KR20050079096A - Pad for chemical mechanical polishing - Google Patents

Abstract

A chemical mechanical polishing pad is disclosed. The chemical mechanical polishing pad according to the present invention includes an upper pad and a substrate pad on which grooves are formed, and the groove includes concentric grooves and radial grooves.

Description

Chemical mechanical polishing pad

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to equipment for manufacturing semiconductor devices, and more particularly to polishing pads used when planarizing a material on a semiconductor wafer by chemical mechanical polishing with chemical mechanical polishing (CMP) equipment. will be.

As semiconductor devices are highly integrated, the process of planarizing materials on semiconductor wafers becomes very important. In particular, global planarization of semiconductor wafers is an essential condition for forming a highly integrated semiconductor device having a multilayer wiring structure. CMP equipment is one of the facilities for implementing this planarization process. CMP equipment is being used to perform global planarization processes on wafers. CMP is a process of polishing and planarizing the surface of a wafer with a mechanical element by the polishing pad and a chemical element by the slurry by providing a slurry between the polishing pad and the wafer while the polishing pad is in contact with the wafer. That is, the wafer is caused by CMP by chemically acting on the material on the wafer by the slurry, and simultaneously by mechanical friction force with abrasive particles in the slurry interposed between the polishing pad and the wafer (wafer mounted on the polishing head). The surface planarization process is performed.

Representative examples of the consumable member required for the CMP process include a slurry and a polishing pad. Among these, the polishing pad is usually made of polyurethane, and has a variety of forms, such as a round, roll type, and belt type. In addition, polishing pads currently produced include polishing pads containing slurry in the pads themselves. Especially, the polishing pad which has a circular double structure is used with respect to manufacture of a semiconductor device. The double polishing pad includes a top pad having a surface on which grooves are formed, and a substrate pad below it. The process surface of the wafer is brought into contact with the upper pad of the polishing pad mounted on the turn tape to be polished to achieve a planarization process.

When using such a double-layer polishing pad, it is necessary to use a top pad thicker than the thickness of a normal top pad in order to increase the life of the polishing pad. Excessive use or deformation of soft pads due to prolonged use should be replaced. In order to increase the life of such a polishing pad, the thickness of the upper pad in direct contact with the wafer is made larger than that of the conventional upper pad.

However, as the thickness of the upper pad increases, the uniformity of the CMP profile obtained after the CMP process tends to be worsened. That is, in the CMP profile, the CMP profile of the edge portion of the wafer is less polished than the center of the wafer. The relatively low tendency of CMP polishing at the edges relative to the center of the wafer is a common phenomenon in CMP profiles, but the thicker the upper pad, the more uneven the CMP profile becomes.

The deterioration of the CMP profile uniformity caused by the use of the thick upper pad is because the flexibility of the polishing pad is reduced by increasing the thickness of the upper pad, and the degree of deformation of the pad is lowered. In a CMP process, a wafer mounted on a polishing head is generally subjected to a lower pressing force (force pushing the wafer against the polishing pad) at the edge portion compared to the center portion. Since the nonuniformity of the CMP profile may occur due to the nonuniformity of the pressing force, a retaining ring presses the smoke pad area near the outside of the wafer edge to compensate for this. When the polishing pad portion near the outside of the wafer edge is pressed by the retaining ring as described above, the upper pad of the wafer edge portion may be rebound by elasticity to increase the pressing force of the wafer edge portion than before. However, the use of a thick top pad to increase the life of the polishing pad reduces the flexibility of the polishing pad, thus reducing the extent of rebound at the wafer edge. Accordingly, as the thickness of the upper pad increases, the non-uniformity of the CMP profile deepens.

1A is a plan view showing a conventional chemical mechanical polishing pad. Referring to FIG. 1A, a groove 3 for polishing is formed on an upper surface of the upper pad of the polishing pad 100. In the plan view, the grooves 3 are formed in the form of several concentric circles forming equal intervals. FIG. 1B is a cross-sectional view taken along the line II ′ of FIG. 1A. As shown in FIG. 1B, the polishing pad 100 includes a substrate pad 50 and an upper pad 70, and a groove 3 is formed on an upper surface of the upper pad 70. The upper surface on which the groove 3 is formed is in contact with the wafer to polish the wafer.

FIG. 2 is a graph showing a CMP profile that appears when a wafer planarization process is performed using a conventional chemical mechanical polishing pad. FIG. 2, the horizontal axis represents the position on the diameter of the wafer and the vertical axis represents the removal rate by CMP. The length of one cell on the horizontal axis is 2 mm and the unit on the vertical axis is Å / min. As shown in FIG. 2, it can be seen that the CMP profile of the wafer edge region is very deteriorated when the thick upper pad is used as compared with the upper pad having a conventional thickness. That is, it can be seen that the polishing rate of the wafer edge portion is lowered when the thick upper pad is used as compared with the case where the thick upper pad is used.

3 is a partial cross-sectional view schematically illustrating a chemical mechanical polishing apparatus using a conventional chemical mechanical polishing pad. Referring to FIG. 3, the CMP process is performed by rubbing in the presence of a slurry in a state where the wafer 10 mounted on the polishing head 300 is pressed against the polishing pad 100. At this time, the retaining ring 350 of the polishing head 300 presses the polishing pad 100 near the outside of the wafer edge so as to increase the pressing force of the wafer edge portion. Accordingly, the polishing pad 100 at the wafer edge portion is rebound upward due to elasticity to form the rebound region 105. The pressing force of the wafer edge portion can be increased by the portion of the polishing pad 100 rebound upward.

However, as described above, the thicker the upper pad of the polishing pad 100 becomes, the lower the extent of rebounding. Accordingly, as the thickness of the upper pad becomes thicker as shown in FIG. 2, the uniformity of the CMP profile becomes worse and the degree of planarization in the wafer is reduced.

Therefore, the technical problem to be achieved by the present invention is to solve the above problems, even if the thickness of the upper pad to increase the life of the polishing pad, chemical mechanical polishing that can prevent the deterioration of the uniformity of the CMP profile To provide a pad.

In order to achieve the above technical problem, the chemical mechanical polishing pad includes an upper pad and a substrate pad on which grooves are formed, and the grooves include concentric grooves and radial grooves. In this case, the concentric grooves and the radial grooves may cross at right angles. In addition, the concentric grooves may be formed at equal intervals. The upper pad may be formed of a pad made of polyurethane.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments illustrated below may be modified in many different forms, and the scope of protection of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

4 is a plan view illustrating a chemical mechanical polishing pad according to an embodiment of the present invention.

Referring to Figure 4, the polishing pad 200 is circular, like a conventionally used polishing pad. In addition, the polishing pad 200 has a double structure by providing an upper pad on which grooves are formed and a substrate pad below it. The upper surface of the polishing pad is a surface in direct contact with the wafer during the CMP process, and grooves 3 and 5 are formed to polish the wafer. When performing the actual CMP process, the polishing pad 200 is fixedly mounted to the turn table and the wafer (not shown) is pressed against the polishing pad. In the state in which the slurry is interposed between the wafer and the polishing pad 200, the surface of the wafer is planarized by polishing the surface of the wafer by the chemical action of the slurry and the frictional force of the abrasive particles in the slurry.

As shown in FIG. 4, not only a plurality of concentric grooves 3 are formed on the upper surface of the polishing pad 200 according to the present embodiment, but also radial grooves along the radius of the polishing pad 200. Many (5) are formed. This radial groove 5 intersects at right angles with the concentric groove 3.

In this way, by forming the radial grooves 5 in addition to the concentric grooves 3, the flexibility of the polishing pad 200 is further increased. Therefore, the rebounding degree due to the elasticity of the polishing pad 200 may also be improved. In particular, it is possible to improve the deterioration of the rebounding degree that occurs when the thickness of the upper pad is large. When the rebounding degree of the polishing pad 200 having the thick upper pad is improved, it is possible to improve the deterioration of the uniformity of the CMP profile at the wafer edge point which is pointed out as a conventional problem.

During the CMP process, the retaining ring (refer to reference numeral 350 of FIG. 3) presses the polishing pad 200 near the outside of the wafer edge to rebound the polishing pad 200 near the wafer edge upward. At this time, even if a thick upper pad is used, since the grooves 3 of the radial shape in addition to the concentric groove 3 is formed on the upper surface of the polishing pad 200 as described above, the flexibility of the polishing pad 200 It is possible to improve the rebounding degree of the polishing pad 200 near the wafer edge. Accordingly, the pressing force of the wafer edge portion is further increased and the polishing rate of the wafer edge portion is improved. Therefore, deterioration of the CMP profile of the wafer edge portion is prevented.

In this embodiment, the radial grooves 5 formed on the upper surface of the polishing pad 200 are formed along the radius of the polishing pad 200, so that the radial grooves 5 are perpendicular to each other with the concentric grooves 3. Doing. However, the present invention is not necessarily limited thereto, and for example, the radial grooves 5 may be formed at an angle with respect to the radius. In other words, the concentric grooves 3 and the radial grooves 5 are not necessarily orthogonal.

Although the present invention has been described in detail through specific examples, the present invention is not limited thereto, and it is apparent that modifications and improvements can be made by those skilled in the art within the technical spirit of the present invention.

As described above, according to the present invention, by additionally forming radial grooves on the upper surface of the upper pad constituting the polishing pad, it increases the flexibility of the polishing pad and rebounds the polishing pad by the retaining ring of the polishing head. It can be easier. Therefore, it is possible to prevent the deterioration of the CMP profile at the wafer edge portion caused by the increase in the thickness of the upper pad, to further improve the uniformity of the CMP profile, and to further improve the flatness of the wafer.

1A is a plan view showing a conventional chemical mechanical polishing pad.

FIG. 1B is a cross-sectional view taken along the line II ′ of FIG. 1A.

FIG. 2 is a graph showing a CMP profile that appears when a wafer planarization process is performed using a conventional chemical mechanical polishing pad. FIG.

3 is a partial cross-sectional view schematically illustrating a chemical mechanical polishing apparatus using a conventional chemical mechanical polishing pad.

4 is a plan view showing a chemical mechanical polishing pad according to the present invention.

Claims (4)

An upper pad having grooves formed therein; And Having a substrate pad, Wherein said groove comprises a concentric groove and a radial groove. 2. The chemical mechanical polishing pad according to claim 1, wherein the concentric grooves and the radial grooves cross at right angles. The chemical mechanical polishing pad according to claim 1, wherein the concentric grooves are formed at equal intervals. The chemical mechanical polishing pad according to claim 1, wherein the upper pad is a pad made of polyurethane.