TWI840128B - Setting plate, polishing equipment and polishing method - Google Patents

Abstract

The present invention relates to a platen, a polishing device and a polishing method. The platen is used in the polishing device. The platen includes a platen plane on which a polishing pad for polishing a silicon wafer is attached. The platen plane includes a liftable portion. The liftable portion can be lifted and lowered relative to the platen plane so that during the polishing process of the silicon wafer, a first portion of the polishing pad corresponding to the edge of the silicon wafer can be lower than a second portion of the polishing pad corresponding to the central area of the silicon wafer in a direction perpendicular to the platen plane.

Description

Setting plate, polishing equipment and polishing method

The present invention belongs to the field of semiconductor processing and manufacturing technology, and specifically, relates to a platen, a polishing device and a polishing method.

With the continuous development of semiconductor technology, the requirements for the flatness of silicon wafer surface are getting higher and higher. In the process of silicon wafer manufacturing, the flatness of silicon wafer can be improved through the polishing process. The polishing process usually includes a double-sided polishing step of polishing both sides of the silicon wafer and a final polishing step of polishing only the front side of the silicon wafer.

In the final polishing, the silicon wafer adsorbed to the polishing head is pressed onto the polishing pad arranged below the polishing head so that the front side of the silicon wafer is polished with the aid of the polishing pad, wherein the silicon wafer and the polishing pad are always rotating during polishing.

However, due to the centrifugal effect caused by rotation, the polishing liquid tends to gather at the edge of the silicon wafer, resulting in a greater degree of polishing at the edge of the silicon wafer than at the center of the silicon wafer; and because the silicon wafer is pressed on the polishing pad, the polishing pad is compressed and deformed and exerts a greater force on the outer edge of the silicon wafer near the chamfer, which will also produce a stronger polishing effect on the edge of the silicon wafer than on the center of the silicon wafer. These will cause the thickness of the edge of the silicon wafer to become thinner than that of the center of the silicon wafer, thereby deteriorating the flatness of the silicon wafer surface.

This section provides a general summary of the invention, and is not a comprehensive disclosure of its full scope or all of its features.

An object of the present invention is to provide a platen for a polishing device which can reduce the degree of polishing of the edge of a silicon wafer.

In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a platen is provided for use in a polishing device, the platen comprising a platen plane on which a polishing pad for polishing a silicon wafer is attached, the platen plane comprising a liftable portion, the liftable portion being able to rise and fall relative to the platen plane, so that during the polishing process of the silicon wafer, a first portion of the polishing pad corresponding to the edge of the silicon wafer can be lower than a second portion of the polishing pad corresponding to the central area of the silicon wafer in a direction perpendicular to the platen plane.

In the above-mentioned fixed plate, the liftable portion may be an annular portion arranged concentrically with the fixed plate.

In the above-mentioned fixed plate, the annular portion may include an outer annular portion close to the outer circumference of the fixed plate and/or an inner annular portion close to the center of the fixed plate, wherein both the outer annular portion and the inner annular portion can make the first part of the polishing pad lower than the second part in this direction by descending relative to the plane of the fixed plate.

In the above-mentioned surface plate, the annular portion may include an intermediate annular portion located between the periphery and the center of the surface plate, wherein the intermediate annular portion can be raised relative to the surface of the surface plate so that the first portion of the polishing pad is lower than the second portion in the direction.

In the above-mentioned fixed plate, the annular portion may be a plurality of annular portions arranged continuously along the radial direction of the fixed plate.

In the above-mentioned fixed plate, the displacement amount of the liftable portion in this direction may be adjustable.

In the above-mentioned fixed plate, the displacement can be adjusted according to the temperature difference between the edge and the central area of the silicon wafer during the polishing process, or can be adjusted according to the flatness condition of the silicon wafer after the previous polishing.

According to another aspect of the present invention, there is provided a polishing apparatus comprising: a platen according to any one of the preceding paragraphs; a polishing pad attached to a platen surface of the platen; and a polishing head for holding a silicon wafer so that it contacts the polishing pad.

In the above polishing apparatus, the materials of the first portion and the second portion of the polishing pad may be different.

According to another aspect of the present invention, a polishing method is provided, which is performed using the polishing device according to any one of the preceding paragraphs, and the polishing method comprises: Operating the elevating portion of the platen so that the first portion of the polishing pad is lower than the second portion in a direction perpendicular to the plane of the platen; and Polishing the silicon wafer by bringing the silicon wafer held by the polishing head into contact with the polishing pad.

According to the present invention, the plate surface includes a liftable portion that can be lifted relative to the plate surface, so that the first portion of the polishing pad attached to the plate surface corresponding to the edge of the silicon wafer is lower than the second portion of the polishing pad corresponding to the central area of the silicon wafer in a direction perpendicular to the plate surface. In this way, on the one hand, the first portion of the polishing pad is generally plastically deformed when in contact with the edge of the silicon wafer during the entire polishing process. On the one hand, the deformation is reduced, thereby reducing the effect of the polishing pad on the outer edge of the silicon wafer and reducing the polishing degree of the silicon wafer edge; on the other hand, the amount of polishing liquid received by the silicon wafer edge from the polishing pad is relatively reduced throughout the entire polishing process, thereby reducing the polishing degree of the silicon wafer edge. Thus, the difference between the polishing degree of the silicon wafer edge and the polishing degree of the silicon wafer central area is reduced, thereby improving the overall flatness of the polished silicon wafer.

The above features and advantages as well as other features and advantages of the present invention will become more apparent through the following detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings.

The present invention is described in detail below with reference to the accompanying drawings by means of exemplary embodiments. It should be noted that the following detailed description of the present invention is only for illustrative purposes and is by no means a limitation of the present invention.

As mentioned before, during the polishing process, the polishing pad and the silicon wafer will both rotate, for example, rotating in the same direction. The resulting centrifugal effect will cause the polishing liquid to tend to gather at the edge of the silicon wafer, resulting in a greater degree of polishing at the edge of the silicon wafer than at the center of the silicon wafer. In addition, the plastic deformation of the polishing pad when in contact with the silicon wafer will exert a greater effect on the outer edge of the silicon wafer near the chamfer, which will also cause the edge of the silicon wafer to be polished more than the center of the silicon wafer, thereby deteriorating the flatness of the silicon wafer surface.

To solve the above problems, it is necessary to eliminate or at least reduce the difference between the polishing degree at the edge of the silicon wafer and the polishing degree at the center of the silicon wafer.

Since both the polishing pad and the silicon wafer rotate during the polishing process, various parts of the edge of the silicon wafer (or, understandably, a certain part) will periodically appear in two areas of the polishing pad during the polishing process, namely, an annular area close to the periphery of the polishing pad and an annular area close to the center of the polishing pad (i.e., for a certain fixed part of the edge of the silicon wafer, it will appear in the above annular area at regular intervals), and various parts of the central area of the silicon wafer will always appear in the middle area of the polishing pad, i.e., the area between the above two annular areas.

To this end, according to one aspect of the present invention, a platen is proposed for use in a polishing device, the platen comprising a platen plane on which a polishing pad for polishing a silicon wafer is attached, the platen plane comprising a liftable portion which can be raised and lowered relative to the platen plane so that during the polishing process of the silicon wafer, a first portion of the polishing pad corresponding to an edge of the silicon wafer can be lower than a second portion of the polishing pad corresponding to a central area of the silicon wafer in a direction perpendicular to the platen plane.

Since various parts of the edge of the silicon wafer will periodically appear in the above-mentioned annular area during the polishing process, the first part of the polishing pad attached to the flat plate plane corresponding to the edge of the silicon wafer is lowered in a direction perpendicular to the flat plate plane than the second part of the polishing pad corresponding to the central area of the silicon wafer by operating the elevating part. On the one hand, the first part of the polishing pad can be generally made to be in contact with the edge of the silicon wafer during the entire polishing process. On the one hand, the plastic deformation is reduced, thereby reducing the effect of the polishing pad on the outer edge of the silicon wafer and reducing the polishing degree of the silicon wafer edge; on the other hand, the amount of polishing liquid received by the silicon wafer edge from the polishing pad can be relatively reduced throughout the entire polishing process, which can also reduce the polishing degree of the silicon wafer edge. Thus, the difference between the polishing degree of the silicon wafer edge and the polishing degree of the silicon wafer central area can be reduced, thereby improving the overall flatness of the polished silicon wafer.

It should be noted that the elevating portion usually still makes the corresponding portion of the polishing pad contact with the silicon wafer after the lifting action, which only reduces the polishing degree of the corresponding portion of the silicon wafer. However, it can be understood that, on the other hand, the elevating portion can also make the corresponding portion of the polishing pad fully lift and lower to break away from the contact with the silicon wafer. Since the edge of the silicon wafer still passes through other parts of the polishing pad such as the middle annular area during rotation, it still serves the purpose of reducing the polishing degree of the edge of the silicon wafer.

Specifically, referring to FIGS. 1 to 3 , the table 1 includes a table plane 11, the polishing pad 2 can be attached to the table plane 11 for polishing the silicon wafer 3, the elevating portion 12 can be raised and lowered relative to the table plane 11, and the elevating portion 12 can be an annular portion arranged concentrically with the table 1. During the polishing process, by operating the elevating portion 12, the first portion 21 (annular region shown in dotted lines) of the polishing pad 2 corresponding to the edge of the silicon wafer 3 can be made lower than the second portion 22 (annular region shown in dotted lines) of the polishing pad 2 corresponding to the central region of the silicon wafer 3 in a direction perpendicular to the table plane 11.

That is, the lifting operation of the liftable portion 12 of the flat plate surface 11 of the flat plate 1 drives the lifting of the corresponding portion of the polishing pad 2 attached to the flat plate surface 11, thereby generally reducing the degree of polishing of the edge of the silicon wafer, thereby eliminating or at least reducing the difference between the degree of polishing of the edge of the silicon wafer and the degree of polishing of the central area of the silicon wafer, and improving the overall flatness of the polished silicon wafer.

It is conceivable that the liftable portion 12 may be a portion of the annular portion, such as one or more arc segments of the annular portion, in addition to being an annular portion arranged concentrically with the plate 1. In this case, since various parts of the edge of the silicon wafer will still periodically appear in the portion of the polishing pad corresponding to the arc segment during the polishing process, the difference between the polishing degree of the edge of the silicon wafer and the polishing degree of the central area of the silicon wafer can still be reduced, thereby improving the overall flatness of the polished silicon wafer.

In an embodiment of the present invention, as shown in FIG. 4 , the annular portion (i.e., the elevating portion) 12 may include an outer annular portion 121 close to the outer periphery of the fixed plate 1 and/or an inner annular portion 122 close to the center of the fixed plate 1, wherein both the outer annular portion 121 and the inner annular portion 122 can make the first portion 21 of the polishing pad 2 lower than the second portion 22 in a direction perpendicular to the fixed plate plane 11 by descending relative to the fixed plate plane 11.

Specifically, when only the outer annular portion 121 or only the inner annular portion 122 is included, since various parts of the edge of the silicon wafer will still periodically appear at the portion of the polishing pad 2 corresponding to the annular portion, the purpose of reducing the polishing degree of the edge of the silicon wafer can still be achieved. Of course, if both the outer annular portion 121 and the inner annular portion 122 are included, the above purpose can be more effectively achieved by making both of them descend relative to the fixed plate plane 11, as shown in FIG. 4, the outer annular portion 121 and the inner annular portion 122 descend from the dotted line position to the solid line position.

According to another embodiment of the present invention, as shown in FIG. 5 , the annular portion (i.e., the elevating portion) 12 may include a middle annular portion 123 located between the periphery and the center of the plate 1, wherein the middle annular portion 123 can be raised relative to the plate plane 11 to make the first portion 21 of the polishing pad 2 lower than the second portion 22 in a direction perpendicular to the plate plane 11.

In this case, since the middle annular portion 123 is raised relative to the plate plane 11 (as shown in FIG. 5 , it is raised from the dotted line position to the solid line position), the second portion 22 of the polishing pad 2 corresponding to the central area of the silicon wafer 3 is higher than the first portion 21 of the polishing pad 2 corresponding to the edge of the silicon wafer 3 in a direction perpendicular to the plate plane 11, thereby reducing the polishing degree of the edge of the silicon wafer as a whole, thereby eliminating or at least reducing the difference between the polishing degree of the edge of the silicon wafer and the polishing degree of the central area of the silicon wafer, and improving the overall flatness of the polished silicon wafer.

It is conceivable that the liftable portion 12 may include the middle annular portion 123 and the outer annular portion 121 and/or the inner annular portion 122 at the same time, and the middle annular portion 123, the outer annular portion 121 and the inner annular portion 122 may all be raised or lowered, as long as the first portion 21 of the polishing pad 2 is lower than the second portion 22 in a direction perpendicular to the fixed plate plane 11.

According to an embodiment of the present invention, the annular portion (i.e., the liftable portion) may be a plurality of annular portions continuously arranged along the radial direction of the fixed plate 1.

For example, the annular portion may be a plurality of annular portions continuously arranged along the radial direction from the center of the fixed plate 1 to the circumferential edge, thereby more finely controlling the polishing degree of the entire silicon wafer along the radial direction, and by reducing the difference between the polishing degrees of each annular portion of the entire silicon wafer in the radial direction, the overall flatness of the silicon wafer can be better improved.

On the other hand, for the outer annular portion 121, the inner annular portion 122 or the middle annular portion 123, it can also be a plurality of annular portions continuously arranged along the radial direction of the fixed plate 1, thereby more finely controlling the polishing degree of the entire silicon wafer along the radial direction for only the area of the single annular portion.

According to the embodiment of the present invention, the displacement of the liftable part 12 in the direction perpendicular to the fixed plate plane 11 can be adjusted.

For example, the liftable part 12 can be driven to move up and down by a controller with the aid of a driver, wherein the controller can control the action amount of the driver and further control the displacement amount of the liftable part 12 in a direction perpendicular to the fixed plate plane 11.

In this way, when the polishing degree of the edge of the silicon wafer is only slightly greater than the polishing degree of the central area of the silicon wafer, the outer annular portion 121 can be slightly lowered relative to the fixed disk plane 11, that is, the displacement of the liftable portion 12 is controlled to be smaller; and when the polishing degree of the edge of the silicon wafer is greater than the polishing degree of the central area of the silicon wafer, the outer annular portion 121 can be lowered more relative to the fixed disk plane 11, that is, the displacement of the liftable portion 12 is controlled to be larger, thereby more flexibly and accurately eliminating or at least reducing the difference between the polishing degrees of the edge and the central area of the silicon wafer.

In an embodiment of the present invention, the displacement can be adjusted according to the temperature difference between the edge and the central area of the silicon wafer during the polishing process, or can be adjusted according to the flatness condition of the silicon wafer that has been polished for the previous time.

The temperature of the edge of the silicon wafer is usually slightly higher than the temperature of the central area of the silicon wafer. If the temperature difference between the two is higher, it means that the polishing degree of the edge of the silicon wafer is greater than that of the central area of the silicon wafer. Therefore, the displacement of the liftable part 12 can be operated accordingly to reduce the difference in polishing degree between the edge and the central area of the silicon wafer. On the other hand, it can also be adjusted according to the flatness of the silicon wafer that has been polished for the previous time. For example, when the difference in polishing degree between the edge and the central area of the silicon wafer that has been polished for the previous time is relatively large, the liftable part 12, such as the outer annular part 121, can be operated to lower a larger displacement, thereby reducing the difference in polishing degree between the edge and the central area of the silicon wafer.

The polishing pad 2 is usually attached to the entire surface of the fixed plate plane 11. As the liftable portion 12 is lifted and lowered, the portion of the polishing pad 2 corresponding thereto will also perform a lifting motion. In order to ensure that the polishing pad 2 is always firmly attached to the fixed plate plane 11 during such a lifting motion, another fixed plate is provided as shown in FIG. 6 .

In FIG. 6 , the outer annular portion 121 can be arranged further inward of the fixed disk plane 11, so that the circumferential edge of the fixed disk plane 11 can leave an annular area 124, which is fixed during the polishing process. In this way, the polishing pad 2 can be firmly attached to the fixed annular area 124 at its circumferential edge, thereby enabling the polishing pad 2 to be firmly attached to the fixed disk plane 11 during the entire polishing process.

According to another aspect of the present invention, there is also provided a polishing apparatus, which includes: a platen 1; a polishing pad 2 attached to a platen surface 11 of the platen 1; and a polishing head (not shown) for holding a silicon wafer so that it contacts the polishing pad.

According to an embodiment of the present invention, the materials of the first portion 21 and the second portion 22 of the polishing pad 2 may be different.

For example, the material of the first portion 21 may be selected to enable a faster flow rate of the polishing liquid than the material of the second portion 22, thereby relatively reducing the polishing ability of the first portion 21.

According to another aspect of the present invention, a polishing method is also provided, which is performed using the above-mentioned polishing device, and the polishing method may include: Operating the liftable part of the platen so that the first part of the polishing pad is lower than the second part in a direction perpendicular to the plane of the platen; and Polishing the silicon wafer by bringing the silicon wafer held by the polishing head into contact with the polishing pad.

The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the patent application.

1: Fixed plate 11: Fixed plate plane 12: Liftable part 121: Outer annular part 122: Inner annular part 123: Middle annular part 124: Annular area 2: Polishing pad 21: First part 22: Second part 3: Silicon wafer

FIG. 1 is a top plan view of a fixed disk according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of the fixed disk taken along the diameter direction of the fixed disk; FIG. 3 shows the fixed disk shown in FIG. 2 with a polishing pad attached in a top plan view, wherein a silicon wafer in contact with the polishing pad during the polishing process is shown; FIG. 4 schematically shows an operation mode of the fixed disk during the polishing process in a cross-sectional view, wherein the outer annular portion and the inner annular portion are lowered relative to the plane of the fixed disk; FIG. 5 schematically shows another operation mode of the fixed disk during the polishing process in a cross-sectional view, wherein the middle annular portion is raised relative to the plane of the fixed disk; and FIG. 6 is a top plan view of a fixed disk according to another embodiment of the present invention.

1: Fixing

11: Fixed plane

12: Liftable part

Claims (10)

A platen for use in a polishing device, the platen comprising a platen plane on which a polishing pad for polishing a silicon wafer is attached, the platen plane comprising a liftable portion, the liftable portion being able to rise and fall relative to the platen plane, so that during the polishing process of the silicon wafer, a first portion of the polishing pad corresponding to the edge of the silicon wafer can be lower than a second portion of the polishing pad corresponding to the central area of the silicon wafer in a direction perpendicular to the platen plane. A fixed plate as described in claim 1, wherein the liftable portion is an annular portion arranged concentrically with the fixed plate. A fixed plate as described in claim 2, wherein the annular portion includes an outer annular portion close to the outer periphery of the fixed plate and/or an inner annular portion close to the center of the fixed plate, wherein both the outer annular portion and the inner annular portion can make the first portion of the polishing pad lower than the second portion in the direction by descending relative to the plane of the fixed plate. A fixed plate as described in claim 2, wherein the annular portion includes an intermediate annular portion located between the periphery and the center of the fixed plate, wherein the intermediate annular portion can make the first portion of the polishing pad lower than the second portion in the direction by rising relative to the plane of the fixed plate. A fixed plate as described in claim 2, wherein the annular portion is a plurality of annular portions arranged continuously along the radial direction of the fixed plate. A fixed plate as described in any one of claims 1 to 5, wherein the displacement of the liftable part in the direction is adjustable. A fixed plate as described in claim 6, wherein the displacement can be adjusted according to the temperature difference between the edge and the central area of the silicon wafer during the polishing process, or can be adjusted according to the flatness condition of the silicon wafer that has been polished for the previous time. A polishing apparatus comprising: a platen as claimed in any one of claims 1 to 7; a polishing pad attached to the platen surface of the platen; and a polishing head for holding a silicon wafer so that it contacts the polishing pad. The polishing apparatus of claim 8, wherein the materials of the first portion and the second portion of the polishing pad are different. A polishing method, which is performed using the polishing apparatus as described in claim 8 or 9, and comprises: operating the elevating portion of the platen so that the first portion of the polishing pad is lower than the second portion in a direction perpendicular to the plane of the platen; and polishing the silicon wafer by bringing the silicon wafer held by the polishing head into contact with the polishing pad.

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