JP2001150330A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of realizing a high flatness by reducing nonuniformity of the polishing amount on the peripheral edge of a wafer. SOLUTION: The wafer 1 is absorbed to the lower surface of a top plate 6 through a backing pad 8 and guided from the periphery by a guide ring 7. A ring-shaped piston 10 is housed between the top plate 6 and the guide ring 7, a ring-shaped protrusion part 10c provided on the tip extends to the lower surface side of the top plate 6 through a clearance between the top plate 6 and the guide ring 7. Pressure chambers 11, 12 are formed on the upper surface and the lower surface of the protrusion part 10a of the piston 10, and O-rings 16, 17 are respectively mounted on the outer peripheral sides of the pressure chambers 11, 12. The position in the vertical direction of the piston 10 is adjusted by controlling pressure in the pressure chambers 11, 12, and the contact pressure distribution between the wafer 1 on the peripheral edge part and an abrasive cloth is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus used for flatly polishing the surface of a thin disk-shaped workpiece such as a silicon wafer. The present invention relates to a structure of a polishing head for holding the polishing head.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, the wiring has become finer and more multilayered, and the wavelength of an exposure beam of an exposure apparatus used for pattern formation has been gradually reduced. For this reason, the depth of focus at which resolution can be ensured in the photolithography process becomes gradually smaller, and it is required to increase the flatness of the wafer surface in order to ensure processing at a shallower depth of focus.

FIG. 3 shows the structure of a "substrate holding device" described in Japanese Patent Laid-Open No. 11-207602 as an example of a conventional polishing head. In the drawing, 60 is a turntable, 61 is a polishing pad (polishing cloth), 65 is a substrate holding device (polishing head), and 62 is a substrate (wafer).

The substrate holding device 65 includes a rotating shaft 66, a substrate holding head 67 provided integrally with the rotating shaft 66, and a guide member 69 fixed to a peripheral portion of a lower surface of the substrate holding head 67. I have. Further, a sealing member 7 is provided on the lower surface of the substrate holding head 77 along the inner periphery of the guide member 69.
0 is provided to be able to move up and down. Substrate holding head 6
7, a first space 71 is formed by the seal member 70 and the substrate 62, and a second space 72 is formed by the substrate holding head 67 and the seal member 70.

The central portion of the substrate 62 is pressed against the polishing pad 61 by a pressurized fluid supplied into the first space 71. The periphery of the substrate 62 is
(Pressurized by the pressurized fluid supplied into the second space 72), the pressure is applied to the polishing pad 61.

The above-described substrate holding device has the following problems.

(A) Since the pressure for polishing the wafer (substrate 62) is as small as 65 kPa at the maximum, it is practically difficult to control the pressure on the seal member 70, which is the same level of pressure.

(B) Since the seal member 70 has sliding resistance, it is difficult to accurately control the pressure on the seal member 70 with a small value. Further, in order to accurately control the pressure on the seal member 70, it is necessary to enhance the sealing performance. However, when the sealing performance is enhanced, the sliding resistance increases,
Control becomes increasingly difficult.

(C) On the other hand, if the sealing performance is low, the pressurized fluid leaks from the second space 72 to the first space 71, making it difficult to control the polishing rate at the center of the wafer.

(D) Since the length of the sealing member 70 is shorter than the diameter, the sliding surface between the sealing member 70 and the adjacent substrate holding head 67 is apt to be galled.
May not work correctly.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional polishing head, and an object of the present invention is to accurately adjust the surface pressure distribution at the peripheral portion of the wafer. To be able to do
Improve the uniformity of the distribution of the polishing amount in the plane of the wafer,
An object of the present invention is to provide a polishing apparatus capable of improving the flatness of a wafer.

[0012]

A polishing apparatus according to the present invention comprises a turntable on which an abrasive cloth is mounted on an upper surface, and a disk-shaped polishing device which is disposed above and opposed to the turntable and has a lower surface with a backing pad interposed therebetween. A top plate on which the workpiece is adsorbed, a top block arranged on the upper surface side of the top plate and holding the top plate on the lower surface, and attached to a peripheral portion of the top block so as to surround the periphery of the top plate, A guide ring that guides the workpiece from the outer peripheral side, and is disposed between the outer peripheral surface of the top plate and the inner peripheral surface of the guide ring, and is driven vertically along the inner peripheral surface of the guide ring, and its tip portion A ring-shaped piston for applying a pressing force to a peripheral portion of the workpiece via the backing pad, and rotating the workpiece to face the polishing cloth. In a polishing apparatus for performing polishing by pressing against the outside, a protrusion protruding in a radial direction is provided on a body of the piston, and first and second pressure chambers are provided on an upper surface side and a lower surface side of the protrusion. First and second ring-shaped elastic seals that expand and contract in the vertical direction are mounted between the upper and lower surfaces of the first and second inner surfaces of the first and second pressure chambers facing the first and second pressure chambers. At the same time, the horizontal cross-sectional area of the first and second pressure chambers is defined by the second elastic seal body, and the horizontal cross-sectional area of the second pressure chamber is set to be smaller than that of the first pressure chamber. ,
A through-hole is formed in the protrusion of the piston to allow the first pressure chamber and the second pressure chamber to communicate with each other, and the pressure of the pressurized fluid supplied to the inside of the first pressure chamber and the second pressure chamber is formed. , Whereby the vertical position of the piston is adjusted.

According to the polishing apparatus of the present invention, when the pressurized fluid is supplied to the inside of the first pressure chamber and the second pressure chamber, based on the difference in the horizontal sectional area between the two pressure chambers, A downward force acts on the piston. When the piston moves downward by this force, the first elastic seal body expands and the second elastic seal body contracts, thereby generating a force for pushing the piston upward. As a result, the piston stops at a position where both forces balance.

This makes it possible to precisely adjust the pressing force acting on the peripheral edge of the workpiece from the piston via the backing pad.

[0015]

FIG. 1 shows the structure of a polishing head constituting a main part of a polishing apparatus according to the present invention. In FIG. 1, 1 is a wafer, 5 is a top block,
6 is a top plate, 6a is a flange portion, 7 is a guide ring, 8 is a backing pad, 10 is a ring-shaped piston, 10b is a protrusion, 11 is a first pressure chamber, 12 is a second pressure chamber, and 15 is The through hole, 16 indicates an O-ring (first elastic seal), and 17 indicates an O-ring (second elastic seal).

The top block 5 is attached to the lower end of the drive shaft 4a. Flanges 5a and 5b are formed at the upper end and the lower end of the top block 5, respectively. The upper flange portion 5a is fixed to the lower end of the drive shaft 4a with bolts. The diameter of the lower flange portion 5b is slightly larger than the wafer 1 to be polished.

A top plate 6 is attached to the center of the lower surface of the lower flange portion 5b. A guide ring 7 is attached to the peripheral edge of the lower surface of the lower flange portion 5b so as to surround the outer periphery of the top plate 6 at intervals in the radial direction. The outer peripheral side of the wafer 1 is guided by a guide ring 7.

The top plate 6 has a circular concave portion formed in the center on the upper surface side, and a portion surrounded by the concave portion and the lower surface of the top block 5 is a hollow portion 27. A plurality of through holes 28 are formed between the bottom surface of the cavity 27 and the lower surface of the top plate 6. An O-ring is arranged on the upper surface of the top plate 6 along the outer periphery of the hollow portion 27, and the inside of the hollow portion 27 is sealed.

A backing pad 8 is adhered to the lower surface of the top plate 6 with a double-sided tape. Through holes 29 are formed in the backing pad 8 at positions corresponding to the plurality of through holes 28 formed in the top plate 6. The wafer 1 is attracted to the lower surface of the top plate 6 via the backing pad 8.

The top plate 6 is provided with a flange 6a on the lower surface thereof so as to project radially from the outer peripheral surface. A ring-shaped space is formed on the upper surface side of the flange 6a between the outer peripheral surface of the top plate 6 and the inner peripheral surface of the guide ring 7, and the body of the ring-shaped piston 10 is formed in this space. Department is housed. The body of the piston 10 has a protrusion 10a projecting radially inward, and a protrusion 10b projecting upward from the upper surface of the body and projecting downward from the lower surface of the body on the outer peripheral side of the body. Projection 1
0c is formed.

An O-ring 16 (first elastic seal) is mounted on the inner peripheral side of the protrusion 10b on the upper surface side. The protruding portion 1 of the piston 10 is
A first pressure chamber 11 to which a pressurized fluid is supplied is formed between the upper surface of Oa and the lower surface of the top block 5. O-rings are also arranged on the upper surface of the top plate 6 along the outer periphery, and the inside of the first pressure chamber 11 is sealed by these O-rings.

A step portion 10d is formed on the inner peripheral side on the lower surface side of the projecting portion 10a so as to slightly project downward, and an O-ring 17 (a second elastic seal body) is formed on the inner peripheral side of the step portion 10d. )
Is installed. On the inner peripheral side of the O-ring 17, a second pressure chamber 12 to which a pressurized fluid is supplied is formed between the lower surface of the protrusion 10a of the piston 10 and the upper surface of the flange 6a. When the O-ring 17 is mounted, a slight gap is formed between the lower surface of the step 10d and the upper surface of the flange 6a.

The first pressure chamber 11 and the second pressure chamber 12 are
The plurality of through-holes 15 penetrate the protrusion 10a of the piston 10 in the up-down direction and communicate with each other. Where O
The inner diameter of the ring 16 is larger than the inner diameter of the O-ring 17, so that the horizontal cross-sectional area of the first pressure chamber 11 is
It is larger than the horizontal cross-sectional area of the second pressure chamber 12.

The protrusion 10 on the lower surface side of the body of the piston 10
“b” penetrates a gap formed between the outer circumference of the flange portion 6 a and the guide ring 7 and reaches the lower surface side of the top plate 6. The periphery of the upper surface of the backing pad 8 is adhered to the lower end surface of the projection 10c with a double-sided tape.

A plate-shaped sliding member 19 is mounted on the inner peripheral surface of the guide ring 7. The sliding member 19 prevents galling between the inner peripheral surface of the guide ring 7 and the outer peripheral surface of the piston 10.

A ventilation hole 23 is formed inside the drive shaft 4a. Flange part 5 on the upper end side of top block 5
A ventilation hole 25a is formed inside a, and a ventilation hole 25b is formed inside the lower flange portion 5b. Vent 23
Is connected to a vacuum source and a high-pressure air source via a rotary joint (not shown). The tip of the ventilation hole 23 is the ventilation hole 25
a, and the tip of the ventilation hole 25a communicates with the ventilation hole 25b via the tube 24. The distal end of the ventilation hole 25 b opens to the lower surface of the top block 5 and communicates with the cavity 27.

Vent hole 23, vent hole 25a, tube 24
By reducing the pressure in the cavity 27 through the ventilation holes 25b, the wafer 1 is adsorbed, and by pressurizing the cavity 27, the wafer 1 is released.

Inside the drive shaft 4a, a ventilation hole 33 is further provided.
Are formed. A vent hole 35a is provided inside the upper end flange 5a of the top block 5, and a lower end flange 5b is provided.
Is formed with a ventilation hole 35b. Vent 33
Is connected to a high-pressure air source via a rotary joint (not shown) and a pressure adjusting device 31. The tip of the ventilation hole 33 communicates with the ventilation hole 35a, and the tip of the ventilation hole 35a communicates with the ventilation hole 35b via the tube 34. Vent 3
The tip of 5 b is opened on the lower surface of the top block 5 and communicates with the first pressure chamber 11. As described above, the first pressure chamber 11 is connected to the second pressure chamber 12 through the through hole 15.
Is in communication with

Vent 33, vent 35a, tube 34
When high-pressure air is supplied to the inside of the first pressure chamber 11 and the second pressure chamber 12 through the ventilation hole 35b, the piston 10 is supplied to the piston 10 based on the difference between the horizontal sectional areas of the two pressure chambers. A downward force acts. When the piston 10 moves downward by this force, the O-ring 16 on the upper surface is deformed (returns) so as to increase the thickness, and the O-ring 16 on the lower surface is
The ring 17 is compressed in the thickness direction, thereby generating a force that pushes the piston 10 upward. as a result,
The piston 10 stops at a position where the force of the high-pressure air and the elastic force of the O-rings 16 and 17 are balanced.

By forming such pressure chambers 11 and 12 above and below the projecting portion 10a of the piston 10, the pressing force acting on the peripheral edge of the wafer 1 from the piston 10 via the backing pad 8 can be precisely controlled. It becomes possible to control. As a result, the contact pressure distribution between the surface of the wafer 1 and the polishing pad at the peripheral portion of the wafer 1 can be adjusted precisely.

FIG. 2 shows an example of the result of measuring the relationship between the pressure of the high-pressure air and the amount of movement of the piston 10. In this example, the ring diameter of the O-ring 16 was 190 mm, the ring diameter of the O-ring 17 was 180 mm, and the outer diameter of the top plate 6 above the flange portion 6a was 160 mm. It can be seen that the pressure of the high-pressure air and the amount of movement of the piston 10 are proportional. In FIG. 2, the movement amount in the plus direction means that the piston 10 protrudes below the lower surface of the top plate 6.

[0032]

According to the polishing apparatus of the present invention, the pressing force acting on the peripheral portion of the wafer from the piston via the backing pad can be precisely controlled. This makes it possible to precisely adjust the contact pressure distribution between the surface of the wafer and the polishing cloth at the peripheral portion of the wafer, and to improve the flatness of the wafer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a polishing head constituting a main part of a polishing apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a result obtained by measuring a relationship between a pressure of high-pressure air and a movement amount of a piston.

FIG. 3 is a diagram showing an example of the structure of a conventional polishing head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Wafer, 5 ... Top block, 5a, 5b ... Flange part, 6 ... Top plate, 6a ... Flange part, 7 ... Guide ring, 8 ... Backing pad, DESCRIPTION OF SYMBOLS 10 ... Ring-shaped piston 10a ... Protrusion 10b, 10c ... Protrusion, 10d ... Step, 11 ... First pressure chamber, 12 ... Second pressure chamber , 15 ... through-hole, 16 ... O-ring (first elastic seal), 17 ... O-ring (second elastic seal), 23 ... vent, 24 ... tube , 25a, 25b ... vent, 27 ... cavity, 28, 29 ... through-hole, 31 ... pressure control device, 33 ... vent, 34 ... tube, 35a, 35b ... Vent holes.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takahiro Kawamo 2068-3 Ooka, Numazu-shi, Shizuoka F-term within Toshiba Machine Co., Ltd. (reference) 3C058 AA07 AA09 AA12 AB04 BA05 BA07 BB04 CB01 DA17

Claims (1)

[Claims] 1. A turntable on which an abrasive cloth is mounted on an upper surface, and a top plate disposed above and opposed to the turntable, and a lower surface on which a disk-shaped workpiece is sucked via a backing pad. A top block arranged on the upper surface side of the top plate and holding the top plate on the lower surface; and a guide ring attached to a peripheral portion of the top block so as to surround the top plate and guide the workpiece from the outer peripheral side. And disposed between the outer peripheral surface of the top plate and the inner peripheral surface of the guide ring, driven vertically along the inner peripheral surface of the guide ring, and at the tip end of the workpiece through the backing pad. A ring-shaped piston that applies pressure to the periphery, and performs polishing by pressing against the polishing cloth while rotating the workpiece In the piston device, a protrusion protruding in the radial direction is provided on the body of the piston, and first and second pressure chambers are provided on an upper surface side and a lower surface side of the protrusion. Ring-shaped first and second elastic seals which expand and contract in the vertical direction between inner wall surfaces of the first and second pressure chambers facing the first and second pressure chambers, and these first and second elastic seals At the same time, the horizontal sectional area of the first and second pressure chambers is defined, and at the same time, the horizontal sectional area of the second pressure chamber is set to be smaller than that of the first pressure chamber; Forming a through-hole communicating the first pressure chamber and the second pressure chamber with each other, and controlling the pressure of the pressurized fluid supplied to the inside of the first pressure chamber and the second pressure chamber. The vertical position of the piston is adjusted. Polishing apparatus and butterflies.