JP2003025218A - Wafer polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of stably holding a wafer at a position specified in a retainer ring and improving controllability and stability of a polishing shape in the neighborhood of a wafer edge part without changing the position of the wafer even during the polishing. SOLUTION: A wafer carrier 14 is constituted of a carrier main body 22, a membrane 32 to transmit pressurizing force to the wafer W, a back plate 24 to supply air pressure to the membrane 32 and the retainer ring 26 to hold the membrane 32 in the circumference, and a guide 30 to regulate movement of the wafer in the radial direction is provided in the proximity of an outer periphery of the wafer besides the retainer ring 26 on the wafer carrier 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus, and more particularly to chemical mechanical polishing (CMP).
sing) wafer polishing apparatus.

[0002]

2. Description of the Related Art In recent years, due to the development of semiconductor technology, design rules are becoming finer and multilayer wiring is being made, and in order to reduce costs, the diameter of wafers is also being made larger. On the other hand, in the wafer, the area for polishing uniformity evaluation in the polishing step in the CMP apparatus is also expanding to the vicinity of the wafer edge portion in order to further expand the area where the chip can be obtained. In particular, recently, when evaluating the polishing uniformity over the entire area of the wafer, the polishing shape near the edge greatly affects the evaluation of the polishing uniformity,
In order to secure stable polishing uniformity, controllability and stability of the polishing shape near the wafer edge have become indispensable.

In order to meet such demands, a method of applying a pressing force to a wafer through a membrane which is a thin film material is used. This is because air is blown from multiple positions on the lower surface of the back plate placed on the upper part of the membrane to form an air float, and the back surface of the wafer is pressed with an even pressure through the membrane to improve the uniformity. This is what we are aiming for. During the polishing process, a retainer ring is arranged outside the outer peripheral portion of the wafer in order to prevent the wafer from moving in the radial direction. However, the inside diameter of this retainer ring is 1 to 2 m from the outside diameter of the wafer in order to stably fit the inside of the wafer.
It is made as large as m and has a margin. However, considering the controllability and stabilization of the polished shape of the wafer edge portion in the future, this margin of about 1 to 2 mm becomes a big problem. The contents will be described below. FIG. 4 shows a plan view of the polishing apparatus in the lower part and a partially enlarged sectional view in the upper part. Under the condition that the wafer is not polished, the wafer is located in the center of the retainer ring. However, once polishing is started, as shown in FIG. 4, the wafer has a frictional force with the polishing pad in the retainer ring. The polishing pad slides in the moving direction and is pressed against the inner wall of the retainer ring. The position where the polishing pad moves from the retainer ring side to the wafer side is called the Leading Edge on the wafer, and the position where the polishing pad moves from the wafer side to the retaining ring side is the Trailing Edge on the wafer. That is, during polishing, there is a clear difference in the gap between the retainer ring and the wafer on the leading edge side and the trailing edge side. That is, the gap becomes large on the leading edge side and becomes small on the trailing edge side. However, since the wafer is rotated by rotating the wafer carrier that holds the wafer in order to evenly polish the entire surface of the wafer, a gap difference between the leading edge side and the trailing edge side occurs at a certain moment. However, at the next moment, the wafer carriers rotate and move while maintaining the respective gap differences. Then, at the moment when the frictional force of polishing becomes larger than the frictional force between the wafer and the membrane, a slip occurs between the wafer and the membrane, the wafer is pushed into the inner wall of the retainer ring, and this is repeated intermittently. Polishing proceeds in this state.

[0004]

However, in such a polishing situation in which the wafer moves irregularly in the retainer ring during polishing, it is very difficult to improve the controllability and ensure the stability of the polishing shape near the edge of the wafer. Becomes difficult.

The present invention has been made in view of the above circumstances and stably holds a wafer at a predetermined position in a retainer ring so that the wafer can change its position even during polishing. It is an object of the present invention to provide a polishing apparatus that can improve the controllability and stability of the polishing shape in the vicinity of the wafer edge.

[0006]

In order to achieve the above-mentioned object, the present invention provides a wafer polishing apparatus for polishing a wafer held by a wafer carrier by pressing it against a polishing pad while supplying a slurry, wherein the wafer carrier is ,
A carrier body, a membrane that transmits a pressing force to the wafer, a back plate that supplies air pressure to the membrane, and a retainer ring that holds the membrane around, and the wafer carrier further includes the retainer ring. Separately, a guide for restricting the radial movement of the wafer is provided near the outer circumference of the wafer, and the guide is formed on the membrane. Further, the surface of the retainer ring that comes into contact with the polishing pad is made of a hard and highly wear-resistant material.

According to the first aspect of the present invention, in addition to the retainer ring, a guide is provided in the vicinity of the outer periphery of the wafer to restrict the radial movement of the wafer.
Even during polishing, the wafer does not change its position, and the controllability and stability of the polished shape in the vicinity of the wafer edge can be improved.

According to the second aspect of the present invention, since the guide for restricting the radial movement of the wafer is formed in the membrane, the elasticity of the membrane absorbs the variation in the outer diameter of the wafer, and thus the wafer has a smaller diameter. Can be held in place.

According to the third aspect of the present invention, the surface of the retainer ring that contacts the polishing pad is made of a hard and highly wear-resistant material. Little wear on the contact surface.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In each drawing, the same members are given the same numbers or symbols.

FIG. 1 is a perspective view showing the overall structure of a wafer polishing apparatus 10. Wafer polishing apparatus 10 shown in FIG.
Is mainly composed of a polishing platen 12 and a wafer carrier 14. The polishing platen 12 is rotated 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 slurry is supplied onto the polishing pad 20 from a nozzle (not shown).

As shown in FIG. 2, the wafer carrier 14 mainly includes a carrier body 22, a back plate 24,
Air bag 40 for back plate, retainer ring 2
6, a retainer air bag 42, a guide 30, a membrane 32, and the like.

The carrier body 22 is formed in a disk shape, and the rotating shaft 36 is connected to the center of the upper surface thereof. Carrier body 2
The motor 2 is rotated by driving a motor (not shown) connected to the rotary shaft 36.

The back plate 24 is formed in a disk shape and is arranged at the center of the lower part of the carrier body 22. A pressing plate 24A is provided on the lower surface of the back plate 24 facing the membrane 32, and a plurality of air outlets 24B, 24B, ... Are formed on the outer circumference of the pressing plate concentrically at predetermined intervals. The air outlets 24B, 24B, ... Are connected to an air line 64, and are connected to an air pump P via a regulator R ₃ via a rotary joint (not shown) attached to the carrier body 22.

The retainer ring 26 arranged outside the outer circumference of the wafer W includes a retainer body 26A and a membrane 32.
The contact ring 27 that comes into contact with the surface of the wafer, the holding ring 28 that clamps the membrane, the clamp ring 29, and the like, and the membrane 32 that transmits the pressing force from the back plate 24 to the wafer W are the holding ring 28 and a plurality of them on the circumference. It is clamped by a clamp ring 29 which is divided into A guide 30 that supports the wafer W in the vicinity of the outer diameter portion is integrally formed on the membrane 32. Figure 3
Is a retainer ring 26, a guide 30, and a wafer W.
Shows the positional relationship of. FIG. 3A shows the overall positional relationship, and FIG. 3B is an enlarged view of the C portion in FIG. 3A. As shown in FIG. 3, the guide 30 for restricting the radial movement of the wafer W has a taper shape with a triangular cross section or a taper shape in which one side of the inside is curved to connect the wafer W easily. Is doing. Also guide 30
Is slightly larger than the outer diameter of the wafer W, so that the wafer W housed in the guide 30 does not move in the radial direction. The guide 30 is integrally formed on the lower surface of the membrane 32 with the same material as the membrane 30. In addition, the retaining ring 28 and the clamp ring 29 that sandwich the membrane 32 are the retainer body 26.
It is fitted between A and the contact ring 27, and the screw 2
It is pulled up to the contact ring 27 at 7A. On the surface of the retainer body 26A that contacts the polishing pad 20, ceramics, SiC (silicon carbide),
A hard material 26B such as SiN (silicon nitride) or DLC (Dia Like Carbon) coat is embedded.

Carrier body 22 and retainer ring 26,
Since the retainer ring 26 and the back plate 24 are respectively prevented from rotating by locking means (not shown), when the carrier body 22 rotates, the retainer ring 26 and the back plate 24 rotate together with the carrier body 22. It is supposed to do.

A rubber sheet 34 is screwed to the carrier body 22 via mounting rings 38 and 39.
The carrier body 22 and the rubber sheet 34 form a back plate air bag 40 that presses the back plate 24 and a retainer air bag 42 that presses the retainer ring 26. Both the back plate air bag 40 and the retainer air bag 42 are connected via a rotary joint (not shown) attached to the carrier body 22, and one is connected to the air pump P via the regulator R ₁ in the air line 60, The other is connected to the air pump P via the regulator R ₂ in the air line 62, respectively.

Next, the operation of the wafer carrier 14 thus constructed will be described. First, the wafer W
Are held on the lower surface of the membrane 32 attached to the retainer ring 26 of the wafer carrier 14. Since the guides 30 that are slightly larger than the outer diameter of the wafer W are formed on the membrane 32, the wafer W has a guide 3
It is fitted in the center of 0. At this time, even if the outer diameter of the wafer W varies, the guide 30 and the membrane 32 integrated with the guide 30 have elasticity and thus absorb the variation. In this state, the processing surface of the wafer W is brought into contact with the rotating polishing pad 20, and a processing pressure is applied through the membrane 32 and the wafer W rotates on its axis. Wafer W at this time
Tends to move by the rotation of the polishing pad 20, but is stable because it is supported in the radial direction by the guide 30 and does not move. Slurry is supplied from a nozzle (not shown) to the vicinity of the processed portion of the polishing pad 20, and the wafer W is combined with a chemical action of a chemical contained in the slurry and a mechanical action of the polishing pad 20.
Are polished.

Next, the application of processing pressure to the wafer W in processing will be described. As shown in FIG. 2, the pressure of the compressed air generated by the air pump P is adjusted by the regulator R ₃ of the air line 64, and the compressed air is ejected from the air outlet 24B provided in the pressing plate 24A of the back plate 24 to generate the pressure plate 24A. Void 46 with the membrane 32
Then, an air float is formed and the wafer W is pressed through the membrane 32. On the other hand, the compressed air whose pressure is adjusted by the regulator R ₁ of the air line 60 expands the back plate air bag 40 and presses the entire back plate 24. That is, the processing pressure applied to the entire back plate 24 is equal to the pressing plate 24A of the back plate 24.
It is transmitted to the membrane through the pressure air layer jetted from the air outlet 24B provided in, and is further transmitted from the membrane to the wafer W. Therefore, even if the wafer W has irregularities or the thickness varies, a uniform processing pressure is transmitted to the processed surface of the wafer W. In addition, the air outlet 24 provided in the pressing plate 24A of the back plate 24
A plurality of Bs may be provided not only in the outer peripheral portion of the pressing plate 24A but also in the central portion, and the air outlets at the outer peripheral portion and the central portion may be connected to the air pump P via independent regulators by independent air lines. With this configuration, the pressing force can be adjusted separately for the central portion and the outer peripheral portion of the wafer W. Next, the compressed air whose pressure is adjusted by the regulator R ₂ expands the retainer air bag 42 via the air line 62 and the retainer ring 26.
Apply pressing force to. The retainer ring 26 is a wafer W
Moves in the radial direction due to abnormal force, and wafer carrier 1
In addition to restricting jumping out of 4, polishing pad 2
It also has an effect of suppressing the waviness of the surface of the polishing pad 20 by pressing 0 to stabilize the surface.

Next, a means for adjusting the tension of the membrane 32 which is in direct contact with the wafer W and transmits the pressing force from the back plate 24 will be described. The membrane 32 is sufficiently flexible to transmit the air dynamic pressure distribution formed by the pressure air layer formed by the air ejected from the air outlet 24B formed in the pressing plate 24A of the back plate 24 to the wafer W. In addition, it requires appropriate rigidity.
Therefore, a resin material, a rubber material, a thin metal material coated with a resin, or the like is used. For example, PET sheet, polyethylene sheet, polypropylene sheet, polyimide sheet, urethane sheet, Teflon (registered trademark) sheet such as PFT and PTFE, rubber sheet such as chloroprene rubber and nitrile rubber, resin-coated ultra-thin (100 μm or less) SUS Sheets etc. can be applied.
The means for adjusting the tension of the membrane 32 is, as shown in FIG. 2, a contact ring 27 that constitutes the retainer ring 26 and a holding ring 28 that holds the membrane 32.
And a clamp ring 29 and a screw 27A. The contact ring 27 is inserted into the inner diameter portion of the holding ring 28 holding the membrane 32, and the plurality of screws 27A,
The retaining ring 28 is pulled up by 27A, .... By closing the plurality of screws 27A, 27A, ..., Since the end of the membrane 32 is pulled up while the upper surface of the membrane 32 is in contact with the contact ring 27, the tension of the membrane 32 is increased. Therefore, the screws 27A, 27A, ...
The tension of the membrane 32 can be adjusted depending on the strength of the tightening force of.

Next, the retainer protrusion amount adjusting means for adjusting the step between the lower surface of the membrane 32 and the lower surface of the retainer ring 26, which is an important factor in controlling the thickness of the edge portion of the wafer W, will be described. As shown in FIG. 2, the retainer protrusion amount adjusting means is composed of a retainer body 26A constituting the retainer ring 26, a contact ring 27, a shim 27C, a plurality of screws 27B, 27B ,. The contact ring 27 is fixed to the retainer body 26 by a plurality of screws 27B, 27B, ... Through shims 27C. Since the retainer protrusion amount corresponds to the distance between the surface of the contact ring 27 that contacts the membrane 32 and the lower surface of the retainer body 26A, when adjusting the retainer protrusion amount, the shim 27C is made of an elastic body and Screw 27
It can be adjusted by the strength of the tightening force of B, 27B, .... Alternatively, the shim 27C may be made of a rigid body, and the shim 27C
The thickness may be adjusted and fixed with screws 27B, 27B, ....

In the embodiment of the present invention described above, the guide 30 for supporting the wafer W in the radial direction is formed on the membrane 32. However, the guide is not limited to this and may be provided at any other appropriate portion. Although the guide 30 is described as a ring having a triangular cross section, the cross sectional shape is not limited to this.

[0023]

As described above, according to the present invention, since the wafer carrier is provided with a guide for restricting the radial movement of the wafer in the vicinity of the outer periphery of the wafer, in addition to the retainer ring. It is possible to improve the controllability and stability of the polishing shape in the vicinity of the wafer edge portion without the wafer moving its position due to the frictional force. Furthermore, since the surface of the retainer ring that contacts the polishing pad is made of a hard and highly wear-resistant material, the contact surface of the retainer ring with the polishing pad is less worn.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a wafer polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a wafer carrier of a wafer polishing apparatus according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a guide position of the wafer of the wafer polishing apparatus according to the embodiment of the present invention.

FIG. 4 is a conceptual diagram illustrating a problem of a conventional wafer polishing apparatus.

[Explanation of symbols]

W ... Wafer, 10 ... Wafer polishing device, 14 ... Wafer carrier, 20 ... Polishing pad, 22 ... Carrier body,
24 ... Back plate, 26 ... Retainer ring, 26B
… Hard material, 30… Guide, 32… Membrane

Claims (3)

[Claims] 1. A wafer polishing apparatus for polishing a wafer held by a wafer carrier by pressing it against a polishing pad while supplying a slurry, wherein the wafer carrier comprises a carrier body, and a membrane for transmitting a pressing force to the wafer. The wafer carrier comprises a back plate for supplying air pressure to the membrane and a retainer ring for holding the membrane around the wafer carrier, and the wafer carrier is provided separately from the retainer ring in the vicinity of the outer circumference of the wafer in the radial direction of the wafer. A wafer polishing apparatus having a guide for restricting movement. 2. The wafer polishing apparatus according to claim 1, wherein the guide is formed on the membrane. 3. The wafer polishing apparatus according to claim 1, wherein a surface of the retainer ring that contacts the polishing pad is made of a hard and highly wear-resistant material.