KR20040056634A - Chemical and mechanical polishing apparatus - Google Patents

Abstract

PURPOSE: A CMP(chemical mechanical polishing) apparatus is provided to improve polishing uniformity at the edge of a wafer by minimizing the unevenness of a polishing pad portion contacting the edge of the wafer during a polishing process. CONSTITUTION: A platen is prepared. A polishing pad is located on the platen. A polishing head(200) pressurizes a semiconductor substrate to the polishing pad to polish the substrate. A membrane(250) holds and releases the semiconductor substrate by vacuum, located on the bottom. A retainer ring(260) prevents the semiconductor substrate to which the membrane is absorbed from being separated from the polishing head during a process. The polishing head includes the membrane and the retainer ring. The retainer ring includes an inner retainer ring(262) surrounding the membrane and an outer retainer ring(264) surrounding the inner retainer ring.

Description

Chemical mechanical polishing device {CHEMICAL AND MECHANICAL POLISHING APPARATUS}

The present invention relates to an apparatus for manufacturing a semiconductor wafer, and more particularly to an apparatus for chemically and mechanically polishing a surface of a semiconductor wafer.

In recent years, the structure of semiconductor devices has been multilayered with high integration. Accordingly, a polishing process for planarizing each layer of the semiconductor wafer is essentially included in the manufacturing process of the semiconductor device. Various polishing methods for performing such a polishing process have been proposed, and among them, a chemical mechanical polishing (CMP) apparatus for chemically and mechanically polishing a wafer is widely used.

Mechanical polishing is the polishing of the wafer surface by friction between the polishing pad and the wafer surface by rotating the wafer while applying the predetermined load to the wafer while the wafer is placed on the rotating polishing pad. The surface of the wafer is polished by a slurry, which is a chemical abrasive supplied between the wafers.

In such a CMP apparatus, it is important to uniformly polish the entire surface of the wafer, and in particular, as the wafer is largely sized, the polishing uniformity of the wafer edge portion is more important. In general, the polishing head is located at the bottom and a membrane for holding or releasing the wafer and one retainer ring for preventing the wafer from exiting the polishing head during the polishing process. The pressure applied to the retainer ring is greater than the pressure applied to the membrane to hold the wafer. However, since the surface of the polishing pad attached to the platen is soft, the portion of the polishing pad contacting the retainer ring is recessed downward, and the portion adjacent to the recessed portion is rebound back to the upper portion, and the portion adjacent to the rebound portion. Is again embedded. That is, the top surface of the polishing pad is bent rather flat than the portion abutting the retainer ring to the portion abutting the wafer edge. This results in overpolishing of the outermost edge of the wafer abutting the rebound portion and underpolishing of the inner portion of the overpolishing portion, i.e., the portion in which the pad is embedded. Therefore, the uniformity of polishing is not achieved in the region corresponding to the width of approximately 5 mm to 10 mm of the wafer edge portion.

An object of the present invention is to provide a chemical mechanical polishing apparatus capable of improving the polishing uniformity of a wafer by minimizing over-polishing and under-polishing of the wafer edge.

1 is a perspective view of a CMP apparatus according to an embodiment of the present invention;

2 is a cross-sectional view of the polishing head;

Figure 3a shows the curvature of the polishing pad top surface in the general case with only one retainer ring; And

3B is a view showing the curvature of the polishing pad top surface when the two retainer rings are provided.

Explanation of symbols on the main parts of the drawings

10: base 20: polishing head assembly

120: polishing station 122: platen

124: polishing pad 200: polishing head

220: membrane support 240: membrane clamp

250: membrane 254: first supply line

256: second supply line 262: internal retainer ring

264: Outer Retainer Ring

In order to achieve the above object, the chemical mechanical polishing apparatus of the present invention includes a platen, a polishing pad positioned on the platen, a polishing head for pressing and polishing the semiconductor substrate on the polishing pad, and the polishing head Is located at the bottom and has a membrane for holding or releasing the semiconductor substrate by vacuum and retainer rings which prevent the semiconductor substrate adsorbed on the membrane from being released from the polishing head during the process. Preferably, the retainer rings include an inner retainer ring surrounding the membrane and an outer retainer ring surrounding the inner retainer ring, the first supply line being supplied with fluid for pressurizing the inner retainer ring in the polishing head; A second supply line is formed through which fluid for pressurizing the outer retainer ring is supplied.

Preferably the outer retainer ring is located spaced a predetermined distance from the inner retainer ring.

Hereinafter, an embodiment of the present invention will be described in more detail with reference to FIGS. 1 and 3.

The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. This embodiment is provided to more completely explain the present invention to those skilled in the art. Therefore, the shape of the elements in the drawings are exaggerated to emphasize a clearer description.

1 is a perspective view of a chemical mechanical polishing (CMP) apparatus according to a preferred embodiment of the present invention, and FIG. 2 is a cross-sectional view of the polishing head of FIG.

Referring to FIG. 1, the CMP apparatus of the present invention includes a base 10 having three polishing stations 120 and one transfer station 140 and four carrier head systems. a polishing head assembly 20 having a carrier head assembly 30.

During the process, three carrier head systems 30 receive and hold the wafer and perform the polishing process by pressing the wafer on the polishing pad 124 of the polishing station 120. One carrier head system 30 then sends wafers to or receives wafers from the transfer station 140.

The polishing station 120 includes a platen 122 having a flat top surface installed on top and a polishing pad 124 installed on the platen 122. The polishing pad 124 is in direct contact with the wafer with a flat plate having a predetermined thickness to mechanically polish the wafer, and the platen 122 supports the polishing pad 124 from below. A drive motor (not shown) may be positioned in the base 110 to rotate the platen 122 at a predetermined speed.

In order to maintain the polishing conditions of the polishing pad 124, each polishing station 120 may include a pad conditioner 128. On one side of the polishing pad 124 is a slurry supply arm 126 for supplying a slurry to the surface of the polishing pad 124.

Each carrier head system 30 includes a polishing head 200 and a drive shaft 300 and a motor 400 for driving the polishing head 200.

Referring to FIG. 2, which shows a cross section of the polishing head 200 shown in FIG. 1, the polishing head 200 includes a membrane supporting plate 220, a membrane clamp 240, and a membrane. 250, and a retainer ring 260.

A membrane support plate 220 having a plurality of vacuum holes 222 is formed under the polishing head 200. The membrane 250 is mounted on the bottom and outer peripheral surfaces of the membrane support plate 220. The membrane 250 is a portion of the circular thin rubber membrane that directly contacts the rear surface of the wafer to adsorb or pressurize the wafer W. The membrane 250 is fixed to the membrane support plate 220 by an annular membrane clamp 240 positioned above the edge of the membrane support plate 220. A gimbal plate 270 having an air supply line 252 is formed on the membrane clamp 240. The first space 282 is formed by the gimbal plate 270, the membrane support plate 220, and the membrane clamp 240. Air supplied through the air supply line 256 formed in the gimbal plate 270 flows into the first space 282, and the membrane 250 contracts or expands according to these air pressures.

At the lower edge of the polishing head 200 is an annular retainer ring 260. The retainer ring 260 is to prevent the wafer W from being separated from the polishing head 200 by stably holding the wafer W during the polishing process.

In the present invention, the polishing head 200 has two retainer rings 262 and 264 to improve the polishing uniformity of the wafer edge. That is, the inner retainer ring 262 is positioned to surround the membrane 250 and the outer retainer ring 264 is positioned to surround the inner retainer ring 262. Pressurization of the inner retainer ring 262 and the outer retainer ring 264 are performed respectively. The polishing head 200 has a first supply line 254 through which air pressurizes the inner retainer ring 262 and a second supply line 256 through which air pressurizes the outer retainer ring 264 is supplied. The air supplied through the first supply line 254 flows into the second space 284 to pressurize the inner retainer ring 262, and the air supplied through the second supply line 256 passes through the third space 286. ) And pressurizes the outer retainer ring 264. The outer retainer ring 264 is preferably at least 0.2 mm away from the inner retainer ring 262 so that no side friction occurs between each other when the outer retainer ring 264 and the inner retainer ring 262 are moved, respectively.

As described above, the effect obtained by providing the inner retainer ring 262 and the outer retainer ring 264 will be described with reference to FIGS. 3A and 3B. FIG. 3A is a view showing a problem when only one retainer ring is provided, and FIG. 3B is a view showing minimizing the problem when two retainer rings are provided.

The pressure applied to the retainer ring 266 is greater than the pressure applied to the membrane 250 to prevent the wafer W from escaping out of the polishing head during the polishing process. Since the upper surface of the polishing pad 124 is made of a soft material, as shown in FIG. 3A, a portion ('A') contacting the retainer ring 266 is recessed downward, and the portion adjacent to the recessed portion is shown. Is rebounded ('B'), and the portion adjacent to the rebounded portion is re-embedded ('C'). That is, the portion of the polishing pad 124 in contact with the wafer edge is not flat but curved. Accordingly, the outermost portion of the wafer edge that abuts the rebound portion is overpolishing, and the inner portion of the portion that is over-polishing at the wafer edge, i.e., the portion where the polishing pad 124 abuts, is under-polishing ( underpolishing). As a result, no uniform polishing occurs at the edge of the wafer, which is exacerbated as high pressure is applied to the retainer ring 266.

Referring to FIG. 3B, in the present invention, the inner bounder ring 262 presses the rebounded portion ('B' portion ') to a proper pressure by the pressure of the outer retainer ring 264, so that the polishing pad contacts the edge of the wafer. (124) The portion ('C' portion ') is reduced in the degree of curvature compared to the general case. Therefore, since the upper surface of the polishing pad 124 is kept flat than the general case having only one retainer ring, the polishing uniformity of the wafer edge can be improved. In FIG. 3B, the portion indicated by the dotted line in the regions of the B 'and C' portions shows the top surface curvature of the polishing pad when the inner retainer ring 262 is not provided.

In the present exemplary embodiment, two retainer rings 260 are mounted in the polishing head 200. However, as the number of retainer rings 260 increases, the flatness of the top surface of the polishing pad 124 increases, so that more retainer rings may be mounted.

According to the chemical mechanical polishing apparatus of the present invention, it is possible to minimize the bending of the polishing pad portion in contact with the wafer edge during the polishing process, thereby improving the polishing uniformity of the wafer edge portion.

Claims (3)

An apparatus for chemically and mechanically polishing a semiconductor substrate, Platen; A polishing pad located on the platen; A polishing head for pressing and polishing the semiconductor substrate on the polishing pad; The polishing head is located on a bottom surface and has a membrane for holding or releasing the semiconductor substrate by vacuum and retainer rings for preventing the semiconductor substrate adsorbed on the membrane from being released from the polishing head during the process; And the retainer rings comprise an inner retainer ring surrounding the membrane and an outer retainer ring surrounding the inner retainer ring. The method of claim 1, The chemical mechanical polishing device, A first supply line to which fluid for pressurizing the inner retainer ring is supplied; And a second supply line to which fluid for pressurizing the outer retainer ring is supplied. The method of claim 1, And the outer retainer ring is located at a predetermined distance from the inner retainer ring.