JP3327378B2 - Wafer polishing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus, and more particularly to a wafer polishing apparatus for polishing a wafer made of a brittle material such as silicon, glass or ceramic.

[0002]

2. Description of the Related Art With the recent increase in the density and the number of layers of semiconductor devices, it has been required to flatten wafers with high precision in the manufacturing process. As a method of flattening a wafer, there is a method of pressing a wafer against a rotating polishing platen and polishing while supplying a slurry to a contact surface thereof. When a wafer is polished by this method, it is necessary to always keep the wafer and the polishing plate parallel in order to flatten the wafer with higher precision.

[0003] In the conventional polishing apparatus, in order to hold the wafer and the polishing platen in parallel, for example, a method of pressing the wafer against the polishing platen via an airbag, or a method of directly blowing compressed air to the back surface of the wafer, Is pressed against a polishing platen.

[0004]

However, in the method using the airbag, the pressing force from the airbag is transmitted to the wafer through the plate having high rigidity, so that a polished surface with high flatness can be obtained. There is a disadvantage that it cannot be done. In other words, when a swelled wafer is pressed with a rigid plate, the back surface of the wafer is forcibly adjusted to a flat plate, and the swell is transferred to the front surface of the wafer. As a result, the wafer cannot be polished flat. There are drawbacks.

In order to improve the flatness and the throughput, a polishing method in which the wafer is rotated and pressed against a polishing platen is effective. However, the wafer is polished by blowing compressed air to the back surface of the wafer. There is a drawback that this method cannot be adopted in the method of pressing against a surface plate. In any of the above methods,
Since no consideration is given to the slurry entering the back surface of the wafer, there is a disadvantage that the wafer and the plate are contaminated.

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wafer polishing apparatus capable of polishing a wafer accurately and efficiently.

[0007]

According to the present invention, there is provided a wafer polishing apparatus for pressing a wafer held by a wafer holding device against a rotating polishing platen to polish a surface of the wafer. , The wafer holding device, a head installed facing the polishing platen,
A rotating means for rotating the head, a frame provided on an end face of the head and holding the wafer, and an elastic plate formed of an elastic member and a metal plate formed of a flexible metal are superimposed. A plate member which is formed together, is loosely fitted to the inner peripheral portion of the frame, and has its elastic plate side in contact with the wafer; a regulating member which regulates rotation of the plate material; and an end face of the head. Fluid supply means for supplying a fluid from the fluid supply means to the plate material, and the pressure of the fluid supplied from the fluid supply means is transmitted to the wafer via the plate material, and the wafer is pressed against the polishing platen. It is characterized by the following.

According to the present invention, the wafer is pressed against the plate pressed by the fluid pressure and pressed against the polishing platen. The plate rotates with the head, and the rotation of the plate is transmitted to the wafer to rotate. Therefore, the wafer is pressed against the polishing plate while being rotated and polished. Also, since the plate material is formed of a flexible member,
The undulation of the wafer is absorbed by this plate material. Therefore, the wafer is polished in a state where the undulation is absorbed by the plate material.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an embodiment of a wafer polishing apparatus according to the present invention. As shown in FIG. 1, the wafer polishing apparatus 10 includes a polishing platen 12 and a wafer holding device 1.
4 is provided.

The polishing platen 12 is formed in a disk shape, and a polishing cloth 16 is adhered on an upper surface thereof. A spindle 18 is connected to the polishing platen 12, and a motor (not shown) is connected to the spindle 18. The polishing platen 12 is rotated by driving the motor, and slurry is supplied from a nozzle (not shown) onto the rotating polishing platen 12.

The wafer holding device 14 has a disk-shaped head 20, as shown in FIGS. The head 20 is installed so as to face the polishing platen 12, and has a spindle 22
Are connected. The spindle 22 is rotatably supported by a lifting slider (not shown), and a lifting driving device (not shown) is connected to the lifting slider.
The head 20 is driven by the elevation drive device to move forward and backward with respect to the polishing platen 12.

A motor (not shown) mounted on the lifting slider is connected to the spindle 22, and the head 20 is rotated by driving the motor. An annular top ring 24 is fixed to the end face of the head 20. A ring-shaped holding ring 26 is loosely fitted to the inner peripheral portion of the top ring 24. The holding ring 26 has a flange 26A formed on an outer peripheral portion of an upper end thereof. The flange 26A is engaged with a step portion 24A formed on an inner peripheral portion of a lower end of the top ring 24, whereby the top ring 24 is formed. Is prevented from coming off.

The holding ring 26 has a stepped portion 26B formed on an inner peripheral portion of a lower end thereof, and an upper surface of the stepped portion 26B is provided on a stopper pin 2 provided on the head 20.
8, 28,... The stopper pins 28, 28,... Are arranged at four locations at a constant pitch on the concentric circle of the end face of the head 20, and are attached to the springs 32, 32,. The head 20 is provided so as to be urged and retractable from the end face of the head 20.

With the above configuration, the holding ring 26
The inner peripheral portion of the top ring 24 is
Is supported so as to be movable forward and backward and tiltable. A wafer W to be polished is arranged on an inner peripheral portion of the holding ring 26. A pressure plate 34 formed in a disc shape is loosely fitted on the inner peripheral portion of the holding ring 26. Notch portions 34C, 34 with which the stopper pins 28, 28,.
.. Are formed, and the notches 34C, 34
By engaging the stopper pins 28, 28,... With C, the circumferential movement of the pressure plate 34 is restricted. As a result, the pressure plate 34
Rotates together with the head 20 when the head 20 rotates.

By the way, the pressure plate 34 is
As shown in the detailed sectional view of FIG. That is, an elastic plate 34A formed of an elastic member and a metal plate 34B formed of a flexible metal are overlapped. The pressure plate 34 is loosely fitted to the holding ring 26 with the metal plate 34B facing upward.

The metal plate 34B constituting the pressure plate 34 is flexibly deformed by compressed air supplied into an air chamber 36, which will be described later, and is rotated by the rotation transmitted through the stopper pin 28. Is desirably formed of a material having such a hardness as to transmit to the wafer W. The elastic plate 34A is desirably formed of soft rubber or the like.

The pressure plate 34 arranged as described above forms an air chamber 36 below the head 20 together with the top ring 24 and the holding ring 26. Compressed air supplied from air supply means (not shown) is supplied to the air chamber 36 through an air supply path 38 formed inside the spindle 22. When the compressed air is supplied to the air chamber 36, the pressure plate 34 is pressed toward the polishing platen 12 (the lower side in the figure) by the air pressure of the compressed air. As a result, the wafer W placed in the holding ring 26 is pressed against the polishing platen 12.

A vacuum pump (not shown) is connected to the air supply passage 38, and the vacuum pump sucks air in the air chamber 36, thereby the wafer disposed in the holding ring 26 is sucked. W is held by suction. The compressed air supplied from the air supply path 38 formed in the spindle 22 is supplied into the air chamber 36 from a supply hole 40 formed in the end face of the head 20. In order that air can be quickly supplied to the entire inside of the air chamber 36, the end face of the head 20 is provided with a structure shown in FIG.
, The guide grooves 42 are formed radially.

The compressed air supplied into the air chamber 36 flows out of a gap V formed between the holding ring 26 and the pressure plate 34. Pure water supply paths 44, 4 provided in
A small amount of pure water is supplied from 4,. This pure water supply channel 4
4, 44,... Are formed at four locations at a constant pitch near the outer peripheral portion of the head 20, and are connected to a pure water supply means (not shown).

By the way, the pure water supply paths 44, 44,.
From the gap V between the holding ring 26 and the pressure plate 34
Is supplied to the air chamber 36, and the pure water also flows out of the gap V together with the compressed air supplied to the air chamber 36. At this time, the flowability of pure water is lower than that of air,
The pure water gives a resistance to the gap V, and reduces the outflow of compressed air from the gap V. As a result, it is possible to prevent a later-described slurry from entering the holding surface of the wafer W or the inside of the holding ring 26.

Next, a method of polishing a wafer W by the wafer polishing apparatus 10 of the present embodiment configured as described above will be described. First, the wafer W is held by the holding ring 26.
The wafer W is sucked and held by driving a vacuum pump (not shown). Then, the head 20 is lowered toward the polishing platen 12 while holding the wafer W by suction.

When the head 20 is located at a predetermined height from the polishing platen 12, the lowering of the head 20 is stopped, and then the driving of the vacuum pump is stopped. As a result,
The wafer W is placed on the polishing pad 16. Here, the polishing platen 12 is driven and rotated by a motor (not shown) when the wafer W is placed, and a slurry is supplied from a nozzle (not shown) onto the polishing pad 16. I have.

When the wafer W is placed on the polishing pad 16, the air supply means (not shown) is driven, and compressed air is supplied from the air supply path 38 into the air chamber 36. At the same time, pure water supply means (not shown) is driven, and pure water is supplied to the gap V between the holding ring 26 and the pressure plate 34 from the pure water supply paths 44, 44,. When the compressed air is supplied into the air chamber 36, the air chamber 3
6 is filled with compressed air. As a result, the pressure plate 34 is pressed toward the polishing pad 16 by the air pressure. Since the wafer W is disposed on the lower surface of the pressure plate 34, the pressure plate 34 is pressed toward the polishing pad 16 so that the wafer W
It is pressed by the pressure plate 34 and pressed against the polishing pad 16. Thereby, the wafer W is polished.

As described above, the wafer W is polished by pressing the wafer W against the polishing pad 16. In the wafer polishing apparatus 10 according to the present embodiment, in order to polish the wafer W efficiently, the wafer W is polished. Is pressed against the polishing pad 16 while rotating. That is, a motor (not shown) is driven simultaneously with the supply of the compressed air to rotate the head 20. When the head 20 rotates, the rotation of the head 20 is transmitted to the pressure plate 34 via the stopper pin 28, and the rotation of the pressure plate 34
The wafer W is transmitted to the wafer W pressed by the pressure plate 34, and the wafer W rotates. As a result, the wafer W
Is pressed while rotating against the polishing cloth 16, and efficient polishing is enabled.

When transmitting the rotational force to the wafer W, the rotation of the head 20 is transmitted to the metal plate 34B.
Furthermore, since the rotation of the metal plate 34B is transmitted to the wafer W via the elastic plate 34A, a spiral non-uniformity defect occurs on the polished surface of the wafer W as compared with the case where only the elastic plate 34A is used. Can be effectively prevented.

As described above, the wafer polishing apparatus 10 of the present embodiment can efficiently polish the wafer W by pressing the wafer W against the polishing pad 16 while rotating the wafer W. As a result, the throughput is dramatically improved. On the other hand, since the pressure plate 34 for pressing the wafer W against the polishing pad 16 is pressed by compressed air,
Pressure can be uniformly applied to the entire surface of the wafer W.
Therefore, it is possible to polish a wafer W having extremely high flatness without polishing unevenness.

Further, since the pressure plate 34 pressing the wafer W is flexible, even when the undulating wafer W is polished, the undulation can be absorbed by the pressure plate 34. Therefore, uneven removal of the oxide film or metal layer due to undulation can be avoided. That is, in the conventional wafer polishing apparatus,
Since the wafer W is pressed by a plate having high rigidity, the back surface of the wafer W is forcibly adjusted to a flat plate. As a result, the undulation of the wafer
The oxide film or the metal layer could not be uniformly removed even when the polishing amount was fixed, since the oxide film or metal layer was transferred to the surface of the wafer.

However, when the wafer W is pressed by the flexible pressure plate 34 as in this embodiment, the undulation of the wafer W is reduced by the pressure plate 3.
4, so that uneven removal of the oxide film or metal layer due to undulation can be avoided. Similarly, by pressing the wafer W with the flexible pressure plate 34, even if dust and the like adhere to the pressure plate 34, the dust is locally adhered to the surface of the wafer W due to local deformation of the pressure plate 34. Can be prevented from being generated.

Further, in the present embodiment, since the pressure plate 34 is swingably supported with respect to the holding ring 26, even if the inclination of the polishing pad 16 fluctuates, the wafer W can follow the fluctuation. Can be tilted. Therefore, the wafer W and the polishing pad 16 can always be kept parallel, and the formation of a processing taper on the polishing surface can be prevented.

Further, by supporting the pressure plate 34 in this manner, the wafer W can be freely moved up and down according to its thickness and processing. The compressed air supplied to the air chamber 36 flows out of the gap V between the holding ring 26 and the pressure plate 34. By supplying pure water to the gap, the slurry is formed on the holding surface of the wafer W or the holding ring. 26 can be prevented from entering.
That is, the supplied pure water flows out of the gap V together with the compressed air supplied to the air chamber 36. However, since the fluidity of the pure water is lower than that of the air, the pure water exerts a resistance against the gap V. Thus, the outflow of compressed air from the gap V can be reduced. As a result, it is possible to prevent the slurry from entering the holding surface of the wafer W or the inside of the holding ring 26.

Further, the wafer polishing apparatus 1 of the present embodiment
At 0, the processing pressure of the wafer W can be adjusted by adjusting the air pressure of the compressed air supplied to the air chamber 36. In this case, the automatic control of the attitude of the polished surface of the wafer W and the control of the processing pressure have good responsiveness and are performed at a very short distance of the wafer W, so that uniform polishing can be performed.

[0032]

As described above, in the wafer polishing apparatus of the present invention, the wafer can be polished very efficiently by polishing while rotating the wafer. In addition, the polishing pressure can be uniformly applied to the entire surface of the wafer, and the wafer and the polishing platen can always be kept parallel, so that extremely high-precision polishing can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a wafer polishing apparatus according to the present invention.

FIG. 2 is a side sectional view of the wafer holding device.

FIG. 3 is a sectional view of a main part of FIG. 2;

FIG. 4 is a bottom view of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wafer polishing apparatus 12 ... Polishing surface plate 14 ... Wafer holding apparatus 16 ... Polishing cloth 20 ... Head 24 ... Top ring 26 ... Holding ring 28 ... Stopper pin 34 ... Pressure plate 36 ... Air chamber 38 ... Air supply path 44 ... Pure Water supply channel W ... Wafer

Claims (1)

(57) [Claims] 1. A wafer polishing apparatus for polishing a surface of a wafer by pressing a wafer held by the wafer holding device against a rotating polishing platen, wherein the wafer holding device is installed to face the polishing platen. And a rotating means for rotating the head, a frame provided on an end face of the head and holding the wafer, and an elastic plate formed of an elastic member and a metal having flexibility. A plate member which is formed by superimposing a metal plate, is loosely fitted to the inner peripheral portion of the frame, and has a side of the elastic plate abutting on the wafer, and a regulating member which regulates rotation of the plate member. Fluid supply means for supplying a fluid from the end face of the head toward the plate material, wherein the pressure of the fluid supplied from the fluid supply means is increased via the plate material. By transfer to Doha, wafer polishing and wherein the pressing of the wafer to the polishing platen.