JP2003179014A - Wafer polishing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer polishing apparatus which can correct elongation of a protection sheet and can keep a polishing quality. <P>SOLUTION: In the wafer polishing apparatus, a retainer ring 28 is mounted to a holder 50 provided to a wafer holding head, a protective sheet 52 is extended into inside of the retainer ring, and polishing is carried out by pushing a wafer W against a polishing pad 20 via the protective sheet. The outer peripheral edge portion of the protective sheet 52 is held between the retainer ring 26 and the holder 50, and a means 78 for adjusting the tension of the protective sheet 52 is provided in the inner peripheral side of the held outer peripheral edge portion of the sheet. The tension of extended the sheet 53 can be made variable by the tension adjusting means 78. <P>COPYRIGHT: (C)2003,JPO

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 for polishing a wafer or the like by a chemical mechanical polishing (CMP) method.

[0002]

2. Description of the Related Art Wafer polishing by CMP is performed by pressing a rotating polishing pad at a predetermined pressure while rotating the wafer and supplying a mechanochemical polishing agent (slurry) between the polishing pad and the wafer. Be seen. At this time, the wafer is surrounded by the retainer ring, and the back surface of the wafer is held by the carrier and pressed by the polishing pad.

However, in the conventional wafer polishing apparatus disclosed in Japanese Patent No. 2897207, the back surface of the wafer is directly contacted with the hard surface of the carrier to press the wafer, so that the back surface of the wafer is damaged. It was

Therefore, the applicant of the present application proposed a wafer polishing apparatus in which a protective sheet is provided below a carrier in Japanese Patent Application No. 11-18558 in order to eliminate such a drawback. This wafer polishing apparatus uses a protective sheet to prevent the hard surface of the carrier from directly contacting the back surface of the wafer, thereby preventing the back surface of the wafer from being scratched. .

In this case, as shown in FIG. 6, the protective sheet 1 is attached to the retainer ring holder 3 arranged around the carrier 2 with its peripheral edge adhered, and the retainer ring 4 is attached to the protective sheet 1. It is attached to the bottom of by adhesive. The retainer ring 4 presses the polishing pad 20, reduces the impact applied to the edge (edge) of the wafer W, and controls the polishing amount of the edge so that the surface of the edge is not sagged.

The protection sheet 1 is required to have flexibility, and a resin material is used for the reason that it is necessary to prevent the back surface of the wafer from being scratched, the need to prevent contamination, and the like. Is common.

[0007]

However, in the case of the protective sheet 1 made of a resin material, it is often the case that elongation is gradually caused by repeating polishing. In addition, the bonded portion between the protective sheet 1 and the retainer ring holder 3 may stretch or slip.

In this case, the pressing state at the outer peripheral portion of the wafer W as shown in FIG. 7 changes. As a result, surface sagging or the like of the edge portion occurs on the wafer, resulting in poor quality.

Further, the protective sheet 1 needs to be uniformly attached to the whole without wrinkles, but the above-mentioned attaching method has a drawback that it is difficult to attach without wrinkles. Also,
Even if it is possible to install without wrinkles,
There is also a drawback that it is very difficult to maintain the degree of tension of the protective sheet 1 constant every day.

The present invention has been made in view of the above circumstances, and the protective sheet can be easily attached without wrinkles, and the elongation of the protective sheet caused by repeated polishing can be corrected. Even if you replace the retainer ring holder that has several protective sheets with the same specifications,
An object of the present invention is to provide a wafer polishing apparatus that can maintain stable polishing quality.

[0011]

In order to achieve the above-mentioned object, the present invention is to attach a retainer ring to a holder provided on a wafer holding head, and to extend a protective sheet inside the retainer ring. In a wafer polishing apparatus that polishes a wafer by pressing it against a polishing pad through a material, the outer peripheral edge portion of the protective sheet is sandwiched between the retainer ring and the holder, and the protective sheet is provided on the inner peripheral side of the sandwiching portion. There is provided a wafer polishing apparatus characterized in that a tension adjusting means is provided and the tension of a protective sheet stretched by the tension adjusting means is variable.

According to the present invention, since the tension of the protective sheet is made variable, the quality of the wafer edge can be maintained,
As a result, the polishing quality of the wafer can be maintained. In addition, excessive wear of the wafer edge can be prevented, and the strength and durability of the retainer ring can be maintained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a wafer polishing apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the overall structure of the wafer polishing apparatus 10. As shown in the figure, the wafer polishing apparatus 10 mainly includes a polishing platen 12 and a holding head (wafer holding head) 14.

The polishing platen 12 is formed in a disk shape, and a rotating shaft 16 is connected to the center of the lower surface thereof. Polishing surface plate 12
Rotates by driving a motor 18 connected to the rotating shaft 16. A polishing pad 20 is attached to the upper surface of the polishing platen 12, and a polishing agent (slurry) is supplied onto the polishing pad 20 from a nozzle (not shown).

As shown in FIG. 2, the wafer holding head 14 is mainly composed of a head body 22, a carrier 24, a carrier pressing means 26, a retainer ring 28, a retainer ring pressing means 30, a protective sheet 52, an air control means and the like. ing.

The head body 22 is formed in a disk shape, and a rotating shaft 32 is connected to the center of the upper surface of the head body 22. The head main body 22 is driven by a motor (not shown) connected to the rotating shaft 32 to rotate.

The carrier 24 is formed in a disk shape and is arranged at the center of the lower part of the head body 22. A cylindrical recess 34 is formed in the center of the upper surface of the carrier 24. The shaft portion 36 of the head body 22 is fitted into the recess 34 through a pin 38. The rotation of the carrier 24 is transmitted from the head main body 22 via the pin 38.

A carrier pressing member 40 is provided on the peripheral portion of the upper surface of the carrier 24. Carrier 24
Through this carrier pressing member 40, the carrier pressing means 2
The pressing force is transmitted from 6.

On the lower surface of the carrier 24, an air suction / blowing groove 42 which is an air supply path for injecting air to the protective sheet is formed. An air passage 44 formed inside the carrier 24 communicates with the suction / blowing groove 42. An intake pump and an air supply pump are connected to the air passage 44 via an air pipe (not shown). Suction and blowout of air from the suction / blowing groove 42 are performed by switching between the intake pump and the air supply pump.

The air control means is constituted by the air suction / blowing groove 42, the air flow path 44, the air pipe, the intake pump, the air supply pump, the means for switching between the intake pump and the air supply pump, and the like. .

The carrier pressing means 26 is composed of the head body 22.
The carrier 24, which is arranged on the outer peripheral portion of the lower surface of the carrier, is coupled to the carrier pressing member 40 by applying a pressing force to the carrier 24.
The pressing force is transmitted to. The carrier pressing means 26 is preferably composed of an air bag 46 made of a rubber sheet that expands and contracts by sucking and discharging air. An air supply mechanism 48 for supplying air is connected to the airbag 46, and the air supply mechanism 48 is provided with a regulator (not shown) that adjusts the pressure of the air that is pumped from a pump (not shown).

The retainer ring 28 is formed in a ring shape and is arranged on the outer periphery of the carrier 24. The retainer ring 28 is attached to a holder (retainer ring holder) 50 provided on the wafer holding head 14, and a protective sheet 52 is stretched around the inner peripheral portion thereof.

The retainer ring holder 50 is formed in a ring shape, and as shown in FIGS. 2 to 4, an annular recess 54 is formed on the lower surface thereof. On the other hand, on the upper surface of the retainer ring 28, a convex portion 56 that fits into the concave portion 54 is formed. The retainer ring 28 is attached to the retainer ring holder 50 by fitting the convex portion 56 into the concave portion 54 of the retainer ring holder 50 via the protective sheet 52.

FIG. 3 is a sectional view showing an example of the structure of the holding portion of the protective sheet 52. In the figure, a retaining groove 50C having a rectangular cross section, which is a circumferential groove, is provided on the surface (lower surface) of the retainer ring holder 50, and the retaining groove 50C is fitted on the surface (upper surface) of the retainer ring 28. A holding ridge 28C having a rectangular cross section is provided. By sandwiching the protective sheet 52 by the sandwiching portion composed of the retaining groove 50C and the retaining ridge 28C, the protective sheet 52
Can be prevented from slipping from the retainer ring holder 50.

Further, a tension adjusting means 78 for a protective sheet is provided on the retainer ring holder 50 and the retainer ring 28 on the inner peripheral side of the holding portion.
A groove 94 for a convex ring having a rectangular cross section, which is a groove in the circumferential direction, is provided on the surface (lower surface) of the retainer ring holder 50, and a convex ring 92 is fitted in the groove 94 for a convex ring. ing. The convex ring 92 has a groove 94 for the convex ring.
It can move up and down inside.

A screw hole (female screw) 90 penetrating the back surface (upper surface) of the retainer ring holder 50 is provided at the upper end of the groove 94 for the convex ring, and the screw hole 90 has a bolt (male screw) 88 from the top. Is screwed in. Therefore, by tightening the bolt 88, the convex ring 92
Can be lowered.

On the surface (upper surface) of the retainer ring 28,
At a location corresponding to the convex ring 92, a fitting groove 96 that is a circumferential groove having a rectangular cross section into which the convex ring 92 is fitted,
96 are provided. The positions and the cross-sectional shapes of the fitting grooves 96, 96 correspond to the two protruding portions 92A, 92A provided at the tip (lower end) of the convex ring 92.

The convex ring 92 and the fitting grooves 96, 96
The tension adjusting means 78 of the protective sheet 52 is configured by the above. That is, the protective sheet 52 sandwiched between the retainer ring 28 and the retainer ring holder 50 is
Tension is applied by being pushed into the fitting grooves 96, 96 by the convex ring 92. Then, the tension of the protective sheet 52 is adjusted by adjusting the pushing amount.

FIG. 4 is a sectional view showing another example of the structure of the holding portion of the protective sheet 52. In addition, the same as the configuration of FIG.
Similar members are designated by similar reference numerals, and description thereof will be omitted. In FIG. 4, the tip (bottom end) of the convex ring 92
Has a convexly rounded cross section, and the fitting groove 9
The bottom of 8 also has a shape corresponding to this. The tip of the convex ring 92 is made of a member having an A hardness of 10 to 90 defined by JIS K6301.

By constructing the tip portion of the convex ring 92 with a member made of such a material, the effect of preventing the protective sheet from slipping can be obtained.

In this case, the tip portion of the convex ring 92 is J
More preferably, it is composed of a member having an A hardness of 50 to 98 defined by IS K6301. In addition,
Even if only the tip of the convex ring 92 has a convexly rounded cross-sectional shape shown in FIG. 4 and the A hardness is made of a member other than the above range, Advantageous effects are obtained.

The protective sheet 52 is formed in a circular shape and has a plurality of holes 52A. This protective sheet 52
The peripheral edge portion is sandwiched between the retainer ring 28 and the retainer ring holder 50 so that the peripheral edge portion is stretched inside the retainer ring 28. That is, the protective sheet 52 is formed in a thin disk shape, and when the retainer ring 28 is attached, the peripheral edge of the protective sheet 52 is formed by the protrusion 56 of the retainer ring 28 and the recess 5 of the retainer ring holder 50.
By retaining it between 4 and the retainer ring 28
Is stretched inside. By stretching in this way,
The protective sheet 52 is pulled in the outer peripheral direction at the same time as it is attached, and is stretched uniformly over the entire surface without wrinkles.

The air ejected from the suction / blowing groove 42 of the carrier 24 forms an air layer between the carrier 24 and the protective sheet 52 by the pressing force applied by the carrier pressing means 26, so-called static pressure bearing. The wafer W is pressed against the polishing pad 20 via the protective sheet 52 according to the above principle (the principle of the air bearing).

The protective sheet 52 serves to attract the carrier 24.
It is required that the elastic member is sufficiently flexible to transmit the air dynamic pressure distribution formed by the air layer formed by the blowout grooves 42 to the wafer W, and that the material does not damage the wafer W and does not contaminate it. To be

Further, even when the retainer ring 28 is worn, the retainer ring 28 needs to be flexible enough to change the amount of flexure following the wear and have sufficient strength against contact and friction with the wafer W during polishing. To be

Normally, the pressing force of the wafer W is 20 to 70 k.
The range of Pa is adopted. For example, the outline is 300
When the wafer W having a size of mm is polished with a pressing force of 70 kPa, the protective sheet 52 having a JIS-A hardness of 90 and a thickness of 1 mm can be used.

As the material of the protective sheet 52, as the rubber-based material, chloroprene rubber, nitrile rubber or the like is used.
As resin materials such as tetrafluoroethylene resin, PET,
Polyethylene, polypropylene, PFA, PTFE and the like are PEE as resin materials such as polyimide resin.
K, Vespel (trade name), etc. can be used.

As shown in FIGS. 3 and 4, the retainer ring 28 has bolts 58, 58, ... After the protrusion 56 is fitted into the recess 54 of the retainer ring holder 50.
Retainer ring holder 5 by screwing with
It is fixed at 0. Therefore, the retainer ring holder 5
0 are formed with screw holes 60, 60, ... at regular intervals, and the retainer ring 28 has through holes 6 at regular intervals.
2, 62, ... Are formed.

Further, the convex portion 56 formed on the retainer ring 28 and the concave portion 54 formed on the retainer ring holder 50 have inner wall surfaces 54A and 56A formed in a tapered shape (the tapered portion is This is done so that the fitting work can be done easily.

FIG. 5 is a bottom view of the wafer holding head 14 and shows the positional relationship between the retainer ring 28, the protective sheet 52 and the like. In addition, in the same drawing, the holding groove 50C and the holding convex strip 28C are not shown. In the figure, the fitting groove 98 shown in FIG. 4 is continuously provided in the circumferential direction without interruption, but may be provided so as to be divided in the circumferential direction. In this case, the corresponding convex ring 92 may also be divided and provided in the circumferential direction.

Incidentally, FIGS. 3 and 4 described above are sectional views taken along the line AA in FIG.

As shown in FIG. 2, the carrier 24 and the protective sheet 5 are provided below the carrier 24 on which the protective sheet 52 is stretched.
An air reservoir 74 is formed between the two. Wafer W
Are pressed against the carrier 24 via the air reservoir 74. The internal pressure of the air reservoir 74 is increased by blowing air from the suction / blowing groove 42 of the carrier 24. Further, the holes 52A formed in the protective sheet 52 act as suction holes when holding and transporting the wafer W, and as air ejection holes during polishing. The retainer ring holder 50 is attached to a ring-shaped attachment member 64 via a snap ring 66. The snap ring 66 is formed in a ring shape, and a groove 66A is formed on the inner peripheral portion thereof as shown in FIGS. The snap ring 66 is formed with a slit so that it can be expanded and contracted.

As shown in FIGS. 3 and 4, the retainer ring holder 50 and the mounting member 64 have outer peripheral flange portions 50A, 64A formed on the outer periphery of the upper end portion and the outer periphery of the lower end portion, respectively.
Are fitted into the groove 66A formed in the snap ring 66, and are integrated and fixed to each other.

An inner peripheral flange portion 50B is formed on the inner peripheral portion of the retainer ring holder 50, and the flange portion 24A formed on the outer peripheral portion of the carrier 24 is loosely inserted into the inner peripheral flange portion 50B. There is. As a result, an air layer is formed between the carrier 24 and the protective sheet 52.

The retainer ring pressing member 68 shown in FIG. 2 is connected to the mounting member 64. Retainer ring 2
8, the pressing force from the retainer ring pressing means 30 is transmitted via the retainer ring pressing member 68.

The retainer ring pressing means 30 is arranged on the peripheral edge of the central portion of the lower surface of the head main body 22 and applies a pressing force to the retainer ring pressing member 68 to attach the retainer ring 28 to the polishing pad 20. Press down. The retainer ring pressing means 30 is also preferably composed of an airbag 70 made of a rubber sheet, like the carrier pressing means 26. An air supply mechanism 72 for supplying air is connected to the airbag 70, and the air supply mechanism 72 is provided with a regulator (not shown) that adjusts the pressure of the air sent from a pump (not shown).

The wafer polishing method of the wafer polishing apparatus 10 configured as described above is as follows.

First, the wafer W is attached to the wafer holding head 1
4 and hold it on the polishing pad 20. At this time, the wafer W is suction-held using the suction / blowing groove 42 formed on the lower surface of the carrier 24. Due to this suction, a plurality of holes 52A are formed in the protective sheet 52 (see FIGS. 3 and 4). The wafer W is suction-held through this hole 52A.

Next, from the pump (not shown) to the airbag 4
Supply air to 6, 70. At the same time carrier 24
Air is blown out from the suction / blowing groove 42 of. This allows
As the internal pressure of the air reservoir 74 increases, the airbag 4
6 and 70 swell, the wafer W and the retainer ring 28
Are pressed against the polishing pad 20 with a predetermined pressure. In this state, the polishing platen 12 is rotated in the direction of FIG. 1A and the wafer holding head 14 is rotated in the direction of FIG. 1B. Then, the slurry is supplied onto the rotating polishing pad 20 from a nozzle (not shown). As a result, the lower surface of the wafer W is polished by the polishing pad 20.

The protective sheet 52 has a plurality of holes 52A.
Since the holes are formed (see FIGS. 3 and 4), the air supplied to the air reservoir 74 presses the back surface of the wafer W from the holes 52A through the protective sheet 52. A direct pressing force does not work between the protective sheet 52 existing in the air layer and the back surface of the wafer W. Therefore, the uneven thickness of the protective sheet 52 does not affect the processing accuracy of the wafer W.

Further, since the protective sheet 52 has a plurality of holes 52A for adsorption, a thin air layer is formed between the protective sheet 52 and the back surface of the wafer W. There is almost no air flow between and, and even if there is an air flow, the amount of air is very small, so that the slurry does not aggregate.

Next, a method of stretching the protective sheet 52 will be described. First, the retainer ring 28 and the retainer ring holder 50 are separated. Then, the protective sheet 52 is arranged between the separated retainer ring 28 and the retainer ring holder 50.

Next, the convex portion 56 formed on the retainer ring 28 is fitted into the concave portion 54 formed on the retainer ring holder 50. As a result, the protective sheet 52 is stretched inside the retainer ring 28, with its peripheral portion being sandwiched between the retainer ring 28 and the retainer ring holder 50.

At the same time, the peripheral edge of the protective sheet 52 is sandwiched between the convex portion 56 of the retainer ring 28 and the concave portion 54 of the retainer ring holder 50 and is stretched.
At this time, since the protective sheet 52 is sandwiched while being pulled in the outer peripheral direction, it is stretched uniformly over the entire surface without wrinkles.

Finally, the retainer ring 28 is fixed to the retainer ring holder 50 with bolts 58, 58, ... Thus, the tensioning work is completed. Since the peripheral edge of the protective sheet 52 is sandwiched between the retaining projection 28C of the retainer ring 28 and the retaining groove 50C of the retainer ring holder 50, slipping can be prevented even if tension is applied.

When the protective sheet 52 is stretched by repeating the polishing work, the tension of the protective sheet 52 may be properly adjusted by the tension adjusting means 78 to remove the inappropriate bending.

Specifically, the retainer ring holder 50 may be separated from the head body 22 by removing the snap ring 66, and the bolts 88, 88 ... may be tightened. At that time, in order to uniformly tighten the plurality of bolts 88,
It is preferable to use a tool such as a torque wrench.

As described above, according to the wafer polishing apparatus 10 of the present embodiment, the protective sheet 52 can be easily stretched inside the retainer ring 28 without wrinkles.

Further, the wafer polishing apparatus 1 of the present embodiment
In 0, since the tension of the protective sheet was made variable, the quality of the wafer edge and the like can be maintained, and as a result, the polishing quality of the wafer can be maintained. In addition, excessive wear of the wafer edge can be prevented, and the strength and durability of the retainer ring can be maintained.

The configuration described above is an embodiment of the present invention, but the configuration of the present invention is not limited to these, and various configurations can be adopted. For example, the tension adjusting means 7
The shape, material, etc. of the tip of the convex ring 92 used in FIG. 8 may be other than those shown in FIGS.

Further, in the tension adjusting means 78, the convex ring 92 is arranged on the retainer ring 28, and the fitting groove 98 is formed.
(96) may be arranged on the retainer ring holder 50. With this configuration, the tension adjusting means 7
When the tension of the protective sheet 52 is adjusted by 8, the retainer ring holder 50 is not separated from the head body 22,
The tension can be adjusted by tightening the bolt 88 from the lower side.

[0063]

As described above, according to the present invention,
By varying the tension of the protective sheet, the quality of the wafer edge portion and the like can be maintained, and as a result, the polishing quality of the wafer can be maintained. In addition, excessive wear of the wafer edge can be prevented, and the strength and durability of the retainer ring can be maintained.

[Brief description of drawings]

FIG. 1 is a perspective view showing the entire structure of a wafer polishing apparatus.

FIG. 2 is a vertical sectional view showing the structure of a wafer holding head.

FIG. 3 is a cross-sectional view showing an example of a configuration of a sandwiching portion of a protective sheet.

FIG. 4 is a cross-sectional view showing another example of the configuration of the holding portion of the protective sheet.

FIG. 5 is a bottom view showing the structure of a wafer holding head.

FIG. 6 is a front view showing a configuration of a main part of a conventional wafer holding head.

FIG. 7 is a cross-sectional view showing a configuration of a sandwiching portion of a conventional protective sheet.

[Explanation of symbols]

10 ... Wafer polishing apparatus, 12 ... Polishing platen, 14 ... Wafer holding head, 20 ... Polishing pad, 24 ... Carrier,
28 ... Retainer ring, 42 ... Suction / blowing groove, 44 ...
Air flow path, 46 ... Air bag, 48 ... Air supply mechanism, 5
0 ... Retainer ring holder, 52 ... Protective sheet, 72
... Air supply mechanism, 74 ... Air reservoir, 78 ... Tension adjusting means, 88 ... Bolt, 90 ... Screw hole, 92 ... Convex ring,
96 ... Fitting groove, 98 ... Fitting groove, W ... Wafer

Claims (5)

[Claims] 1. A wafer polisher for attaching a retainer ring to a holder provided on a wafer holding head, tensioning a protective sheet inside the retainer ring, and pressing a wafer against a polishing pad through the protective sheet to polish the wafer. In the device, an outer peripheral edge portion of the protective sheet is sandwiched between the retainer ring and the holder, and a tension adjusting means for the protective sheet is provided on an inner peripheral side of the sandwiching portion. A wafer polishing apparatus characterized in that the tension of a protective sheet provided is variable. 2. The tension adjusting means includes a fitting groove that is a circumferential groove provided on one surface of the retainer ring and the holder, and a fitting groove provided on the other surface side. The wafer polishing apparatus according to claim 1, which is a combination with a convex ring that fits. 3. The wafer polishing apparatus according to claim 2, wherein the tension adjusting means fits the convex ring into the fitting groove by a linear moving means that is a combination of a male screw and a female screw. 4. The tip portion of the convex ring is JIS K
The wafer polishing apparatus according to claim 1, comprising a member having an A hardness of 10 to 90 defined by 6301. 5. A carrier for pressing a portion of the protective sheet corresponding to the wafer region toward the wafer is provided on the back surface of the protective sheet, and a protective sheet is provided on the surface of the carrier facing the protective sheet. An air supply path for injecting air is provided, and the air supply path is connected to air control means for controlling the amount of supplied air, and the air control means controls the air pressure supplied from the air supply path. The wafer polishing apparatus according to claim 1, wherein the wafer is polished by being applied to the wafer via a protective sheet.