KR20050084767A - Polishing method - Google Patents

Abstract

A semiconductor wafer (W) and a polishing table (100) are rotated. The polishing table (100) has a polishing surface thereon. The semiconductor wafer (W) is pressed against the polishing surface on the polishing table (100) rotated at a first rotational speed to polish the semiconductor wafer (W). The semiconductor wafer (W) is separated from the polishing surface after the semiconductor wafer (W) is pressed against the polishing surface. Before the semiconductor wafer (W) is separated from the polishing surface, a rotational speed of the polishing table (100) is reduced to a second rotational speed lower than the first rotational speed to provide a difference between a rotational speed of the semiconductor wafer (W) and the rotational speed of the polishing table (100).

Description

Polishing method {POLISHING METHOD}

FIELD OF THE INVENTION The present invention relates to a polishing method, and more particularly to a method of polishing a workpiece, such as a semiconductor wafer, with a "flat mirror finish".

As semiconductor devices have become more integrated in recent years, circuit wirings have become smaller and the distance between these circuit wirings has become shorter. In the case of photolithography that can form wirings that are only 0.5 mu m wide, since the depth of focus of the optical system must be relatively small, the surface on which the pattern images are to be focused by the stepper needs to be as flat as possible. However, conventional devices for planarizing semiconductor wafers, such as self-planarizing CVD apparatuses and etching apparatuses, cannot produce semiconductor wafers having completely flat surfaces. In recent years, attempts have been made to planarize a semiconductor wafer with a polishing apparatus that is expected to achieve complete planarization of the semiconductor wafers more easily than the conventional apparatus.

1 shows a basic arrangement of a polishing apparatus of this kind. As shown in FIG. 1, the polishing apparatus includes a polishing table 151 having a polishing pad 161 thereon and a semiconductor wafer W as a workpiece to be polished in such a manner that the surface to be polished faces the polishing pad 161. It has a top ring 152 to hold it. The polishing pad 161 has a top surface that serves as a polishing surface for polishing the workpiece. The top ring 152 is connected to the lower end of the top ring shaft 153 by the ball joint 154 in such a way that the top ring 152 can be tilted with respect to the top ring shaft 153. As the top ring 152 presses the semiconductor wafer W against the polishing table 151 under a predetermined pressure, the polishing table 151 and the top ring 152 are rotated independently. Polishing liquid Q, such as polishing liquid or pure water, is supplied from the polishing liquid supply nozzle 155 onto the polishing pad 161. Therefore, the surface of the semiconductor wafer W is polished by the polishing liquid Q. At this time, the surface of the semiconductor wafer W is in sliding contact with the surface of the polishing pad 161 so as to follow the surface of the polishing pad 161 via the ball joint 154.

Until now, a polishing pad made of a nonwoven fabric has been adopted as the polishing pad attached to a polishing table. In recent years, the higher levels of integration achieved for IC and LSI circuits require surface irregularities or smaller steps on the surface of the semiconductor wafer. To meet this need, polishing pads made of hard materials such as polyurethane foams have been used.

Accordingly, after the semiconductor wafer W is polished by the polishing apparatus, it is necessary to remove (or separate) the semiconductor wafer W from the polishing surface (polishing pad 161) on the polishing table 151. However, due to the polishing liquid Q inserted between them, a large surface tension is applied between the polishing pad 161 and the semiconductor wafer W. Therefore, when the top ring 152 holding the semiconductor wafer W is raised to the polishing position in order to remove the semiconductor wafer W from the polishing pad 161, only the top ring 152 is raised and the semiconductor wafer W is lifted. There are several cases attached to the polishing pad 161 and left on the polishing pad 161.

This problem can be solved by the overhanging action of the top ring. In the overhanging action, after the polishing process is completed, the top ring 152 is not lifted at the polishing position, but moved to the peripheral edge of the polishing pad 161, and beyond the peripheral edge of the polishing pad 161, the semiconductor wafer W And partially exposed the polished surface of < RTI ID = 0.0 >) < / RTI > This overhanging action reduces the surface tension between the polishing pad 161 and the semiconductor wafer W, and the semiconductor wafer W can be reliably removed or separated from the polishing pad 161.

As described above, the overhanging action can reduce the surface tension between the polishing pad 161 and the semiconductor wafer W. FIG. However, the top ring 152 may be inclined when the polished semiconductor wafer W protrudes from the peripheral edge of the polishing pad 161. In this case, the semiconductor wafer W is concentrated at the peripheral edge of the polishing pad 161 so that the semiconductor wafer W is cracked or scratched.

The polishing capacity of the polishing pad is gradually degraded due to deposition of polishing particles and polishing wastes of semiconductor wafers and changes in the characteristics of the polishing pad. Thus, when the same polishing pad is used to repeatedly polish the semiconductor wafers, the polishing speed of the polishing apparatus is lowered, and polishing irregularities tend to occur in the polished semiconductor wafers. Therefore, it is customary to adjust the polishing pad according to a dressing process which restores the surface of the polishing pad with a diamond dresser or the like before, after or during polishing.

When the dresser dresses up the polishing surface of the polishing pad, the thin layer is scraped off with the polishing pad. Thus, after the polishing surface of the polishing pad has been dressed many times, the polishing pad becomes uneven, that is, its flatness is lost, thereby forming steps. As a result, while the polished semiconductor wafer is moved to the peripheral edge of the polishing pad, in the above-described overhanging action, the semiconductor wafer may be cracked or scratched due to the irregularity of the polishing pad.

1 is a schematic view showing a basic arrangement of a polishing apparatus;

2 is a front view showing a polishing apparatus employing a polishing method according to an embodiment of the present invention;

3 is a plan view of the polishing apparatus shown in FIG. 2;

4 is a sectional view showing a top ring in the polishing apparatus shown in FIG. 2;

5 is a bottom view of the top ring shown in FIG. 4;

6 is a timing diagram illustrating an example of a polishing process for polishing a semiconductor wafer and a separation process for separating the semiconductor wafer from the polishing surface according to an embodiment of the present invention;

Fig. 7 is a perspective view showing a polishing apparatus having a web-type (belt-type) polishing table in which the present invention can be adopted.

The present invention has been made in view of the above disadvantages. Accordingly, it is an object of the present invention to provide a polishing method that can easily and safely separate a polished workpiece from a polishing surface and increase throughput without an overhanging action.

According to the first aspect of the present invention, in order to achieve the above object, a polishing method is provided. The workpiece and the polishing table are rotated. The polishing table has a polishing surface thereon. The workpiece is pressed against the polishing surface on the polishing table that is rotated at a first rotational speed to polish the workpiece. After the workpiece is pressed against the polishing surface, the workpiece is separated from the polishing surface. Before the workpiece is separated from the polishing surface, the rotation speed of the polishing table is reduced to a second rotation speed lower than the first rotation speed to provide a difference between the rotation speed of the workpiece and the rotation speed of the polishing table.

According to the first aspect of the present invention, the rotational speed of the polishing table is reduced from the rotational speed of the polishing table rotated during polishing in order to provide a difference between the rotational speeds of the polishing table and the workpiece. At this time, the workpiece is suspended in the liquid layer of the polishing liquid formed between the lower surface of the workpiece and the polishing surface. In detail, a hydroplaning phenomenon occurs. Water slides reduce the surface tension between the polishing surface and the workpiece due to the polishing liquid. Thus, even if the workpiece is raised directly at the position where the polishing process is completed, the workpiece can be easily removed or separated from the polishing surface without overhanging action. Thus, it is possible to prevent the workpiece from being cracked or scratched, which may be caused by the overhanging action, without being left on the polishing surface. Also, since there is no need to perform the overhanging operation, the polishing tact time can be shortened and the throughput can be improved.

According to a preferred form of the invention, a reduction in the rotational speed of the polishing table is carried out during the polishing process. When the rotational speed of the polishing table is reduced, the cleaning process of the polishing surface is performed. In this case, the separation of the workpiece from the polishing surface is promoted, and the conditions for the workpiece can then be adjusted in a timely manner. Thus, throughput is improved.

According to a preferred form of the invention, during the polishing process, the polishing liquid on the polishing surface is supplied at a first flow rate. Upon or before separation of the workpiece from the polishing surface, the flow rate of the polishing liquid is increased to a second flow rate greater than the first flow rate. In this case, the effect of the water slide phenomenon can be increased and the workpiece can be easily separated from the polishing surface.

According to a preferred form of the invention, a mixture of gas and pure water or chemical liquid is ejected to the polishing surface to clean the polishing surface prior to separation of the workpiece from the polishing surface. In this case, the cleaning process of the polishing surface which can increase the water slide phenomenon and can be performed after the polishing process can be started during the polishing process.

According to a preferred form of the invention, the workpiece is raised from the polishing surface to separate the workpiece from the polishing surface. The ascending speed of the workpiece is reduced until the workpiece is substantially separated from the polishing surface. Thus, stress generated in the workpiece can be reduced when the workpiece is separated from the polishing surface.

According to a second aspect of the present invention, a polishing method is provided. The workpiece and the polishing surface are moved relative to each other. The workpiece is pressed against the polishing surface moved to the first frequency to polish the workpiece. The workpiece is separated from the polishing surface after the workpiece is pressed against the polishing surface. Before the workpiece is separated from the polishing surface, the frequency of movement of the polishing surface is reduced to a second frequency less than the first frequency. The workpiece and polishing surface may be orbital.

According to the second aspect of the present invention, the workpiece is suspended in the liquid layer of the polishing liquid formed between the lower surface of the workpiece and the polishing surface. In detail, the water slide phenomenon occurs. Water slides reduce the surface tension between the polishing surface and the workpiece due to the polishing liquid. Thus, even if the workpiece is raised directly at the position where the polishing process is completed, the workpiece can be easily removed or separated from the polishing surface without overhanging action.

According to a third aspect of the present invention, a polishing method is provided. The polishing surface is moved relative to the workpiece. The workpiece is pressed against a polishing surface that is moved at a first speed to polish the workpiece. The workpiece is separated from the polishing surface after the workpiece is pressed against the polishing surface. Before the workpiece is separated from the polishing surface, the moving speed of the polishing surface is reduced to a second speed lower than the first speed. The polishing surface can be moved linearly.

According to the third aspect of the present invention, when the moving speed of the polishing surface is reduced, water slide phenomenon occurs in order to reduce the surface tension between the polishing surface and the workpiece due to the polishing liquid. Thus, even if the workpiece is raised directly at the position where the polishing process is completed, the workpiece can be easily removed from the polishing surface without overhanging action.

According to the fourth aspect of the present invention, a polishing method is provided. The workpiece and the polishing table are rotated. The polishing table has a polishing surface thereon. The workpiece is pressed against the polishing surface on the polishing table. After the workpiece is pressed against the polishing surface, the workpiece is separated from the polishing surface. Before the workpiece is separated from the polishing surface, the ratio of the rotation speed of the top ring to the rotation speed of the polishing table is reduced.

The above and other objects, features and advantages of the present invention will become apparent from the following description, which is made by way of example only in conjunction with the accompanying drawings illustrating preferred embodiments of the present invention.

A polishing method according to embodiments of the present invention is described below with reference to FIGS. 2 to 7.

FIG. 2 is a front view showing the arrangement of the polishing apparatus employing the polishing method according to the embodiment of the present invention, and FIG. 3 is a plan view of the polishing apparatus shown in FIG. As shown in FIGS. 2 and 3, the polishing apparatus has a top ring 1 holding the semiconductor wafer W and a polishing table 100 disposed below the top ring 1. The polishing table 100 has a polishing pad 101 attached to an upper surface of the polishing table 100. The polishing pad 101 has an upper surface in sliding contact with the semiconductor wafer W. As shown in FIG. Thus, the upper surface of the polishing pad 101 serves as a polishing surface for polishing the semiconductor wafer W. As shown in FIG. The polishing apparatus also includes a plurality of jets connected to the polishing liquid supply nozzle 102, the nitrogen gas supply source, and the liquid supply source disposed on the polishing table 100 to supply the polishing liquid Q onto the polishing pad 101. It has an atomizer 103 provided with a nozzle 103a. In FIG. 3, the nebulizer 103 may be disposed at a position indicated by a solid line or a position indicated by a dashed two-dot line.

The polishing liquid supply nozzle 102 supplies a polishing liquid Q, such as polishing liquid or pure water, used to polish the semiconductor wafer W, onto the polishing surface on the polishing table 100. The atomizer 103 ejects a mixture of nitrogen gas and pure water or chemical liquid on the polishing surface on the polishing table 100. Nitrogen gas and pure water or chemical liquid are adjusted to a preset value through a regulator or air operator valve (not shown) connected to a nitrogen gas supply source, and then supplied to the ejection nozzle 103a of the sprayer 103. It is supplied in a mixed state. In this case, it is preferable that the ejection nozzle 103a of the nebulizer 103 can eject the mixture toward the peripheral edge of the polishing table 100. The nebulizer 103 may employ an inert gas other than nitrogen gas. The nebulizer 103 may eject only liquids such as pure water or chemical liquids.

The mixture of nitrogen gas and pure water or chemical liquid may be supplied in the form of (1) fine liquid particles, (2) fine solid particles as a result of solidification of the liquid, or (3) gas as a result of evaporation of the liquid. These states (1), (2), and (3) are called automations. In this state, the mixture may be ejected from the ejection nozzle 103a of the sprayer 103 toward the polishing surface on the polishing table 100. For example, the pressure or temperature of the nitrogen gas and / or the pure or chemical liquid or the shape of the nozzle determines the state of the mixture to be ejected, i.e. fine liquid particles, fine solid particles or gas. Thus, the state of the ejected mixture can be changed, for example, by appropriately adjusting the pressure or temperature of the nitrogen gas and / or pure water or chemical liquid used in the regulator or the like, or by appropriately adjusting the shape of the nozzle.

Various types of polishing pads are available commercially. For example, SUBA800, IC-1000 and IC-1000 / SUBA400 (two-layer cluster) manufactured by Rodel Inc., and Surfin xxx-5 and Surfin 000 manufactured by Fujimi Inc. are included. SUBA800, Surfin xxx-5 and Surfin 000 are non-woven fabrics bonded with urethane resin, and IC-1000 is made of a rigid polyurethane foam (single layer). Polyurethane foam is porous and has many fine recesses or holes formed on its surface.

As shown in FIG. 2, the top ring 1 is connected to the top ring drive shaft 11 via a universal joint 10. The top ring drive shaft 11 is coupled to the top ring air cylinder 111 fixed to the top ring head 110. The top ring air cylinder 111 operates to move the top ring drive shaft 11 vertically, thereby raising and lowering the top ring 1 as a whole, and polishing the retainer ring 3 fixed to the lower end of the top ring body 2. Pressurize against the table 100. The top ring air cylinder 111 is connected to the compressed air source 120 through a regulator R1 capable of adjusting the pressure of the compressed air or the like supplied to the top ring air cylinder 111. Therefore, the pressing force for pressing the polishing pad 101 with the retainer ring 3 can be adjusted.

The top ring drive shaft 11 is connected to the rotary sleeve 112 by a key (not shown). The rotary sleeve 112 has a timing pulley 113 fixedly disposed at its periphery. The top ring motor 114 is fixed to the top ring head 110. The timing pulley 113 is coupled to the timing pulley 116 mounted on the top ring motor 114 by the timing belt 115. Thus, when the top ring motor 114 is activated for rotation, the rotary sleeve 112 and the top ring drive shaft 11 rotate in harmony with each other by the timing pulley 116, the timing belt 115 and the timing pulley 113. As a result, the top ring 1 is rotated. The top ring head 110 is supported on a top ring head shaft 117 which is fixedly supported on a frame (not shown).

The top ring 1 of the polishing apparatus is described below. 4 is a cross-sectional view showing the top ring 1 of the polishing apparatus, and FIG. 5 is a bottom view of the top ring 1 shown in FIG. As shown in FIG. 4, the top ring 1 has a top ring body 2 and a retainer ring 3 fixed to the lower end of the top ring body 2 in the form of a cylindrical housing in which a receiving space is formed. The top ring body 2 is made of a material having high strength and rigidity, such as metal or ceramic. The retainer ring 3 is made of very strong synthetic resin, ceramics and the like.

The top ring body 2 has a cylindrical housing 2a, an annular pressurized seat support 2b fitted into the cylindrical portion of the housing 2a and an annular shape fitted over the peripheral edge of the upper surface of the housing 2a. It has a seal 2c. The retainer ring 3 is fixed to the lower end of the housing 2a of the top ring body 2. The retainer ring 3 has a lower portion projecting radially inward. The retainer ring 3 may be integrally formed with the top ring body 2.

The top ring drive shaft 11 is disposed above the center of the housing 2a of the top ring body 2. The top ring body 2 is coupled to the top ring drive shaft 11 by a universal joint 10. The universal joint 10 transmits the rotation of the spherical bearing mechanism and the top ring drive shaft 11 to the top ring body 2 to allow the top ring body 2 and the top ring drive shaft 11 to incline with respect to each other. Have a mechanism. The spherical bearing mechanism and the rotation transmission mechanism transmit the pressing force and rotational force from the top ring driving shaft 11 to the top ring body 2 while allowing the top ring body 2 and the top ring drive shaft 11 to be inclined with respect to each other.

The spherical bearing mechanism is very hard like hemispherical concave recess 11a formed in the center of the lower surface of the top ring drive shaft 11, hemispherical concave recess 2d formed in the center of the upper surface of the housing 2a and ceramic. It has a bearing ball 12 made of material and interposed between the recessed recesses 11a and 2d. The rotational transmission mechanism includes a drive pin (not shown) fixed to the top ring drive shaft 11 and a driven pin (not shown) fixed to the housing 2a. Although the top ring body 2 can be inclined with respect to the top ring drive shaft 11, the contact pins are displaced because the drive pins and the driven pins stay engaged with each other, while the drive pins and the driven pins can move perpendicular to each other. do. Therefore, the rotation transmission mechanism can reliably transmit the rotational torque of the top ring drive shaft 11 to the top ring body 2.

The top ring body 2 and the retainer ring 3 fixed to the top ring body 2 have a seal ring 4 having a bottom surface in contact with the periphery of the semiconductor wafer W held by the top ring 1. It has a space formed therein for receiving and a disc-shaped chucking plate 6 which can move vertically in the receiving space in the top ring body 2. The seal ring 4 has a radially outer edge clamped between the holder ring 5 and the chucking plate 6 fixed to the lower surface of the holder ring 5, and near the peripheral edge of the chucking plate 6. It extends radially inwardly to cover the bottom surface. The bottom surface of the sealing ring 4 is in contact with the top surface of the semiconductor wafer W to be polished. The semiconductor wafer W has a recess formed at its outer edge to recognize (identify) the orientation of the semiconductor wafer, which is referred to as a notch or orientation flat. The sealing ring 4 may preferably extend radially inward of the chucking plate 6 from the innermost position, such as a notch or azimuth flat.

The chucking plate 6 may be made of metal. However, if the thickness of the thin film formed on the surface of the semiconductor wafer is measured by a method using eddy current while the semiconductor wafer to be polished is held by the top ring, the chucking plate 6 is for example It would be desirable to be made of a nonmagnetic material, such as an insulating material such as fluororesin, epoxy resin or ceramic.

The press sheet 7 made of an elastic membrane extends between the holder ring 5 and the top ring body 2. The pressurizing seat 7 is clamped between the radially outer edge clamped between the housing 2a and the pressurizing seat support 2b of the top ring body 2 and the upper end 5a of the holder ring 5 and the stopper 5b. Have a radially inner edge. The top ring body 2, the chucking plate 6, the holder ring 5 and the press seat 7 jointly form a pressure chamber 21 in the top ring body 2. As shown in FIG. 4, a fluid passage 31 consisting of tubes and connectors is connected to a pressure chamber 21 connected to a compressed air source 120 through a regulator R2 provided on the fluid passage 31. Communicate with Pressurized sheets are made of very strong and durable rubber materials such as ethylene propylene rubber (EPDM), polyurethane rubber or silicone rubber.

When the presser sheet 7 is made of an elastic material such as rubber, when the presser sheet 7 is fixedly clamped between the retainer ring 3 and the top ring body 2, the presser sheet 7 as an elastic material Due to its elastic deformation, the necessary horizontal surface on the lower surface of the retainer ring 3 cannot be maintained. In order to prevent this disadvantage, the pressurized sheet 7 is clamped between the housing 2a of the top ring body 2 and the pressurized sheet support 2b provided as a separate member in this embodiment. The retainer ring 3 may move vertically relative to the top ring body 2 or the retainer ring 3 may have a structure capable of pressing the polishing surface separately from the top ring body 2. In this case, the press seat 7 does not necessarily need to be fixed in the manner described above.

The cleaning liquid passage 51 is formed in the form of an annular groove on the upper surface of the housing 2a near its peripheral edge where the seal 2c of the top ring body 2 is fitted. The cleaning liquid passage 51 communicates with the fluid passage 32 through the through hole 52 formed in the seal 2c. The cleaning liquid (pure water) is supplied to the cleaning liquid passage 51 through the fluid passage 32. The plurality of communication holes 53 are formed in the pressurizing sheet support 2b communicating with the housing 2a and the cleaning liquid passage 51. The communication holes 53 communicate with a small gap G formed between the outer circumferential surface of the seal ring 4 and the inner circumferential surface of the retainer ring 3.

The ring tube 9 and the center bag 8 serving as abutting member in contact with the semiconductor wafer W are mounted in the space formed between the chucking plate 6 and the semiconductor wafer W. As shown in FIG. In the present embodiment, as shown in FIGS. 4 and 5, the center bag 8 is disposed at the center on the lower surface of the chucking plate 6, and the ring tube 9 surrounds the center bag 8 in a relation to surround it. ) Is disposed radially outward. The seal ring 4, the center bag 8 and the ring tube 9 are each made of a very strong and durable rubber material such as ethylene propylene rubber (EPDM), polyurethane rubber or silicone rubber.

The space formed between the chucking plate 6 and the semiconductor wafer W is separated into a plurality of spaces by the center bag 8 and the ring tube 9. Thus, a pressure chamber 22 is formed between the center bag 8 and the ring tube 9, and the pressure chamber 23 is formed radially outward of the ring tube 9.

The center bag 8 has an elastic film 81 in contact with the upper surface of the semiconductor wafer W and a center back holder 82 which detachably holds the elastic film 81 in place. The center back holder 82 has a threaded hole 82a formed therein, and the center bag 8 is detached to the center of the bottom surface of the chucking plate 6 by screws 55 screwed into the threaded holes 82a. Possibly fixed. The central bag 8 has a central pressure chamber 24 formed therein by the elastic membrane 81 and the central back holder 82.

Similarly, the ring tube 9 has an elastic film 91 in contact with the top surface of the semiconductor wafer W and a ring tube holder 92 for detachably holding the elastic film 91 in place. The ring tube holder 92 has threaded holes 92a formed therein, and the ring tube 9 is detachably attached to the lower surface of the chucking plate 6 by a screw 56 screwed into the threaded holes 92a. It is fixed. The ring tube 9 has an intermediate pressure chamber 25 formed therein by the elastic membrane 91 and the ring tube holder 92.

In this embodiment, the pressure chamber 24 is formed by the elastic membrane 81 and the central back holder 82 of the center bag 8, and the pressure chamber 25 is the elastic membrane 91 of the ring tube 9. And ring tube holder 92. The pressure chambers 22 and 23 may be formed by holders for fixing the elastic membrane and the elastic membrane, respectively. In addition, elastic membranes and holders may be appropriately added to increase the number of pressure chambers.

The fluid passages 33, 34, 35 and 36 including the tubes and connectors communicate with the pressure chambers 22, 23, the central pressure chamber 24 and the intermediate pressure chamber 25, respectively. The pressure chambers 22 to 25 are connected to the compressed air source 120 as a feed source through separate regulators R3, R4, R5 and R6 respectively connected to the fluid passages 33 to 36. The fluid passages 31 to 36 are connected to the individual regulators R1 to R6 via rotary joints (not shown) mounted on top of the top ring shaft 11.

The pressure chamber 21 and the pressure chambers 22 to 25 on the chucking plate 6 have air or atmosphere pressurized through the fluid passages 31, 33, 34, 35 and 36 connected to the individual pressure chambers. The same pressurized fluids are supplied or discharged. As shown in FIG. 2, the regulators R2 to R6 connected to the fluid passages 31, 33, 34, 35 and 36 of the pressure chambers 21 to 25 are pressurized and supplied to the individual pressure chambers. The pressure of the fluids can be adjusted individually. Therefore, it is possible to independently control the pressure in the pressure chambers 21 to 25 or to introduce atmospheric or vacuum into the pressure chambers 21 to 25 independently. In this manner, the pressure in the pressure chambers 21 to 25 is independently changed by the regulators R2 to R6 so that the pressing force for pressing the semiconductor wafer W against the polishing pad 101 is the semiconductor wafer W. Can be adjusted in the local areas of In some applications, pressure chambers 21-25 may be connected to vacuum source 121.

In this case, the temperature of the atmosphere supplied to the pressurized fluid or pressure chambers 22 to 25 can be controlled independently. According to this configuration, it is possible to directly control the temperature of the workpiece such as the semiconductor wafer from the back side of the surface to be polished. In particular, when the temperature of each pressure chamber is controlled independently, the rate of chemical reaction can be controlled in the chemical polishing process of CMP.

The chucking plate 6 has a radially inner suction 61 extending downwardly therebetween between the center bag 8 and the ring tube 9. The chucking plate 6 has a radially outer suction 62 extending outwardly therefrom outside of the ring tube 9. In this embodiment, eight suction portions 61 and 62 are provided.

The inner suction part 61 and the outer suction part 62 have communication holes 61a and 62a communicating with the fluid passages 37 and 38, respectively. The inner suction portions 61 and the outer suction portions 62 are connected to a vacuum source 121 such as a vacuum pump through the fluid passages 37 and 38 and the valves V1 and V2. When the communication holes 61a and 62a of the suction parts 61 and 62 are connected to the vacuum source 121, the semiconductor wafer W is attracted to the lower ends of the inner suction part 61 and the outer suction part 62. To this end, negative pressure is formed in the lower end openings of the communication holes 61a and 62a. The inner suction part 61 and the outer suction part 62 have elastic sheets 61b and 62b such as thin rubber sheets attached to the lower end thereof, and elastically contact the semiconductor wafer W on the lower end face thereof. Can be maintained.

Since there is a small gap G between the outer circumferential surface of the seal ring 4 and the inner circumferential surface of the retainer ring 3, the seal ring 4 attached to the holder ring 5, the chucking plate 6, and the chucking plate 6. ) Can be moved vertically with respect to the top ring body 2 and the retainer ring 3, so that they are floating structures for the top ring body 2 and the retainer ring 3. The stopper 5b of the holder ring 5 has a plurality of teeth 5c protruding radially outward from its peripheral edge. The downward movement of the members comprising the holder ring 5 is limited to a preset range by engaging the teeth 5c with the top surface of the radially inner projection of the retainer ring 3.

Accordingly, the operation of the top ring 1 will be described later in detail.

In the polishing apparatus constructed according to this, when the semiconductor wafer W is transferred to the polishing apparatus, the top ring 1 is moved to the portion where the semiconductor wafer W is transported as a whole, and communication holes of the suction portions 61 and 62 are moved. 61a and 62a are connected to vacuum source 121 through fluid passages 37 and 38. The semiconductor wafer W is attracted to the lower ends of the suction parts 61 and 62 by the suction effect of the communication holes 61a and 62a under vacuum. With the semiconductor wafer W attracted to the top ring 1, the top ring 1 is moved to a position above the polishing table 100 having the polishing surface (polishing pad 101) thereon. The peripheral edge of the semiconductor wafer W is held by the retainer ring 3 so that the semiconductor wafer W cannot be removed from the top ring 1.

In order to polish the semiconductor wafer W, suction of the semiconductor wafer W by the suction portions 61 and 62 is released, and the semiconductor wafer W is held on the lower surface of the top ring 1. At the same time, the top ring air cylinder 111 connected to the top ring drive shaft 11 is operated to press the retainer ring 3 fixed to the lower end of the top ring 1 against the polishing surface on the polishing table 100 under a predetermined pressure. do. In this state, the pressurized fluid is supplied to the pressure chambers 22, 23, the central pressure chamber 24, and the intermediate pressure chamber 25, respectively, under separate pressures, so that the semiconductor wafer W is polished to the polishing table 100. Press against the polishing surface of the bed. The polishing liquid supply nozzle 102 supplies the polishing liquid Q on the polishing pad 101 in advance, so that the polishing liquid Q is held on the polishing pad 101. Therefore, the semiconductor wafer W is polished by the polishing pad 101 in a state in which a polishing liquid Q exists between the (bottom) surface of the semiconductor wafer W to be polished and the polishing pad 101. In polishing, the rotational speed of the polishing table 100 is kept substantially the same as the rotational speed of the top ring 1.

Local regions of the semiconductor wafer W located below the pressure chambers 22, 23 are pressed against the polishing surface under the pressure of the pressurized fluids supplied to the pressure chambers 22, 23. The local region of the semiconductor wafer W positioned below the central pressure chamber 24 is polished under the pressure of the pressurized fluid supplied to the central pressure chamber 24 through the elastic membrane 81 of the central bag 8. Pressed against the surface. The local region of the semiconductor wafer W located below the intermediate pressure chamber 25 is subjected to the pressure of the pressurized fluid supplied to the intermediate pressure chamber 25 by the elastic membrane 91 of the ring tube 9. Pressed against the polishing surface.

Thus, the polishing pressure acting on the respective local regions of the semiconductor wafer W can be adjusted independently by controlling the pressure of the pressurized fluids supplied to the individual pressure chambers 22 to 25. Specifically, the individual regulators R3 to R6 can independently adjust the pressure of the pressurized fluids supplied to the pressure chambers 22 to 25, so that the semiconductor with respect to the polishing pad 101 on the polishing table 100 can be controlled. The pressing force applied can be adjusted to press the local regions of the wafer W. In the state where the polishing pressures on the respective local regions of the semiconductor wafer W are independently adjusted to predetermined values, the semiconductor wafer W is pressed against the polishing pad 101 on the rotating polishing table 100. . Similarly, the pressure of the pressurized fluid supplied to the top ring air cylinder 111 can be adjusted by the regulator R1 which adjusts the force by which the retainer ring 3 presses the polishing pad 101. While the semiconductor wafer W is being polished, the force that the retainer ring 3 presses the polishing pad 101 and the pressing force that the semiconductor wafer W is pressed against the polishing pad 101 can be adjusted appropriately, so that the center region (C1 in FIG. 5), the inner region C2 between the central region and the intermediate region, the intermediate region C3, the peripheral region C4 of the semiconductor wafer W, and the retainer ring located outside the semiconductor wafer W Polishing pressure can be applied to the periphery of (3) at a predetermined pressure distribution.

In this way, the semiconductor wafer W is divided into four concentric annular regions C1 to C4, which can each be pressed under independent pressing force. The polishing rate depends on the pressing force applied to the semiconductor wafer W against the polishing surface. As described above, since the pressing force applied to these regions can be controlled independently, the polishing rates of the four circular and annular regions C1 to C4 of the semiconductor wafer W can be controlled independently. Therefore, even if the thickness of the thin film to be polished on the surface of the semiconductor wafer W varies in the radial direction, the thin film on the surface of the semiconductor wafer W is not polished over or overly over the entire surface of the semiconductor wafer, and is polished uniformly. Can be. More specifically, even if the thickness of the thin film to be polished on the surface of the semiconductor wafer W varies depending on the radial position on the semiconductor wafer W, the pressure chambers in which the pressure in the pressure chamber located over the thick area of the thin film are different. The pressure in the pressure chamber, which is made higher than the pressure in, or located over a thin area of the membrane, is made lower than the pressure in the other pressure chambers. In this way, the pressing force applied to the thick region of the thin film against the polishing surface is made higher than the pressing force applied to the thin region of the thin film against the polishing surface, thereby selectively increasing the polishing rate of the thick region of the thin film. Thus, the entire surface of the semiconductor wafer W can be accurately polished to a predetermined level over the entire surface of the semiconductor wafer W regardless of the film thickness distribution generated when the thin film is formed.

Any unnecessary edge surrounding the peripheral edge of the semiconductor wafer W can be prevented by controlling the pressing force applied to the retainer ring 3. If the thickness change of the thin film to be polished on the peripheral edge of the semiconductor wafer W is large, the pressing force applied to the retainer ring 3 is intentionally increased or decreased to control the polishing rate of the peripheral edge of the semiconductor wafer W. Can be. When the pressurized fluid is supplied to the pressure chambers 22 to 25, the chucking plate 6 is likely to be forced upward. In this embodiment, the pressurized fluid is supplied to the pressure chamber 21 through the fluid passage 31 to prevent the chucking plate 6 from being raised by the force caused by the pressure chambers 22 to 25. have.

As described above, the pressing force applied by the top ring air cylinder 111 to press the retainer ring 3 against the polishing pad 101 and to press the local regions of the semiconductor wafer W against the polishing pad 101. The pressing force applied by the pressurized air supplied to the pressure chambers 22 to 25 is appropriately adjusted to polish the semiconductor wafer W. As shown in FIG. When polishing of the semiconductor wafer W is completed, the semiconductor wafer W is attracted to the lower ends of the inner suction part 61 and the outer suction part 62 under vacuum in the same manner as described above. At this time, the supply of pressurized fluid to the pressure chambers 22 to 25 for pressing the semiconductor wafer W against the polishing surface is stopped, and the pressure chambers 22 to 25 are vented to the atmosphere. Therefore, the lower ends of the suction portions 61 and 62 come into contact with the semiconductor wafer W. FIG. The pressure chamber 21 is vented or exhausted to the atmosphere to create a negative pressure therein. When the pressure chamber 21 is maintained at a high pressure, the semiconductor wafer W is strongly pressed against the polishing surface only in the regions in contact with the suction portions 61 and 62. Therefore, it is necessary to immediately reduce the pressure in the pressure chamber 21. Thus, as shown in FIG. 4, a relief port 39 penetrating through the pressure chamber 21 through the top ring body 2 may be provided to immediately reduce the pressure in the pressure chamber 21. In this case, when the pressure chamber 21 is pressurized, it is necessary to continuously supply the pressurized fluid to the pressure chamber 21 through the fluid passage 31. The relief port 39 includes a check valve for preventing the outside air from flowing into the pressure chamber 21 when a negative pressure is formed in the pressure chamber 21.

As described above, it is necessary to remove (or separate) the semiconductor wafer W from the polishing pad 101 after the semiconductor wafer W is attracted by suction to the suction portions 61 and 62. In this case, as described above, a large surface tension works oppositely between the polishing pad 101 and the semiconductor wafer W. As shown in FIG. According to the present invention, in order to reduce the surface tension between the polishing pad 101 and the semiconductor wafer W, the rotational speed of the polishing table 100 is reduced from the rotational speed of the polishing table 100 rotated during polishing. . In this case, the rotation speed of the top ring 1 is maintained at the same rotation speed as the rotation speed of the top ring 1 that is rotated at the time of polishing.

Specifically, the rotational speed of the polishing table 100 is reduced from the rotational speed of the polishing table 100 rotated during polishing to provide a difference between the rotational speeds of the polishing table 100 and the top ring 1. At this time, the semiconductor wafer W held by the top ring 1 is suspended on the liquid layer of the polishing liquid Q formed between the lower surface of the semiconductor wafer W and the upper surface of the polishing pad 101. This phenomenon is also referred to as water slide phenomenon. The water slide reduces the surface tension between the polishing surface and the semiconductor wafer W due to the polishing liquid. Thus, even if the top ring 1 is raised directly at the position where the polishing process is completed, the semiconductor wafer W can be reliably removed or separated from the polishing pad 101 without overhanging action. Thus, the semiconductor wafer W does not remain on the polishing pad 101, and cracking or scratching that may be generated by the overhanging action is prevented.

When the top ring 1 is raised to separate the semiconductor wafer W from the polishing surface, the rising speed of the top ring 1 is relatively low until the semiconductor wafer W is substantially separated from the polishing surface. After the semiconductor wafer W is separated from the polishing surface, the ascending speed of the top ring 1 is increased. Specifically, the top ring 1 is raised at a low speed when the semiconductor wafer W is separated from the polishing surface, and is raised at a high speed after the semiconductor wafer W is separated from the polishing surface. Therefore, when the semiconductor wafer W is separated from the polishing surface, the pressure applied to the semiconductor wafer W is made possible to minimize the stresses applied to the circuit elements formed on the semiconductor wafer W. It is made small. The ascending speed of the top ring 1 can be controlled by adjusting the pressure of the compressed air to be supplied to the top ring air cylinder 111. For example, a sensor (not shown) is used to detect the top ring air cylinder to detect the position of the semiconductor wafer W when the semiconductor wafer W is substantially separated from the polishing surface to control the ascending speed of the top ring 1. It may be provided near the rod of 111.

According to the present invention, since it is not necessary to perform the overhanging operation, the polishing tact time can be shortened and the throughput can be improved.

In order to provide a difference between the rotational speed of the top ring 1 and the polishing table 100 during the polishing process and before the semiconductor wafer W is separated from the polishing surface, the rotational speed of the polishing table 100 is reduced, and the polishing process When this is completed, it is preferable that the top ring 1 be raised. Specifically, just before the polishing process is completed, the rotation speed of the polishing table 100 is reduced to provide a difference between the rotation speeds of the top ring 1 and the polishing table 100. The polishing process continues in this state. When the polishing process is completed, the top ring 1 is raised to separate the semiconductor wafer W from the polishing surface. According to this method, preparation for separating the semiconductor wafer W from the polishing surface can be started in the polishing process. Therefore, the polishing tact time can be shortened and throughput can be improved.

The amount of polishing liquid Q supplied from the polishing liquid supply nozzle 102 is increased before or upon separation of the semiconductor wafer W from the polishing surface. In this case, the influence of the water slide phenomenon can be increased, and the semiconductor wafer W can be easily separated from the polishing surface. The sprayer 103 is used to clean a polishing surface of a mixture of pure water or a chemical liquid and a gas for cleaning the polishing surface (for example, an inert gas such as N ₂ gas) immediately before the semiconductor wafer W is separated from the polishing surface. It would be desirable to start squirting toward. Therefore, the effect of the water slide phenomenon can be increased, and the cleaning process of the polishing surface to be performed after the polishing process can be started during the polishing process.

As described above, after the top ring 1 is raised, the top ring 1 is moved to the position where the semiconductor wafer is transferred. Then, a fluid (for example, compressed air or a mixture of nitrogen and pure water) is ejected to the semiconductor wafer W through the communication holes 61a and 62b of the suction portions 61 and 62 to form a semiconductor wafer ( W) is released.

The polishing liquid Q used to polish the semiconductor wafer W flows through a small gap G between the outer circumferential surface of the seal ring 4 and the retainer ring 3. When the polishing liquid Q is stably held in the gap G, the holder ring 5, the chucking plate 6 and the seal ring 4 are smoothly perpendicular to the top ring body 2 and the retainer ring 3. To prevent them from moving. In order to avoid this disadvantage, the cleaning liquid (pure water) is supplied to the cleaning liquid passage 51 through the fluid passage 32. Accordingly, pure water is supplied to the area above the gap G through the plurality of communication holes 53 to clean the gap G to prevent the polishing liquid Q from accumulating in the gap G. Pure water is preferably supplied after the polished semiconductor wafer W is released until the next semiconductor wafer to be polished is attracted to the top ring 1. Then, before the semiconductor wafer is polished, it is preferable to discharge all the supplied pure water to the outside of the top ring 1, so that it is desirable to provide the retainer ring 3 with a plurality of through holes 3a shown in FIG. desirable. In addition, if a pressure buildup is formed in the space 26 formed between the retainer ring 3, the holder ring 5 and the press seat 7, this will cause the chucking plate 6 in the top ring body 2. Acts to prevent elevate. Therefore, in order to allow the chucking plate 6 to be smoothly lifted and lowered in the top ring body 2, it is preferable that through holes 3a are provided to equalize the pressure in the space 26 to atmospheric pressure.

In this embodiment, as shown in FIG. 2, fluid passages 37 and 38 are connected to the top ring 2 as a vacuum line in communication with the vacuum discharge source 121. The semiconductor wafer W is held on the bottom surface of the top ring 2 by vacuum suction. When the semiconductor wafer W is separated from the polishing surface, the top ring 1 is raised mechanically. When the semiconductor wafer W is removed from the top ring 1 and remains on the polishing pad 101, the pressure in the vacuum line (fluid passages 37 and 38) changes to a vacuum closer to atmospheric pressure. Therefore, the pressure of the vacuum line is monitored to determine whether or not the semiconductor wafer W is normally separated from the polishing pad 101.

In this embodiment, as shown in Fig. 2, a vacuum pressure sensor 40 is provided in the vacuum line to measure and monitor the pressure in the vacuum line, so that the semiconductor wafer W is normally separated from the polishing pad 101. It is determined whether or not. Specifically, after the starting operation of the top ring 1 is started, the pressure in the vacuum line is measured by the vacuum pressure sensor 40. If the measured value is lower than the preset pressure value, it is determined that the semiconductor wafer W is normally separated from the polishing pad 101 with the semiconductor wafer W being attracted to the top ring 1. More specifically, if pressures greater than 10 kPa greater than a preset pressure value determined to be normally sucked into the top ring 1 are measured during a preset period or longer period, the semiconductor wafer W is It is determined that it is removed from the top ring 1.

FIG. 6 is a timing chart showing an example of a polishing process for polishing a semiconductor wafer and a separation process for separating the semiconductor wafer from the polishing surface in this embodiment. 6, the rotation of the top ring, the rotation of the top ring, the rotation of the polishing table, the rotation speed of the polishing table, the rotation of the polishing table, the rotation of the polishing table, the supply of the polishing liquid from the polishing liquid supply nozzle, the supply of the polishing liquid, the sprayer Processes are described from which a supply of a mixture of nitrogen gas and pure or chemical liquids and a stop of the feed from the sprayer are described.

The polishing process continues to T2. For example, the rotation speed of the top ring 1 is 71 rpm (71 min ^-1 ), and the rotation speed of the polishing table 100 is 70 rpm (70 min ^-1 ). The polishing liquid is supplied from the polishing liquid supply nozzle 102 at a flow rate of 150 ml / min. At this time, the nebulizer 103 does not supply a mixture of gas and pure water or chemical liquid.

The conditions change between T1 and T2 before the top ring 1 is raised (ie, before the semiconductor wafer is separated from the polishing surface). At this time, the rotation speed of the top ring is 71 rpm (71 min ^-1 ), which is the same as the rotation speed of the top ring rotated during the polishing process. The rotational speed of the polishing table 100 begins to decrease from 70 rpm (70 min ⁻¹ ) at T1 and reaches 25 rpm (25 min ⁻¹ ) in a short time after T1. The polishing table 100 then maintains a rotational speed of 25 rpm (25 min ⁻¹ ). The flow rate of the polishing liquid supplied from the polishing liquid supply nozzle starts to increase at T1, and reaches 300 ml / min in a short time after T1. Then, the polishing liquid supply nozzle 102 is maintained at a flow rate of 300 ml / min. The nebulizer 103 begins to eject a mixture of nitrogen gas and pure water or chemical liquid onto the polishing surface at T1.

The top ring 1 starts to rise at T2 to separate the semiconductor wafer W from the polishing surface. The raising operation of the top ring 1 is completed at T3. At this time, the semiconductor wafer W is separated from the polishing surface by a predetermined distance.

The top ring 1 starts to stop rotation at T4 and the polishing table 100 also starts to stop rotation at T4. The rotation of the top ring 1 and the polishing table 100 is completely stopped at T '. At this time, the supply of the polishing liquid is also completely stopped. The supply of a mixture of nitrogen gas and pure water or chemical liquid from the atomizer continues to T5 and stops at T5. The sprayer generally begins to feed the mixture at T 'when the rotation of the top ring and polishing table is completely stopped, and continues to feed the mixture for a while after T5, as indicated by the dashed line.

As described above, according to this embodiment, the nebulizer 103 starts to eject the mixture before the top ring is raised. Therefore, the nebulizer 103 can complete the cleaning process of the polishing surface faster than the conventional method. Thus, the conditions for the next workpiece can be adjusted in time to improve throughput.

In this example, the amount of polishing liquid supplied from the polishing liquid supply nozzle 102 is increased at T1. In this case, the cleaning liquid (pure water) for cleaning the retainer ring 3 can be supplied synchronized with the increase in the amount of the polishing liquid supplied from the polishing liquid supply nozzle 102.

The present invention can be applied not only to the polishing apparatus with the rotatable polishing table shown in FIGS. 2 and 3, but also to a polishing apparatus having a scroll polishing table or a web (belt) polishing table.

The scroll polishing table has a diameter considerably smaller than the diameter of the polishing table 100 shown in FIGS. 2 and 3. Specifically, the scrollable polishing table has a diameter equal to or greater than the sum of the diameter of the semiconductor wafer and the twofold eccentric distance. Thus, even if the polishing table makes a translational movement (scrolling movement or orbital movement) with the radius of the eccentric distance, the semiconductor is moved in the polishing table. The scroll polishing table performs parallel orbital motion (scrolling motion) at a predetermined frequency by the operation of the motor. In a polishing apparatus having a scroll polishing table, the semiconductor wafer is held and pressed against the polishing surface on the scroll polishing table by the same top ring as shown in FIGS. 2 and 4. The polishing liquid is supplied to the polishing surface through the holes formed in the polishing table. The polishing apparatus provides relative motion between the polishing surface and the semiconductor wafer to make small parallel orbital movements with a radius of eccentric distance. The semiconductor wafer is polished uniformly over its entire surface. If the polishing apparatus has the same positional relationship continuously between the surface of the semiconductor wafer and the polishing surface, the polished surface of the semiconductor wafer may be affected by local differences in the polishing surface. Thus, the top ring is rotated gradually to prevent the surface of the semiconductor wafer from being polished only by the same portion of the polishing surface.

When a scroll polishing table is used in the polishing apparatus, the semiconductor wafer is separated from the polishing surface as follows. Before the semiconductor wafer is separated from the polishing surface, the frequency of orbital movement of the polishing table is reduced. When the polishing process is complete, the top ring is raised as before. Therefore, the semiconductor wafer held by the top ring is suspended on the liquid layer of the polishing liquid formed between the lower surface of the semiconductor wafer and the polishing surface. In detail, the water slide phenomenon occurs. Thus, the surface tension due to the polishing liquid is reduced between the polishing surface and the semiconductor wafer. Thus, even if the top ring is raised directly at the position where the polishing process is completed, the semiconductor wafer can be easily removed or separated from the polishing surface without overhanging action.

7 is a perspective view showing a polishing apparatus having a web type (belt) polishing table. As shown in FIG. 7, the web polishing table includes a belt 215 having abrasive particles attached to the surface of the belt 215, a pair of rotatable drums 216 and 217 spaced apart from each other, and a belt. A support table 218 is disposed between the upper surface 215a and the lower surface 215b of the belt. Belt 215 is wound on rotatable drums 216 and 217. As the rotatable drums 216 and 217 rotate, the belt 215 moves linearly in the direction indicated by arrow A. FIG. The polishing apparatus has the same top ring 1 as shown in FIGS. 2 and 4. The semiconductor wafer held by the top ring 1 is pressed against the upper surface (ie, the polishing surface) of the belt 215. The polishing liquid Q is supplied from the polishing liquid supply nozzle 102 to the upper surface of the belt 215 to polish the semiconductor wafer.

With the polishing apparatus shown in FIG. 7, the semiconductor wafer is separated from the polishing surface as follows. Before the semiconductor wafer is separated from the polishing surface, the moving speed of the belt 215 is reduced. When the polishing process is complete, the top ring is raised as before. Therefore, the semiconductor wafer held by the top ring is suspended on the liquid layer of the polishing liquid formed between the lower surface of the semiconductor wafer and the upper surface of the belt 215. In detail, the water slide phenomenon occurs. Thus, the surface tension due to the polishing liquid is reduced between the polishing surface and the semiconductor wafer. Thus, even if the top ring is raised directly at the position where the polishing process is completed, the semiconductor wafer can be easily removed or separated from the polishing surface without overhanging action. The amount of polishing liquid supplied from the polishing liquid supply nozzle 102 may be increased before or upon separation of the semiconductor wafer from the polishing surface.

In the embodiment described above, the polishing surface is formed by a polishing pad. However, the polishing surface is not limited to the polishing pad. For example, the polishing surface may be formed by a fixed abrasive. The fixed abrasive is formed into a flat plate containing fixed abrasive particles by a binder. With a fixed abrasive, the polishing process is performed by abrasive particles that are self-generated from the fixed abrasive. Fixed abrasives include abrasive particles, binders, and pores. For example, cerium dioxide (CeO ₂ ) having an average particle diameter of 0.5 μm or less is used as abrasive particles, and an epoxy resin is used as a binder. Fixed abrasives form a harder polishing surface. The fixed abrasive includes a fixed abrasive pad having a two-layer structure formed by a thin layer of the fixed abrasive and an elastic polishing pad attached to the lower surface of the thin layer of the fixed abrasive.

With the polishing apparatus shown in Figs. 2 to 5, the stress generated in the semiconductor wafer is measured. Strain gauges are attached to the center and perimeter of the semiconductor wafer held by the top ring. The rotation speeds of the polishing table and the top ring change when the semiconductor wafer is separated from the polishing surface. At this time, the stress generated in the semiconductor wafer is measured for some examples under the following experimental conditions. The measured results are shown in Table 1 below.

1. A semiconductor wafer with a diameter of 300 mm is used.

2. The semiconductor wafer is separated from the polishing surface under the following conditions.

Example 1: The rotation speed of the polishing table is maintained at 60 rpm (60 min ⁻¹ ), and the rotation speed of the top ring is maintained at 60 rpm (60 min ⁻¹ ). These conditions are the same as in the conventional method. The top ring is raised for 0.5 seconds.

Example 2: increased to 70 rpm (70 min ^-1) at a rotation speed of the polishing table was 60 rpm (60 min ^-1), the rotational speed of the top ring is 71 rpm at ^{60 rpm (60 min -1) (} 71 min - Increased to ¹ ). The top ring is raised for 0.5 seconds.

Example 3: The rotation speed of the polishing table is increased from 70 rpm (70 min ⁻¹ ) to 120 rpm (120 min ⁻¹ ), and the rotation speed of the top ring is increased to 120 rpm (120 min ⁻¹ ). The top ring is raised for 0.5 seconds.

Example 4: The rotation speed of the polishing table is reduced from 70 rpm (70 min ⁻¹ ) to 25 rpm (25 min ⁻¹ ), and the rotation speed of the top ring is maintained at 71 rpm (71 min ⁻¹ ). The top ring is raised for 1.5 seconds.

Example 5: The rotation speed of the polishing table is reduced from 70 rpm (70 min ⁻¹ ) to 25 rpm (25 min ⁻¹ ), and the rotation speed of the top ring is maintained at 71 rpm (71 min ⁻¹ ). The top ring is raised for 0.5 seconds.

Example 6: The rotational speed of the polishing table is reduced to 25 rpm (25 min ^-1) at 70 rpm (70 min ^-1), the rotational speed of the top ring is 50 rpm at ^{70 rpm (70 min -1) (} 50 min - Reduced to ¹ ). The top ring is raised for 0.5 seconds.

Example 7: the rotational speed of the polishing table is reduced to 25 rpm (25 min ^-1) at 70 rpm (70 min ^-1), the rotational speed of the top ring is 40 rpm at ^{70 rpm (70 min -1) (} 40 min - Reduced to ¹ ). The top ring is raised for 0.5 seconds.

Example 8: The rotation speed of the polishing table is reduced from 70 rpm (70 min ⁻¹ ) to 50 rpm (50 min ⁻¹ ), and the rotation speed of the top ring is maintained at 71 rpm (71 min ⁻¹ ). The top ring is raised for 0.5 seconds.

In Table 1, the stress levels of the semiconductor wafer are represented in 11 steps. The minimum level of stress is represented by 1 and the maximum level of stress is represented by 11.

In Table 1, it can be seen that Example 4 has the lowest level of stress generated in the semiconductor wafer, and therefore a minimum force is needed to raise the top ring. In this case, the semiconductor wafer can be easily separated from the polishing pad. Example 5 has the second lowest level generated in the semiconductor wafer, thus requiring the second minimum force to raise the top ring. Therefore, when the ratio of the rotation speed of the top ring to the rotation speed of the polishing table is large, the semiconductor wafer can be easily separated from the polishing pad.

In the above experiment, when the semiconductor wafer is separated from the polishing surface, it is preferable that the rotational speed of the polishing table is reduced below 50 rmp (50 min ⁻¹ ). When the polishing table is rotated at a rotation speed higher than 50 rpm (50 min ⁻¹ ), the pure water or polishing liquid on the polishing table is scattered under centrifugal force, and the effect of the water slide phenomenon is weakened.

As described above, according to the present invention, even if the top ring is directly raised at the position where the polishing process is completed, the workpiece can be easily removed or separated from the polishing surface without overhanging action. Thus, the workpiece does not remain on the polishing surface, and cracking or scratching which may be caused by the overhanging action is prevented.

Further, since there is no need to perform the overhanging operation, the polishing tact time can be shortened, so that the throughput can be improved.

When the rotational speed of the polishing table is reduced, the cleaning process of the polishing surface can be performed. In this case, the separation of the workpiece from the polishing surface is facilitated, and the conditions for the workpiece can then be adjusted in a timely manner. Thus, throughput is improved.

In the case of a scroll polishing table, if the workpiece is separated from the polishing surface, the frequency of movement of the scroll polishing table is reduced. In the case of a web type (belt) polishing table, the moving speed of the belt is reduced. In both cases, the workpiece can be easily separated from the polishing surface.

While certain preferred embodiments of the invention have been shown and described in detail, those skilled in the art will understand that various changes and modifications can be made without departing from the scope of the appended claims.

The present invention can be suitably used in a polishing apparatus for polishing a workpiece such as a semiconductor wafer with a flat mirror finish.

Claims (16)

In the polishing method, Rotating the workpiece; Rotating a polishing table having a polishing surface thereon; Pressing the workpiece against the polishing surface on the polishing table that is rotated at a first speed to polish the workpiece; After the pressing, separating the workpiece from the polishing surface; And Reducing the rotational speed of the polishing table to a second rotational speed lower than the first rotational speed before the separating step to provide a difference between the rotational speed of the workpiece and the rotational speed of the polishing table. Polishing method comprising a. The method of claim 1, And said reducing step is performed during said pressing step. The method of claim 1, During the pressurizing step, supplying a polishing liquid to the polishing surface at a first flow rate; And Before or during said separating, increasing the flow rate of said polishing liquid to a second flow rate higher than said first flow rate. The method of claim 1, And prior to said separating, ejecting a mixture of gas and pure water or chemical liquid onto said polishing surface for cleaning said polishing surface. The method of claim 1, And wherein said separating comprises lifting said workpiece from said polishing surface. The method of claim 5, And said lifting step includes reducing the speed of lifting said workpiece until said workpiece is substantially separated from said polishing surface. In the polishing method, Moving the workpiece and the polishing surface relative to each other; Pressing the workpiece against the polishing surface moved to a first frequency to polish the workpiece; After the pressing, separating the workpiece from the polishing surface; And Prior to said separating, reducing the frequency of movement of said polishing surface to a second frequency lower than said first frequency. The method of claim 7, wherein And the moving step includes moving the workpiece and the polishing surface in orbital motion. In the polishing method, Moving the polishing surface relative to the workpiece; Pressing the workpiece against the polishing surface moved at a first speed to polish the workpiece; After the pressing, separating the workpiece from the polishing surface; And Prior to said separating, reducing the movement speed of said polishing surface to a second speed less than said first speed. The method of claim 9, And wherein said moving comprises linearly moving said polishing surface. In the polishing method, Rotating the workpiece; Rotating a polishing table having a polishing surface thereon; Pressing the workpiece against the polishing surface of the polishing table; After the pressing, separating the workpiece from the polishing surface; And Prior to said separating, reducing the ratio of the rotational speed of the top ring to the rotational speed of the polishing table. The method of claim 11, And said reducing step is performed during said pressing step. The method of claim 11, During the pressurizing step, supplying the polishing liquid to the polishing surface at a first flow rate; And Before or during said separating, increasing the flow rate of said polishing liquid to a second flow rate higher than said first flow rate. The method of claim 11, And prior to said separating, ejecting a mixture of gas and pure water or chemical liquid to said polishing surface for cleaning said polishing surface. The method of claim 11, And wherein said separating comprises lifting said workpiece from said polishing surface. The method of claim 15, And said lifting step includes reducing the speed of lifting said workpiece until said workpiece is substantially separated from said polishing surface.