KR20050077098A - Chemical mechanical polishing apparatus and polishing pad used in the apparatus - Google Patents

Abstract

The present invention relates to a polishing pad for use in a chemical mechanical polishing apparatus, wherein the polishing pad has a lower pad and an upper pad stacked on each other. Grooves are formed in the upper surface of the upper pad to guide the flow of the slurry, and rebound retaining grooves are formed in the lower surface of the upper pad. The rounding retaining grooves prevent the rebound from being reduced upon pressurization by the retainer ring as the polishing pad becomes thicker.

Description

TECHNICAL MECHANICAL POLISHING APPARATUS AND POLISHING PAD USED IN THE APPARATUS}

TECHNICAL FIELD The present invention relates to an apparatus for use in the manufacture of semiconductor devices, and more particularly, to an apparatus for chemical mechanical polishing of a semiconductor substrate such as a wafer and a polishing pad used therein.

The semiconductor device manufacturing process includes a deposition process for forming a thin film layer on a wafer and an etching process for forming a fine circuit pattern on the thin film layer. These processes are repeated until the required circuit pattern is formed on the wafer, and there are very many bends on the surface of the wafer. As semiconductor devices are highly integrated, the line width of circuits decreases, and more wires are stacked on one chip, thereby increasing the step height depending on the location inside the chip. Steps caused by these laminated wirings make it difficult to evenly apply the conductive layer in subsequent processes and cause problems such as defocusing in the photographic process.

In order to solve this problem, a process of planarizing the surface of the wafer is required. In recent years, as the wafer is large-sized, a chemical mechanical polishing ("CMP") method, which is capable of obtaining excellent flatness in not only a narrow region but also a wide region, is mainly used.

According to the above-described CMP method, the wafer surface is mechanically polished by friction between the polishing pad and the wafer surface by pressing and rotating the wafer on the rotating polishing pad, and at the same time, slurry is supplied between the polishing pad and the wafer to be subjected to chemical reaction. Polish the wafer. Such CMP apparatus is disclosed in US Pat. No. 6,217,426. Referring to this, a platen with a polishing pad attached thereto is provided, and the polishing head adsorbs the wafer so that the polishing surface of the wafer faces the polishing pad. The polishing head provides adjustable pressure to the backside of the wafer to press the wafer onto the polishing pad. The polishing head has a retaining ring disposed to wrap around the wafer adsorbed on the membrane to prevent the wafer from leaving the polishing head during processing.

1 is a perspective view of a polishing pad 920 generally used, and FIG. 2 is a cross-sectional view taken along the line I-I of FIG. 1. 3A and 3B are diagrams illustrating the extent to which the polishing pads 920 and 920 'are rebounded when the thin polishing pad 920 and the thick polishing pad 920' are used, respectively. 3A and 3B are graphs comparing polishing rates when using the polishing pads 920 and 920 'illustrated in FIGS. 3A and 3B. 1 and 2, the polishing pads 920 and 920 ′ are formed in a circular shape, and grooves 922 for guiding the movement of the slurry are formed on the upper surfaces of the polishing pads 920 and 920 ′. Is formed. If the thickness of the polishing pads 920 and 920 'is thin, the groove 922 of the polishing pad wears quickly, and thus the life of the polishing pad 920 is very short. Recently, in order to increase the life time of the polishing pad 920, the thickness of the polishing pad 920 becomes thick, and the groove 920 is deeply dug. However, when the polishing pads 920 and 920 'are pressed by the retaining ring as shown in FIGS. 3A and 3B, if the polishing pad 920' is thick, the rebounding is reduced as compared to when the polishing pad 920 is thin, As shown in FIG. 4, the polishing rate is reduced at the edge of the wafer, thereby greatly reducing the polishing uniformity. In FIG. 4, the X axis is a position in the radial direction of the wafer, and the Y axis is a polishing rate for each region of the wafer. In FIG. 4, the line with the hollow circles is the polishing rate of the wafer when the thin polishing pad 920 is used, and the line with the rectangle filled with the inside is the polishing rate of the wafer when the thick polishing pad 920 ′ is used.

It is an object of the present invention to provide a polishing pad which can be used for a long time as well as preventing rebounding from being reduced when pressed by the retaining ring and a chemical mechanical polishing apparatus including the same.

In order to achieve the above object, the chemical mechanical polishing apparatus of the present invention has a polishing pad attached to a platen and a polishing head for adsorbing and fixing a semiconductor substrate and pressing the semiconductor substrate on the polishing pad. The polishing pads are stacked on each other and have upper pads and lower pads of different hardness, and grooves for guiding the flow of the slurry are formed in the upper surface of the upper pad. In addition, the polishing pad is formed with a rebounding retaining groove which improves the rebound when in contact with the retainer ring of the polishing head.

In one example, the rebounding retaining groove is formed on the lower surface of the upper pad. The groove formed on the upper surface of the upper pad and the rebounding retaining groove may be formed concentrically, and the rebounding retaining grooves may be disposed to be symmetrical with the grooves formed on the upper surface of the upper pad. Optionally, the rebound retaining groove may be disposed between adjacent grooves formed in the upper surface of the upper pad. In addition, the upper end of the rebounding retaining groove is preferably located lower than the lower end of the groove formed on the upper surface of the upper pad.

In another example, the rebounding retaining groove is formed in the lower surface of the lower pad. The groove formed on the upper surface of the upper pad and the rebounding retaining groove may be formed concentrically, and the rebounding retaining grooves may be disposed to be symmetrical with the grooves formed on the upper surface of the upper pad. Optionally, the rebound retaining groove may be disposed between adjacent grooves formed in the upper surface of the upper pad.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 14. 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.

5 is a perspective view of the chemical mechanical polishing apparatus 1 of the present invention. Referring to FIG. 5, the chemical mechanical polishing apparatus 1 has a transfer station 10, polishing stations 20, and a polishing head assembly 30. The polishing stations 20 and the transmission station 10 are installed on the base 2. Three polishing stations 20 are arranged, which together with the transmission station 10 form a square arrangement. Each polishing station 20 directly polishes the wafer with a polishing head 300 to be described later, and the transfer station 10 cleans the wafer. The wafer is loaded into the transfer station 10 by the polishing head 300 and unloaded back to the polishing head 300 when cleaning is completed.

Each polishing station 20 has a polishing pad 200, a platen 202, a slurry supply arm 204, and a pad conditioner 206. Has The platen 202 is formed into a cylindrical shape having a flat top surface and is provided on the base 2. The polishing pad 200 is attached to the upper surface of the platen 202, and the polishing pad 200 will be described in detail later. The base 2 may be provided with a driving unit (not shown) for rotating the platen 202 during the process. The slurry feed arm 204 is disposed on one side of the platen 202 and supplies slurry to the surface of the polishing pad 200. The pad conditioner 206 maintains polishing conditions of the polishing pad 200 during the polishing process. The pad conditioner 206 has an arm 206a rotatably mounted to the base 2 and a conditioner head 206b that is coupled to one bottom of the arm 206a and independently rotates.

The polishing head assembly 30 is disposed above the base 2 and is rotated about its central axis. The polishing head assembly 30 has a support plate 32 and four polishing heads 300 positioned at the bottom. Four slit-shaped holes 34 are formed in the support plate 32, and the rotation shaft 302 of the polishing head is inserted in each slit 34, respectively. Each polishing head 300 is independently rotated about the rotation axis 302 by the drive unit 304 during the polishing process. The three polishing heads 300 polish the wafers by pressing the wafers to the polishing pads 200 disposed below, and the other polishing head 300 unloads the wafers from the transfer station 10 or transfers the wafers ( 10) Load the wafer.

The polishing head 300 sucks and fixes the wafer W so that the polishing surface of the wafer W faces the polishing pad 200 and presses the wafer W against the polishing pad 200 during the process. 6 is a cross-sectional view of the polishing head 300. Referring to FIG. 6, the polishing head 300 includes a carrier 320, a manifold 340, a supporter 360, a retainer ring 380, And a membrane 390. The carrier 320 has a cylindrical bowl shape with an open lower portion, and forms a body of the polishing head 300. The first fluid movement path 322 and the second fluid movement path 324 are formed on the upper surface of the carrier 320, and the air introduced from the outside is the manifold 340 disposed on the upper surface of the carrier 320. The first fluid movement path 322 and the second fluid movement path 324 by the ().

The support 360 is disposed in the carrier 320. The support 360 has an outer support 360a in contact with the inner wall of the carrier 320 and an inner support 360b positioned inside the outer support 360a. The outer support 360a has a ring-shaped side surface 361 and a pedestal 362 protruding inwardly from the lower end of the side surface 361. The inner support 360b is formed with a first chamber 352, which is a space in which air flowing through the first fluid movement path 322 stays, and is fixed to the pedestal 362. The upper surface of the inner support (360b) is coupled to the connecting pipe (366) connecting the first fluid path and the first chamber (352). By the above-described structure, a second chamber 354, which is a space surrounded by the inner support 360b, the outer support 360a, and the carrier 320, is formed, and the second chamber 354 is the second fluid movement path ( Air flowing through 324 stays. The lower surface of the inner support 360b protrudes downward from the chucking rings 367 in which the first holes 372, which are the movement paths of air in the first chamber 352, are formed. Second holes 374, which are air moving paths in the second chamber 354, are formed.

The retaining ring 380 is coupled to the carrier 320 below the sidewall of the carrier 320, and is disposed to surround the wafer W that is sucked and fixed to the polishing head 300. The retaining ring 380 is subjected to a pressure greater than the pressure applied to the wafer W to prevent the wafer W from being separated from the polishing head 300 during the process.

The membrane 390 is disposed below the support 360 in a circular thin rubber film and presses the wafer by being in direct contact with the wafer during the process. The edge of the membrane 390 is inserted and fixed between the retaining ring 380 and the carrier 320. The membrane 390 is formed with third holes 392 in which the chucking rings 367 are inserted at positions opposite to the chucking rings 367. Since the wafer W is directly vacuum sucked through the third hole 392 formed in the chucking ring 367, the wafer W may be fixed to the polishing head 300 with high stability. Air provided from the second chamber 354 through the second holes 374 pressurizes the wafer W during the polishing process. The above-described structure of the polishing head 300 is only one example, and may be variously changed.

The polishing pad 200 is made of polyurethane and has a rough surface. The polishing pad 200 mechanically polishes the wafer by being in direct contact with the wafer. 7 is a perspective view of a polishing pad 200 according to an embodiment of the present invention, Figure 8 is an exploded perspective view of the polishing pad 200 of Figure 7, from below to see the bottom surface of the lower pad 240 This is the view. 7 and 8, the polishing pad 200 has an upper pad 220 and a lower pad 240 stacked on each other. Since the hard pad having high hardness has an excellent step improvement effect in the wafer, when the polishing process is performed using the hard pad, the flatness of the wafer is excellent but the uniformity is low. On the other hand, when the polishing process is performed using a soft pad of low hardness, the entire wafer can be polished evenly, so that the uniformity is improved, but the polishing removal rate is increased depending on the size and distribution of the pattern of the polishing surface. Deviation occurs. In order to evenly improve flatness and uniformity, the upper pad 220 and the lower pad 240 have different hardnesses, and a hard pad is used as the upper pad 220 and a soft pad is used as the lower pad 240. It is preferable.

The lower pad 240 has a shape of a disc having a flat upper surface and a lower surface, and is attached to the platen 202 by an adhesive. The upper pad 220 is formed in the same size and shape as the lower pad 240 and is attached to the upper surface of the lower pad 240 by an adhesive. Grooves 222 are formed on the upper surface of the upper pad 220 for the flow and uniform distribution of the slurry during the polishing process. The groove 222 is formed to form a plurality of concentric circles about the center of the upper surface of the upper pad 220, as shown in FIG. In contrast, the groove 222 may be formed in various shapes.

The depth of the groove 222 formed in the upper surface of the upper pad 220 is proportional to the thickness of the upper pad 220. As pointed out in the problem of the prior art, if the thickness of the upper pad 220 becomes thick to use the upper pad 220 for a long time, the rebounding of the polishing pad 200 is reduced during the process, thereby reducing the polishing rate at the edge of the wafer. Abruptly lowers. In order to prevent this, the polishing pad 200 of the present invention is provided with a groove 260 (hereinafter referred to as a "rebounding holding groove") for improving the rebounding of the polishing pad 200. According to one embodiment, the rebounding retaining groove 260 is formed on the lower surface of the upper pad 220, and the rebounding retaining groove 260 is lower than the lower end of the groove 260 formed on the upper surface of the upper pad 220. It is preferred to be located.

As shown in FIG. 8, the rebounding retaining groove 260 is formed to form a plurality of concentric circles about the center of the lower surface. Optionally, the rebounding retaining groove 260 may be formed of a plurality of grooves 260 having a circular shape disposed at equal intervals as shown in FIG. 9. The shape of the groove 260 is not limited to the above-described example and may be variously changed.

FIG. 10 is a cross-sectional view taken along the line II-II of FIG. 7. 10 illustrates an example of an arrangement position of the rebounding retaining grooves 260 when both the grooves and the rebounding retaining grooves 260 formed on the upper surface of the upper pad 220 are formed in a concentric shape. FIG. 11 is a cross-sectional view of FIG. 10, showing another example of an arrangement position of the rebounding holding grooves 260. As shown in FIG. 10, the rebounding retaining grooves 260 are formed on the upper pad 220 such that the grooves 222 formed on the upper surface of the upper pad 220 and the rebounding retaining grooves 260 formed on the lower surface thereof are staggered from each other. It may be disposed between adjacent grooves 222 formed in the upper surface of the. Optionally, as shown in FIG. 11, the grooves 222 and the rebound holding grooves 260 formed on the upper surface of the upper pad 220 may be disposed to be symmetrical to each other. By forming the rebounding retaining grooves 260 on the lower surface of the upper pad 220 as described above, even if the thickness of the upper pad 220 becomes thick, the rebounding of the polishing pad 200 is reduced during the polishing process. Can be minimized.

12 is a cross-sectional view illustrating another embodiment of the polishing pad 200. Referring to FIG. 12, the polishing pad 200 has an upper pad 220 and a lower pad 240 stacked on each other, and grooves 222 are formed in the upper surface of the upper pad 220 to guide the flow of the slurry. Rebounding retaining grooves 260 are formed in the lower surface of the lower pad 240 to improve the rebound of the polishing pad 200. When the grooves 222 and the rebounding retaining grooves 260 formed in the upper pad 220 have a concentric shape, as shown in FIG. 12, the rebounding retaining grooves 260 are upper pads 220 so that their positions are staggered from each other. It may be disposed between the adjacent grooves 222 formed in the. Optionally, as shown in FIG. 13, the grooves 222 and the rebound holding grooves 260 formed in the upper pad 220 may be disposed to be symmetrical to each other. .

14 is a cross-sectional view illustrating another modified example of the polishing pad 200. Referring to FIG. 14, the polishing pad 200 has an upper pad 220 and a lower pad 240 stacked on each other, and grooves 222 for guiding the flow of the slurry are formed in the upper surface of the upper pad 220. Rebounding retaining grooves 260 are formed on the upper surface of the lower pad 240 to improve the rebound of the polishing pad 200.

In the present exemplary embodiment, the rebounding retaining grooves 260 are formed in either the upper pad 220 or the lower pad 240. However, the rebounding retaining grooves may be simultaneously formed on the lower surface of the upper pad 220 and the lower surface of the lower pad 240. In addition, the width and the shape of the grooves 222 and the rebounding retaining grooves 260 formed on the upper surface of the polishing pad 200 are not limited to the above embodiments, and may vary if the same function can be performed. Can be.

According to the present invention, even when the thickness of the polishing pad is increased to improve the life of the polishing pad, it is possible to prevent the rebounding of the polishing pad due to the pressing of the retaining ring of the polishing head during the process. This increases the polishing rate at the edge of the wafer, thereby improving the polishing uniformity.

1 is a perspective view of a polishing pad generally used;

2 is a cross-sectional view taken along the line II of FIG. 1;

3A and 3B illustrate the extent to which a polishing pad is rebound when using a thin polishing pad and a thick polishing pad, respectively;

4 is a graph comparing the polishing rate when using the polishing pad shown in FIGS. 3A and 3B;

5 is a perspective view of the chemical mechanical polishing apparatus of the present invention

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

7 is a perspective view of a polishing pad according to an embodiment of the present invention;

8 is an exploded perspective view of the polishing pad of FIG. 7;

9 is an exploded perspective view of a polishing pad having rebounded retaining grooves of a deformed shape;

FIG. 10 is a cross-sectional view taken along the line II-II of FIG. 7;

FIG. 11 is a sectional view like FIG. 10 showing a modified arrangement position of the rebounding retaining grooves; FIG.

12 is a cross-sectional view of the polishing pad showing another embodiment of the polishing pad;

FIG. 13 is a cross-sectional view showing a modified arrangement position of rebound holding grooves in the polishing pad of FIG. 12; FIG. And

14 is a cross-sectional view illustrating a modified example of the polishing pad of FIG. 12.

Explanation of symbols on the major parts of the drawings

10 transmission station 20 polishing station

30: polishing head assembly 200: polishing pad

220: upper pad 240: lower pad

260: Rebound Home

Claims (21)

An apparatus for chemically and mechanically polishing a semiconductor substrate, Platen; A polishing pad attached to the platen; And And a polishing head configured to suck and fix the semiconductor substrate and pressurize the semiconductor substrate on the polishing pad. The polishing pad includes an upper pad having a groove for guiding the flow of the slurry on an upper surface thereof and a rebounding retaining groove formed on the lower surface thereof, so that the rebounding of the polishing pad is improved when pressed by the polishing head. Chemical mechanical polishing device. The method of claim 1, And the upper end of the rebound retaining groove is located lower than the lower end of the groove formed on the upper surface of the upper pad. The method of claim 1, And a groove formed on the upper surface of the upper pad and the rebound retaining groove are formed in a concentric shape. The method of claim 3, wherein And the rebound retaining grooves are arranged to be symmetrical with the grooves formed in the upper surface of the upper pad. The method of claim 3, wherein And the rebound retaining grooves are disposed between adjacent grooves formed in the upper surface of the upper pad. The method of claim 1, And the polishing pad further comprises a lower pad disposed between the upper pad and the platen and attached to the upper pad and the platen and having a different hardness than the upper pad. An apparatus for chemically and mechanically polishing a semiconductor substrate, Platen; A polishing pad attached to the platen; And And a polishing head configured to suck and fix the semiconductor substrate and pressurize the semiconductor substrate on the polishing pad. The polishing pad is, An upper pad having a groove formed in the upper surface to guide the flow of the slurry; A lower pad having a different hardness than the upper pad and attached to the upper pad to be disposed below the upper pad, and having a rebounding groove formed on a lower surface thereof so that the polishing when pressed by the polishing head Chemical mechanical polishing apparatus, characterized in that the rebound of the pad is improved. The method of claim 7, wherein And a groove formed in the upper pad and the rebound retaining groove are formed in concentric shapes, respectively. The method of claim 8, And the rebounding retaining groove is disposed to face the position of the groove formed in the upper pad. The method of claim 8, And the rebound retaining groove is disposed between adjacent grooves formed in the upper pad. A polishing pad used in a chemical mechanical polishing apparatus, Grooves are formed in the upper surface to assist the flow of the slurry, and rebounding grooves are formed in the lower surface, thereby improving the rebounding of the polishing pad when pressed by the polishing head during the process. Polishing pad. The method of claim 11, And an upper end of the rebound retaining groove is located lower than a lower end of the groove formed on the upper surface. The method of claim 11, The rebounding retaining groove and the groove formed on the upper surface are each formed in a concentric circle polishing pad. The method of claim 13, And the rebound retaining groove is disposed to face the position of the groove formed on the upper surface. The method of claim 13, And the rebound retaining groove is disposed between adjacent grooves formed in the upper surface. A polishing pad used in a chemical mechanical polishing apparatus, A lower pad; When pressurized by the polishing head having an upper pad having a different hardness from the lower pad and attached to the lower pad, and having a groove formed in the upper surface to assist the flow of the slurry, and having a rebounding retaining groove formed in the lower surface. And rebounding of the polishing pad. The method of claim 16, And a groove formed in the upper pad and the rebound holding groove are formed in a concentric shape, respectively. The method of claim 17, And the rebounding retaining groove is disposed to face the position of the groove formed on the upper surface of the upper pad. The method of claim 17, And the rebound retaining groove is disposed between adjacent grooves formed in the upper surface of the upper pad. A polishing pad used in a chemical mechanical polishing apparatus, An upper pad having a groove formed in the upper surface to guide the flow of the slurry; A lower pad having a different hardness than the upper pad and attached to the upper pad to be disposed below the upper pad, and having a rebounding retaining groove formed on a lower surface thereof, thereby rebounding the polishing pad when pressed by the polishing head. The polishing pad characterized by the above-mentioned improvement. The method of claim 20, The groove formed in the upper pad and the rebounding retaining groove have a concentric shape. And the rebound retaining groove is disposed between adjacent grooves formed in the upper pad.