JPH10286750A - Wafer grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grind a surface flat by absorbing the waviness of a wafer by a waviness absorber which is installed between a chuck table and the wafer. SOLUTION: A surface 10b is grinded by lowering a grinding means while rotating an abrasive grinder 29. On this occasion, a face at a side to be absorbed to a chuck table 30, of a waviness absorber 11, is flat, and is not deformed by the suction force from the chuck table 30. On the other hand, a face on which a wafer immediately after the slicing, is affixed, is kept in a condition that it absorbs the waviness of the wafer immediately after the slicing as it is. Accordingly by grinding the surface 10b of the wafer 10 immediately after the slicing by the abrasive grinder 29 under this condition, the surface 10b side can be flattened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method for removing undulations of a wafer cut from an ingot and flattening a front surface and a back surface, and more particularly, to a chuck table of a polishing apparatus for holding a wafer and a wafer. The present invention relates to a method of polishing a wafer in which polishing is performed with a wave absorber capable of absorbing the wave of the wafer therebetween.

[0002]

2. Description of the Related Art In conventional wafer making,
As shown in FIG. 3A, first, an ingot 40 made of silicon or the like is sliced to a thickness of about 2 to 3 mm by using an inner peripheral blade 41 or the like, so that FIGS. )
The wafer 42 immediately after slicing as shown in FIG.

[0003] The wafer 42 immediately after the slicing includes a wafer 42 shown in FIG.
As shown in (b), a slight swell often occurs. After the wafer is sliced, the polishing of the front and back surfaces is performed by a polishing apparatus in order to remove such waviness and flatten the front and back surfaces.

The polishing of the wafer 42 is carried out by a lapping apparatus for simultaneously polishing the front and back of the wafer using free abrasive grains. However, due to problems in productivity and automation, recently, as shown in FIG. Then, the wafer 42 immediately after slicing is placed and held on a chuck table 43 provided in a polishing apparatus, and a predetermined pressing force is applied from a rotating polishing grindstone 44.

When the polishing is completed, the polished wafer 45 is taken out from the chuck table 43, and the wafer 45 shown in FIG.
It is formed in a shape as shown in FIG.

[0006]

However, in the chuck table 43 of the polishing apparatus during polishing, the wafer 42 immediately after slicing is sucked and held by the negative pressure of the vacuum generator provided below the chuck table 43. In addition, the swell of the wafer 42 immediately after slicing is temporarily absorbed by the suction force due to the negative pressure, and the wafer is slightly flattened.

Therefore, during polishing, the undulations immediately after slicing are eliminated, and the undulations inherent in the wafer cannot be completely removed by polishing.

When it is determined that the surface has been completely flattened by the polishing, the polishing is terminated, and the suction force of the chuck table 43 is released to take out the polished wafer 45 from the chuck table 43. In the later wafer 45, a slight undulation is caused again by so-called rebound. That is, since all undulations could not be removed by polishing, some undulations remain.

Therefore, the conventional wafer polishing method has a problem to be solved in that the wafer is polished so that the surface of the wafer can be maintained in a flat state even after the suction holding of the wafer is released. I have.

[0010]

As a specific means for solving the above-mentioned problems, the present invention provides a polishing apparatus including a chuck table for holding a wafer, and a polishing grindstone arranged to face the chuck table. A wafer polishing method for holding a wafer cut from an ingot on a chuck table and polishing the wafer with a polishing grindstone, wherein a swell absorber that absorbs undulation of the wafer between the chuck table and the wafer. The present invention provides a method for polishing a wafer in which the undulation absorber is held on a chuck table and the surface of the wafer is polished with a polishing grindstone.

As described above, since the wave absorber is interposed between the chuck table and the wafer, the wave absorber can absorb the wave of the wafer.

Further, according to the present invention, after the surface of a wafer is polished with a polishing grindstone, the undulation absorber is peeled off, and the polished wafer is placed on a chuck table with the front side down, and the back surface of the wafer is polished. Polishing with a grindstone is included as an additional requirement.

By polishing the back surface in this manner, the back surface can be polished with the front surface being flat.

Further, the present invention provides that the undulation absorber is any one of an elastic pad, wax, and a liquid whose solid state can be obtained by a temperature difference.
A plurality of bubbles are formed, and when the back surface of the wafer is pressed against the front side of the elastic pad, the plurality of bubbles are crushed to absorb undulations and hold the wafer as an additional requirement.

[0015] By making the undulation absorber either a wax or a liquid whose solid state can be obtained by a temperature difference,
Even in the case of thin polishing, it can be easily separated from the wafer by heating or cooling.

The swell absorber is an elastic pad, and countless air bubbles are formed on the surface of the elastic pad.
When the back side of the wafer is pressed against the front side of the elastic pad,
Since a myriad of air bubbles are crushed to absorb the undulation and hold the wafer, the wafer can be stably held while maintaining the undulation.

[0017]

Next, an example of a preferred embodiment of a wafer polishing method according to the present invention will be described in detail with reference to the drawings.

It is the same as the conventional method until the wafer is sliced from an ingot of silicon or the like to a thickness of about 2 to 3 mm using an inner peripheral blade or the like and a wafer immediately after slicing is formed.

Next, in the wafer polishing method according to the present invention, first, as shown in FIG. 1A, a wave absorber 11 is attached to the back surface 10a of the wafer 10 immediately after the slice to be polished.

Here, the undulation absorber 11 adhered to the back surface 10a of the wafer 10 immediately after slicing is, for example, an elastic pad made of a synthetic resin material. Innumerable fine bubbles appear. Then, when the wafer 10 immediately after slicing is pressed against the surface on which the bubbles are exposed, the bubbles are crushed and become negative pressure, and the swell of the wafer 10 immediately after slicing is absorbed as it is. That is, the surface 1 of the wafer 10 immediately after slicing.
On the 0b side, the original swell appears as it is, and in this state, it is stably held by the swell absorber 11.

As described above, the back surface 10a has the wave absorber 11
The wafer 10 immediately after slicing attached to FIG.
As shown in (B), it is placed on the chuck table 30 of the polishing apparatus with the wave absorber 11 side down, and is suction-held as in the conventional case.

As shown in FIG. 2, a polishing apparatus 20 used for polishing is a slide plate which is slidably supported in a vertical direction with respect to a wall 22 provided upright from an end of a work table 21. A polishing means 24 is fixed to 23.

The polishing means 24 includes a body 25 fixedly attached to the slide plate 23, a motor 26 provided on the upper part of the body 25, and a spindle 27 which is driven by the motor 26 and protrudes downward from the body 25. , A wheel 28 attached to the spindle 27, and a polishing grindstone 29 detachably attached to the lower part of the wheel 28.

On the work table 21, there is provided a chuck table 30 having a vacuum generating part (not shown) at a lower part and capable of holding a wafer to be polished by suction under a negative pressure. Further, the slide plate 2 is provided on the back side of the wall 22.
3 is provided with a control unit 31 for controlling the up and down movement.

When polishing the surface 10b of the wafer 10 immediately after slicing using the polishing apparatus 20 configured as described above, the slide plate 23 is moved down by the control of the control unit 31. Then, the polishing means 24 is also lowered accordingly.
Also, by rotating the motor 26, the spindle 2
7 rotates and the wheel 28 mounted on the spindle
And the grinding wheel 29 attached to this also rotates. The surface 10b is polished by further lowering the polishing means 24 while the polishing grindstone 29 rotates.

At this time, the surface of the swell absorber 11 on the side sucked by the chuck table 30 is flat, and is not deformed by the suction force from the chuck table 30.

On the other hand, the surface on the side where the wafer 10 immediately after slicing is adhered is held in a state where the undulation of the wafer 10 immediately after slicing is absorbed as it is. Therefore,
If the surface 10b of the wafer 10 immediately after slicing is polished by the polishing grindstone 29 in this state, the surface 10b side becomes flat.

When the suction force of the chuck table 30 is released and the wafer 12 whose surface has been polished is taken out while maintaining the state of being adhered to the undulation absorber 11, as shown in FIG. The flat state on the polished surface (12b) side is maintained. That is, as in the prior art, the chuck table 3
There is no rebound when removed from 0.

Next, the undulation absorber 11 is peeled off from the wafer 12 whose front surface has been polished. I do. At this time,
Since the front surface 12b adsorbed to the chuck table 30 is polished flat, the undulation on the back surface 12a side is not absorbed even if adsorbed, and the undulation state of the back surface 12a is maintained as it is. Note that the wave absorber 11 may be attached to the surface 12b or a protective tape may be attached to avoid direct contact with the chuck table 30.

Therefore, if the back surface 12a is polished by the polishing grindstone 29, the back surface 12a is also flat, and as a result, FIG.
As shown in (E), a wafer 13 having both surfaces polished and flat on both surfaces is formed.

As described above, first, the wave absorber is attached to one surface of the wafer, and then the other surface is polished, then the wave absorber is peeled off, and the surface from which the wave absorber is peeled is polished. It is possible to form a flat wafer without rebound after the suction is released.

The swell absorber 11 is not limited to the one used in the present embodiment, and may be, for example, a wax disposed on a hard plate, a liquid capable of obtaining a solid state by a temperature difference, or the like. . In this case, since the wafer can be easily separated from the hard plate by heating or cooling, even a thin and easily damaged wafer is not damaged.

[0033]

As described above, according to the present invention, since the undulation absorber is interposed between the chuck table and the wafer, the undulation absorber can absorb the undulation of the wafer. The chuck table does not absorb the undulation. Therefore, undulation does not occur again due to rebound after polishing, and the surface can be polished flat.

After the surface of the wafer is polished with a polishing grindstone, the undulation absorber is peeled off, the polished wafer is placed on a chuck table with the front side down, and the back surface of the wafer is polished with a polishing grindstone. By doing
Since the back surface can be polished in a state where the front surface is flat, the back surface can also be polished flat, and a wafer having flat front and back surfaces can be formed, and good wafer making can be performed.

Further, by using either wax or a liquid capable of obtaining a solid state due to a temperature difference, even if it is polished thinly, it can be easily separated from the wafer by heating or cooling. Can be prevented.

The undulation absorber is an elastic pad, and countless bubbles are formed on the surface of the elastic pad.
When the back side of the wafer is pressed against the front side of the elastic pad,
Since the countless bubbles are crushed to absorb the undulation and hold the wafer, the wafer can be stably held while maintaining the undulation, and the reliability of the flatness of the wafer is increased.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a wafer polishing method according to the present invention in the order of steps.

FIG. 2 is a perspective view showing an example of a polishing apparatus used in the wafer polishing method.

FIG. 3 is an explanatory view showing a conventional wafer polishing method in the order of steps.

[Explanation of symbols]

10: wafer immediately after slicing 10a: back surface 10
b: Front surface 11: Wave absorber 12: Wafer after surface polishing 12a: Back surface 12b:
Surface 13: Wafer after double-side polishing 20: Polishing device 21: Workbench 22: Wall 23: Slide plate 24: Polishing means 25: Body 26: Motor 27: Spindle 28: Wheel 29: Polishing grindstone 30: Chuck table 31 : Control unit 40: Ingot 41: Inner peripheral blade 42: Wafer immediately after slicing 43: Chuck table 44: Polishing whetstone 45: Wafer after polishing

Claims (4)

[Claims] A chuck table for holding a wafer;
A method for polishing a wafer, comprising: holding a wafer cut out of an ingot on the chuck table using a polishing apparatus including a polishing grindstone disposed to face the chuck table, and polishing the wafer with the polishing grindstone. A swell absorber for absorbing undulations formed on the wafer is interposed between the chuck table and the wafer, the swell absorber is held on the chuck table, and the surface of the wafer is ground with the grinding wheel. Polishing method for the wafer to be polished by the method. 2. The wafer surface is polished with a polishing grindstone, the undulation absorber is peeled off, and the polished wafer is placed on a chuck table with the front side down, and the back surface of the wafer is polished with a polishing grindstone. The method for polishing a wafer according to claim 1, wherein 3. The swell absorber includes an elastic pad, wax,
The method for polishing a wafer according to claim 1, wherein the liquid is one of liquids capable of obtaining a solid state by a temperature difference. 4. An infinite number of air bubbles are formed on the front side of the elastic pad, and when the back surface of the wafer is pressed against the front side of the elastic pad, the innumerable air bubbles are crushed,
4. The wafer polishing method according to claim 3, wherein the wafer is held by absorbing undulations.