of silicon oxide, aluminum, etc., which is the material of the circuit, is formed on the wafer, and ions are struck against metals such as aluminum to peel off molecules and atoms, which are then deposited on the wafer by sputtering. , Electroplating method for forming a copper wiring, CVD method, in which a chemical reaction is caused by supplying a special gas to the surface of the wafer, and the resulting molecular layer is made into a film, and the surface is oxidized by heating the wafer. Thermal oxidation, which forms a silicon film, and the like are known.

When manufacturing a bonded wafer or a wafer with a film layer, in order to prevent the generation of particles due to peeling and detachment, a process for removing the unbonded portion that inevitably remains on the outer peripheral portion of the bonded wafer, that is, a terrace portion forming process, Alternatively, it is necessary to process the ovalized or distorted outer peripheral portion due to the bonding error to make the diameter uniform and finish it into a perfect circle. In other words, a chamfering machine is used to remove the crystal unstable region near the edge of an integrated wafer (physically bonded or crystal grown product) having two or more different material properties, or a portion that causes deterioration of device characteristics such as shape sagging. Removal processing is carried out in

As a chamfering device for performing terrace processing, the back surface of a wafer is held by a chuck table, and a cutting blade that rotates perpendicularly to the wafer surface is cut into the outer peripheral edge of the wafer to a predetermined thickness and depth. It is known to rotate the chuck table to leave a part of the chamfered portion, which is described in Japanese Patent Application Laid-Open No. 2002-200016.

The terrace shape requires a large diameter removal amount in the upper layer of the wafer, and a large grindstone contact area and processing resistance are applied. Then, abnormal wear, shape variation, and clogging of the grindstone are likely to occur due to the load. Furthermore, in order to maintain the terrace shape with high accuracy, it is necessary for the grindstone to give priority to shape retention. However, in order to ensure shape retention, it is necessary to reduce clogging, maintain sharpness, prevent an increase in surface pressure on the grindstone, and eliminate the occurrence of grindstone collapse.

Therefore, it was necessary to perform dressing manually or remove the used diamond layer by electrical discharge machining before the clogging increased. For example, when finishing the surface of a substrate made of difficult-to-cut materials such as sapphire and silicon carbide, it is known to perform dressing of the grinding wheel while grinding the substrate, which is the workpiece, with the grinding wheel. It is described in Patent Literature 2.

JP 2016-127098 A JP 2015-171760 A

Among the above prior arts, the one described in Patent Document 1 cuts the outer peripheral edge of the wafer with a cutting blade that rotates perpendicularly to the surface of the wafer. ), the grinding resistance was large and the contact area of the grindstone was small, so that the shape accuracy could not be obtained due to stress concentration at the tip. In addition, due to tangential resistance, the bonding tends to peel off, and there is a risk of cracking in the thinned portion. In order to prevent these problems, a vitrify grindstone is required that has a self-growing action and maintains the grinding ability. Met. Furthermore, the machining efficiency is low for continuous grinding, and sludge tends to accumulate, resulting in abnormal wear at the tip, which inevitably shortens the life of the grindstone.

The one described in Patent Document 2 is for performing surface grinding of a substrate, and by simply pressing a dressing member against the grinding wheel by means of a pressing mechanism, the abrasive grains are separated from the grinding wheel, thereby promoting the autogenous action. It causes self-sharpening. Therefore, the technique described in Patent Document 2 cannot be applied to processing of a terrace shape. In other words, in order to maintain the terrace shape with high accuracy, simply dressing the grinding wheel while grinding the substrate, which is the workpiece, with the grinding wheel cannot achieve this.

In addition, in the case of a wafer with a film layer, the film-forming component may adhere and wrap not only on the surface of the wafer but also on the outer periphery of the wafer. and become a factor of peeling of the deposited layer. Therefore, it was necessary to remove the film-forming components in the outer peripheral portion.

The object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the shape accuracy by preventing abnormal wear and shape variation in the processing for forming a terrace shape and the end face processing, as well as clogging, shortening of the life of the grindstone, To improve machining efficiency by preventing grindstone replacement. Another object of the present invention is to eliminate cracks in the substrate surface layer portion of the bonded wafer and separation of the bonding buffer layer, etc., so as to achieve low-damage processing.

In order to achieve the above object, the present invention has the following configurations.

[1] A wafer chamfering apparatus for grinding the outer periphery of a wafer, comprising: a wafer feeding unit that mounts the wafer and moves and rotates it in XYZ directions; a trimming grindstone that rotates and processes the outer periphery of the wafer; a dressing grindstone that rotates around an axis parallel to the rotation axis of the trimming grindstone, the dressing grindstone being arranged in a rotation circumference of the trimming grindstone, and the trimming grindstone processing the outer peripheral portion of the wafer while processing the trimming grindstone. A wafer chamfering device characterized by enabling dressing with a dressing grindstone.
[2] The wafer chamfering apparatus according to [1], wherein the trimming grindstone and the wafer rotate in the same direction.
[3] The wafer chamfering apparatus according to [1] or [2], wherein the trimming grindstone is a metal bond.
[4] A wafer chamfering method for grinding an outer peripheral portion of a wafer by a wafer feeding unit that moves and rotates a wafer placed thereon in XYZ directions, and a trimming grindstone that rotates and processes the outer peripheral portion of the wafer, arranging a dressing grindstone rotating around an axis parallel to the rotation axis of the trimming grindstone on the rotating circumference of the trimming grindstone, and dressing the wafer with the dressing grindstone while processing the outer peripheral portion of the wafer with the trimming grindstone. A wafer chamfering method characterized by:
[5] The wafer chamfering method according to [4], wherein the trimming grindstone and the wafer rotate in the same direction.
[6] The wafer chamfering method according to [4] or [5], wherein the trimming grindstone is a metal bond.

According to another aspect of the present invention, there is provided a wafer chamfering apparatus for grinding an outer peripheral portion of a wafer, wherein a suction table on which the wafer is placed and horizontally rotated is provided with a table for moving in XYZ directions; A grinding unit having a metal-bonded trimming grindstone for processing the outer periphery of a wafer and rotating the trimming grindstone in the same manner as the wafer; and a dressing device provided with a dressing grindstone that rotates around an axis parallel to the rotation axis of the trimming grindstone, wherein the dressing device is arranged on the rotation circumference of the trimming grindstone, and the outer peripheral portion of the wafer is trimmed by the trimming grindstone. Dressing can be performed with the dressing grindstone while processing.

Further, in the above, it is desirable to provide a master grindstone stacked in the rotation axis direction of the dressing grindstone so that the trimming grindstone can be trued with the master grindstone.

Furthermore, in the above, it is desirable that a nozzle for discharging coolant is arranged upstream in the rotation direction of the trimming grindstone, and the order of the nozzle, the wafer processing point, and the dressing processing point is arranged when processing the wafer. .

Furthermore, in the above, it is desirable that the trimming grindstone is metal bond with a mesh size of #800 to #1500, and the mesh size of the dressing grindstone is #1000 to #2000.

Furthermore, in the above, it is desirable that the dressing of the trimming grindstone with the dressing grindstone is such that the holding of the dressing grindstone and the feeding amount in the Z direction are determined so as to bring about a spark-out state.

Further, in the above, it is desirable that the feed amount of the dressing grindstone in the Z direction is set to 0.1 to 1 μm.

Furthermore, in the above, it is desirable to provide a displacement sensor for detecting the position of the dressing grindstone in the Z-axis direction.

Further, in the above, it is desirable to determine the pressing amount of the dressing grindstone against the trimming grindstone from the difference between the vertical feed command value of the dressing grindstone and the detection position of the dressing grindstone by the displacement sensor.

Further, the present invention is provided with a wafer feed unit provided with a table for moving in XYZ directions a suction table that horizontally rotates on which a wafer is placed, and a trimming grindstone for processing the outer periphery of the wafer. A wafer chamfering method for grinding an outer peripheral portion of a wafer by a grinding unit that rotates in the same manner as the rotation of the wafer, wherein the dressing device is provided with a dressing grindstone that rotates around an axis parallel to the rotation axis of the trimming grindstone. is provided on the table of the wafer feeding unit, arranged on the rotation circumference of the trimming grindstone, and dressing is performed by the dressing grindstone while the outer peripheral portion of the wafer is processed by the trimming grindstone.

Further, in the above method, it is desirable that the trimming grindstone can be trued with master grindstones stacked in the direction of the rotational axis of the dressing grindstone.

Further, in the above method, a nozzle for discharging coolant is arranged on the upstream side in the rotation direction of the trimming grindstone, and when processing the wafer, the order is the nozzle, the wafer processing point, and the dressing processing point. is desirable.

Furthermore, in the above method, it is desirable that the dressing of the trimming grindstone with the dressing grindstone is such that the holding of the dressing grindstone and the feeding amount in the Z direction are determined so as to bring about a spark-out state.

Furthermore, in the above method, it is desirable to perform dressing by detecting the current value of the outer peripheral motor that rotates the trimming grindstone and the position of the dressing grindstone in the Z-axis direction.

According to the present invention, when chamfering the outer peripheral portion of the wafer by the wafer feeding unit on which the wafer is mounted and the grinding unit rotating the trimming wheel, the dressing device is provided in the wafer feeding unit to rotate the trimming wheel. Arrange in a circle. And since the trimming wheel is dressed with the dressing wheel while chamfering, the shape maintenance performance of the trimming wheel is improved, and the dressing interval due to clogging and downtime such as shape correction outside the machine are reduced, and productivity is improved. . Furthermore, cracking of the surface layer of the substrate of the bonded wafer, peeling of the bonding buffer layer, scratches generated on the surface layer, and the like can be eliminated, and low-damage processing can be achieved.

1 is a plan view showing the main parts of a wafer chamfering apparatus according to one embodiment of the present invention; FIG. Side view in FIG. 1 is a side view showing a trimming whetstone according to one embodiment of the present invention; FIG. FIG. 2 is a side view showing the relationship between the trimming grindstone and the dressing unit according to one embodiment of the present invention; Detail view showing the arrangement of nozzles for discharging coolant (grinding fluid) according to one embodiment of the present invention. Partial cross-sectional view showing details of terrace processing Partial cross-sectional view showing processing of the end face of the wafer W Plan view showing correction of bonding error Partial cross-sectional view showing outer peripheral processing of a wafer with a film layer

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a plan view showing the main parts of a wafer chamfering apparatus according to one embodiment of the present invention, FIG. 2 is a side view, FIG. 3 is a side view showing a trimming grindstone 108, and FIG. 4 is a trimming grindstone 108 and a dressing unit. 200 is a side view showing the relationship with FIG.

The trimming grindstone of the wafer chamfering device that forms a terrace shape on the upper surface layer side of the bonded wafer is implemented by transferring the shape of the master grindstone. At that time, the terrace shape requires a large amount of removal, and a large grindstone contact area and processing resistance are applied. Then, the load tends to cause abnormal wear, deformation, and clogging of the grindstone.

In order to maintain the terrace shape with high accuracy, a high-hardness grindstone that prioritizes shape retention, such as a metal-bond grindstone, is required. However, metal-bonded grindstones, like vitrified grindstones, have a small autogenous action, and are therefore likely to clog and lose sharpness.

Also, if the wafer feeding amount (cutting in the Z direction with respect to the wafer) is superior to the grindability (removal ability), a force will act to press the wafer, making it difficult to obtain the intended terrace shape. Since the grinding wheel side is also deformed by the load, the elastic deformation of both the wafer and the tool (grinding wheel) becomes an error factor of the terrace shape. Moreover, since the wafer is pressed, there is a risk of internal damage due to deformation and distortion of the wafer. Furthermore, the grindstone tends to collapse in the terraced portion due to the increase in surface pressure, and the shape cannot be maintained.

The wafer chamfering device 50 can process wafers and plates (workpieces) of various shapes of brittle materials, such as sapphire, SiC (silicon carbide), GaN (gallium nitride), compound semiconductors such as LT (lithium tantalate), oxidation This is a device for chamfering the outer periphery of a workpiece. However, it is not necessarily limited to the plate-shaped body of a brittle material, and it is also possible to chamfer the outer peripheral portion of the plate-shaped body of any material. In the following description, it is assumed that the work to be chamfered is a wafer.

As shown in the figure, the wafer chamfering device 50 comprises a wafer feeding unit 50A, a grinding unit 50B, and a dressing device 50C. A pair of Y-axis guide rails 52, 52 are laid at a predetermined interval on the horizontally arranged base plate 51 of the wafer feed unit 50A. A Y-axis table 56 is slidably supported on the pair of Y-axis guide rails 52, 52 via a pair of Y-axis linear guides 54, 54, .

A nut member 58 is fixed to the lower surface of the Y-axis table 56 , and a Y-axis ball screw 60 is screwed into the nut member 58 . The Y-axis ball screw 60 is rotatably supported at both ends by bearing members 62, 62 disposed on the base plate 51 between the pair of Y-axis guide rails 52, 52, and has a Y-axis at one end. A shaft motor 64 is coupled.

By driving the Y-axis motor 64, the Y-axis ball screw 60 rotates, and the Y-axis table 56 slides along the Y-axis guide rails 52, 52 in the horizontal direction (Y-axis direction) via the nut member 58. .

A pair of X-axis guide rails 66 , 66 are laid on the Y-axis table 56 so as to be orthogonal to the pair of Y-axis guide rails 52 , 52 . An X-axis table 70 is slidably supported on the pair of X-axis guide rails 66, 66 via X-axis linear guides 68, 68, .

A nut member 72 is fixed to the lower surface of the X-axis table 70 , and an X-axis ball screw 74 is screwed into the nut member 72 . The X-axis ball screw 74 is rotatably supported at both ends by bearing members 76, 76 arranged on the X-axis table 70 between a pair of X-axis guide rails 66, 66. An output shaft of an X-axis motor (not shown) is connected to the end. Therefore, by driving the X-axis motor, the X-axis ball screw 74 rotates, and the X-axis table 70 slides in the horizontal direction (X-axis direction) along the X-axis guide rails 66 , 66 via the nut member 72 . do.

A Z-axis base 80 is erected vertically on the X-axis table 70, and a pair of Z-axis guide rails 82, 82 are laid on the Z-axis base 80 at a predetermined interval. A Z-axis table 86 is slidably supported by the pair of Z-axis guide rails 82 , 82 via Z-axis linear guides 84 , 84 . Although the X-axis table 70 is arranged on the Y-axis table 56 , the Y-axis table 56 may be arranged on the X-axis table 70 .

A nut member 88 is fixed to the side surface of the Z-axis table 86 , and a Z-axis ball screw 90 is screwed into the nut member 88 . The Z-axis ball screw 90 is rotatably supported at its both ends by bearing members 92, 92 disposed on the Z-axis base 80 between a pair of Z-axis guide rails 82, 82, and its lower end is connected to the output shaft of the Z-axis motor 94 .

By driving the Z-axis motor 94, the Z-axis ball screw 90 rotates, and the Z-axis table 86 slides in the vertical direction (Z-axis direction) along the Z-axis guide rails 82, 82 via the nut member 88. . A θ-axis motor 96 is installed on the Z-axis table 86 . As described above, the wafer feed unit 50A is installed on each table serving as the base of the numerically controlled axes XYZθ when the wafer W is moved.

An output shaft of the θ-axis motor 96 is connected to a θ-axis shaft 98 whose axis is the θ-axis (rotational axis θ) parallel to the Z-axis. ) 10 are horizontally connected. A wafer W to be terraced is placed on a suction table 10 and held by vacuum suction. The outer diameter of the suction table 10 is set to be smaller than the outer diameter of the wafer W so that the wafer W protrudes and overhangs the suction table 10 .

The dressing device 50C is arranged on the side of the wafer feed unit 50A, that is, on the X-axis table 70 or the Y-axis table 56, similarly to the control axes during wafer processing. Also, as shown in the figure, the trimming grindstone 108 is arranged in a rotating circumference. As a result, the formation direction of the crater and the trench, which will be the sludge pocket, is formed in the same direction as the sludge generation direction and the sludge discharge direction at the wafer grinding point, and an optimum sludge discharge path can be formed.

The two dress guides 201 of the dressing device 50C stand vertically on the X-axis table 70. As shown in FIG. A dressing unit 200 in which a dressing grindstone 203 and a master grindstone 204 are coaxially provided is supported by the dressing guide 201 via a dressing arm 202 so as to be slidable in the Z-axis direction.

The dress arm 202 is supported by a ball screw mechanism 205 with a cantilever structure, and the ball screw mechanism 205 is driven by a dress motor 206 . Therefore, the dressing unit 200 can be moved in the Z-axis direction along the dressing guide 201 by the dressing motor 206 . When the Y-axis table 56 is arranged on the X-axis table 70 , the dress guide guide 201 may be erected on the Y-axis table 56 .

By arranging the dressing device 50C on the side of the wafer feed unit 50A, it is possible to avoid the effects of thermal and vibrational displacement elements due to the high-speed rotation of the trimming wheel 108 compared to the case where it is provided on the side of the grinding unit 50B. It is possible to achieve stability in machining accuracy. In particular, it is possible to avoid the influence of disturbance when the X-axis table 70 or the Y-axis table 56 is moved and numerically controlled. Further, since the dressing unit 200 moves in synchronization with the wafer W by arranging it on the wafer feeding unit 50A side, a guide mechanism for controlling the position of the dressing unit 200 becomes unnecessary.

In addition, the movement directions of the wafer processing point (the region where the trimming grindstone 108 is used) and the dressing processing point (the dressing region) can be aligned in the tangential direction. As a result, the direction of the crater for collecting the grinding sludge formed on the surface layer of the trimming wheel 108 by dressing and the direction of the trench for discharging chips are the same at the wafer processing point and the dressing point, resulting in an optimum dressing position. Then, dressing can be performed in-process while processing the terrace shape of the wafer W by the trimming grindstone 108 in the wafer chamfering device.

In the wafer feeding unit 50A, the suction table 10 moves horizontally in the Y-axis direction in the drawing by driving the Y-axis motor 64, and moves horizontally in the X-axis direction in the drawing by driving the X-axis motor. By driving the Z-axis motor 94, it moves vertically in the Z-axis direction in the drawing, and by driving the .theta.-axis motor 96, it rotates approximately horizontally, that is, rotates around the .theta.-axis.

A mount 102 is installed on the base plate 51 of the grinding unit 50B. A peripheral motor 104 is installed on the frame 102, and the output shaft of the peripheral motor 104 is connected to a spindle 106 having a rotation axis CH parallel to the Z-axis. A trimming grindstone 108 for chamfering the outer peripheral portion of the wafer W is detachably attached to the spindle 106, and driven by the outer peripheral motor 104, horizontally rotates around an axis parallel to the θ axis which is the rotation axis of the wafer W. .

A nozzle 121 for discharging coolant (grinding liquid) toward a position on the upstream side in the rotational direction with respect to the processing point where the wafer W contacts the trimming grindstone 108 is provided. In terrace processing, the nozzle 121, the wafer processing point, and the dressing processing point are arranged in this order. Therefore, the wafer processing point is a wet type, and the cooling function and the sludge of the grinding dust and the abrasion powder of the grindstone are sufficiently discharged. , the state is close to that of a dry type, and residual stress is small, so that the trimming grindstone 108 can maintain its shape with high accuracy.

FIG. 3 shows a trimming grindstone 108 for processing a terrace shape, and a grindstone 24 is provided on the lower surface of the outer circumference thereof. The whetstone 24 is formed with a tapered portion 26 in which the upper side is larger and the lower side is smaller. The dimensions in the figure are an example in which the width of the terrace shape of the wafer W is processed to 4 mm, and a finishing accuracy of 4 mm±10 μm is obtained.

A flat portion 27 on the right end face in the figure is used for processing the outer peripheral (end face edge) portion. The grindstone 24 may be segmented in the circumferential direction of the trimming grindstone 108, that is, divided into a plurality of parts, and a discharge hole may be provided between each of the divided parts to discharge grinding dust and the like.

The trimming grindstone 108 is a metal bond with a mesh size of about #800 to #1500, and is adjusted in consideration of life and processing quality. Desirably, the rotation speed of the spindle 106 is 1000 to 4000 rpm, the rotation speed of the wafer W on the work side is 50 to 200 rpm, and the cutting speed is 0.1 to 5 mm/sec. In addition, by using a metal bond, the holding power of the abrasive grains (the power to grip the abrasive grains) is strong, and the shape holding power of the grindstone itself (shape retention) is high, which contributes to the improvement of the accuracy of terrace processing.

In the chamfering apparatus 50 configured as described above, the wafer W is chamfered as follows. As a preparatory step before chamfering, the wafer W to be chamfered is placed on the suction table 10 and held by suction. Then, the outer circumference motor 104 and the .theta.-axis motor 96 are driven to rotate both the trimming grindstone 108 and the suction table 10 in the same direction at high speed. For example, the rotation speed of the trimming grindstone 108 is set to 3000 rpm, and the rotation speed of the suction table 10 is set so that the peripheral speed of the wafer W is 5 mm/sec.

Also, the Z-axis motor 94 is driven to adjust the height of the suction table 10 so that the height of the wafer W corresponds to the height of the grinding groove of the trimming grindstone 108 . Further, the X-axis motor is driven to align the θ-axis (rotational axis θ), which is the rotational axis of the wafer W, with the rotational axis CH of the trimming grindstone 108 in the X-axis direction.

Next, as a chamfering step, the Y-axis motor 64 is driven to move the wafer W toward the trimming grindstone 108 . Immediately before the outer peripheral portion of the wafer W comes into contact with the trimming grindstone 108, the speed is reduced, and thereafter the wafer W is sent toward the trimming grindstone 108 at a low speed.

As a result, the outer peripheral portion of the wafer W is brought into sliding contact with the trimming grindstone 108, and as will be described below, the wafer W is ground by minute amounts to be terraced. In addition, the coolant is discharged from the nozzle 121 toward the machining point to cool the machining point and discharge the grinding debris and grinding powder (crushed and dropped abrasive grains) of the grindstone. At the same time, the trimming grindstone 108 is dressed while processing the terrace shape of the wafer W with the trimming grindstone 108 . The mesh size of the dressing grindstone 203 is selected from #1000 to #2000.

A displacement sensor (not shown) is provided on the vertical guide shaft of the dressing guide 201 so that the position of the dressing grindstone 203 in the Z-axis direction can always be detected during processing. From the difference between the vertical feed command value of the dressing grindstone 203 and the detection position of the dressing grindstone 203 by the displacement sensor, the pressing amount and usage amount to the trimming grindstone 108 can be determined. It is also possible to monitor the spark-out condition by this pressing amount.

Further, the result of calculating the remaining amount of the dressing grindstone 203 is fed back. As a result, even when the next wafer W is processed, the movement amount of the dressing grindstone 203 can be corrected so as not to cause an error. In addition, the power fluctuation of the spindle 106 that rotates the trimming grindstone 108 and the load fluctuation (current value) of the outer peripheral motor 104 are monitored, and dressing is performed in-process based on the detected value and the position of the dressing grindstone 203 detected by the displacement sensor. It switches between both control modes, that is, to perform dressing and to simply perform dressing.

The trimming grindstone 108 is a metal bond with high shape retention (shape maintenance). Since the metal bond type grindstone does not self-sharpen, its sharpness decreases in clogging mode, and if the wafer feeding amount (wafer up/down - Z direction cutting) is greater than the grindability (removal ability), the force to press the wafer is reduced. works, and the intended terrace shape cannot be obtained. Alternatively, since the grinding wheel side is also deformed by the load, the elastic deformation of both the wafer and the tool (grinding wheel) becomes a factor that deteriorates the shape accuracy.

Furthermore, pressing the wafer may cause internal damage due to deformation and distortion of the wafer, and an increase in surface pressure may cause the grindstone to collapse in the terrace-shaped portion, making it difficult to maintain the shape.

Therefore, the dressing unit 200 is supported and held by a cantilever structure in the Z-axis direction via the dressing arm 202, and the feeding amount of the dressing grindstone 203 in the Z direction is set to 0.1 μm to 1 μm. Dressing is performed so that elastic deformation of the grinding wheel 203 due to pressing is prevented, and the grinding wheels are brought into rigid contact with each other so that the shape of the trimming grinding wheel 108 is not destroyed, i.e., a spark-out state.

This also applies to the initial dressing of the trimming grindstone 108 , grinding of the wafer W, and truing of the trimming grindstone 108 . The cutting and feeding of the workpiece by the trimming grindstone 108 is performed by the wafer feed unit 50A, and the dressing grindstone 203 is vertically moved by the dressing motor 206 of the dressing device 50C.

Chamfering is performed by moving the wafer W in a direction away from the trimming grindstone 108 to a position where the wafer W is recovered after a predetermined time has elapsed since the outer peripheral portion of the wafer W reached the deepest portion of the grinding groove. finish.

In FIG. 4, reference numeral 204 denotes a master whetstone provided coaxially with the dressing whetstone 203. The figure shows a state during truing by the trimming whetstone 108, which is appropriately performed when processing a large number of wafers W continuously. there is During truing, the dressing unit 200 is moved to the right in the drawing, then moved lower than during grinding of the outer peripheral portion of the wafer W, and moved to the left.

As a result, the master groove of the master grindstone 204 contacts the trimming grindstone 108 and is ground. By stacking the master grindstone 204 having a shape having a master groove on the rotating shaft of the dressing grindstone 203, the shape of the trimming grindstone 108 can be corrected using the same mechanism as the in-process dressing mechanism in the wafer chamfering device. That is, since truing is performed, the shape of the master groove is accurately transferred to the trimming grindstone 108 . The master grindstone 204 is selected to be harder than the trimming grindstone 108 for processing the wafer W and have a lower count.

FIG. 5 is a detailed view showing the arrangement of nozzles 121 for discharging coolant (grinding fluid). The coolant is supplied to the trimming grindstone 108, which is a diamond grindstone, and the wafer processing point for lubrication. The nozzle 121 for discharging the coolant is arranged on the upstream side in the rotation direction of the trimming grindstone 108 .

As a result, the coolant at the grinding point maintains a state in which water adheres to the bond of the trimming grindstone 108 and the diamond abrasive grain surface layer even after passing through the grinding point. Since the contact surface with the dressing grindstone 203 maintains wettability, it is possible to prevent deterioration of the diamond due to seizure and heat. Further, since the dressing grindstone 203 is arranged at a position at a maximum of 45° from the grinding point, it is arranged so as to easily receive the coolant scattered in the normal direction due to the centrifugal force due to the rotation of the trimming grindstone 108 .

The coolant for the dressing grindstone 203 for dressing and the nozzle for discharging to the dressing point are not installed. As a result, the dressing grindstone 203 shaved by the trimming grindstone 108 is applied in the form of free abrasive grains to the trimming grindstone 108, which is a metal bond of the diamond grindstone, so that the dressing grindstone in the state of free abrasive grains is not washed away. At the dressing point, the condition is close to that of a dry process, so residual stress is small, and the shape maintenance accuracy of the trimming grindstone 108 can be increased.

FIG. 6 is a partial cross-sectional view showing the details of the terrace processing, showing the state of trimming the upper layer 30 on the bonded device side. 31 is an adhesive layer as an intermediate layer, 32 is a lower substrate, the intermediate layer 31 is formed of an oxide film or the like (insulating layer) and has relatively low bonding strength, and the upper layer 30 on the device side has relatively low material strength. Material.

The finished thickness on the upper layer 30 side is thin (Si thin film processing, GaAs film thin film), the lower substrate 32 is a P phase, the intermediate layer 31 is an insulating layer, and the terrace width is set to 3 to 5 mm. ing. If the wafer W is cut vertically and in the Z direction, the portions marked with circles in the figure are likely to be deformed.

FIG. 7 is a partial cross-sectional view showing processing of the end face of the wafer W, and the flat surface formed on the upper portion of the trimming grindstone 108 is used to process the outer periphery. It shows a case where the upper layer 30 on the side of the bonded device, the adhesive layer that is the intermediate layer 31, and the lower substrate 32 are removed at the same time. The protrusion amount of the wafer W with respect to the suction table 10 is about 1 mm when the end face is flattened, and about 3 mm when beveled.

FIG. 8 is a plan view showing the correction of the bonding error, and is an example in which the outer peripheral portion is ground so that the upper and lower substrates have the same diameter as indicated by the dashed line. This is a process to process the ovalized and distorted outer peripheral portion due to the error of lamination to make the diameter uniform and finish it into a perfect circle.

FIG. 9 is a partial cross-sectional view showing the processing of the outer circumference of the wafer with a film layer. In addition to the surface of the wafer, film-forming components may adhere to the outer periphery of the film-forming portion, and it is necessary to remove the film-forming components from the outer peripheral portion. In other words, there is a risk that peeling from the edge part, cracks, and damage to the surface layer and the film layer may occur during wafer outer periphery transportation, positioning, and storage in the wafer storage cassette in the post-process. Processing up to is required.

As described above, even during initial dressing of the trimming grindstone 108, grinding of the wafer W, and truing of the trimming grindstone 108, elastic deformation of the grindstone due to pressing of the dressing grindstone 203 is prevented, and the shape of the trimming grindstone 108 is maintained. A so-called spark-out state, which does not collapse, enables low-damage processing.

Therefore, even if one of the upper layer 30 and the lower substrate 32 has a large grinding resistance and is made of a highly brittle material that easily loses its shape and the bonding is easily peeled off, the upper layer 30 and the lower substrate on the side of the bonded device can be used. 32 can be removed at the same time. In particular, by stacking grindstones having master grooves on the rotating shaft of the dresser, it is possible to transfer the shape of the master grooves and make corrections to the target shape of the grindstone, so that the processing accuracy can always be improved.

W wafer (workpiece), 10 suction table, 24 grindstone, 26 taper part, 27 flat part, 30 upper layer, 31 intermediate layer, 32 lower base, 50 wafer chamfering device, 50A wafer feeding unit, 50B grinding unit, 50C dress Device, 51 base plate, 52 Y-axis guide rail, 54 Y-axis linear guide, 56 Y-axis table, 58 nut member, 60 Y-axis ball screw, 62 bearing member, 64 Y-axis motor, 66 X-axis guide rail, 68 X-axis linear Guide, 70 X-axis table, 72 Nut member, 74 X-axis ball screw, 80 Z-axis base, 82 Z-axis guide rail, 84 Z-axis linear guide, 86 Z-axis table, 88 Nut member, 90 Z-axis ball screw, 92 Bearing member , 94 Z-axis motor, 96 θ-axis motor, 98 θ-axis shaft, 102 stand, 104 outer peripheral motor, 106 spindle, 108 trimming wheel, 121 nozzle,
200 dressing unit, 201 dressing guide, 202 dressing arm, 203 dressing grindstone, 204 master grindstone, 205 ball screw mechanism, 206 dressing motor

Claims (6)

In a wafer chamfering device that grinds the outer periphery of a wafer,
a wafer feeding unit for placing the wafer thereon and moving and rotating it in XYZ directions;
a trimming grindstone that rotates to process the outer periphery of the wafer;
a dressing grindstone rotating around an axis parallel to the rotation axis of the trimming grindstone;
, wherein the dressing grindstone is arranged on the rotation circumference of the trimming grindstone so that dressing can be performed by the dressing grindstone while the outer peripheral portion of the wafer is processed by the trimming grindstone. 2. A wafer chamfering apparatus according to claim 1, wherein said trimming grindstone and said wafer rotate in the same direction. 3. A wafer chamfering apparatus according to claim 1, wherein said trimming grindstone is a metal bond. A wafer chamfering method for grinding the outer peripheral portion of a wafer by a wafer feed unit that moves and rotates a wafer on which it is placed in XYZ directions, and a trimming grindstone that rotates and processes the outer peripheral portion of the wafer,
A dressing grindstone that rotates about an axis parallel to the rotation axis of the trimming grindstone is arranged on the rotation circumference of the trimming grindstone, and dressing is performed by the dressing grindstone while the outer peripheral portion of the wafer is processed by the trimming grindstone. Wafer chamfering method characterized by: 5. A wafer chamfering method according to claim 4, wherein said trimming grindstone and said wafer rotate in the same direction. 6. The wafer chamfering method according to claim 4, wherein said trimming grindstone is metal bond.

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