WO2004080654A1

WO2004080654A1 - Polishing tool and polishing apparatus

Info

Publication number: WO2004080654A1
Application number: PCT/JP2004/003378
Authority: WO
Inventors: Katsuya Okumura; Manabu Tsujimura
Original assignee: Ebara Corporation; Octec, Inc.
Priority date: 2003-03-14
Filing date: 2004-03-12
Publication date: 2004-09-23
Also published as: US20060172665A1; JP2006520273A

Abstract

A polishing tool is used for polishing a workpiece (13) such as a semiconductor wafer to a flat mirror finish. The polishing tool has a polishing table (10) and a polishing pad (11) attached to an upper surface of the polishing table (10). The polishing pad (11) has a plurality of polishing pad pieces (111) attached to the polishing table (10). It is possible to facilitate adjustment of polishing performance over a surface of the workpiece (13) and replacement of a polishing pad (10).

Description

DESCRIPTION

POLISHING TOOL AND POLISHING APPARATUS

Technical Field The present invention relates to a polishing tool, and more particularly to a polishing tool for polishing a workpiece such as a semiconductor wafer to a flat mirror finish. The present invention also relates to a polishing apparatus having such a polishing tool and a method of a polishing a workpiece with such a polishing apparatus. Further, the present invention is concerned with a method of attaching a polishing pad to a polishing table.

Background Art

As semiconductor devices have become more highly integrated in recent years, circuit interconnections have become finer and distances between those circuit interconnections have become smaller. In the case of photolithography, which can form interconnections that are at most 0.5 μm wide, it is required that surfaces on which pattern images are to be focused by a stepper should be as flat as possible because the depth of focus of an optical system is relatively small. In order to planarize such a semiconductor wafer, there has been used a polishing apparatus for performing chemical mechanical polishing (CMP).

This type of polishing apparatus comprises a polishing table having a polishing pad (polishing cloth) attached on an upper surface of the polishing table, and a top ring for holding a workpiece to be polished, such as a semiconductor wafer. The polishing table and the top ring are rotated at independent rotational speeds, respectively. The top ring presses the workpiece against the polishing pad at a predetermined pressure. A polishing liquid is supplied from a polishing liquid supply nozzle onto the polishing pad. Thus, a surface of the workpiece is polished to a flat mirror finish.

In such a polishing apparatus, polyurethane foam is mainly used as a material for the polishing pad mounted on the polishing table. Such a polishing pad is generally formed by cutting a molded block-like compact. Polishing performance is influenced by hardness, cross-link density, and foaming density of the polishing pad. Hardness is determined by a compounding ratio of a prepolymer and a hardener. Cross-link density is determined by a curing temperature after compounding. Foaming density is determined by a compounding ratio of polymeric fine materials.

The particularly important factors are cross-link density and foaming density in view of polishing performance. For example, if the cross-link density of the polishing pad is low, a workpiece tends to be polished at a high polishing rate and to have a good flatness on a polished surface thereof. Further, when the foaming density of the polishing pad is high, a high polishing rate can be achieved. When a polishing pad has a cross-link density and a foaming density in predetermined ranges, stable polishing performance can be achieved. However, it is not easy to produce a polishing pad having a uniform cross-link density and a uniform foaming density because it is difficult to uniformly diffuse compounding materials in a compact in a molding process and to uniformly control temperatures in the compact. For example, a temperature gradient is produced between a central area and a peripheral area of a compact when the compact is heated for molding. Thus, a difference of the cross-link density is produced between the central area and the peripheral area of the compact. As a result, the block-like compact has variations in cross-link density and foaming density. When a polishing pad produced by cutting such a compact is used for polishing a workpiece, polishing rates become non-uniform over a surface of the workpiece, and polishing performance becomes unstable. Further, polishing pads produced by cutting different portions of a compact have different polishing performance. Accordingly, polishing performance may vary each time a polishing pad is replaced with another one. In order to solve the above drawbacks, there have been made efforts to maintain uniformity of compounding materials in a compact or a uniform temperature distribution in the compact when the compact is heated for molding.

However, a polishing pad used for polishing 8-inch wafers has a diameter of about 600 mm, and a polishing pad used for polishing 12-inch wafers has a diameter of at least 700 mm. Accordingly, a block-like compact becomes large in size. Thus, it becomes more difficult to eliminate non-uniformity of properties of the compact. Thus, it is difficult to achieve stable polishing performance and adjust polishing performance over a surface of a workpiece. Disclosure of Invention

The present invention has been made in view of the above drawbacks. It is, therefore, a first object of the present invention to provide a polishing tool which can achieve stable polishing performance and facilitate adjustment of polishing performance over a surface of a workpiece and replacement of a polishing pad.

A second object of the present invention is to provide a method of polishing a workpiece which achieve stable polishing performance.

A third object of the present invention is to provide a method of attaching a polishing pad to a polishing table which can facilitate adjustment of polishing performance over a surface of a workpiece and replacement of a polishing pad.

A fourth object of the present invention is to provide a polishing apparatus which can achieve stable polishing performance and facilitate adjustment of polishing performance over a surface of a workpiece and replacement of a polishing pad.

In order to achieve the first object, according to a first aspect of the present invention, there is provided a polishing tool for polishing a workpiece. The polishing tool has a polishing table and a polishing pad attached to an upper surface of the polishing table. The polishing pad has a plurality of polishing pad pieces attached to the polishing table.

According to a second aspect of the present invention, there is provided a polishing tool for polishing a workpiece. The polishing tool has a polishing table, a plurality of pedestals attached to an upper surface of the polishing table, and a polishing pad having a plurality of polishing pad pieces attached to the plurality of pedestals.

In order to produce a polishing pad having uniform properties, it is desirable to cut only a particular portion (or area) having uniform properties in a compact. When a produced polishing pad has a large area, properties have variations over a surface of the polishing pad. Thus, it is desirable to cut a compact with a possible smallest area. When small polishing pads thus produced, which are hereinafter referred to as polishing pad pieces, are attached onto a polishing table for polishing a workpiece such as a semiconductor wafer, a surface of the workpiece is polished more uniformly, and stable polishing performance can also be achieved.

As described above, when a compact is large in size, properties of the compact are likely to be non-uniform. Therefore, it is also effective to use a small compact for molding. When a compact is small in size, a temperature gradient becomes small between a central area and a peripheral area of the compact. Thus, variations of properties are unlikely to be produced in the compact, and a polishing pad having uniform properties can be obtained. When small polishing pads thus produced are attached onto the polishing table for polishing the workpiece, a surface of the workpiece is polished more uniformly, and stable polishing performance can be achieved.

A semiconductor wafer to be actually polished may have non-uniform thickness of films formed on a surface of the semiconductor wafer. When such a semiconductor wafer is polished, areas having larger thickness should be polished at a higher polishing rate and areas having smaller thickness should be polishing at a lower polishing rate so as to uniformize the thickness of films remaining on the surface of the semiconductor wafer after polishing. In order to meet such demands, it is desirable to change properties and surface shapes of the respective small polishing pads through which wafers pass, instead of to uniformize properties and surface shapes of the small polishing pads. Specifically, it is desirable that a polishing pad is divided into possible smallest polishing pad pieces so as to accurately control polishing performance over a surface of a semiconductor wafer.

According to the present invention, when the plurality of polishing pad pieces has the same material properties including foaming density, cross-link density, and hardness, and the same surface shapes including grooves and holes, a workpiece can be polished at a uniform polishing rate over a surface thereof. On the other hand, when the plurality of polishing pad pieces includes at least one polishing pad piece having different material properties including foaming density, cross-link density, and hardness, or different surface shapes including grooves and holes than those of other polishing pad pieces, a polishing rate distribution can be adjusted over a surface of a workpiece to be polished.

According to a preferred aspect of the present invention, the polishing table has a plurality of recesses for receiving the plurality of polishing pad pieces or the plurality of pedestals. The plurality of recesses should preferably have the same shape as the plurality of polishing pad pieces or the plurality of pedestals. With this arrangement, it is possible to facilitate positioning of the polishing pad pieces or the pedestals when the polishing pad pieces or the pedestals are attached to the polishing table. According to a preferred aspect of the present invention, the polishing table includes a holding plate having a plurality of through-holes for receiving the plurality of polishing pad pieces or the plurality of pedestals. The plurality of through-holes should preferably have the same shape as the plurality of polishing pad pieces or the plurality of pedestals. With this arrangement, it is not necessary to form the recesses for receiving the plurality of polishing pad pieces or the plurality of pedestals in the upper surface of the polishing table. The shape and the arrangement of the through-holes can arbitrarily be selected by changing holding plates.

According to a preferred aspect of the present invention, at least one of the polishing pad pieces or at least one of the pedestals is attached to the polishing table by a thermo- sensitive adhesive which is softened and lowered in adhesive strength under a high temperature while it is hardened and increased in adhesive strength under a room temperature.

Small polishing pads require a considerably long period of time to be attached onto an upper surface of a polishing table. Generally, an adhesive is applied in advance onto surfaces of the polishing pads. Since the adhesive used has a large adhesive strength, it is difficult to remove the polishing pads once they have been bonded to the upper surface of the polishing table. On the other hand, once the polishing pads have been removed from the upper surface of the polishing table, they cannot be bonded again to the upper surface of the polishing table. Therefore, when polishing pad pieces into which a conventional polishing pad having an adhesive thereon is divided are used, it is necessary to carefully position and attach each piece onto the polishing table. Thus, a considerably long period of time is required to replace a polishing pad with another one. Since the polishing apparatus is stopped during replacement of the polishing pad, the number of lots produced per hour is reduced. In order to improve the number of lots produced, it is desired to attach polishing pad pieces onto a polishing table at a time, instead of to attach each polishing pad piece onto a polishing table. According to the present invention, since a portion or all of the polishing pad pieces or the pedestals is bonded to the polishing table by a thermo-sensitive adhesive, a portion or all of the polishing pad pieces or the pedestals can readily be attached to and removed from the upper surface of the polishing table. When a thermo-sensitive adhesive is used as an adhesive, the polishing pad piece or pedestal can be bonded to the polishing table as follows. The thermo-sensitive adhesive is applied between the polishing pad piece or pedestal and the polishing table and heated so as to be softened and lowered in adhesive strength. At that time, the polishing pad piece or pedestal is pressed against the upper surface of the polishing table so as to produce no air bubbles between the polishing pad piece or pedestal and the polishing table. Then, the thermo-sensitive adhesive is cooled to a room temperature so as to bond the polishing pad piece or pedestal to the polishing table. The polishing pad piece or pedestal can be removed or separated from the polishing table as follows. The thermo-sensitive adhesive is heated so as to be softened and lowered in adhesive strength. At that time, the polishing pad piece or pedestal can be removed or separated from the polishing table.

The thermo-sensitive adhesive should preferably comprise a liquid crystal material or a hot-melt adhesive. The liquid crystal material and the hot-melt adhesive have characteristics that they are softened and lowered in adhesive strength under a high temperature while they are hardened and increased in adhesive strength under a room temperature. Thus, with a liquid crystal material or a hot-melt adhesive, it is possible to bond the polishing pad piece or pedestal to the polishing table, or remove the polishing pad piece or pedestal from the polishing table.

The polishing table may have a rough surface onto which the thermo-sensitive adhesive is applied. The plurality of pedestals may have a rough surface onto which the thermo-sensitive adhesive is applied. Specifically, a surface onto which the thermo-sensitive adhesive is applied may be roughened by sandblasting or the like to form a rough surface. With such a rough surface, it is possible to enhance the adhesive strength of the adhesive.

According to a preferred aspect of the present invention, the plurality of pedestals is attached to the polishing table by vacuum attraction. Thus, the pedestals may be attached to the polishing table by vacuum attraction. In this case, when the vacuum attraction is stopped and vacuum is released to the atmosphere, the pedestals can be removed or separated from the polishing table.

According to a preferred aspect of the present invention, the polishing pad pieces are arranged so as to form gaps between adjacent polishing pad pieces. With this arrangement, a polishing liquid can be supplied uniformly. Thus, the polishing rate distribution can effectively be uniformized over the surface of the workpiece. It is also possible to arbitrary change the polishing rate distribution. Further, it is possible to efficiently supply the polishing liquid to a polishing interface, i.e. between the workpiece and the polishing pad. As a result, it is possible to reduce the amount of polishing liquid, which is expensive, and hence to reduce operating cost.

It is desirable that the polishing tool also has at least one weir disposed in the gaps. With such a weir, the flow of the polishing liquid is disturbed in the gap. Thus, the polishing liquid overflowing the weir in the gap can efficiently be introduced into the polishing interface, i.e. between the workpiece and the polishing pad. Accordingly, it is possible to further reduce the amount of polishing liquid supplied.

It is desirable that each of the polishing pad pieces has a size smaller than the workpiece. Since each of the polishing pad pieces has a size smaller than the workpiece, such polishing pad pieces can have uniform material properties and surface shape. Thus, it is possible to further facilitate the uniformity of the polishing rate over the surface of the workpiece or adjustment of the polishing rate distribution over the surface of the workpiece. According to a preferred aspect of the present invention, the polishing pad pieces have the same material properties and surface shape. With this arrangement, since the plurality of polishing pad pieces has the same material properties including foaming density, cross-link density, and hardness, and the same surface shapes including grooves and holes, a workpiece can be polished at a uniform polishing rate over a surface thereof.

According to another preferred aspect of the present invention, the plurality of polishing pad pieces includes at least one first polishing pad piece and at least one second polishing pad piece having different material properties or surface shape than material properties or surface shape of the at least one first polishing pad piece. With this arrangement, since the plurality of polishing pad pieces includes at least one polishing pad piece having different material properties including foaming density, cross-link density, and hardness, or different surface shapes including grooves and holes than those of other polishing pad pieces, a polishing rate can be adjusted over a surface of a workpiece to be polished.

According to a preferred aspect of the present invention, the polishing table is made of a material having a high thermal conductivity, and the plurality of pedestals is made of a material having a low thermal conductivity. Thus, the polishing table may be made of a material having a high thermal conductivity such as SiC, and the plurality of pedestals may be made of a material having a low thermal conductivity such as resin. With this configuration, the polishing pad pieces and the pedestals can effectively be attached to and removed from the polishing table. In order to achieve the second object, according to a third aspect of the present invention, there is provided a method of polishing a workpiece. According to this method, the workpiece is pressed against the aforementioned polishing tool. At that time, a polishing liquid is supplied to an upper surface of the polishing tool, and the polishing tool and the workpiece are moved relative to each other to polish the workpiece. This method can achieve the same advantageous effects as described above in connection with the polishing tool.

In order to achieve the third object, according to a fourth aspect of the present invention, there is provided a method of attaching a polishing pad to a polishing table. According to this method, a thermo-sensitive adhesive is applied between the polishing table and the polishing pad. The thermo-sensitive adhesive is softened and lowered in adhesive strength under a high temperature while it is hardened and increased in adhesive strength under a room temperature. The thermo-sensitive adhesive is heated when the polishing pad is disposed on the polishing table. Then, the thermo-sensitive adhesive is cooled to bond the polishing pad to the polishing table. The polishing pad may have a plurality of polishing pad pieces attached to the polishing table.

A heating medium adjusted in temperature may be introduced into the polishing table to heat the thermo-sensitive adhesive. Alternatively, the thermo-sensitive adhesive may be heated by a heating device provided near an unbonded surface of the polishing pad. A cooling medium adjusted in temperature may be introduced into the polishing table to cool the thermo-sensitive adhesive. Alternatively, the thermo-sensitive adhesive may be cooled by a cooling device provided near an unbonded surface of the polishing pad.

With this method, a portion or all of the polishing pad pieces can readily be attached to the polishing table in a short term. In order to prevent change of properties from being caused to the polishing pad, the heating temperature should preferably be at most 200°C, more preferably at most 100°C. In order to achieve the fourth object, according to a fifth aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table, a polishing pad attached to an upper surface of the polishing table, and a top ring for pressing the workpiece against the polishing pad. The polishing pad has a plurality of polishing pad pieces attached to the polishing table. The polishing apparatus includes a light source provided in the polishing table for emitting light to a surface of the workpiece through an opening formed between adjacent polishing pad pieces. The polishing apparatus also includes a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece. According to a sixth aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table, a plurality of pedestals attached to an upper surface of the polishing table, and a polishing pad having a plurality of polishing pad pieces attached to the plurality of pedestals. The polishing apparatus also has a top ring for pressing the workpiece against the polishing pad. The polishing apparatus includes a light source provided in the polishing table for emitting light to a surface of the workpiece through an opening formed between adjacent polishing pad pieces. The polishing apparatus also includes a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece. According to a seventh aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table and a polishing pad attached to an upper surface of the polishing table. The polishing apparatus also has a top ring for pressing the workpiece against the polishing pad. The polishing pad has at least one light-transmissive piece and a plurality of polishing pad pieces attached to the polishing table. The polishing apparatus includes a light source provided in the polishing table for emitting light to a surface of the workpiece through the at least one light-transmissive piece. The polishing apparatus also includes a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece.

According to an eighth aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table, a plurality of pedestals attached to an upper surface of the polishing table, and a polishing pad having at least one light-transmissive piece and a plurality of polishing pad pieces attached to the plurality of pedestals. The polishing apparatus also has a top ring for pressing the workpiece against the polishing pad. The polishing apparatus includes a light source provided in the polishing table for emitting light to a surface of the workpiece through the at least one light-transmissive piece. The polishing apparatus also includes a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece.

With these arrangements, light can be emitted from the polishing table to a surface of the workpiece through an opening formed between adjacent polishing pad pieces or through the at least one light-transmissive piece. The light reflected from the workpiece is received in the polishing table. Thus, it is possible to measure the film thickness of the surface of the workpiece during polishing or detect an end point of the polishing process. Accordingly, the polishing process can be adjusted so as to control excessive polishing or insufficient polishing. As a result, productivity can be improved.

According to a ninth aspect of the present invention, there is provided a polishing apparatus for a polishing a workpiece. The polishing apparatus has a polishing table, a polishing pad attached to an upper surface of the polishing table, and a top ring for pressing the workpiece against the polishing pad. The polishing pad has a plurality of polishing pad pieces attached to the polishing table. At least one of the polishing pad pieces has at least one through-hole formed therein. The polishing apparatus includes a light source provided in the polishing table for emitting light to a surface of the workpiece through the through-hole, and a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece. The polishing apparatus also includes a fluid supply passage aligned with the at least one through-hole for supplying measurement fluid, and a fluid discharge passage aligned with the at least one through-hole for discharging the measurement fluid.

According to a tenth aspect of the present invention, there is provided a polishing apparatus for a polishing a workpiece. The polishing apparatus has a polishing table, a plurality of pedestals attached to an upper surface of the polishing table, and a polishing pad having a plurality of polishing pad pieces attached to the plurality of pedestals. The polishing apparatus includes a top ring for pressing the workpiece against the polishing pad. At least one of the polishing pad pieces has at least one through-hole formed therein. At least one of the pedestals has at least one through-hole formed therein. The polishing apparatus also includes a light source provided in the polishing table for emitting light to a surface of the workpiece through the through-holes formed in the at least one of the polishing pad pieces and the at least one of the pedestals. The polishing apparatus has a light-receiving portion provided in the polishing table for receiving light reflected from the workpiece. The polishing apparatus also includes a fluid supply passage for supplying measurement fluid and a fluid discharge passage for discharging the measurement fluid. The fluid supply passage is aligned with the through-holes formed in the at least one of the polishing pad pieces and the at least one of the pedestals. The fluid discharge passage is aligned with the through-holes formed in the at least one of the polishing pad pieces and the at least one of the pedestals. According to an eleventh aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table and a polishing pad attached to an upper surface of the polishing table. The polishing apparatus also has a top ring for pressing the workpiece against the polishing pad. The polishing pad includes a groove formed in the upper surface of the polishing pad for allowing a polishing liquid to pass therethrough, and a weir provided in the groove to disturb flow of the polishing liquid.

With such a groove formed in the upper surface of the polishing pad, the polishing liquid can effectively be introduced into a polishing interface, i.e. between the workpiece and the polishing pad. As a result, it is possible to reduce the amount of polishing liquid, which is expensive, and hence to reduce operating cost. With the weir provided in the groove to disturb the flow of the polishing liquid, since the flow of the polishing liquid in the groove is disturbed by the weir, the polishing liquid can more effectively be introduced into the polishing interface.

According to a twelfth aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece. The polishing apparatus has a polishing table and a polishing pad bonded to an upper surface of the polishing table by an adhesive made of a liquid crystal material. The polishing apparatus also has a top ring for pressing the workpiece against the polishing pad.

As described above, a liquid crystal material has characteristics that it is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. Therefore, the polishing pad can easily be bonded to and removed from the polishing table.

The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

Brief Description of Drawings FIG. 1A is a side view showing a polishing apparatus according to an embodiment of the present invention;

FIG. IB is a plan view of FIG. 1A; FIG. 2A is a plan view showing a polishing pad in the polishing apparatus shown in FIG. 1 A;

FIG. 2B is a plan view showing a variation of the polishing pad shown in FIG. 2A;

FIG. 3 A is a plan view showing a polishing pad according to another embodiment of the present invention;

FIG. 3B is a plan view showing a polishing pad according to still another embodiment of the present invention;

FIG. 4A is a plan view showing a polishing pad according to still another embodiment of the present invention;

FIG. 4B is an enlarged view of a portion A in FIG. 4A;

FIG. 5A is a plan view showing a polishing pad according to another embodiment of the present invention; FIG. 5B is a plan view showing a polishing pad according to still another embodiment of the present invention;

FIG. 6A is a cross- sectional view showing an attachment structure of a polishing tool according to an embodiment of the present invention;

FIG. 6B is a cross- sectional view showing an attachment structure of a polishing tool according to another embodiment of the present invention;

FIG. 7A is a plan view showing a portion of a polishing pad according to another embodiment of the present invention;

FIG. 7B is a plan view showing a portion of a polishing pad according to still another embodiment of the present invention; FIG. 8 A is a plan view showing a modification of the polishing pad shown in FIG. 7A;

FIG. 8B is a cross-sectional view of FIG. 8 A;

FIG. 9A is a plan view showing a portion of a polishing pad according to another embodiment of the present invention; FIG. 9B is a partial cross-sectional view of FIG. 9 A;

FIG. 9C is a plan view showing a variation of the polishing pad shown in FIG. 9A;

FIGS. 10A through 10C are cross-sectional views showing examples of a light-transmissive plate shown in FIG. 9B; FIG. 11 A is a plan view showing a portion of a polishing pad according to another embodiment of the present invention;

FIG. 1 IB is a partial cross- sectional view of FIG.11 A;

FIG. 11C is a plan view showing a variation of the polishing pad shown in FIG. 11 A; FIGS. 12A through 12C are cross-sectional views showing a polishing tool according to other embodiments of the present invention;

FIGS. 13 A through 13D are schematic views showing a method of attaching a polishing pad to a polishing table according to an embodiment of the present invention;

FIGS. 14A through 14C are schematic views showing a method of attaching a polishing pad to a polishing table according to another embodiment of the present invention; FIGS. 15A through 15C are schematic views showing a method of attaching a polishing pad to a polishing table according to still another embodiment of the present invention;

FIGS. 16A through 16D are schematic views showing a method of removing a polishing pad from a polishing table according to an embodiment of the present invention;

FIGS. 17A through 17C are schematic views showing a method of removing a polishing pad from a polishing table according to another embodiment of the present invention;

FIGS. 18A through 18C are schematic views showing a method of removing a polishing pad from a polishing table according to still another embodiment of the present invention;

FIGS. 19A through 19C are schematic views showing a method of removing a polishing pad from a polishing table according to still another embodiment of the present invention; FIGS. 20A through 20D are cross-sectional views showing a polishing tool according to embodiments of the present invention; and

FIGS. 21A and 21B are cross-sectional views showing a polishing pad according to the present invention.

Best Mode for Carrying Out the Invention

Embodiments of the present invention will be described below with reference to FIGS. 1A through 21B. Like or corresponding parts are denoted by like or corresponding reference numerals throughout drawings, and will not be described below repetitively. FIG. 1A is a side view showing a polishing apparatus according to an embodiment of the present invention, and FIG. IB is a plan view of FIG. 1A. As shown in FIGS. 1 A and IB, this polishing apparatus has a polishing table 10 having a polishing pad 11 (polishing cloth) attached on an upper surface of the polishing pad 11, and a top ring 12 for holding a workpiece 13 to be polished, such as a semiconductor wafer. The polishing table 10 and the top ring 12 are rotated at independent rotational speeds, respectively. The top ring 12 presses the workpiece 13 against the polishing pad 11 at a predetermined pressure. A polishing liquid Q is supplied from a polishing liquid supply nozzle 14 onto the polishing pad 11. Thus, a surface of the workpiece 13 is polished to a flat mirror finish.

Generally, a polishing pad which has the same size as a polishing table is attached onto an upper surface of the polishing table. A pressure sensitive adhesive sheet for bonding is attached to a rear face of the polishing pad. The pressure sensitive adhesive sheet is protected by a protective film. At the time of use, the protective film is peeled so as to expose the pressure sensitive adhesive sheet. Then, the pressure sensitive adhesive sheet is pressed against the upper surface of the polishing table so as to be bonded to the upper surface of the polishing table. At that time, the pressure sensitive adhesive sheet should carefully be bonded so as not to produce air between the pressure sensitive adhesive sheet and the polishing table. If air is produced between the pressure sensitive adhesive sheet and the polishing table, then the pressure sensitive adhesive sheet is raised at points where air is formed, so that polishing pressures are not maintained at proper values at those points. Further, the pressure sensitive adhesive sheet has a large adhesive strength, it is difficult to remove the polishing pad once it has been bonded to the upper surface of the polishing table. On the other hand, once the polishing pad has been removed from the upper surface of the polishing table, it cannot be bonded again to the upper surface of the polishing table. Therefore, when the polishing pad is attached onto the polishing table, it is necessary to carefully position the polishing pad on the polishing table.

FIG. 2A is a plan view showing the polishing pad 11 in the polishing apparatus shown in FIG. 1A. As shown in FIG. 2A, the polishing pad 11 is divided into a plurality of polishing pad pieces 111. In order to produce a polishing pad 11 having uniform properties including density and hardness, it is desirable to select and use polishing pad pieces 111 having the same properties. The sizes of the polishing pad pieces 111 are not limited to the illustrated example. For example, as shown in FIG. 2B, the polishing pad 11 may be divided into a plurality of polishing pad pieces 111 having sizes larger than those of the polishing pad pieces shown in FIG. 2A. In these cases, the sizes of the polishing pad pieces 111 should preferably be smaller than the workpiece 13. If the polishing pad pieces 111 have a large area, properties of the polishing pad pieces 111 are likely to have variations on surfaces thereof. Thus, it is desirable that the polishing pad pieces 111 should have an area as small as possible. When the polishing pad pieces 111 have a size smaller than the workpiece 13, a surface of the workpiece 13 can be polished more uniformly, and uniform polishing performance can be maintained on the surface of the workpiece 13.

As shown in FIGS. 2 A and 2B, the polishing pad pieces 111 should preferably have a hexagonal shape because the small polishing pad pieces 111 can be disposed efficiently without any gaps on a circular upper surface of the polishing table 10. However, the shapes of the polishing pad pieces 111 are not limited to hexagonal shapes. As shown in FIG. 3 A, a circular polishing pad 21 may be divided concentrically and radially into elongated arcuate pieces 211. Alternatively, as shown in FIG. 3B, a circular polishing pad 31 may be divided into rectangular pieces 311. Polishing pad pieces having different shapes, such as regular hexagons and rectangles, may be combined with each other, which are not shown.

FIG. 4 A is a plan view showing a polishing pad 41 according to another embodiment of the present invention, and FIG. 4B is an enlarged view showing a portion A in FIG. 4A. As shown in FIGS. 4A and 4B, the polishing pad 41 is divided into polishing pad pieces 411. Since the polishing pad pieces 411 can be attached and detached individually, material properties and surface shapes of the polishing pad pieces 411 can arbitrarily be selected. FIG. 5 A is a plan view showing a polishing pad 51 according to still another embodiment of the present invention. The polishing pad 51 is divided into polishing pad pieces 511 having the same material properties including foaming density, cross-link density, and hardness, and the same surface shapes including grooves and holes in the polishing pad 51. As the polishing pad pieces 511 are smaller in size, properties of the polishing pad pieces 511 become uniform. Thus, when each of the polishing pad pieces 511 has a size smaller than the diameter of the workpiece 13 such as a semiconductor wafer and the same material properties and surface shapes as those of the workpiece 13, polishing rates become more uniform over a surface of the workpiece 13.

FIG. 5B is a plan view showing a polishing pad 61 according to still another embodiment of the present invention. The polishing pad 61 includes polishing pad pieces 611 and polishing pad pieces 612 having different material properties including foaming density, cross-link density, and hardness, or different surface shapes including grooves and holes than those of the polishing pad pieces 611. Thus, in the present embodiment, polishing rates at a peripheral portion of a workpiece 13 is different from those at a central portion of the workpiece 13. The workpiece 13 may have non-uniform thickness of films formed on a surface of the workpiece 13. For example, the workpiece 13 may have a large thickness at the peripheral portion of the workpiece 13 and a small thickness at the central portion of the workpiece 13. Since a workpiece should have a uniform film thickness after polishing, the peripheral portion of the workpiece 13 should be polished at a higher polishing rate when the workpiece 13 is polished. For these purpose, as shown in FIG.5B, the polishing pad pieces 612 having properties to achieve a higher polishing rate as compared to the polishing pad pieces 611 are arranged at the central area of the polishing table 10. The polishing pad pieces 612 arranged at the central area of the polishing table 10 affect only the peripheral portion of the workpiece 13. With such a polishing pad 61, the peripheral portion of the workpiece 13, which has a larger thickness, can be polished at a higher polishing rate. Thus, the workpiece 13 can be polished so as to have a uniform film thickness.

The arrangement of the polishing pad pieces 612 having different material properties or surface shapes and the polishing pad pieces 611 is not limited to the illustrated example. The polishing pad pieces 612 and the polishing pad pieces 611 may be arranged in various manners according to intended purpose and the shape of the polishing pad 61. For example, polishing pad pieces having different material properties or surface shapes may be disposed at a peripheral area of the polishing table 10. Alternatively, polishing pad pieces having different material properties or surface shapes may be disposed at areas through which the center of the workpiece 13 passes over the polishing table 10.

FIG. 6A is a cross-sectional view showing an attachment structure of a polishing tool according to an embodiment of the present invention. As shown in FIG. 6 A, the polishing table 10 has a plurality of recesses 101 formed on an upper surface thereof. The recesses have the same shape as polishing pad pieces 711 so as to easily position the polishing pad pieces 711 on the upper surface of the polishing table 10. Typically, an adhesive layer 151 is formed on a rear face of each polishing pad piece 711. If the polishing pad pieces 711 are attached and bonded to the upper surface of the polishing table 10 without the recesses 101, then the polishing pad pieces 711 may deviate from proper positions because the adhesive layers 151 have viscosity. If each polishing pad piece 711 is carefully positioned, a considerably long period of time would be required to attach a large number of polishing pad pieces 711. In the present embodiment, as shown in FIG. 6 A, since the polishing table 10 has the recesses 101 in the upper surface thereof, each polishing pad piece 711 can properly be positioned without deviation. Thus, the polishing pad pieces 711 can readily be attached to the upper surface of the polishing table 10 in a short term. FIG. 6B is a cross-sectional view showing an attachment structure of a polishing tool according to another embodiment of the present invention. As shown in FIG. 6B, instead of the recesses 101 shown in FIG. 6A, the polishing table 10 has a holding plate 76 for the same purpose as the recesses 101. Specifically, the holding plate 76 has a plurality of through-holes 761 having the same shape as the polishing pad pieces 711. The holding plate 76 is placed on the upper surface of the polishing table 10. The polishing pad pieces 711 are disposed and positioned in the through-holes 761 of the holding plate 76. Thus, the polishing pad pieces 711 are attached and bonded to the polishing table 10. In this manner, it is not necessary to form the recesses 101 in the polishing table as shown in FIG. 6 A. The shape and the arrangement of the through-holes 761 can arbitrarily be selected by changing holding plates 76.

FIG. 7A is a plan view showing a portion of a polishing pad 81 according to another embodiment of the present invention. As shown in FIG. 7A, the polishing pad 81 has hexagonal polishing pad pieces 811 arranged with gaps 87 formed between adjacent polishing pad pieces 811 and 811. The gaps 87 communicate with each other so as to form grooves through which a polishing liquid flows as shown by arrows 88. When a large number of polishing pad pieces 811 are arranged in this manner, a polishing liquid easily flows through the grooves formed by the gaps 87. Thus, it is possible to efficiently supply the polishing liquid to a polishing interface between a workpiece and the polishing pad 81. As a result, it is possible to reduce the amount of polishing liquid, which is expensive, and hence to reduce operating cost. FIG. 7B is a plan view showing a portion of a polishing pad 91 according to another embodiment of the present invention. As shown in FIG. 7B, the polishing pad 91 has rectangle polishing pad pieces 911 arranged with gaps 97 formed between adjacent polishing pad pieces 911 and 911. The gaps 97 communicate with each other so as to form grooves through which a polishing liquid flows as shown by arrows 98. When a large number of polishing pad pieces 911 are arranged in this manner, a polishing liquid easily flows through the grooves formed by the gaps 97. Thus, it is possible to efficiently supply the polishing liquid to a polishing interface between a workpiece and the polishing pad 91. As a result, it is possible to reduce the amount of polishing liquid, which is expensive, and hence to reduce operating cost.

When the polishing pad has deep grooves, a polishing liquid may be discharged to the exterior of the polishing pad without overflowing the grooves. In order to prevent such a phenomenon, it is desirable to arrange the polishing pad pieces so as to form refracted grooves as shown in FIG. 7A. With this arrangement, a polishing liquid hits walls of the grooves at refracted portions of the grooves and overflows the walls of the grooves. Thus, the polishing liquid can be supplied to the polishing interface. In order to enhance this effect, as shown in FIG. 8A, it is desirable to provide weirs 89 located in the grooves 87. With such weirs 89, when a polishing liquid flows through the grooves 87, it overflows the weirs 89 as shown by arrows 88 in FIG. 8B. Thus, it is possible to efficiently supply the polishing liquid to a polishing interface. Such weirs 89 are also applicable to any polishing pad having grooves in a polishing surface.

The weirs 89 should preferably be made of the same material as the polishing pad pieces 811 or a material that is more likely to be worn than the polishing pad pieces 811. The pattern of the formed grooves and the arrangement of the weirs 89 are not limited to the illustrated example. The grooves may be formed in various patterns, and the weirs 89 may be arranged in various manners. For example, not all of the grooves may communicate with each other, and some of the grooves may be blocked. The grooves may have different widths. Specifically, the gaps 87 between the polishing pad pieces 811 and 811 may have different widths. The gap 87 may not be formed in part between the polishing pad pieces 811 and 811. FIG. 9 A is a plan view showing a portion of a polishing pad 101 according to another embodiment of the present invention, and FIG. 9B is a partial cross-sectional view of FIG. 9A. As shown in FIG. 9A, a polishing pad 101 has hexagonal polishing pad pieces 1011 arranged with gaps 107 formed between adjacent polishing pad pieces 1011 and 1011. As shown in FIGS. 9A and 9B, the polishing table 100 has an opening 110, extending through the polishing table 100, in the groove between the polishing pad pieces 1011 and 1011. Light 114 is emitted through the opening 110 to a surface 13a of a workpiece 13 from a light source 112 provided in the polishing table 100. Reflected light 115 is received by a light-receiving portion 113 provided in the polishing table 100. FIG. 9A shows that an opening 110 is formed in the groove 107 between the polishing pad pieces 1011 and 1011. However, as shown in FIG. 9C, the opening 110 may be disposed in a space between a small polishing pad piece 1012 and a polishing pad piece 1011. In either case, the polishing table 100 has a space for the opening 110 extending through the polishing table 100. Therefore, it is possible to emit light 114 from the polishing table 100 to the surface 13a of the workpiece 13 and then receive reflected light 115 in the polishing table 100.

As shown in FIG. 9B, a light-transmissive plate 111 may be provided on the upper surface of the polishing table 100 to prevent a polishing liquid from entering the interior of the polishing table 100. The light-transmissive plate may have a flat shape 11 la as shown in FIG. 10 A, or a curved shape 111b or 111c facing the workpiece as shown in FIG. 10B or IOC. When the light-transmissive plate has an upper curved surface, a polishing liquid is less likely to accumulate on the top of the upper surface. In such a case, the light transmittance is not lowered.

FIG. 11A is a plan view showing a portion of a polishing pad 121 according to another embodiment of the present invention, and FIG. 1 IB is a partial cross-sectional view of FIG. 11 A. As shown in FIG. 11 A, the polishing pad 121 has polishing pad pieces 1211 including at least one light-transmissive piece 120. As shown in FIG. 1 IB, light 114 is emitted from a light source 112 provided in the polishing table 10 through the light-transmissive piece 120, and reflected light 115 is received by a light-receiving portion 113 provided in the polishing table 10. It is desirable to position an upper surface of the light-transmissive piece 120 at the same height as an upper surface of the polishing pad pieces 1211. Material of the light-transmissive piece 120 is not limited to a specific one, but should preferably be a material that allows light having a wavelength of at least 300 nm to pass therethrough. For example, the light-transmissive piece 120 may include the same material as the polishing pad pieces 1211, e.g. polyurethane. Alternatively, the light-transmissive piece 120 may comprise a material that is worn to the same degree as the polishing pad pieces 1211 or is more likely to be worn than the polishing pad pieces 1211, quartz glass, or liquid crystal material. Further, the light-transmissive piece 120 may be formed by a combination of the above materials in a piled manner.

The formation of the opening 110 and the arrangement of the light-transmissive piece 120 are not limited to the illustrated examples. The opening 110 may be formed in various manners, and the light-transmissive piece 120 may be arranged in various manners. For example, all of the polishing pad pieces 1211 may comprise a light-transmissive piece 120. FIG. 11C shows another variation of the polishing pad 121 shown in FIG. 11 A. With the above configuration, it is possible to monitor states of the workpiece 13 during polishing, such as film thickness or exposure of different materials. Thus, end point detection of the polishing process can readily be performed. Accordingly, the polishing process can be adjusted so as to control excessive polishing or insufficient polishing. As a result, productivity can be improved.

A stream-type measurement device may be used as a substrate measuring device for the above purposes. The stream-type measurement device has a water supply passage and a water discharge passage provided in a polishing table. A supply port of the fluid supply passage and a discharge port of the fluid discharge passage are provided in the polishing table. One of the polishing pad pieces, or one of the polishing pad pieces and one of the pedestals have a through-hole aligned with the supply port of the fluid supply passage and the discharge port of the fluid discharge passage. Pure water is ejected through the fluid supply passage and the through-hole or the through-holes to the substrate. Two optical fibers are disposed in a stream of the pure water. These optical fibers are connected to a light source and a light-receiving portion. Measurement light is emitted through one of the optical fibers to the substrate from the light source, and reflected light is received through the other of the optical fibers from the substrate by the light-receiving portion. Thus, the film thickness or exposure of different materials can be monitored based on the reflected light.

With such an arrangement, the measurement fluid such as pure water is supplied through the fluid supply passage and discharged through the fluid discharge passage. Accordingly, the through-hole or the through-holes are filled with transparent pure water, and hence polishing slurry is prevented from entering the through-hole or the through-holes, thus allowing measurement with use of transmitted light to be performed.

FIGS. 12A through 12C are cross-sectional views showing a polishing tool according to other embodiments of the present invention. As shown in FIGS. 12A through 12C, polishing pad pieces 711 are attached onto an upper surface of the polishing table 10. In FIG. 12A, the polishing pad pieces 711 are attached directly to recesses 101 in the polishing table 10 by thermo-sensitive adhesive layers 151. Specifically, the adhesive layer 151 is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature.

In FIG. 12B, the polishing pad pieces 711 are attached to recesses 101 in the polishing table 10 by upper thermo-sensitive adhesive layers 151, pedestals 251, and lower thermo-sensitive adhesive layers 152. Specifically, the upper and lower adhesive layers 151 and 152 are softened and lowered in adhesive strength under high temperatures while they are hardened and increased in adhesive strength under a room temperature. Each polishing pad piece 711 is attached to each pedestal 251, and each pedestal 251 is attached to recess 101 in the polishing table 10 by the lower thermo-sensitive adhesive layer 152. In FIG. 12C, the polishing pad pieces 711 are attached to a recess 102 in the polishing table 10 by upper thermo-sensitive adhesive layers 151, a pedestal 261, and a lower thermo-sensitive adhesive layer 152. Specifically, a plurality of polishing pad pieces 711 is attached to the pedestal 261, and the pedestal 261 is attached to the recess 102 in the polishing table 10 by the lower thermo-sensitive adhesive layer 152.

In FIGS. 12A through 12C, the recesses 101 and 102 are formed in the polishing table 10 to facilitate positioning of the polishing pad pieces 711, and the pedestals 251 and 261. However, a holding plate 76 as shown in FIG. 6B may be used for positioning instead of the recesses 101 and 102 formed in the upper surface of the polishing table 10. The thermo-sensitive adhesive layers may comprise a liquid crystal material or a hot-melt adhesive.

The liquid crystal material is an organic material as follows. The liquid crystal material has no long-range order with respect to positions of molecules and is fluidic. However, the liquid crystal material has a long-range order with respect to orientation (mainly uniaxial orientation) and is elastic in a liquid crystal state. A liquid crystal material includes a thermotropic liquid crystal, which shows a liquid crystal state as an intermediate state between a crystal and an isotropic liquid, and a lyotropic liquid crystal, which has an order of orientation in a solution state. The above embodiments employ a thermotropic liquid crystal as an adhesive.

The hot-melt adhesive is an adhesive including resin, wax, plasticizer, tackifier, antioxidant, and filler. The resin in the hot-melt adhesive should preferably comprise resin mainly including a copolymer of ethylene and vinyl acetate, or resin including one of polyethylene, polyamide, and polyester. The thermo-sensitive adhesive should preferably have a softening and melting temperature of 200°C or lower, at which properties of the polishing pad pieces 711 are not changed. More specifically, the thermo-sensitive adhesive should preferably have a softening and melting temperature of 100°C or lower, more preferably 70°C or lower.

FIGS. 13 A through 13D are schematic views showing a method of attaching a polishing pad to a polishing table 10 according to an embodiment of the present invention. FIGS. 13A through 13D show processes in which polishing pad pieces 711 are attached directly onto the recesses 101 in the polishing table 10. As shown in FIG. 13 A, an adhesive is applied onto rear faces of a plurality of polishing pad pieces 711 to form adhesive layers 151. As shown in FIG. 13B, the polishing pad pieces 711 are disposed within the recesses 101 in the polishing table 10. Unbonded surfaces of the polishing pad pieces 111, which are opposite to the adhesive layers 151, are pressed by a device 127. At that time, the adhesive layers 151 are heated to a high temperature (at most 200°C, preferably at most 100°C, more preferably at most 70°C) by the device 127 to attach the polishing pad pieces 711 onto bottom surfaces of the recesses 101. Then, the polishing pad pieces 711 are cooled to a room temperature. Thus, as shown in FIG. 13C, the polishing pad pieces 711 are attached directly to the recesses 101.

Alternatively, there may be used a pressing device 128 for pressing the unbonded surfaces of the polishing pad pieces 711 and a heating and cooling device 129 disposed within the polishing table 10 for heating and cooling the adhesive layers 151. Specifically, as shown in FIG. 13 A, an adhesive is applied onto rear faces of a plurality of polishing pad pieces 711 to form adhesive layers 151. As shown in FIG. 13D, the polishing pad pieces 711 are disposed within the recesses 101 in the polishing table 10. While the polishing pad pieces 711 are pressed by the pressing device 128, the adhesive layers 151 are heated to a high temperature (at most 200°C, preferably at most 100°C, more preferably at most 70°C) by the heating and cooling device 129 provided in the polishing table 10 to thereby attach the polishing pad pieces 711 onto the bottom surfaces of the recesses 101. Then, the polishing pad pieces 711 are cooled to a room temperature. Thus, as shown in FIG. 13C, the polishing pad pieces 711 are attached directly to the recesses 101. For example, the device 127 employs a high-temperature fluid or other heating media, which are adjusted in temperature, to heat the polishing pad pieces 711, and also employs a low-temperature fluid or other cooling media, which are adjusted in temperature, to cool the polishing pad pieces 711. For example, the heating and cooling device 129 introduces a high-temperature fluid or other heating media, which are adjusted in temperature, into the interior of the polishing table 10 to heat the polishing pad pieces 711, and also introduces a low-temperature fluid or other cooling media, which are adjusted in temperature, into the interior of the polishing table 10 to cool the polishing pad pieces 711.

With the above processes as shown in FIGS. 13A through 13D, a plurality of polishing pad pieces 711 can be attached directly to a plurality of recesses 101 formed in the upper surface of the polishing table 10 at a time.

FIGS. 14A through 14C are schematic views showing a method of attaching a polishing pad to a polishing table 10 according to another embodiment of the present invention. FIGS. 14A through 14D show processes in which polishing pad pieces 711 are attached via pedestals 251 mounted onto recesses 101 in the polishing table 10. As shown in FIG. 14 A, the pedestals 251 are attached via adhesive layers 152 onto a plurality of recesses 101 in the polishing table 10. An adhesive is applied onto rear faces of a plurality of polishing pad pieces 711 to form adhesive layers 151. The adhesive layer 151 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. The adhesive layer 152 comprises a general adhesive. As shown in FIG. 14B, the polishing pad pieces 711 are placed on the pedestals 251. While the polishing pad pieces 711 are pressed by a device 127, the adhesive layers 151 are heated to a high temperature (at most 200°C, preferably at most 100°C, more preferably at most 70°C) by the device 127 to attach the polishing pad pieces 711 onto upper surfaces of the pedestals 251. Then, the polishing pad pieces 711 are cooled to a room temperature. Thus, as shown in FIG. 14C, the polishing pad pieces 711 are attached via the pedestals 251 to the recesses 101.

FIGS. 15A through 15C are schematic views showing a method of attaching a polishing pad to a polishing table 10 according to still another embodiment of the present invention. FIGS. 15A through 15C show processes in which polishing pad pieces 711 are attached via pedestals 251 onto recesses 101 in the polishing table 10. As shown in FIG. 15 A, the pedestals 251 are attached via adhesive layers 151 onto rear faces of the polishing pad pieces 711. An adhesive is applied onto rear faces of the pedestals 251 to form adhesive layers 152. The adhesive layer 152 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. The adhesive layer 151 comprises a general adhesive. As shown in FIG. 15B, while the polishing pad pieces 711 are pressed by a pressing device 128, the adhesive layers 152 are heated to a high temperature (at most 200°C, preferably at most 100°C, more preferably at most 70°C) by a heating and cooling device 129 in the polishing table 10 to thereby attach the pedestals 251 onto bottom surfaces of the recesses 101. Then, the pedestals 251 are cooled to a room temperature. Thus, as shown in FIG. 15C, the polishing pad pieces 711 are attached via the pedestals 251 to the recesses 101. With the above processes as shown in FIGS. 15A through 15C, a plurality of polishing pad pieces 711 can be attached via pedestals 251 to a plurality of recesses 101 formed in an upper surface of the polishing table 10 at a time.

FIGS. 16A through 16D are schematic views showing a method of removing a polishing pad from a polishing table 10 according to an embodiment of the present invention. FIGS. 16A through 16D show processes in which polishing pad pieces 711 are removed from recesses 101 in the polishing table 10. As shown in FIG. 16A, the polishing pad pieces 711 are bonded to the recesses 101 in the polishing table 10 by an adhesive layers 151. As shown in FIG. 16B, the adhesive layers 151 are heated to a high temperature by a heating device 131 provided near unbonded surfaces of the polishing pad pieces 711 so as to reduce an adhesive strength of the adhesive layers 151. Then, as shown in FIG. 16C, the polishing pad pieces 711 are removed (or separated) from the recesses 101. Alternatively, as shown in FIG. 16D, the adhesive layers 151 may be heated to a high temperature by a heating device 132 provided within the polishing table 10 so as to reduce an adhesive strength of the adhesive layers 151. Then, as shown in FIG. 16C, the polishing pad pieces 711 may be removed (or separated) from the recesses 101.

FIG. 17A through 17C are schematic views showing a method of removing a polishing pad from a polishing table 10 according to another embodiment of the present invention. FIGS. 17A through 17C show processes in which polishing pad pieces 711 attached via pedestals 251 to the recesses 101 are removed from the pedestals 251. As shown in FIG. 17A, the polishing pad pieces 711 are attached via the pedestals 251 to the recesses 101 in the polishing table 10. Adhesive layers 151 between the polishing pad pieces 711 and the pedestals 251 comprise an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. Adhesive layers 152 between the pedestals 251 and the recesses 101 comprise a general adhesive.

As shown in FIG. 17B, the adhesive layers 151 are heated to a high temperature by a heating device 131 provided near unbonded surfaces of the polishing pad pieces 711 so as to reduce an adhesive strength of the adhesive layers 151. Then, as shown in FIG. 17C, the polishing pad pieces 711 are removed (or separated) from the pedestals 251. FIG. 18 A through 18C are schematic views showing a method of removing a polishing pad from a polishing table 10 according to still another embodiment of the present invention. FIGS. 18A through 18C show processes in which polishing pad pieces 711 attached via pedestals 251 to recesses 101 are removed from the recesses 101 in the polishing table 10 together with the pedestals 251. As shown in FIG. 18 A, the polishing pad pieces 711 are attached via the pedestals 251 to the recesses 101 in the polishing table 10. Adhesive layers 151 between the polishing pad pieces 711 and the pedestals 251 comprise a general adhesive. Adhesive layers 152 between the pedestals 251 and the recesses 101 comprise an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature.

As shown in FIG. 18B, the adhesive layers 152 are heated to a high temperature by a heating device 132 provided within the polishing table 10 so as to reduce an adhesive strength of the adhesive layers 152. Then, as shown in FIG. 18C, the polishing pad pieces 711 are removed (or separated) from the recesses 101 together with the pedestals 251 attached to the rear surfaces of the polishing pad pieces 711.

FIG. 19 A through 19C are schematic views showing a method of removing a polishing pad from a polishing table 10 according to still another embodiment of the present invention. FIGS. 19A through 19C show processes in which a portion of polishing pad pieces 711 attached to pedestals 251 by adhesive layers 151 is removed from the pedestals 251 bonded to the recesses 101 in the polishing table 10 by adhesive layers 152. As shown in FIG. 19 A, the polishing pad pieces 711 are attached to the pedestals 251 bonded to the recesses 101 in the polishing table 10. The adhesive layers 151 between the polishing pad pieces 711 and the pedestals 251 comprise an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. As shown in FIG. 19B, the adhesive layer 151 of a portion of the polishing pad pieces 711 is heated to a high temperature by a heating device 131 provided near unbonded surfaces of the polishing pad pieces 711 so as to reduce an adhesive strength of the adhesive layer 151. Then, as shown in FIG. 19C, the polishing pad piece 711 are removed (or separated) from the pedestal 251.

FIGS. 20A through 20D are cross- sectional views showing a polishing tool according to embodiments of the present invention. FIGS. 20A through 20D show examples of bonding arrangement of the polishing pad pieces 711 and the pedestals 251. In FIG. 20 A, a bottom surface of the recess in a polishing table 10 is roughened by sandblasting or the like to form a rough surface 101a. An adhesive layer 151 is applied between the rough surface 101a and the polishing pad piece 711 to attach the polishing pad piece 711 onto the recess 101. The adhesive layer 151 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. With this arrangement, the adhesive layer 151 can have a larger adhesive strength.

In FIG. 20B, a pedestal 251 is attached to a recess 101 of a polishing table 10 by an adhesive layer 152 of a general adhesive. An upper surface of the pedestal 251 is roughened by sandblasting or the like to form a rough surface 251a. An adhesive layer 151 is applied between the rough surface 251a and the polishing pad piece 711 to attach the polishing pad piece 711 onto the pedestal 251. The adhesive layer 151 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. With this arrangement, the adhesive layer 151 can have a larger adhesive strength. In FIG. 20C, a bottom surface of a recess 101 in a polishing table 10 is roughened by sandblasting or the like to form a rough surface 101a. An adhesive layer 152 is applied between the rough surface 101a and the pedestal 251 to attach the pedestal 251 onto the recess 101. The adhesive layer 152 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. The polishing pad piece 711 is attached to an upper surface of the pedestal 251 by an adhesive layer 151 of a general adhesive. With this arrangement, the adhesive layer 152 can have a larger adhesive strength.

In FIG. 20D, a bottom surface of a recess 101 in a polishing table 10 is roughened by sandblasting or the like to form a rough surface 101a. An adhesive layer 152 is applied between the rough surface 101a and the pedestal 251 to attach the pedestal 251 onto the recess 101. The adhesive 152 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature. An upper surface of the pedestal 251 is roughened by sandblasting or the like to form a rough surface 251a. An adhesive layer 152 is applied between the rough surface 251a and the polishing pad piece 711 to attach the polishing pad piece 711 onto the pedestal 251. The adhesive layer 152 comprises an adhesive that is softened and lowered in adhesive strength under high temperatures while it is hardened and increased in adhesive strength under a room temperature.

As described above, the bottom surface of the recess 101 to which the polishing pad piece 711 is to be attached (FIG. 20 A), the upper surface of the pedestal 251 to which the polishing pad piece 711 is to be attached (FIG. 20B), the bottom surface of the recess 101 to which the pedestal 251 is to be attached (FIG. 20C), and the bottom surface of the recess 101 to which the pedestal 251 is to be attached and the upper surface of the pedestal 251 to which the polishing pad piece 711 is to be attached (FIG. 20D) are roughened by sandblasting or the like so as to form rough surfaces. In these cases, it is possible to enhance an adhesive strength of an adhesive.

In the above examples, an adhesive is used to bond the pedestal 251, to which the polishing pad piece 711 is attached, to the polishing table 10. However, the pedestal 251 may be bonded to the polishing table 10 in various manners. For example, the pedestal 251 may be fixed to the polishing table 10 by vacuum attraction. FIGS. 21 A and 21B show an example in which pedestals 2511, 2512, and 2513 each having a polishing pad piece 1111, 1112, and 1113 attached thereon are fixed to a polishing table 10 by vacuum attraction. As shown in FIGS. 21 A and 21B, valves VI 1, V12, and V13 for vacuum are provided in vacuum lines, and valves V21, V22, and V23 for the atmosphere are provided in vacuum lines. The valves VI 1, V12, and V13 are connected to a vacuum source 134 through vacuum lines 133.

As shown in FIG. 21 A, the valves VI 1, V12, and V13 are opened, and the valves V21, V22, and V23 are closed to attract the respective pedestals 1511, 1512, and 1513 so as to fix the polishing pad pieces 1111, 1112, and 1113 to the polishing table 10. In this state, as shown in FIG. 21B, the valve V12 is closed, and the valve V22 is opened (or released to the atmosphere) while the valves VI 1 and VI 3 are opened and the valves V21 and V23 are closed. As a result, only the pedestal 2512 having the polishing pad piece 1112 attached thereon can be removed or separated from the polishing table 10. When the pedestal 2512 having the polishing pad piece 1112 is attached again to the polishing table, the valve 22 is closed and the valve V12 is opened. The valves VI 1, V12, V13, V21, V22, and V23 are not limited to specific types of valves, but should preferably comprise a solenoid valve capable of opening and closing based on electric signals. In the example shown in FIGS. 21 A and 2 IB, the pedestals 2511, 2512, and 2513 are individually attached to and removed from the polishing table 10. However, the attachment and removal of the pedestals 2511, 2512, and 2513 are not limited to this example. For example, a plurality of pedestals 2511, 2512, and 2513 may simultaneously be replaced by simultaneously releasing vacuum for the pedestals 2511, 2512, and 2513, and may simultaneously be attracted under vacuum. Alternatively, after simultaneously releasing vacuum for a plurality of pedestals, part of the pedestals may simultaneously be replaced and then attracted under vacuum.

For example, the polishing table 10 as described above is made of a material having a high thermal conductivity such as SiC, and the pedestals 2511, 2512, and 2513 may be made of a material having a low thermal conductivity such as resin. With this configuration, the polishing pad pieces 1111, 1112, and 1113 and the pedestals 2511, 2512, and 2513 can be attached to and removed from the polishing table 10 effectively.

In the polishing apparatus according to the present invention, a polishing pad to be attached to an upper surface of a polishing table may have an upper surface with grooves for allowing a polishing liquid to pass therethrough. Further, weirs may be provided in the grooves to disturb the flow of the polishing liquid. With this arrangement, the polishing liquid can effectively be introduced into a polishing interface, i.e. between a workpiece and the polishing pad. As a result, it is possible to reduce the amount of polishing liquid, which is expensive, and hence to reduce operating cost. With the weirs provided in the grooves to disturb the flow of the polishing liquid, since the flow of the polishing liquid in the grooves is disturbed by the weirs, the polishing liquid can more effectively be introduced into the polishing interface.

In the polishing apparatus according to the present invention, a polishing pad may be bonded and fixed to an upper surface of a polishing table by an adhesive of a liquid crystal material. As described above, the liquid crystal material is softened and lowered in adhesive strength under high temperatures at which properties of the polishing pad are not changed while it is hardened and increased in adhesive strength under a room temperature. Therefore, the polishing pad can easily be bonded to and removed from the polishing table.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

Industrial Applicability

The present invention is suitable for use in a polishing tool for polishing a workpiece such as a semiconductor wafer to a flat mirror finish.

Claims

1. A polishing tool for polishing a workpiece, said polishing tool comprising: a polishing table; and a polishing pad attached to an upper surface of said polishing table, said polishing pad having a plurality of polishing pad pieces attached to said polishing table.

2. The polishing tool as recited in claim 1, wherein said polishing table has a plurality of recesses for receiving said plurality of polishing pad pieces.

3. The polishing tool as recited in claim 2, wherein said plurality of recesses has the same shape as said plurality of polishing pad pieces.

4. The polishing tool as recited in claim 1, wherein said polishing table includes a holding plate having a plurality of through-holes for receiving said plurality of polishing pad pieces.

5. The polishing tool as recited in claim 4, wherein said plurality of through-holes has the same shape as said plurality of polishing pad pieces.

6. The polishing tool as recited in claim 1, wherein at least one of said polishing pad pieces is attached to said polishing table by a thermo-sensitive adhesive which is softened and lowered in adhesive strength under a high temperature while it is hardened and increased in adhesive strength under a room temperature.

7. The polishing tool as recited in claim 6, wherein the thermo-sensitive adhesive comprises a liquid crystal material or a hot-melt adhesive.

8. The polishing tool as recited in claim 6 or 7, wherein said polishing table has a rough surface onto which the thermo-sensitive adhesive is applied.

9. A polishing tool for polishing a workpiece, said polishing tool comprising: a polishing table; a plurality of pedestals attached to an upper surface of said polishing table; and a polishing pad having a plurality of polishing pad pieces attached to said plurality of pedestals.

10. The polishing tool as recited in claim 9, wherein said polishing table has a plurality of recesses for receiving said plurality of pedestals.

11. The polishing tool as recited in claim 10, wherein said plurality of recesses has the same shape as said plurality of pedestals.

12. The polishing tool as recited in claim 9, wherein said polishing table includes a holding plate having a plurality of through-holes for receiving said plurality of pedestals.

13. The polishing tool as recited in claim 12, wherein said plurality of through-holes has the same shape as said plurality of pedestals.

14. The polishing tool as recited in any one of claims 9 through 13, wherein at least one of said pedestals is attached to said polishing table by a thermo-sensitive adhesive which is softened and lowered in adhesive strength under a high temperature while it is hardened and increased in adhesive strength under a room temperature.

15. The polishing tool as recited in claim 14, wherein the thermo-sensitive adhesive comprises a liquid crystal material or a hot- melt adhesive.

16. The polishing tool as recited in claim 14 or 15, wherein said plurality of pedestals has a rough surface onto which the thermo-sensitive adhesive is applied.

17. The polishing tool as recited in any one of claims 9 through 13, wherein said plurality of pedestals is attached to said polishing table by vacuum attraction.

18. The polishing tool as recited in any one of claims 9 through 17, wherein said polishing table is made of a material having a high thermal conductivity, wherein said plurality of pedestals is made of a material having a low thermal conductivity.

19. The polishing tool as recited in any one of claims 1 through 18, wherein said polishing pad pieces are arranged so as to form gaps between adjacent polishing pad pieces.

20. The polishing tool as recited in claim 19, further comprising at least one weir disposed in said gaps.

21. The polishing tool as recited in any one of claims 1 through 20, wherein each of said polishing pad pieces has a size smaller than the workpiece.

22. The polishing tool as recited in any one of claims 1 through 21, wherein said polishing pad pieces have the same material properties and surface shape.

23. The polishing tool as recited in any one of claims 1 through 21, wherein said plurality of polishing pad pieces comprises: at least one first polishing pad piece; and at least one second polishing pad piece having different material properties or surface shape than material properties or surface shape of said at least one first polishing pad piece.

24. A method of polishing a workpiece, said method comprising: pressing the workpiece against the polishing tool as recited in any one of claims 1 through 23; supplying a polishing liquid to an upper surface of the polishing tool; and moving the polishing tool and the workpiece relative to each other to polish the workpiece.

25. A method of attaching a polishing pad to a polishing table, said method comprising: applying a thermo-sensitive adhesive between the polishing table and the polishing pad, the thermo-sensitive adhesive being softened and lowered in adhesive strength under a high temperature while being hardened and increased in adhesive strength under a room temperature; heating the thermo-sensitive adhesive when the polishing pad is disposed on the polishing table; and cooling the thermo-sensitive adhesive after said heating to bond the polishing pad to the polishing table.

26. The method as recited in claim 25, wherein the polishing pad has a plurality of polishing pad pieces attached to the polishing table.

27. The method as recited in claim 25 or 26, wherein said heating comprising introducing a heating medium adjusted in temperature into the polishing table.

28. The method as recited in claim 25 or 26, wherein said cooling comprising introducing a cooling medium adjusted in temperature into the polishing table.

29. The method as recited in claim 25 or 26, wherein said heating comprising heating the thermo-sensitive adhesive by a heating device provided near an unbonded surface of the polishing pad.

30. The method as recited in claim 25 or 26, wherein said cooling comprising cooling the thermo-sensitive adhesive by a cooling device provided near an unbonded surface of the polishing pad.

31. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a polishing pad attached to an upper surface of said polishing table, said polishing pad having a plurality of polishing pad pieces attached to said polishing table; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through an opening formed between adjacent polishing pad pieces; and a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece.

32. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a plurality of pedestals attached to an upper surface of said polishing table; a polishing pad having a plurality of polishing pad pieces attached to said plurality of pedestals; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through an opening formed between adjacent polishing pad pieces; and a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece.

33. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a polishing pad attached to an upper surface of said polishing table, said polishing pad having at least one light-transmissive piece and a plurality of polishing pad pieces attached to said polishing table; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through said at least one light-transmissive piece; and a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece.

34. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a plurality of pedestals attached to an upper surface of said polishing table; a polishing pad having at least one light-transmissive piece and a plurality of polishing pad pieces attached to said plurality of pedestals; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through said at least one light-transmissive piece; and a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece.

35. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a polishing pad attached to an upper surface of said polishing table, said polishing pad having a plurality of polishing pad pieces attached to said polishing table; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through at least one through-hole formed in at least one of said plurality of polishing pad pieces; a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece; a fluid supply passage aligned with said at least one through-hole for supplying measurement fluid; and a fluid discharge passage aligned with said at least one through-hole for discharging the measurement fluid.

36. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a plurality of pedestals attached to an upper surface of said polishing table; a polishing pad having a plurality of polishing pad pieces attached to said plurality of pedestals; a top ring for pressing the workpiece against said polishing pad; a light source provided in said polishing table for emitting light to a surface of the workpiece through at least one through-hole formed in at least one of said plurality of polishing pad pieces and at least one through-hole formed in at least one of said plurality of pedestals; a light-receiving portion provided in said polishing table for receiving light reflected from the workpiece; a fluid supply passage for supplying measurement fluid, said fluid supply passage being aligned with said at least one through-hole formed in said at least one of said plurality of polishing pad pieces and said at least one through-hole formed in said at least one of said plurality of pedestals; and a fluid discharge passage for discharging the measurement fluid, said fluid discharge passage being aligned with said at least one through-hole formed in said at least one of said plurality of polishing pad pieces and said at least one through-hole formed in said at least one of said plurality of pedestals.

37. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a polishing pad attached to an upper surface of said polishing table, said polishing pad including: a groove in said upper surface of said polishing pad for allowing a polishing liquid to pass therethrough; and a weir provided in said groove to disturb flow of the polishing liquid; and a top ring for pressing the workpiece against said polishing pad.

38. A polishing apparatus for polishing a workpiece, said polishing apparatus comprising: a polishing table; a polishing pad bonded to an upper surface of said polishing table by an adhesive made of a liquid crystal material; and a top ring for pressing the workpiece against said polishing pad.