JP2001252863A - Method for polishing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for polishing a wafer, capable of optimizing the effect of a retainer ring and preventing sagging of the peripheral part of the wafer. SOLUTION: In the method for polishing the wafer 4, slurry is dripped on a surface plate 3 fitted with a polishing cloth 2 and a plate 6 holding the wafer 4 is pressed and rotated in order to polish the surface of the wafer 4. The retainer ring 5 is mounted on the plate 6 in a manner such as to form clearance C in the peripheral part of the wafer 4 for the purpose of polishing the wafer 4 with the clearance C adjusted automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing method for polishing a wafer surface, and more particularly to a wafer polishing method for eliminating excessive polishing of the outer peripheral portion of a wafer.

[0002]

2. Description of the Related Art To manufacture a semiconductor wafer, a single-crystal semiconductor ingot is made from polycrystalline silicon by, for example, the Czochralski method, and the ingot is sliced to a predetermined thickness by a multi-wire saw or the like, and the sliced product is sliced. The semiconductor wafer thus obtained is ground by a grinding device and mirror-polished by a polishing device to produce a semiconductor wafer.

However, in recent years, as the degree of integration of semiconductor devices has increased, flatness of the semiconductor wafer has been required. In the mirror polishing step, excessive polishing (peripheral sag) of the outer periphery of the semiconductor wafer has become a problem. I have. This is thought to be due in part to the effect of the submersion of the polishing cloth, and the depression of the semiconductor wafer into the polishing cloth is performed by pressing the polishing cloth in advance by hardening the polishing cloth itself and retaining it. Measures such as mitigation have been taken.

In order to obtain such a polishing effect by the retainer ring, the distance (clearance) between the semiconductor wafer and the retainer ring is one of the important factors.

More specifically, FIGS. 8 and 9 show the results of a static analysis of retainer ring, pressure distribution of a semiconductor wafer, and a polishing pad. As shown in FIG. 8, when the clearance C is large as shown in FIG. Once crushed, the polishing cloth 11 recovers its shape until it comes into contact with the semiconductor wafer 13 based on the compression elastic modulus of the polishing cloth 11, so that the pressure at the peripheral portion 13c of the semiconductor wafer 13 does not greatly change. The reaction force which the peripheral portion 13c receives from the polishing cloth 11 becomes large, and the retainer ring 12
Cannot be obtained. When the clearance C is small as shown in FIG. 9, the reaction force that the peripheral portion 13 c receives from the polishing pad 11 by the retainer ring 12 becomes small,
The effect of providing the retainer ring 12 is sufficiently obtained.

Therefore, it is possible to maximize the retainer effect by making the clearance as close to zero as possible. However, in practice, processing the retainer ring inside diameter that is the same as the diameter of the semiconductor wafer requires the diameter of the semiconductor wafer. It is difficult to consider the variation and the variation of the inner diameter of the retainer ring.

Japanese Patent Laid-Open No. 5-326468 discloses a method of suppressing the surface sagging of a wafer by using a retainer ring.
The polishing method described in this publication is a method in which a wafer is polished in a state in which a ring having a thickness smaller than the finished thickness of the wafer is attached to a peripheral edge of the wafer, and a surface sag of the wafer is suppressed.

However, according to the method of this disclosure, since the clearance is constant during the polishing process, the clearance cannot be brought close to zero as much as possible, and the retainer effect cannot be maximized.

[0009]

Therefore, there has been a demand for a method of polishing a wafer capable of maximizing the effect of retainer ring and preventing sagging of a peripheral portion of the wafer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method of polishing a wafer which can maximize the effect of retainer ring and prevent sagging of the peripheral portion of the wafer. .

[0011]

Means for Solving the Problems According to the first aspect of the present invention, which has been made to achieve the above object, a slurry is dropped on a surface plate provided with a polishing cloth, and a plate holding a wafer is pressed and rotated. By doing so, in the wafer polishing method for polishing the surface of the wafer, a retainer ring is mounted on the plate so that a clearance is formed around the wafer, and the wafer is polished while automatically adjusting the clearance. The present invention is characterized in that the method is a polishing method for a wafer.

In the invention of claim 2 of the present application, the automatic adjustment of the clearance is performed by attaching a retainer ring to a plate holding a wafer by utilizing surface tension of water. The gist is that the method is a polishing method for a wafer.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer polishing method according to the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a polishing apparatus 1 used for a wafer polishing method according to the present invention is provided with a polishing plate 2 provided with a rotating platen 3 and a polishing plate 2 pressed against the polishing plate 2 to be polished. A polishing plate 6 on which a semiconductor wafer 4 such as a semiconductor wafer 4 is fixedly attached using wax, and a retainer ring 5 is attached so that a clearance C is formed between the polishing wafer 6 and the polishing plate 6. And a rotating shaft 7 for rotating the rotating shaft 6.

Further, as shown in FIGS. 2 and 3, the retainer ring 5 is attached to the polishing plate 6 by using water to form a water film W and utilizing the surface tension of the water film W. The clearance C formed between the peripheral portion 4 c of the semiconductor wafer 4 and the retainer ring 5 can be changed by the movement of the retainer ring 5.

Next, a method for mirror polishing a wafer according to the present invention will be described.

As shown in FIGS. 4A and 4B, the semiconductor wafer 4 is fixedly held on a polishing plate 6 with wax, and thereafter, the retainer ring 5 having an inner diameter slightly larger than the diameter of the semiconductor wafer 4 is polished. A water film W is formed on the plate 6 using water, and is attached using the surface tension of the water film W. In this state, a slurry in which silica is dispersed is dropped on the surface plate 3 on which the polishing cloth 2 is provided, and the surface of the semiconductor wafer 4 is polished by pressing and rotating.

As shown in FIGS. 5 (a) and 5 (b), in this polishing step, a retainer ring 5 is adhered to the semiconductor wafer 4 on the entry side of the polishing cloth 2 by utilizing the surface tension of water. Since the retainer ring 5 is movable (rotatable) to the plate 6 and is not fixed, the retainer ring 5 is pushed by the polishing pad 2 and the semiconductor wafer 4
Contact Thus, the clearance C between the retainer ring 5 and the peripheral portion 4c of the semiconductor wafer 4 is infinitely zero.
(Up to the beveling width), the retainer effect can be maximized, the peripheral portion 4c of the semiconductor wafer 4 from the polishing pad 2 does not receive a large reaction force, and excessive polishing can be prevented. Of the peripheral portion 4c of the semiconductor wafer 4 can be prevented.

Further, there is no need to manufacture the retainer ring 5 with the inner diameter approaching the limit of the diameter of the semiconductor wafer 4, so that the manufacture of the retainer ring 5 is easy, and the work of attaching and detaching the retainer ring 5 is also easy. .

Further, the automatic adjustment of the clearance C during the polishing process is performed by using a polishing plate 6 for holding the semiconductor wafer 4.
In addition, since the retainer ring 5 is attached by utilizing the surface tension of water, the clearance C can be easily adjusted automatically without requiring a special member separately. There is no risk of contamination.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Purpose of test: The sagging state of the peripheral portion of a semiconductor wafer polished by the wafer polishing method according to the present invention is examined.

(2) Test method: The semiconductor wafer after chemical polishing is mirror-polished by the wafer polishing method according to the present invention as shown in FIG. 3, and then the thickness of the semiconductor wafer is measured. Create a contour map. A contour map is also prepared for a semiconductor wafer polished by a conventional mirror polishing method.

(3) Test results: The results are shown in FIG. 6 (Example) and FIG. 7 (Conventional example). As shown in FIG. 6, in the embodiment, no sag occurs in the peripheral portion. On the other hand, as shown in FIG. 7, in the conventional example, a sagging region is seen in the peripheral portion.

[0024]

According to the method of polishing a wafer according to the present invention, the effect of the retainer ring can be maximized and sagging of the peripheral portion of the wafer can be prevented.

That is, in a wafer polishing method in which a slurry is dropped on a surface plate provided with a polishing cloth, and a plate holding the wafer is pressed and rotated to polish the surface of the wafer, a retainer ring is attached to the plate. Attached so that a clearance is formed around the wafer, and polished the wafer while automatically adjusting the clearance, so that the clearance between the retainer ring and the wafer approaches zero as much as possible, maximizing the retainer effect. The peripheral portion of the wafer is not subjected to a large reaction force from the polishing cloth, so that excessive polishing can be prevented, dripping of the peripheral portion of the semiconductor wafer due to excessive polishing can be prevented, and retainer ring There is no need to manufacture the inner diameter as close as possible to the diameter of the wafer, and manufacturing of retainer rings is easy. Further, it is easy like attachment and detachment of the retainer ring.

Automatic adjustment of the clearance during the polishing process is made possible by attaching a retainer ring to the polishing plate holding the wafer by utilizing the surface tension of water, so that a special member is required separately. In this case, the clearance can be easily adjusted automatically, and there is no risk of contaminating the wafer.

[Brief description of the drawings]

FIG. 1 is a side view of a polishing apparatus used for a wafer polishing method according to the present invention.

FIG. 2 is a cross-sectional view showing a retainer ring mounted state of a polishing apparatus used in the wafer polishing method according to the present invention.

FIG. 3 is a plan view of a polishing plate of a polishing apparatus used in the wafer polishing method according to the present invention.

FIGS. 4 (a) and 4 (b) are an enlarged plan view and a vertical cross-sectional view of a main part showing a retainer ring mounted state at the start of polishing in the wafer polishing method according to the present invention.

5 (a) and 5 (b) are an enlarged plan view and a longitudinal sectional view of a main part showing a state of movement of a retainer ring during polishing in a wafer polishing method according to the present invention.

FIG. 6 is a contour diagram of a semiconductor wafer polished using the wafer polishing method according to the present invention.

FIG. 7 is a contour diagram of a semiconductor wafer polished using a conventional wafer polishing method.

FIG. 8 is a diagram showing a simulation result of a pressure distribution of a polishing pad generated near a retainer ring by static analysis (in the case of a large clearance).

FIG. 9 is a view showing a simulation result of a pressure distribution of a polishing pad generated near a retainer ring by static analysis (in the case of a small clearance).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Polishing cloth 3 Surface plate 4 Semiconductor wafer 4c Peripheral part 5 Retainer ring 6 Polishing plate 7 Rotation axis C Clearance W Water film

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Katsuaki Kamashi 6-866-1, Higashiko, Seiro-cho, Kitakanbara-gun, Niigata 5 Inside Niigata Toshiba Ceramics Co., Ltd. (72) Inventor Katsuyoshi Kojima 30 Soya, Hadano-shi, Kanagawa Prefecture Inside the Corporate Development Laboratory (72) Inventor Masayoshi Saito 686-1 86, Higashiko, Seirocho, Kitakanbara-gun, Niigata Prefecture Inside Niigata Toshiba Ceramics Co., Ltd. (72) Yoshihiko Hoshi 6861-81, Higashiko, Seikocho, Kitakanbara-gun, Niigata Ceramics Co., Ltd. F term (reference) 3C043 BA09 BC07 CC04 3C058 AB04 AC04 BA07 CB02 DA17

Claims (2)

[Claims] 1. A wafer polishing method for polishing a surface of a wafer by dropping a slurry on a surface plate provided with a polishing cloth and pressing and rotating a plate holding the wafer, wherein a retainer is provided on the plate. A method of polishing a wafer, comprising: mounting a ring on a peripheral portion of the wafer so as to form a clearance, and polishing the wafer while automatically adjusting the clearance. 2. The wafer polishing method according to claim 1, wherein the automatic adjustment of the clearance is performed by attaching a retainer ring to a plate holding the wafer using surface tension of water.