JP2000263421A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for a top ring which can adjust distribution of a contact surface pressure between a polished surface of a wafer and an abrasive cloth, in a polishing device. SOLUTION: An abrasive cloth 12 is stuck to an upper surface of a turn table. A top ring 14, opposed to the turn table, is arranged in its upward. A wafer 10 is sucked to a lower surface of the top ring 14 through a packing pad 15. A plurality of circumferential directional grooves 21a to c are formed concentrically in the lower surface of the top ring 14. Hollow elastic units 23a to c are mounted on the inside of each groove 21a to c. Tubes 24a to c are connected to a back surface side of each elastic unit 23a to c, and each tube 24, passing through in a hole formed inside the top ring 14, is connected to a respectively independent compressed air source. Compressed air is supplied through each tube 24a to c to a hollow part of each elastic unit 23a to c.

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 flattening the surface of a disk-shaped workpiece such as a silicon wafer. It relates to a structure suitable when required.

[0002]

2. Description of the Related Art In a polishing apparatus for a wafer, a wafer is usually attracted to a lower surface of a top ring via a backing pad, and the wafer is pressed against a polishing cloth attached to an upper surface of a turntable. The wafer is polished by rotating the table and the top ring.

In recent years, with the progress of miniaturization of semiconductor integrated circuits, the wavelength of a light source used in a lithography process has become shorter and the depth of focus has become shallower, so that the demand for the flatness of the wafer surface has become increasingly severe. In order to meet such demands, various methods and apparatuses have been proposed for controlling the distribution of the contact surface pressure acting between the surface to be polished of the wafer and the polishing cloth to an optimum state.

For example, Japanese Patent Application Laid-Open No. 9-225821 discloses a polishing apparatus having the configuration shown in FIG.

The polishing pad 12 is attached to the upper surface of the turntable 11. The wafer 1 is provided on the lower surface of the top ring 14 via a backing pad 15 (“elastic mat”).
0 is adsorbed and held. A plurality of openings 31 are provided on the lower surface of the top ring 14, and behind these openings 31, a chamber C divided concentrically into a plurality of regions is provided.
1, C2 and C3 are provided. Each chamber C1, C
2, C3 are each connected to a separate source of compressed air (not shown). The backing pad 15 is provided with openings 32 at respective positions corresponding to the openings 31 on the top ring 14 side.

In this apparatus, each of the chambers C1, C2, C
By appropriately adjusting the pressure of the compressed air supplied to the inside 3, the pressure of the compressed air ejected toward the back surface (upper surface) of the wafer 10 via the opening 31 and the opening 32 is adjusted. The distribution of the contact surface pressure between the wafer 10 and the polishing cloth 12 is adjusted.

However, in this apparatus, the wafer 1
Since the compressed air is ejected directly to the back side of the wafer 0, there is a concern that the wafer is contaminated by particles mixed in the compressed air. Further, since the compressed air jetted to the back surface side of the wafer 10 flows out between the backing pad 15 and the back surface of the wafer 10, there is a concern that the holding force of the backing pad 15 on the wafer 10 may be reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional polishing apparatus.
The distribution of the contact surface pressure acting between the polished surface of the wafer and the polishing cloth can be adjusted to an appropriate state, and
An object of the present invention is to provide a top ring structure that does not reduce the holding force of a backing pad on a wafer.

[0009]

According to the present invention, there is provided a polishing apparatus comprising: a turntable on which an abrasive cloth is stuck on an upper surface;
A top ring that is disposed above the turntable so as to face the turntable and that holds a disc-shaped workpiece on the lower surface via a backing pad; and that the workpiece is rotated and pressed against the polishing cloth. In a polishing apparatus for polishing the surface of a workpiece, a plurality of grooves are formed on a lower surface of a top ring, and a hollow elastic body is inserted into each groove, and each hollow body is individually formed in a hollow portion of each elastic body. And a pressurized path for supplying a pressurized fluid to the hopper.

According to the polishing apparatus of the present invention, by controlling the pressure of the pressurized fluid supplied into the hollow portion of each of the elastic members, the back surface of the workpiece is processed via the elastic members and the backing pad. The distribution of the pressing force acting on the side is changed, whereby the surface of the workpiece (the surface to be polished)
The distribution of the contact surface pressure between the polishing pad and the polishing pad can be adjusted.

[0011] Preferably, the plurality of grooves are formed concentrically on the lower surface of the top ring.

Alternatively, a part of the plurality of grooves is formed in a circular planar shape on the lower surface of the top ring, and the other part is
An elliptical planar shape may be formed on the lower surface of the top ring. Alternatively, the plurality of grooves may be formed in a polygonal shape concentric with the lower surface of the top ring.

As described above, instead of inserting a hollow elastic body into each groove, an elastic body having a shape fitting into each groove may be inserted into each groove. . In this case, independent pressure chambers are formed behind each elastic body by providing a pressurization path for individually supplying pressurized fluid into each groove inside the top ring.

[0014]

1 to 3 show an example of a polishing apparatus according to the present invention. In the figure, 10 is a wafer, 11 is a turntable, 12 is a polishing cloth, 14 is a top ring, 15 is a backing pad, 21a to 21c are grooves,
23a to 23c denote hollow elastic bodies, and 24a to 24c denote tubes (pressure paths).

A polishing cloth 12 is provided on the upper surface of the turntable 11.
Is pasted. A top ring 14 is arranged above and opposite to the turntable 11. The wafer 10 is sucked and held on the lower surface of the top ring 14 via the backing pad 15. Further, a guide ring 16 is formed integrally with the periphery of the backing pad 15 along the outer periphery of the wafer 10.
0 radial movement is constrained from the surroundings. Top ring 1
Numeral 4 is attached to the lower end of the main shaft 13 of the polishing head, and a rotational motion and a downward pressing force are given through the main shaft 13.

An abrasive supply nozzle 19 is disposed adjacent to the top ring 14. Abrasive supply nozzle 19
Supplies an abrasive in which abrasive grains are suspended on the polishing cloth 12.

On the lower surface of the top ring 14, a plurality of circumferential grooves 21a to 21c are formed concentrically as shown in FIGS. FIG. 1 shows the inside of each of the grooves 21a to 21c.
As shown in FIG. 3 and FIG.
c is attached. Tubes 24a to 24c are connected to the back sides of the elastic bodies 23a to 23c (the sides opposite to the surface that contacts the backing pad 15).
Each of the tubes 24a to 24c passes through a through hole formed inside the top ring 14, and is connected to an independent compressed air source (not shown). Each elastic body 23a ~
Compressed air is supplied to the hollow portion c through the tubes 24a to 24c.

Next, a method for polishing a wafer by using the above polishing apparatus will be described.

In the polishing apparatus, the wafer 10
Is sucked to the lower surface of the top ring 14 via the backing pad 15 and is transported above the turntable 11. The turntable 11 and the top ring 14 are rotated at a predetermined speed, and an abrasive is supplied onto the polishing pad 12 through an abrasive supply nozzle 19. Usually, the turntable 11 and the top ring 14 are driven in the same rotation direction and substantially the same rotation speed. Then, top ring 1
4 is lowered to press the wafer 10 against the polishing cloth 12, and polishing of the wafer 10 is started. After a predetermined time has elapsed, the top ring 14 is raised and the wafer 10
Finish polishing. After the polishing is completed, the wafer 10 is transported to the next cleaning step.

In the polishing process, when the processing speed in the plane of the wafer becomes non-uniform, the flatness may exceed an allowable value. In such a case, in the polishing apparatus of the present invention, the pressure of the compressed air supplied into the hollow elastic bodies 23a to 23c arranged in the grooves 21a to 21c is independently controlled. Thereby, the distribution of the pressing force acting on the back surface side of the wafer 10 via the elastic members 23a to 23c and the backing pad 15 is adjusted. Thereby, the distribution of the contact surface pressure between the surface (the surface to be polished) of the wafer 10 and the polishing cloth 12 is controlled,
The processing speed in the plane of the wafer 10 can be made uniform.

Specifically, before and after the polishing step, the film thickness distribution of the thin film formed on the surface of the wafer 10 is measured, and the distribution of the processing speed in the plane of the wafer 10 is calculated. Based on the result, the value of the pressure applied to each of the elastic bodies 23a to 23c is set.

For example, the film thickness distribution of the first wafer in the same lot is measured, and based on the measurement result, each elastic body 23 is polished when polishing the second and subsequent wafers.
The value of the pressure applied inside a to c is set. Alternatively, a pressure value at which a uniform film thickness distribution is obtained is empirically obtained.

(Example 2) FIG. 4 shows another example of the polishing apparatus of the present invention (only the main part). In this example, a solid elastic member having a shape that fits into each groove is formed in each of the grooves 21a to 21c formed on the lower surface of the top ring 14 in the same manner as the previous example (FIGS. 1 and 2). The bodies 27a-c are inserted respectively. Inside the top ring 14, through holes 28a to 28c (pressurized paths) for individually supplying compressed air are provided in the grooves 21a to 21c, respectively, behind the elastic bodies 27a to 27c. Pressure chambers 29a to 29c are formed.

In this case, the pressure of the compressed air supplied into each of the pressure chambers 29a to 29c is independently controlled, so that the pressure acts on the back side of the wafer 10 via the elastic members 27a to 27c and the backing pad 15. The distribution of the pressing force to be applied can be adjusted. As a result, the wafer 10
The distribution of the contact surface pressure between the surface (the surface to be polished) and the polishing cloth 12 can be controlled, and the processing speed in the plane of the wafer 10 can be made uniform.

(Example 3) FIG. 5 shows another example of a top ring constituting the polishing apparatus of the present invention. In this example, two grooves are formed on the lower surface of the top ring 14 in the circumferential direction. Of these, the planar shape of the groove 21d formed on the inner diameter side is circular, and the groove 21e formed on the outer diameter side. Has an elliptical planar shape.

[0026]

According to the polishing apparatus of the present invention, the pressure of the pressurized fluid acting inside or behind each elastic body mounted in each groove is independently adjusted, so that the workpiece is processed. By controlling the distribution of the contact surface pressure between the surface of the workpiece and the polishing cloth, the processing speed in the surface of the workpiece can be made uniform. Thereby, the flatness of the surface of the workpiece after the polishing can be increased.

Further, according to the polishing apparatus of the present invention, since the pressurized fluid acting inside or behind each elastic body is not jetted to the lower side of the top ring,
There is no possibility that the holding force of the backing pad on the workpiece is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a polishing apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a planar shape of a groove formed on a lower surface of a top ring in the polishing apparatus according to the present invention.

FIG. 3 is a diagram showing an example of a groove formed on a lower surface of a top ring and a cross-sectional shape of an elastic body inserted into the groove in the polishing apparatus according to the present invention.

FIG. 4 is a view showing another example of the cross-sectional shape of the groove formed on the lower surface of the top ring and the elastic body inserted into the groove in the polishing apparatus according to the present invention.

FIG. 5 is a diagram showing another example of the planar shape of the groove formed on the lower surface of the top ring in the polishing apparatus according to the present invention.

FIG. 6 is a schematic configuration diagram showing an example of a conventional polishing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Wafer, 11 ... Turntable, 12 ... Polishing cloth, 13 ... Spindle (of a polishing head), 14 ... Top ring, 15 ... Backing pad, 16 ... Guide Ring 19: abrasive supply nozzle, 21a, 21b, 21c: groove, 23a, 23b, 23c: (hollow) elastic body, 24a, 24b, 24c: tube (pressurized path), 27a, 27b, 27c ... (solid) elastic body, 28a, 28b, 28c ... through-hole (pressurized path), 29a, 29b, 29c ... pressure chamber, 31, 32 ... opening , C1, C2, C3 ... chamber.

Claims (5)

[Claims] 1. A turntable on which an abrasive cloth is attached on an upper surface, and a top ring which is disposed above and opposite to the turntable and has a lower surface on which a disk-shaped workpiece is held via a backing pad. And presses the workpiece against the polishing cloth while rotating it.
In a polishing device that grinds the surface of the workpiece, a plurality of grooves are formed on the lower surface of the top ring, hollow elastic bodies are inserted into each groove, and individually in the hollow portions of each elastic body. A polishing apparatus characterized by having a pressurizing path for supplying a pressurized fluid. 2. A turntable on which an abrasive cloth is stuck on an upper surface, and a top ring which is disposed above and opposite to the turntable, and has a lower surface on which a disk-shaped workpiece is held via a backing pad. And presses the workpiece against the polishing cloth while rotating it.
In a polishing apparatus for polishing a surface of a workpiece, a plurality of grooves are formed on a lower surface of a top ring, and an elastic body having a shape fitting into each groove is inserted into each groove, and A polishing apparatus characterized in that independent pressure chambers are formed behind each elastic body by providing a pressurized path for individually supplying a pressurized fluid into each groove inside a ring. 3. The polishing apparatus according to claim 1, wherein the plurality of grooves are formed concentrically on a lower surface of the top ring. 4. A part of the plurality of grooves is formed in a circular planar shape on a lower surface of a top ring, and another part is formed in an elliptical planar shape on a lower surface of the top ring. The polishing apparatus according to claim 1 or 2, wherein 5. The polishing apparatus according to claim 1, wherein the plurality of grooves are formed in a concentric polygonal shape on a lower surface of the top ring.