JP7555767B2 - Processing method of original wafer - Google Patents

Description

The present invention relates to a method for processing original wafers, which processes original wafers produced from ingots.

Wafer, in which multiple devices such as ICs and LSIs are formed on the top surface of a silicon substrate and partitioned along planned division lines, is then separated into individual device chips using a dicing machine or laser processing machine, and used in electrical devices such as mobile phones and personal computers.

Also, so-called original wafers, before devices are formed on the surface, are produced by slicing an ingot of silicon or the like to a thickness of about 1 mm using a cutting machine equipped with an inner diameter blade, a wire saw, etc. (see, for example, Patent Document 1). Both sides of the original wafer produced from the ingot are then ground, and the outer corners are then chamfered using a special jig, so that it is in a suitable state for forming devices on the top surface.

Japanese Patent Application Publication No. 08-155948

Conventional methods for processing original wafers require grinding before the surface is ready for device formation, and then multiple processes such as chamfering must be carried out using dedicated equipment and jigs, resulting in poor productivity.

The present invention has been made in consideration of the above facts, and its main technical objective is to provide a method for processing original wafers that can efficiently process original wafers.

In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for processing an original wafer produced from an ingot, comprising: an original wafer holding step of holding an original wafer on a rotatable chuck table having a holding surface for holding a workpiece; a first grinding step of bringing a grinding means having a rotatable grinding wheel with grinding stones arranged annularly facing the holding surface close to the chuck table, and rotating the grinding wheel so that the grinding stone passes through a rotation center of the original wafer held on the chuck table to grind one side of the original wafer; a first outer periphery positioning step of relatively moving the chuck table and the grinding means in a direction parallel to the holding surface to position the grinding wheel above an outer periphery corner of one side of the original wafer , and a first chamfering step of chamfering the outer periphery of one side of the original wafer with the grinding wheel after the first outer periphery positioning step is performed , in which the first chamfering step involves tilting the chuck table and the grinding means relative to one another to position the grinding wheel on the outer periphery of one side of the original wafer and bringing it close to the chuck table to grind it to form a chamfer on the one side.

The method also includes a second grinding step of holding the ground surface on the chuck table and rotating the grinding wheel so that the grinding wheel passes through the center of rotation of the original wafer held on the chuck table to grind the other surface of the original wafer; a second outer periphery positioning step of relatively moving the chuck table and the grinding means in a direction parallel to the holding surface to position the grinding wheel above an outer periphery corner of the other surface of the original wafer ; and a second chamfering step of chamfering the outer periphery of the other surface of the original wafer with the grinding wheel after performing the second outer periphery positioning step , and the second chamfering step can also be performed by tilting the chuck table and the grinding means relatively to position the grinding wheel on the outer periphery of the other surface of the original wafer and bringing it close to the chuck table to grind it to form a chamfer on the other surface.

The processing method of the present invention is a processing method of a primitive wafer for processing a primitive wafer generated from an ingot, and includes a primitive wafer holding step of holding the primitive wafer on a rotatable chuck table having a holding surface for holding a workpiece, a first grinding step of bringing a grinding means having a rotatable grinding wheel with grinding stones arranged in an annular shape facing the holding surface close to the chuck table, rotating the grinding wheel so that the grinding stone passes through the rotation center of the primitive wafer held on the chuck table, and grinding one side of the primitive wafer, and a second grinding step of moving the chuck table and the grinding means relatively in a direction parallel to the holding surface to grind the grinding stone on one side of the primitive wafer . The method includes a first outer periphery positioning step of positioning one side of the original wafer above an outer periphery corner, and a first chamfering step of chamfering the outer periphery of one side of the original wafer with a grinding wheel after carrying out the first outer periphery positioning step. In the first chamfering step, the chuck table and the grinding means are tilted relative to each other, the grinding wheel is positioned on the outer periphery of one side of the original wafer, and the grinding wheel is brought close to the chuck table to grind the one side to form a chamfered portion. Therefore, the first grinding step of grinding one side of the original wafer and the first chamfering step of chamfering the outer periphery of the one side can be carried out in succession without changing the processing device or tool, thereby improving productivity.

1 is an overall perspective view of a grinding device capable of carrying out the processing method of the present embodiment; FIG. 13 is a perspective view showing an embodiment of an original wafer holding step. FIG. 2 is a perspective view showing an embodiment of a first grinding step. FIG. 2A is a perspective view showing an embodiment of a first chamfering process step, and FIG. 2B is a schematic side view showing the process shown in FIG. FIG. 13 is a perspective view showing an embodiment of a second grinding step. FIG. 1A is a perspective view showing an embodiment of a second chamfering process step, and FIG. 1B is a schematic side view showing the process shown in FIG.

Below, an embodiment of a method for processing an original wafer based on the present invention will be described in detail with reference to the attached drawings.

Figure 1 shows an overall perspective view of a grinding device 1 suitable for carrying out the processing method of the original wafer of this embodiment. The grinding device 1 shown in Figure 1 comprises an approximately rectangular parallelepiped device housing 2, an upright wall 3 erected on the rear end side of the device housing 2, a grinding means 4 for grinding the workpiece, and a chuck table mechanism 6 for holding the workpiece.

The chuck table mechanism 6 includes a disk-shaped suction chuck 61a and a frame body 61b surrounding the suction chuck 61a, and a chuck table 61 configured to be rotatable by a rotary drive source (not shown), a rectangular cover plate 62 that protrudes the chuck table 61 upward and covers the periphery of the chuck table 61, a first bellows body 64a connected to the side of the cover plate 62 indicated by the arrow Y1 in the figure, and a second bellows body 64b connected to the side of the cover plate 62 indicated by the arrow Y2 in the figure. The suction chuck 61a is made of a porous material having air permeability and is connected to a suction source (not shown). By operating the suction source, negative pressure is supplied to the holding surface 63 of the suction chuck 61a, and the workpiece placed on the holding surface 63 can be suction-held. Note that the Y-axis direction shown in FIG. 1 is a direction perpendicular to the X-axis direction, and the holding surface 63 under normal conditions is a surface defined by the X-axis direction and the Y-axis direction shown in FIG. 1, and the plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

The cover plate 62 includes an upper plate portion 62a, a lower plate portion 62b, and a lift mechanism (not shown), and by operating the lift mechanism, as shown in the lower right side of the figure, the edge of the upper plate portion 62a on the Y2 side in the figure can be raised and separated from the lower plate portion 62b, and tilted toward the Y1 side in the figure. A third bellows body 64c is disposed between the upper plate portion 62a and the lower plate portion 62b, and prevents grinding water from entering the inside of the device housing 2 of the grinding device 1 when processing is performed by the grinding means 4.

The device housing 2 contains a moving means (not shown) for moving the chuck table mechanism 6 in the Y-axis direction. By operating the moving means, the chuck table mechanism 6 can be moved between a loading/unloading area at the front side of the figure (in the direction indicated by the arrow Y1) where an unmachined workpiece is placed on the chuck table 61, and a processing area at the back side of the figure (in the direction indicated by the arrow Y2) where the workpiece held on the chuck table 61 is subjected to grinding by the grinding means 4.

The grinding means 4 is mounted on a movable base 4a arranged on the front side of the upright wall 3, and the movable base 4a engages with a pair of guide rails 31, 31 arranged on the upright wall 3 of the device housing 2 on the rear side, and is mounted so as to be slidable in the Z-axis direction (up and down direction) relative to the guide rails 31, 31.

The grinding means 4 includes a spindle housing 42 supported by a support portion 4b formed integrally with the movable base 4a, a rotating spindle 43 rotatably held by the spindle housing 42, and an electric motor 41 arranged as a rotation drive means for the rotating spindle 43. The lower end of the rotating spindle 43 protrudes toward the lower end side of the spindle housing 42, and a wheel mount 44 is arranged at the lower end. A grinding wheel 45 is attached to the lower surface of the wheel mount 44, and a plurality of grinding stones 46 are arranged in a ring shape on the lower surface of the grinding wheel 45 so as to face the holding surface 63 of the chuck table 61 when the chuck table 61 is positioned in the processing area directly below the grinding wheel 45. Grinding water L supplied from a grinding water supply means (not shown) is introduced from the upper end 43a of the rotating spindle 43 and supplied to the processing area from the center of the lower end surface of the grinding wheel 45 through a passage in the rotating spindle 43.

The grinding device 1 shown in FIG. 1 is provided with a grinding feed means 7 that moves the grinding means 4 in the Z-axis direction (perpendicular to the holding surface 63 of the chuck table 61) along the pair of guide rails 31, 31. The grinding feed means 7 is provided with a male threaded rod 71 arranged on the front side of the upright wall 3 and extending in the vertical direction, and a pulse motor 72 as a drive source for rotating the male threaded rod 71. The male threaded rod 71 is rotatably supported at its upper and lower ends by the upright wall 3, and the output shaft of the pulse motor 72 is connected to the upper end of the male threaded rod 71. A screw connection part (not shown) is formed on the rear surface of the moving base 4a, and a female threaded hole extending in the vertical direction is formed in the connection part, and the male threaded rod 71 is screwed into the female threaded hole. The grinding feed means 7, which is made up of such a screw mechanism, can rotate the pulse motor 72 forward to lower the grinding means 4 together with the moving base 4a, and rotate the pulse motor 72 in the reverse direction to raise the grinding means 4 together with the moving base 4a.

The grinding device 1 is equipped with a control means (not shown), to which the grinding means 4, grinding feed means 7, the moving means (not shown), etc. are connected, and each means is precisely controlled based on an arbitrary control program.

The grinding device 1 shown in FIG. 1 has a configuration generally as described above, and the method for processing an original wafer according to this embodiment, which is carried out using the grinding device 1, is described below.

Figure 2 shows an original silicon (Si) wafer 10, which is the workpiece of this embodiment. The original wafer 10 is, for example, a circular plate-shaped wafer with a diameter of about 100 mm cut to a thickness of about 1 mm by slicing a cylindrical single crystal ingot (not shown), and is a wafer with no devices or the like formed on either the front or back surface.

When carrying out the processing method of the primitive wafer of this embodiment, the primitive wafer 10 is placed and held on the holding surface 63 of the chuck table 61 positioned in the loading/unloading area with one side 10a of the primitive wafer 10 facing upward and the other side 10b facing downward, as shown in FIG. 2 (primitive wafer holding process). At this time, the primitive wafer 10 is placed so that the center of the primitive wafer 10 coincides with the center of the chuck table 61, and is sucked and held on the holding surface 63 of the chuck table 61 by operating a suction source (not shown) to supply negative pressure to the holding surface 63. Note that after being cut from the ingot, the primitive wafer 10 of this embodiment is in a state in which neither the front nor back surface is processed, and there is no distinction between the front and back surfaces, but for convenience of explanation, the surface that is first processed will be referred to as "one side" and the opposite side will be referred to as "the other side".

After the above-mentioned original wafer holding step is performed, the moving means is operated to move the chuck table 61 to the processing area as shown in FIG. 3. Next, the grinding feed means 7 is operated to move the grinding means 4 close to the chuck table 61, and the electric motor 41 of the grinding means 4 is operated to rotate the grinding wheel 45 in the direction indicated by the arrow R1 at, for example, 6000 rpm, and rotate the chuck table 61 in the direction indicated by the arrow R2 at, for example, a rotational speed of 300 rpm. Furthermore, the grinding wheel 45 is positioned so that the grinding wheel 46 passes through the rotation center O of the original wafer 10 held on the chuck table 61, and the grinding feed means 7 is operated to move the grinding means 4 in the direction indicated by the arrow R3 at a descending speed of, for example, 1.0 μm/sec to abut against one side 10a of the original wafer 10, thereby grinding one side 10a of the original wafer 10 by a predetermined amount (first grinding step). When carrying out the first grinding process, it is preferable to carry out the process while detecting the amount of grinding using a thickness detection means (not shown).

After carrying out the first grinding step described above, the grinding feed means 7 is operated to raise the grinding means 4 once, and while the original wafer 10 is held by suction on the chuck table 61, the chuck table 61 and the grinding means 4 are moved relatively in a direction parallel to the holding surface 63 of the chuck table 61 (in this embodiment, the chuck table 61 is moved in the direction shown by the arrow Y1 in FIG. 1), and the grinding wheel 46 is positioned above the outer circumferential corner 10c of one surface 10a (first outer circumferential positioning step).

After the first outer periphery positioning step is performed, a first chamfering step is performed in which the grinding wheel 46 is used to chamfer the outer periphery corner 10c of one surface 10a of the original wafer 10. When performing the first chamfering step, as shown by the arrow R4 in FIG. 4(a), the lift mechanism (not shown) constituting the cover table 62 is operated to raise the arrow Y2 side of the upper plate portion 62a of the cover table 62 and tilt it toward the arrow Y1 side. Thereafter, while lowering the grinding wheel 46 in the direction shown by the arrow R3 so as to approach the chuck table 61, as shown in FIG. 4(b), the grinding wheel 46 is brought into contact with the outer periphery corner 10c of the original wafer 10 held on the chuck table 61, and the outer periphery corner 10c is ground. As a result, a chamfered portion 11 is formed at an inclination angle corresponding to the inclination of the chuck table 61 with respect to the outer periphery corner 10c of one surface 10a (first chamfering step).

The first chamfering process of this embodiment is carried out consecutively to the first grinding process, and the grinding wheel 45 of the grinding means 4 and the chuck table 61 are carried out while maintaining the rotation during the first grinding process. However, the present invention is not limited to this, and the rotation of the grinding wheel 45 and the chuck table 61 may be temporarily stopped when moving from the first grinding process to the first chamfering process. In addition, the chamfered portion 11 formed in this embodiment is formed with a tapered surface with a straight cross section as shown in FIG. 4(b), but it is also possible to form the chamfered portion 11 with a curved cross section by adjusting the lift mechanism that controls the inclination angle of the upper plate portion 62a of the cover table 62 when performing the first chamfering process, the grinding feed mechanism 7 of the grinding means 4, and the moving means that moves the chuck table 61 in the Y-axis direction.

According to the above-mentioned processing method for the original wafer, the first grinding process for grinding one side 10a of the original wafer 10 and the first chamfering process for chamfering the outer periphery of the one side 10a can be performed in a continuous process without changing the processing device or jig, thereby improving productivity.

According to the processing method for the original wafer of this embodiment, after carrying out the first grinding step and the first chamfering step described above, it is also possible to carry out the second grinding step and the second chamfering step described below.

After the first grinding step and the first chamfering step are performed, the lift mechanism is operated to return the inclination angle of the upper plate portion 62a of the cover table 62 to a state parallel to the horizontal plane defined by the X-axis direction and the Y-axis direction, the moving means of the chuck table 61 is operated to move the chuck table 61 to the loading/unloading area, and the suction source that supplies negative pressure to the chuck table 61 is stopped. Next, the original wafer 10 is removed from the chuck table 61 and turned over, and placed on the holding surface 63 of the chuck table 61 so that the other surface 10b of the original wafer 10 faces upward and one surface 10a faces downward, and the center of the chuck table 61 and the center of the original wafer 10 coincide with each other, and the suction source is operated to hold the original wafer 10 by suction to the chuck table 61 (except for the difference between the front and back, this is the same process as the process described with reference to FIG. 2).

Then, the moving means is operated to move the chuck table 61 to the processing area in the direction indicated by the arrow Y2 in FIG. 1, and the grinding feed means 7 is operated to bring the grinding means 4 close to the chuck table 61, and the grinding wheel 45 is positioned so that the grinding wheel 46 passes the center O of the original wafer 10 held on the chuck table 61 as shown in FIG. 5. Then, the electric motor 41 of the grinding means 4 is operated to rotate the grinding wheel 45 in the direction indicated by the arrow R1 at, for example, 6000 rpm, and the chuck table 61 is rotated in the direction indicated by the arrow R2 at, for example, a rotational speed of 300 rpm, and further, the grinding feed means 7 is operated to bring the grinding means 4 into contact with the other surface 10b of the original wafer 10 in the direction indicated by the arrow R3 at a descending speed of, for example, 1.0 μm/sec, to grind the other surface 10b of the original wafer 10 by a predetermined amount (second grinding process).

After the second grinding step described above has been performed, the grinding feed means 7 is operated to raise the grinding means 4 once, and while the original wafer 10 is being suction-held by the chuck table 61, the chuck table 61 and the grinding means 4 are moved relatively in a direction parallel to the holding surface 63 of the chuck table 61 (in this embodiment, the chuck table 61 is moved in the direction indicated by the arrow Y1 in FIG. 1), and the grinding wheel 46 is positioned above the outer circumferential corner 10d of the other surface 10b (second outer circumferential positioning step).

After the second outer periphery positioning step is performed, a second chamfering step is performed in which the outer periphery corner 10d of the other surface 10b of the original wafer 10 is chamfered with a grinding wheel 46. When performing the second chamfering step, as in the first chamfering step, as shown in FIG. 6(a), the lift mechanism (not shown) constituting the cover table 62 is operated to raise the arrow Y2 side of the upper plate portion 62a of the cover table 62 as shown by the arrow R4, and the chuck table 61 is tilted to the arrow Y1 side. Then, the grinding wheel 46 is lowered in the direction indicated by the arrow R3 so as to approach the chuck table 61, and is brought into contact with the outer circumferential corner 10d of the original wafer 10 held on the chuck table 61, grinding the outer circumferential corner 10d as shown in FIG. 6(b), forming a chamfered portion 12 at an inclination angle corresponding to the inclination of the chuck table 61 at the outer circumferential corner 10d of the other surface 10b (second chamfering process).

The second chamfering process of this embodiment is carried out consecutively to the second grinding process described above, and the grinding wheel 45 and the chuck table 61 of the grinding means 4 are carried out while maintaining their rotation during the second grinding process described above. However, the present invention is not limited to this, and the rotation of the grinding wheel 45 and the chuck table 61 may be temporarily stopped when moving from the second grinding process to the second chamfering process. In addition, the chamfered portion 12 formed in this embodiment is formed with a tapered surface whose cross section is linear, as shown in FIG. 6(b), but it is also possible to form it so that the cross section is curved, as explained in the section on the first chamfering process described above.

According to the above-mentioned processing method for the original wafer, the second grinding process for grinding the other surface 10b of the original wafer 10 and the second chamfering process for chamfering the outer periphery of the other surface 10b can be performed in consecutive steps without changing the processing device or jig, thereby improving productivity.

In the above embodiment, as a means for tilting the chuck table 61 and the grinding means 4 relative to each other, a lift mechanism for tilting the upper plate portion 62a of the cover table 62 is provided on the table mechanism 6 side, and the lift mechanism is operated to tilt the chuck table 61. However, the present invention is not limited to this. For example, it is also possible to provide the lift mechanism on the movable base 4a side of the grinding means 4 and change the angle of the movable base 4a to change the angle of the grinding wheel 45 relative to the chuck table 61, thereby tilting the chuck table 61 relative to the grinding means 4.

1: Grinding device 2: Device housing 3: Upright wall 31: Guide rail 4: Grinding means 4a: Moving base 4b: Support 41: Electric motor 42: Spindle housing 43: Rotating spindle 44: Wheel mount 45: Grinding wheel 46: Grinding wheel 6: Table mechanism 61: Chuck table 61a: Suction chuck 61b: Frame 62: Cover table 62a: Upper plate 62b: Lower plate 63: Holding surface 64a: First bellows portion 64b: Second bellows portion 64c: Third bellows portion 7: Grinding feed means 71: Male threaded rod 72: Pulse motor 10: Original wafer 10a: One surface 10b: Other surface 10c: Outer circumferential corner 10d: Outer circumferential corners 11, 12: Chamfered portions

Claims (2)

A method for processing an original wafer produced from an ingot, comprising the steps of:
an original wafer holding step of holding the original wafer on a rotatable chuck table having a holding surface for holding a workpiece;
a first grinding step in which a grinding means having a rotatable grinding wheel with grinding stones arranged annularly facing the holding surface is brought close to the chuck table, and the grinding wheel is rotated so that the grinding stones pass through a rotation center of the original wafer held on the chuck table, thereby grinding one surface of the original wafer;
a first outer periphery positioning step of relatively moving the chuck table and the grinding means in a direction parallel to the holding surface to position the grinding wheel above an outer periphery corner of one surface of the original wafer ;
a first chamfering process step of chamfering the outer periphery of one surface of the original wafer with the grinding wheel after the first outer periphery positioning process step is performed ,
The first chamfering process is a processing method for an original wafer in which the chuck table and the grinding means are tilted relative to one another, the grinding wheel is positioned on the outer periphery of one surface of the original wafer, and the grinding wheel is brought close to the chuck table to grind the original wafer and form a chamfered portion on the one surface. a second grinding step of holding the ground surface on the chuck table and rotating the grinding wheel so that the grinding wheel passes through a rotation center of the original wafer held on the chuck table to grind the other surface of the original wafer;
a second outer periphery positioning step of relatively moving the chuck table and the grinding means in a direction parallel to the holding surface to position the grinding wheel above an outer periphery corner of the other surface of the original wafer ;
a second chamfering process step of chamfering the outer periphery of the other surface of the original wafer with the grinding wheel after the second outer periphery positioning process step is performed ,
2. The method for processing an original wafer according to claim 1, wherein the second chamfering step comprises tilting the chuck table and the grinding means relative to one another, positioning the grinding wheel on the outer periphery of the other side of the original wafer, and bringing the grinding wheel close to the chuck table to grind the other side to form a chamfered portion.