JP2024111456A - Wafer grinding method - Google Patents

Abstract

[Problem] To provide a wafer grinding method capable of solving the problem of dimples on the grinding surface of the wafer or cracks in the wafer caused by foreign matter adhering to the holding surface of the wafer. [Solution] The method includes a cleaning step for cleaning the first surface, a holding step for holding the second surface, transporting the wafer to a chuck table, and suction-holding the first surface against the chuck table, and a grinding step for grinding the second surface of the wafer held by suction on the chuck table. [Selected Figure] Figure 1

Description

The present invention relates to a method for grinding a wafer having a first surface and a second surface.

The wafer, with multiple devices formed on its front surface along planned dividing lines, has its back surface ground by a grinding machine to form it to the desired thickness, and is then separated into individual device chips by a dicing machine for use in electronic devices such as mobile phones and personal computers.

The grinding device is configured to include a chuck table that holds the wafer, and grinding means equipped with a rotatable grinding wheel that grinds the back surface of the wafer held on the chuck table, and can grind the wafer to the desired thickness. (See, for example, Patent Document 1.)

Grinding devices are also used to grind the surface of bare wafers produced by slicing ingots, and the wafers are ground to the desired precision (see, for example, Patent Document 2).

JP 2006-021264 A JP 2017-204606 A

However, if foreign matter adheres to the holding surface of the wafer held on the chuck table during grinding, the grinding surface corresponding to the location where the foreign matter adheres may be excessively ground, resulting in the formation of dimples (depressions) or cracks.

The present invention has been made in consideration of the above facts, and its main technical objective is to provide a wafer grinding method that can eliminate the problem of foreign matter adhering to the wafer holding surface, causing dimples on the grinding surface of the wafer, or cracks in the wafer.

In order to solve the above-mentioned main technical problem, the present invention provides a method for grinding a wafer having a first surface and a second surface, comprising a cleaning step for cleaning the first surface, a holding step for holding the second surface and transporting it to a chuck table and holding the first surface against the chuck table by suction, and a grinding step for grinding the second surface of the wafer held by suction on the chuck table.

A protective tape may be provided on the first surface, and the protective tape may be cleaned in the cleaning process. The first surface may also have a device area in which a plurality of devices are partitioned by planned division lines.

The method for grinding a wafer of the present invention is a method for grinding a wafer having a first surface and a second surface, and includes a cleaning step for cleaning the first surface, a holding step for holding the second surface and transporting it to a chuck table and suction-holding the first surface against the chuck table, and a grinding step for grinding the second surface of the wafer suction-held on the chuck table. Therefore, even if foreign matter is attached to the first surface side of the wafer held on the chuck table, the first surface is cleaned and the foreign matter is removed before the wafer is held on the chuck table, eliminating the problem of dimples on the grinding surface of the wafer or cracks in the wafer.

1 is an overall perspective view of a grinding device suitable for carrying out the present invention; 1 is a perspective view showing a mode of attaching a protective tape to a wafer processed by the present invention. FIG. FIG. 2 is a perspective view showing a mode in which a wafer is transported to a cleaning means for cleaning a first surface. FIG. 2 is a perspective view illustrating an embodiment of a cleaning step for cleaning a first surface. 11 is a perspective view showing a mode in which a wafer whose first surface has been cleaned is transported to a temporary placement table. FIG. FIG. 2 is a perspective view showing an embodiment of a grinding step for grinding a second surface of a wafer.

The wafer grinding method according to the present invention will be described in detail below with reference to the attached drawings.

Figure 1 shows a grinding device 1 suitable for carrying out the wafer grinding method according to the present invention. The grinding device 1 is equipped with a roughly rectangular parallelepiped device housing 2. In Figure 1, a support wall 21 is erected on the rear end side of the device housing 2. Two pairs of guide rails 22, 22 and 23, 23 extending in the vertical direction (Z-axis direction) are provided on the inner surface of this support wall 21. A rough grinding unit 3 as a rough grinding means is attached to one of the guide rails 22, 22 so as to be movable in the vertical direction, and a finish grinding unit 4 as a finish grinding means is attached to the other guide rails 23, 23 so as to be movable in the vertical direction.

The rough grinding unit 3 includes a unit housing 31, a wheel mount 33 disposed at the lower end of a rotating shaft 32 supported rotatably on the unit housing 31, a rough grinding wheel 34 attached to the wheel mount 33 and having a plurality of grinding wheels 35 arranged in a ring shape on its underside, an electric motor 36 attached to the upper end of the unit housing 31 for rotating the wheel mount 33 in the direction indicated by the arrow R1, and a movable base 38 supporting the unit housing 31 via a support member 37.

The moving base 38 is provided with a guided groove that slidably fits into the guide rails 22, 22 provided on the support wall 21, and the rough grinding unit 3 is supported so as to be movable in the vertical direction. The illustrated grinding device 1 is provided with a grinding feed mechanism 39 arranged as a lifting means for raising and lowering the moving base 38 of the rough grinding unit 3 along the guide rails 22, 22. The grinding feed mechanism 39 is provided with a male screw rod 391 that is arranged in the vertical direction parallel to the guide rails 22, 22 on the support wall 21 and rotatably supported, a pulse motor 392 for rotating the male screw rod 391, and a female screw block (not shown) that is attached to the moving base 38 and screws into the male screw rod 391. The male screw rod 391 is driven forward and reverse by the pulse motor 392 to move the rough grinding unit 3 in the vertical direction.

The finish grinding unit 4 is constructed in a manner similar to the rough grinding unit 3, and includes a unit housing 41, a wheel mount 43 disposed at the lower end of a rotating shaft 42 supported rotatably on the unit housing 41, a finish grinding wheel 44 attached to the wheel mount 43 and having a number of grinding stones 45 arranged in a ring shape on its underside, an electric motor 46 attached to the upper end of the unit housing 41 for rotating the wheel mount 43 in the direction indicated by the arrow R2, and a movable base 48 supporting the unit housing 41 via a support member 47.

The movable base 48 is provided with a guided groove that slidably fits into the guide rails 23, 23 provided on the support wall 21, and the finish grinding unit 4 is supported so as to be movable in the vertical direction. The grinding device 1 in the illustrated embodiment is provided with a grinding feed mechanism 49 arranged as a lifting means for raising and lowering the movable base 48 of the finish grinding unit 4 along the guide rails 23, 23. The grinding feed mechanism 49 is provided with a male screw rod 491 that is arranged in the vertical direction parallel to the guide rails 23, 23 on the support wall 21 and rotatably supported, a pulse motor 492 for rotating the male screw rod 491, and a female screw block (not shown) that is attached to the movable base 48 and screws into the male screw rod 491. The male screw rod 491 is driven forward and reverse by the pulse motor 492 to move the finish grinding unit 4 in the vertical direction.

A grinding water supply means (not shown) is connected to the ends 32a, 42a of the rotating shaft 32 and the rotating shaft 42, which are rotated by the electric motor 36 and the electric motor 46, for supplying pure water L as grinding water to the grinding wheels 35, 45 and the workpiece held on the chuck table 6, which will be described later.

The grinding device 1 is provided with a turntable 5 arranged in front of the support wall 21 so as to be approximately flush with the upper surface of the device housing 2. The turntable 5 is formed in a relatively large diameter disk shape, and is rotated appropriately in the direction indicated by the arrow R3 by a rotation drive mechanism (not shown) in the drain pan 20 on the upper surface of the device housing 2. The turntable 5 is provided with three chuck tables 6 arranged as holding means for holding the workpiece at an angle of 120 degrees. Each chuck table 6 is equipped with a rotation drive means described later and is configured to be rotatable in the direction indicated by the arrow R4. The chuck table 6 is provided with a suction chuck 62 formed in a disk shape from a porous material having air permeability and forming the holding surface of the chuck table 6, and a frame body 61 surrounding the suction chuck 62.

The three chuck tables 6 arranged on the turntable 5 are moved in sequence from the workpiece loading/unloading area A to the rough grinding area B to the finish grinding area C to the workpiece loading/unloading area A by rotating the turntable 5 in the direction indicated by the arrow R3. A cleaning water supply nozzle 15 is arranged near the workpiece loading/unloading area A in the drain pan 20, and sprays pure water L toward the chuck table 6 positioned in the workpiece loading/unloading area A to clean the ground wafer W held on the chuck table 6 and the upper surface of the suction chuck 62.

The illustrated grinding device 1 includes a first cassette 7 arranged on one side of the workpiece loading/unloading area A and housing multiple wafers W before grinding, a second cassette 8 arranged on the other side of the workpiece loading/unloading area A and housing multiple wafers W after grinding, a temporary placement table 9 arranged between the first cassette 7 and the workpiece loading/unloading area A for temporarily placing the workpiece by suction, a cleaning means 11 arranged between the workpiece loading/unloading area A and the second cassette 8, and a cleaning device 11 for removing the wafers W from the first cassette 7 and cleaning the wafers W. The apparatus includes a first transport means 12 having an adsorption part 12a that transports the wafer W cleaned in the cleaning means 11 to the temporary placement table 9 and into the second cassette 8, a second transport means 13 having an adsorption part 13a that transports the wafer W that has been centered on the temporary placement table 9 to the chuck table 6 positioned in the workpiece loading/unloading area A, and a third transport means 14 having an adsorption part 14a that transports the wafer W on the chuck table 6 positioned in the workpiece loading/unloading area A to the cleaning means 11. The second transport means 13 is equipped with an arm member and can rotate in the direction indicated by the arrow R5, and the third transport means 14 is equipped with an arm member and can rotate in the direction indicated by the arrow R6.

Although not shown in the figure, by providing a single transport means capable of transporting the wafer W to the chuck table 6 positioned in the workpiece loading/unloading area A, the temporary placement table 9, and the spinner table 11a of the cleaning means 11, it is possible to use a single transport means both as the second transport means 13 and the third transport means 14.

At the front side of the device housing 2 where the workpiece loading/unloading means 12 is arranged, there is disposed a control means 100 including an operation panel for instructing the grinding operation and specifying the processing conditions. The control means 100 comprises a central processing unit (CPU) which performs calculations according to a control program, a read-only memory (ROM) which stores the control program etc., a readable/writable random access memory (RAM) which serves as a storage means for storing the calculation results etc., an input interface and an output interface (all of which are not shown). The control means 100 thus configured stores a control program for carrying out the wafer grinding method (described in detail later) constructed based on the present invention, and controls and executes each operating part of the grinding device 1 described above.

The illustrated grinding device 1 has a configuration generally as described above, and the wafer grinding method of this embodiment will be explained with reference to Figures 2 to 6 in addition to Figure 1.

Figure 2 shows a wafer W having a device area on its front surface Wa, where multiple devices D are partitioned by planned division lines, as the workpiece to be ground by the illustrated grinding apparatus 1. A protective tape T is attached to the front surface Wa of the wafer W to protect the device area on the front surface Wa when the back surface Wb of the wafer W is ground. In this embodiment, the protective tape T forms the first surface, and the back surface Wb of the wafer W is the second surface.

When grinding the wafer W by the grinding device 1, the first cassette 7 containing a plurality of unprocessed wafers W is set in the grinding device 1, and the turntable 5 is operated to position the chuck table 6 without the wafer W held thereon in the workpiece loading/unloading area A. When the chuck table 6 holding the wafer W after the finish grinding process is positioned in the workpiece loading/unloading area A, the third transport means 14 is operated to transport the wafer W from the chuck table 6 to the cleaning means 11, so that the wafer W is not held on the chuck table 6 positioned in the workpiece loading/unloading area A. Then, pure water L is sprayed from inside the suction chuck 62 onto the holding surface of the wafer W, and pure water is sprayed from the cleaning water supply nozzle 15 onto the suction chuck 62 to make the chuck table 6 clean.

Next, as shown in FIG. 3, the first transport means 12 is operated to suck and carry out the back surface Wb of the unprocessed wafer W contained in the first cassette 7 using the suction portion 12a of the first transport means 12, and the wafer W is placed on the above-mentioned spinner table 11a of the cleaning means 11 with the first surface, i.e., the protective tape T side, facing upward. Then, the suction means (not shown) is operated to suck and hold the wafer W on the spinner table 11a.

After the wafer W is sucked and held on the spinner table 11a of the cleaning means 11, the entire cleaning means 11 is lowered and accommodated inside the housing 2. Next, as shown in FIG. 4, the wafer W sucked and held on the spinner table 11a of the cleaning means 11 is rotated at high speed in the direction indicated by the arrow R7 by a rotary drive means (not shown), and the cleaning water supply nozzle 11b is positioned above the wafer W. Next, the cleaning water supply nozzle 11b is oscillated in the direction indicated by the arrow R8 to spray pure water L as cleaning water for a predetermined time, and then the wafer W is rotated at high speed for a predetermined time to dry the upper surface of the protective tape T. This completes the cleaning process for cleaning the upper surface of the protective tape T that constitutes the first surface. As a result, even if foreign matter is attached to the protective tape T side when the wafer W is carried into the grinding device 1, the foreign matter is removed in this cleaning process.

As described above, when the cleaning process is completed, the second surface of the wafer W, i.e., the back surface Wb, which is the grinding surface, is adsorbed by the suction portion 12a of the first transport means 12 in the same manner as when the wafer W was held when it was transported to the cleaning means 11, and the wafer W is transported from the cleaning means 11. The wafer W transported from the cleaning means 11 by the first transport means 12 is transported to the temporary placement table 9 as shown in FIG. 5. While being transported from the cleaning means 11 to the temporary placement table 9, the suction portion 12a of the first transport means 12 is inverted so that the first surface, the protective tape T side, faces downward and the second surface, the back surface Wb, faces upward. The wafer W thus inverted is placed on the temporary placement table 9 as it is, and centering is performed on the temporary placement table 9.

After centering is performed on the temporary placement table 9 and the center position is corrected, the wafer W is held by the suction portion 13a of the second transport means 13 on its second surface, the back surface Wb, and transported to the chuck table 6 positioned in the workpiece loading/unloading area A. The second transport means 13 places the wafer W on the chuck table 6 with the protective tape T side facing the chuck table 6, and operates the suction means (not shown) to generate negative pressure in the suction chuck 62 of the chuck table 6, thereby suction-holding the wafer W. This completes the holding process.

Once the holding process is completed as described above, the turntable 5 is rotated in the direction indicated by the arrow R3 in FIG. 1, and the chuck table 6, which holds the unprocessed wafer W by suction, is moved from the workpiece loading/unloading area A toward the rough grinding area B.

Once the chuck table 6 is positioned in the rough grinding area B, the rough grinding process described below is carried out. More specifically, as shown in FIG. 6, the wafer W held on the chuck table 6 is positioned at a position where the grinding wheel 35 arranged in an annular shape on the lower surface of the rough grinding wheel 34 passes over the entire back surface Wb of the wafer W. Next, the chuck table 6 is rotated in the direction indicated by the arrow R4 in FIG. 6 at, for example, 300 rpm, and at the same time, the above-mentioned rough grinding unit 3 is operated to rotate the rough grinding wheel 34 in the direction indicated by the arrow R1 in the figure at, for example, 6000 rpm. Then, the above-mentioned grinding feed mechanism 39 is operated to lower the rough grinding unit 3 in the direction indicated by the arrow R9 in FIG. 6, and the grinding wheel 35 is brought into contact with the back surface Wb of the wafer W from above, and is ground and fed at a grinding feed rate of, for example, 1.0 μm/sec. At this time, a grinding water supply means (not shown) is operated to supply grinding water from the underside of the rough grinding wheel 34 toward the grinding stone 35 and the back surface Wb of the wafer W. This grinding process is carried out while detecting the thickness of the wafer W with a thickness detection means (not shown), and the grinding process is carried out until the desired thickness is reached. When the wafer W has reached the desired thickness, the grinding process of roughly grinding the back surface Wb (second surface) of the wafer W is completed.

When carrying out the above-mentioned grinding process, if a wafer W that has been subjected to rough grinding by the rough grinding unit 3 is positioned in the adjacent finish grinding processing area C, the finish grinding unit 4 is operated at the same time as rough grinding is carried out in the rough grinding processing area B, and the finish grinding wheel 44 is brought into contact with the wafer W to carry out the grinding process which is the finish grinding.

As described above, the wafer W that has been subjected to rough grinding in the rough grinding area B and finish grinding in the finish processing area C is positioned in the workpiece loading/unloading area A by the rotation of the turntable 5, and is transported to the cleaning means 11 by the third transport means 14. The wafer W transported to the cleaning means 11 is cleaned and dried in the cleaning means 11, and is transported and stored in the second cassette 7 by the first transport means 12.

According to the above-described embodiment, even if foreign matter is attached to the protective tape T side (first surface) of the wafer W held on the chuck table 6 when the wafer W is loaded into the grinding device 1, the first surface is cleaned immediately before the wafer W is held on the chuck table 6, and the foreign matter is removed, thereby eliminating the problem of dimples on the grinding surface of the wafer or cracks in the wafer.

The present invention is not limited to the above-described embodiment. In the above-described embodiment, a turntable 5 is provided with three chuck tables 6, a rough grinding unit 3, and a finish grinding unit 4, but the present invention is not limited to this, and can also be implemented in a grinding device that has only one chuck table and performs grinding to a specified roughness.

In the above embodiment, the protective tape T is attached to the front surface Wa of the wafer W, the surface on the protective tape T side is the first surface, and the back surface Wb to be ground is the second surface, but the present invention is not limited to this. For example, when grinding the surface of a so-called bare wafer generated by slicing an ingot, no devices are formed on either the front surface or the back surface, and the grinding process is performed without attaching the protective tape T described above. More specifically, when grinding the front surface (first surface) and back surface (second surface) of a bare wafer generated from an ingot, first, a rigid plate is attached by applying wax or the like to the second surface, and the side on which the plate is held is held by a chuck table, and the first surface is ground to a predetermined roughness. Once the first surface has been ground, the plate is removed from the second surface, followed by a cleaning step of cleaning the first surface according to the present invention, a holding step of holding the second surface and transporting it to a chuck table, bringing the first surface facing the chuck table and holding it by suction, and a grinding step of grinding the second surface of the wafer held by suction on the chuck table. By grinding the wafer in this manner, foreign matter is appropriately removed from the first surface before the second surface is ground, eliminating the problem of dimples on the ground surface of the wafer and cracks in the wafer.

1: Grinding device 2: Device housing 20: Drain pan 21: Support wall 22, 23: Guide rail 3: Rough grinding unit 31: Unit housing 32: Rotating shaft 33: Wheel mount 34: Rough grinding wheel 35: Grinding stone 36: Electric motor 37: Support member 38: Mobile base 39: Grinding feed mechanism 4: Finish grinding unit 41: Unit housing 42: Rotating shaft 43: Wheel mount 44: Finish grinding wheel 45: Grinding stone 46: Electric motor 47: Support member 48: Mobile base 49: Grinding feed mechanism 5: Turntable 6: Chuck table 61: Frame 62: suction chuck 7: first cassette 8: second cassette 9: temporary placement table 11: cleaning means 12: first transport means 12a: suction unit 13: second transport means 13a: suction unit 14: third transport means 14a: suction unit 15: cleaning water supply nozzle D: device W: wafer Wa: front surface Wb: back surface T: protective tape

Claims (3)

1. A method for grinding a wafer having a first surface and a second surface, comprising:
a cleaning step of cleaning the first surface;
a holding step of holding the second surface, transporting the workpiece to a chuck table, and holding the first surface by suction so as to face the chuck table;
a grinding step of grinding a second surface of the wafer held by suction on the chuck table;
A wafer grinding method comprising the steps of: A protective tape is disposed on the first surface,
2. The method for grinding a wafer according to claim 1, wherein said protective tape is washed in said cleaning step. The grinding method according to claim 2, wherein the first surface has a device area in which a plurality of devices are partitioned by planned division lines.

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