JP7025249B2 - Grinding method for workpieces. - Google Patents

Description

The present invention relates to a method for processing a workpiece.

In the semiconductor device manufacturing process, a plurality of areas are divided by scheduled division lines called streets arranged in a grid pattern on the surface of a work piece having a substantially disk shape, and ICs, LSIs, etc. are used in these divided areas. A circuit (functional element) is formed. Then, by cutting the workpiece along the scheduled division line, the region where the circuit is formed is divided to manufacture individual semiconductor chips.

The workpiece has a device forming region in which a plurality of functional elements (devices) are formed, and a device non-forming region surrounding the device forming region, and a circuit pattern is formed in the device forming region. .. Therefore, the height position does not match the top of the device forming region and the top of the device non-forming region, and the difference in thickness between the device forming region and the device non-forming region on the surface of the workpiece. Exists.

Further, in recent years, a mounting technique called flip-chip bonding has been put into practical use in which a plurality of metal protrusions called bumps are formed on the surface of a device and these bumps are directly bonded to the electrodes formed on the wiring board. .. Since the bumps are formed only in the device forming region and not in the device non-forming region, there is also a difference in thickness between the device forming region and the device non-forming region.

In this way, since the device forming region is formed thicker than the device non-forming region, a protective member such as a protective tape is attached to the front surface during backside grinding, and the protective member side is sucked and held for backside grinding. If this is done, there is a problem that the device non-formed region is formed thicker than the device formed region. Therefore, before grinding the back surface, the protective member attached to the surface of the workpiece is cut with a tool tool, and the surface of the protective member attached to the device forming region and the protective member are not the device. A method of flattening a portion attached to a forming region has been put into practical use (see, for example, Patent Document 1).

Japanese Patent No. 5877663

However, when the surface of the protective member is flattened, the thickness of the protective member differs between the portion attached to the device forming region and the portion attached to the device non-forming region. When the side is held on the chuck table of the grinding device and a grinding load is applied by a grinding wheel to grind the back surface of the workpiece, the part attached to the device forming area and the part attached to the device non-forming area are attached. There is a problem that there is a difference in the sinking of the protective member between the two, and the thickness of the protective member varies accordingly, and the thickness accuracy of the workpiece after backside grinding deteriorates.

The present invention considers such a problem, and when grinding the back surface of a workpiece having different thicknesses in the device forming region and the device non-forming region, the thickness of the workpiece after backside grinding. The challenge is to reduce variability.

The present invention has a device forming region in which a plurality of devices are formed and a device non-forming region surrounding the device forming region on the surface, and the upper end is formed at a position higher than the upper end of the device non-forming region. A polishing method for grinding the back surface of a work piece having a portion in the device forming region, wherein a protective member having an adhesive layer formed on one surface of a base material thicker than the height of the convex portion is formed on the convex portion. A process of attaching a protective member to be attached to the surface of the work piece so as to be buried in the adhesive layer, and a first step of holding the back surface of the work piece to which the protective member is attached on a chuck table of a polishing device. The holding step and the protective member grinding step of grinding the other surface of the base material of the portion of the protective member attached to the device forming region to form a recess in the base material that does not reach the adhesive layer. After performing the protective member grinding step, a second holding step of holding the workpiece on the chuck table of the grinding apparatus via the protective member, and a back surface side of the workpiece held on the chuck table. The back surface grinding process for thinning the workpiece to a predetermined thickness by grinding with the grinding means of the grinding device.
It is characterized in that, in the back surface grinding step, the subduction of the device non-forming region is suppressed and the thickness variation of the workpiece after back surface grinding is suppressed.
In this grinding method, an adhesive tape is mentioned as an example of the protective member.

In the present invention, only the portion of the base material of the protective member attached to the surface of the workpiece that is attached to the device forming region of the workpiece is ground, and the portion is attached to the device non-forming region. By forming it thinner than the formed portion, it is possible to reduce the difference in subduction of the workpiece due to the grinding load between the device forming region and the device non-forming region when grinding the back surface of the workpiece. Become. Therefore, it is possible to reduce the thickness variation of the workpiece.

It is a perspective view which shows the example of the workpiece. It is a perspective view which shows the state which the protective member was attached to the surface of a work piece. It is sectional drawing which shows the state which the protective member was attached to the surface of a work piece. It is sectional drawing which shows the example of the protective member grinding process schematically. It is a perspective view which shows the example of a grinding apparatus. It is sectional drawing which shows the example of the back surface grinding process schematically.

A plurality of devices D are formed on the surface Wa of the workpiece W shown in FIG. 1, and these devices D are partitioned by vertical and horizontal division schedule lines L. Here, the region in which the device D is formed is referred to as a device forming region W1, and the region in which the device D is not formed is referred to as a device non-forming region W2. The device forming region W1 is surrounded by the device non-forming region W2.

Each device D on the surface Wa is formed with a plurality of bumps B protruding upward. The upper end of the bump B is located higher than the upper end (upper surface) of the device non-forming region W2. That is, the device forming region W1 has a convex portion whose upper end protrudes from the device non-forming region W2.

(1) Protective member attaching process As shown in FIG. 2, a protective member T for protecting the device D is attached to the surface Wa of the workpiece W configured as described above. The protective member T is, for example, an adhesive tape and has flexibility. As shown in FIG. 3, the adhesive layer T1 in close contact with the surface Wa side of the workpiece W and the adhesive material on one surface T2a. The layer T1 is composed of a base material T2 spread over one surface. The adhesive layer T1 is formed to be thicker than the height of the bump B, and the bump B is pressed against the surface Wa of the workpiece W so that the adhesive layer T1 side of the protective member T faces the adhesive layer T1. It will be buried in. Further, the other surface T2b side of the base material T2 projects upward following the bump B. In FIG. 3, the bump B is shown larger than the actual one, and the number of bump B is shown smaller than the actual number. The same applies to the following figures.

In this step, it is preferable to cure the pressure-sensitive adhesive layer T1 by, for example, irradiating the pressure-sensitive adhesive layer T1 with ultraviolet rays after the protective member T is attached to the surface Wa of the workpiece W.

(2) First Holding Step Next, for example, in the rotatable chuck table 10 of the grinding apparatus 1 shown in FIG. 4, the back surface Wb side of the workpiece W is held. The grinding device 1 includes a grinding means 11. The grinding means 11 is mounted on a rotatable spindle 12 having an axial center in the Z-axis direction, a housing 13 that rotatably supports the spindle 12, a mount 14 connected to the lower end of the spindle 12, and a mount 14. It is equipped with a grinding wheel 15. The grinding wheel 15 is composed of a base 151 and a grinding wheel 152 fixed to the lower surface of the base 151. The diameter of the outermost circumference of the rotating track of the grinding wheel 152 is equal to or slightly longer than the radius of the device forming region W1 shown in FIG. 1 of the workpiece W.

(3) Protective member grinding step Next, the chuck table 10 of the grinding device 1 shown in FIG. 4 is rotated in the direction of arrow A1, and the spindle 12 is rotated in the direction of arrow A2, which is the same direction as the direction of arrow A1. Then, in a state where the diameter of the rotation trajectory of the grinding wheel 152 coincides with the radius portion of the workpiece W, the grinding means 11 is lowered to be attached to the device forming region W1 of the protective member T. The other surface T2b of the substrate T2 of the portion is ground. As a result, the recess T3 is formed on the other surface T2b side of the base material T2. Grinding to form the recess T3 in the substrate T2 is completed before the pressure-sensitive adhesive layer T1 is exposed upward, that is, before the bottom surface of the recess T3 reaches the pressure-sensitive adhesive layer T1.

The depth of the recess T3 is adjusted according to the height of the bump B and the material of the base material T2 of the protective member T. For example, when the height of the bump B is 30 μm and the base material T2 is PET (polyethylene terephthalate), the depth of the recess T3 is 11 μm.

The position where the recess T3 is formed does not have to completely coincide with the device forming region W1, and the recess T3 may be formed at least in the region where the bump B is formed.

(4) Second Holding Step Next, for example, in the chuck table 30 of the grinding apparatus 20 shown in FIG. 5, the workpiece W is held via the protective member T after grinding. The grinding device 20 includes a plurality of chuck tables 30.

A load cassette 211 and an unload cassette 212 are mounted in the cassette mounting region 21 at the front portion of the grinding device 20 in the Y direction. The load cassette 211 and the unload cassette 212 are provided with a plurality of slots, the load cassette 211 accommodates a plurality of workpieces before grinding, and the unload cassette 212 accommodates a workpiece after grinding. To.

In the vicinity of the load cassette 211 and the unload cassette 212, a loading / unloading robot 22 which is a transport mechanism for carrying out the workpiece from the load cassette 211 and loading the workpiece into the unload cassette 212 is arranged. There is. The loading / unloading robot 22 is composed of an arm portion 221 and a holding portion 222 provided at the tip of the arm portion 221.

In the movable range of the holding portion 222, a centering means 23 on which the workpiece carried out from the load cassette 211 is placed and the center of the workpiece is aligned at a fixed position is arranged. The centering means 23 includes a mounting table 231 on which the workpiece is mounted, and a plurality of alignment members 232.

A cleaning means 24 for cleaning the workpiece after grinding is provided in the movable range of the holding portion 222.

In the vicinity of the centering means 23, a first transport means 25, which is a transport mechanism for transporting the workpiece before grinding from the centering means 23 to the chuck table 30, is disposed. The first transport means 25 includes an arm portion 251 that can be swiveled and raised and lowered, and a suction portion 252 arranged at the tip of the arm portion 251.

In the vicinity of the cleaning means 24, a second transport means 26, which is a transport mechanism for transporting the work piece after grinding to the cleaning means 24, is arranged. The second transport means 26 includes an arm portion 261 that can be swiveled and raised and lowered, and a suction portion 262 disposed at the tip of the arm portion 261.

The plurality of chuck tables 30 are supported by the turntable 27 so as to revolve and rotate. Further, above the position where the chuck table 30 can be located due to the revolution of the turntable 27, the rough grinding means 31a and the finish grinding means 31b constituting the grinding means 31 are arranged. Around the turntable 27, thickness measuring means 28 for measuring the thickness of the workpiece held on the chuck table 30 are provided at two places corresponding to the rough grinding means 31a and the finish grinding means 31b. ing.

Since the rough grinding means 31a and the finish grinding means 31b are configured in the same manner except for the type of the grinding wheel, the portions to be similarly configured will be described with a common reference numeral.
As shown in FIG. 6, the rough grinding means 31a and the finish grinding means 31b include a spindle 315 having an axis in the Z direction, a housing 316 that rotatably supports the spindle 315, and a mount connected to the lower end of the spindle 315. It includes a 317 and a grinding wheel 311 mounted on the mount 317. Further, as shown in FIG. 5, the rough grinding means 31a and the finish grinding means 31b include a motor 312 for rotating the spindle 315. The grinding wheel 311 constituting the rough grinding means 31a includes a base 313 and a rough grinding wheel 314a which is a plurality of segmented grindstones fixed to the lower surface of the base 313 in an annular shape. On the other hand, the grinding wheel 311 constituting the finish grinding means 31b includes a base 313 and a finish grinding wheel 314b which is a plurality of segment grindstones fixed to the lower surface of the base 313 in an annular shape. The rough grinding wheel 314a and the finishing grinding wheel 314b are formed by shaping diamond abrasive grains with a binder.

As shown in FIG. 5, the rough grinding means 31a and the finish grinding means 31b are each fed in the Z direction by the grinding feed means 32. The grinding feed means 32 includes a ball screw 321 having an axial center in the Z direction, a pair of guide rails 322 arranged in parallel with the ball screw 321, a motor 323 connected to one end of the ball screw 321 to rotate the ball screw 321 and a ball screw. A nut to be screwed to the 321 is provided, and an elevating base 324 whose side portion is in sliding contact with the guide rail 322 is provided. The two elevating bases 324 support the rough grinding means 31a and the finish grinding means 31b, respectively, and when the motor 323 rotates the ball screw 321 the elevating base 324 is guided by the guide rail 322 to move up and down in the Z direction. Along with this, the rough grinding means 31a and the finish grinding means 31b are also configured to move up and down in the Z direction.

In the grinding apparatus 1 configured in this way, a plurality of workpieces W to be ground are accommodated in the load cassette 211. Here, as shown in FIG. 5, a protective member T having a recess T3 formed therein is attached to the surface Wa of the workpiece W.

First, the holding portion 222 of the loading / unloading robot 22 enters the load cassette 211 and adsorbs one workpiece W. Next, the holding portion 222 is retracted from the load cassette 211, and the workpiece WW is placed on the mounting table 231 of the centering means 23 with the protective member T side facing up. Then, all the alignment members 232 move toward the center of the mounting table 231 so that the center position of the workpiece W is aligned with a certain position.

Next, the suction portion 252 of the first transport means 25 sucks the back surface Wb of the workpiece W placed on the mounting table 231, and the arm portion 251 is swiveled to the position closest to the first transport means 25. The workpiece W is conveyed above a certain chuck table 30. Then, the suction portion 252 descends to release the suction, so that the protective member T side of the workpiece W is held.

(5) Backside grinding step Next, the rotation of the turntable 27 causes the workpiece W held by the chuck table 30 to move below the rough grinding means 31a. Then, as shown in FIG. 6, the chuck table 30 is rotated in the direction of arrow A3, the spindle 315 is rotated in the direction of arrow A4, and the grinding feed means 32 lowers the rough grinding means 31a to rotate the rough grinding wheel 314a. Rough grinding is performed by contacting the back surface Wb of the workpiece W with the back surface Wb. At this time, the diameter of the outermost circumference of the rotary track of the rough grinding wheel 314a is slightly longer than the radius of the workpiece W, so that the rough grinding wheel 314a always passes through the center of the back surface Wb of the workpiece W. That is, the grinding load by the coarse grinding wheel 314a is applied to both the device forming region W1 and the device non-forming region W2. Then, since the workpiece W rotates, the entire surface of the back surface Wb is roughly ground and thinned.

During the rough grinding of the workpiece W, the first gauge 281 of the thickness measuring means 28 shown in FIG. 5 comes into contact with the back surface of the workpiece W, and the second gauge 282 of the thickness measuring means 28 is the chuck table 30. Contact the top surface of the. Then, the thickness measuring means 28 obtains the total value of the thickness of the protective member T and the thickness of the workpiece W by the difference in the height positions of both gauges. When the total value of the thickness of the protective member T and the thickness of the workpiece W reaches a predetermined value, the grinding feed means 32 raises the rough grinding means 31a and ends the rough grinding.

During rough grinding, a grinding load is applied by the rough grinding wheel 314a to grind the entire back surface Wb of the workpiece W, so that the entire surface of the flexible protective member T sinks according to the grinding load. The workpiece W also sinks. However, the recess T3 is formed in the base material T2 of the protective member T, and the thickness of the portion attached to the device forming region W1 is thinner than the portion attached to the device non-forming region W2. Therefore, when a grinding load is applied, the amount of sinking of the portion of the protective member T that is attached to the device forming region W1 is smaller than the amount of sinking of the portion that is attached to the device non-forming region W2. Therefore, even though there is a difference in thickness between the device forming region W1 and the device non-forming region W2, the thickness of the protective member T during rough grinding can be made uniform, whereby the work piece can be processed. The amount of sinking of the object W can be made uniform, and the thickness accuracy of the workpiece W can be improved. That is, in the protective member grinding step, the depth of the recess T3 may be adjusted so that the thickness of the protective member T becomes uniform when a grinding load is applied in this step.

Next, as the turntable 27 rotates by a predetermined angle, the chuck table 30 holding the roughly ground workpiece W moves below the finish grinding means 31b. Then, while rotating the chuck table 30, the motor 312 rotates the grinding wheel 311 and the grinding feed means 32 lowers the finish grinding means 31b, so that the rotating finish grinding wheel 314b is brought into contact with the back surface of the workpiece W. Finish grinding. At this time, the diameter of the outermost circumference of the rotation trajectory of the finish grinding wheel 314b is slightly longer than the radius of the workpiece W, so that the finish grinding wheel 314ab always passes through the center of the back surface Wb of the workpiece W. That is, the grinding load by the finish grinding wheel 314b is applied to both the device forming region W1 and the device non-forming region W2. Then, since the workpiece W rotates, the entire surface of the back surface Wb is finish-ground.

During finish grinding, the total value of the thickness of the protective member T and the thickness of the workpiece W is obtained by the thickness measuring means 28 as in the case of rough grinding, and when the total value reaches a predetermined value, the grinding feed is performed. The means 32 raises the finish grinding means 31b and finishes the finish grinding.

During finish grinding, a grinding load is applied by the finish grinding wheel 314b to grind the entire back surface Wb of the workpiece W, so that the entire surface of the flexible protective member T sinks according to the grinding load. The workpiece W also sinks. However, the recess T3 is formed in the base material T2 of the protective member T, and the thickness of the portion attached to the device forming region W1 is thinner than the portion attached to the device non-forming region W2. Therefore, when a grinding load is applied, the amount of sinking of the portion of the protective member T that is attached to the device forming region W1 is smaller than the amount of sinking of the portion that is attached to the device non-forming region W2. Therefore, even though there is a difference in thickness between the device forming region W1 and the device non-forming region W2, the thickness of the protective member T during finish grinding can be made uniform, whereby the work piece can be processed. The amount of sinking of the object W can be made uniform, and the thickness accuracy of the workpiece W can be improved. That is, in the protective member grinding step, the depth of the recess T3 may be adjusted so that the thickness of the protective member T becomes uniform when a grinding load is applied in this step.

After the finish grinding is completed, the turntable 27 rotates by a predetermined angle, and the chuck table 30 holding the finish-ground workpiece W moves to the vicinity of the second transport means 26. Then, the suction portion 262 of the second transport means 26 sucks and holds the back surface Wb of the workpiece W and transports it to the cleaning means 24. Then, after the grinding debris and the like are removed by cleaning, the protective member T side is held by the holding portion 222 of the loading / unloading robot 22, and the holding portion 222 enters the unload cassette 212 to release the adsorption, thereby unloading. The workpiece W is accommodated in a state where the protective member T is still attached to a predetermined slot of the cassette 212. In this way, all the workpieces W housed in the load cassette 211 are subjected to the same grinding and cleaning, and are housed in the unload cassette 212.

In the above embodiment, the case where the back surface grinding is performed in two stages of rough grinding and finish grinding has been described, but the grinding may be performed in only one stage.

Further, even if the workpiece is not formed with bumps, for example, the circuit pattern formed in the device forming region W1 has a convex portion in which the circuit pattern or the like protrudes upward, and the upper end thereof is not formed with the device. Any work piece may be used as long as it protrudes from the upper surface of the region W2.

W: Work piece Wa: Surface W1: Device forming area D: Device L: Scheduled division line B: Bump W2: Device non-forming area T: Protective member T1: Adhesive material layer T2: Base material T2a: One surface T2b: The other surface T3: Concave 1: Grinding device 10: Chuck table 11: Grinding means 12: Spindle 13: Housing 14: Mount 15: Grinding wheel 151: Base 152: Grinding wheel 20: Grinding device 21: Cassette mounting area 211 : Load cassette 212: Unload cassette 22: Carry-in / out robot 221: Arm part 222: Holding part 23: Centering means 231: Mounting table 232: Alignment member 24: Cleaning means 25: First transport means 251: Arm part 252: Suction part 26: Second transport means 261: Arm part 262: Suction part 27: Turntable 28: Thickness measuring means 30: Chuck table 31a: Rough grinding means 31b: Finish grinding means 311: Grinding wheel 312: Motor 313 : Base 314a: Rough grinding wheel 314b: Finishing grinding wheel 315: Spindle 316: Housing 317: Mount 32: Grinding feed means 321: Ball screw 322: Guide rail 323: Motor 324: Lifting base

Claims (2)

The device has a device forming region on which a plurality of devices are formed and a device non-forming region surrounding the device forming region, and a convex portion formed at a position where the upper end is higher than the upper end of the device non-forming region. It is a grinding method that grinds the back surface of the workpiece in the forming area.
A protective member is attached to the surface of the workpiece so that the adhesive layer is formed thicker than the height of the convex portion on one surface of the base material so that the convex portion is buried in the adhesive layer. The landing process and
The first holding step of holding the back surface of the workpiece to which the protective member is attached on the chuck table of the grinding device, and
A protective member grinding step of grinding the other surface of the base material of the portion of the protective member attached to the device forming region to form a recess in the base material that does not reach the adhesive layer.
After performing the protective member grinding step, a second holding step of holding the workpiece on the chuck table of the grinding device via the protective member, and
A back surface grinding step of grinding the back surface side of the workpiece held on the chuck table by the grinding means of the grinding device to thin the workpiece to a predetermined thickness.
Equipped with
A method for grinding a workpiece, which comprises suppressing subduction of the device non-forming region in the back surface grinding step and suppressing variation in thickness of the workpiece after back surface grinding. The method for grinding a workpiece according to claim 1, wherein the protective member is an adhesive tape.

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