JPH11226861A - Abrasive cloth and surface polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a worked surface having high plane accuracy obtainable by using a single rotary surface plate. SOLUTION: A surface part of an abrasive cloth 1 is constituted by a circular constitutional part 11 in a center side and a ring-shaped constitutional part 12 on the peripheral side, these constitutional parts 11, 12 are arranged adjacent to each other in concentric circular shape. The constitutional part 11 on the center side is constituted by foaming polyurethane of one or two layer structure, with a relatively low elastic modulus, and the constitutional part 12 on the peripheral side is constituted by non-woven fabric having a relatively high elastic modulus to the contrary. In the case of polishing a silicon wafer, first the constitutional part 11 on the center side is used, primary polishing of main polishing is performed, next the constitutional part 12 on the peripheral side is used, secondary polishing as finish polishing is performed, a micro scratch or the like in a surface of the silicon wafer is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing cloth used for polishing a flat workpiece, and more particularly, to a polishing cloth requiring a high flatness such as a silicon wafer. The present invention relates to a polishing cloth suitable for a CMP apparatus.

[0002]

2. Description of the Related Art A conventional CMP apparatus comprises a main platen for performing primary polishing (main polishing) of a silicon wafer;
A secondary surface plate for performing secondary polishing (finish polishing) of the silicon wafer was provided. Therefore, the configuration of the device was complicated. In addition, since polishing is performed at each of two locations in the apparatus, it takes a long time to process one silicon wafer.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conventional CMP polishing,
SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing cloth capable of obtaining a surface to be processed with high planar accuracy using one rotary platen.

[0004]

The polishing cloth of the present invention is a polishing cloth which is used by being affixed to the surface of a rotary platen when polishing a flat workpiece. It comprises a plurality of constituent parts made of different materials, and these constituent parts are arranged concentrically adjacent to each other.

According to the polishing cloth of the present invention, since the surface of one polishing cloth is formed by arranging a plurality of constituent parts made of different materials in the radial direction and concentrically, the polishing characteristic is low. Polishing using different polishing surfaces can be continuously performed using the same polishing cloth on the same rotating platen. Therefore, as compared with the conventional case, the configuration of the planar polishing apparatus is simplified, and the number of processed wafers per unit time is increased.

[0006] For example, by setting the width of each of the plurality of constituent parts of the polishing cloth to be larger than the diameter of the workpiece, each part from the rough polishing to the finish polishing can be used by using each constituent part. Step polishing can be performed.

Further, for example, by setting the width of a part or the whole of the plurality of constituent parts of the polishing cloth to be smaller than the diameter of the workpiece, the distance between the central portion and the outer peripheral portion of the workpiece can be improved. The difference in polishing rate between the two can be reduced, and the in-plane uniformity of the polishing amount of the workpiece can be improved.

[0008]

FIG. 1 shows a schematic configuration of a CMP apparatus using a polishing cloth according to the present invention, and FIG. 2 shows an example of a polishing cloth according to the present invention. The CMP apparatus includes a rotary platen 2, a polishing head 6, an abrasive supply nozzle 3, and the like.
The rotating platen 2 has the polishing cloth 1 mounted on the upper surface, and is rotationally driven by a driving mechanism (not shown) arranged on the lower side.
The polishing head 6 is attached to a lower side of a rotating and pressing mechanism (not shown), and is disposed above the rotating platen 2 so as to face the rotating platen 2. The silicon wafer 5 as a workpiece is held by being attracted to the lower surface of the polishing head 6. The abrasive supply nozzle 3 supplies an abrasive to the surface of the polishing cloth 1.

The polishing of the silicon wafer 5 is performed as follows. First, the polishing cloth 1 is mounted on the upper surface of the rotary platen 2, and the silicon wafer 5 is held on the lower surface of the polishing head 6. Next, the rotating platen 2 and the polishing head 6 are rotated, and the abrasive is supplied from the abrasive supply nozzle 3 onto the polishing cloth 1. Next, the polishing head 6 is lowered, and the silicon wafer 5 is pressed against the surface of the polishing cloth 1.

As shown in FIG. 2, the polishing cloth 1 according to the present invention has, as shown in FIG. 2, a surface portion composed of a circular component 11 on the center side and a ring-shaped component 12 on the outer peripheral side. The component 11 and the component 12 are arranged concentrically adjacent to each other. Note that these components 11
The constituent part 12 is made of materials having different elastic moduli, and has different polishing characteristics from each other, as described later.

When the silicon wafer 5 is polished, first, the primary polishing, which is the main polishing, is performed using the component 11 on the center side, and then the final polishing is performed, using the component 12 on the outer peripheral side. Next polishing is performed to remove micro scratches and the like on the surface of the silicon wafer 5. The result is an ultra-precision finished surface. For this reason, a high polishing rate is secured by using a material having a relatively low elasticity for the center-side component 11, while a relatively low elasticity is used for the outer-side component 12. The use of a high material ensures a fine surface roughness after finishing.

For example, a polishing cloth using a one- or two-layer foamed polyurethane for the central component 11 and a non-woven fabric for the outer component 12 satisfies such conditions.

Next, a procedure for polishing a silicon wafer using a polishing cloth having the above-described composite structure will be described with reference to FIGS. First, as shown in FIG. 3A, the silicon wafer 5 is held on the lower surface of the polishing head 6, and primary polishing is performed using a region (component 11) on the center side of the polishing pad 1. The silicon wafer 5a in FIG. 4 indicates the relative positional relationship between the polishing pad 1 and the silicon wafer at this time.

Next, as shown in FIG. 3B, while holding the silicon wafer 5, the polishing head 6 is moved in the radial direction of the polishing cloth 1, and the area on the outer peripheral side of the polishing cloth 1 (the component 12) Is used to perform secondary polishing. The silicon wafer 5b in FIG. 4 indicates the relative positional relationship between the polishing pad 1 and the silicon wafer at this time.

[0015] If necessary, an abrasive different from that used in the primary polishing is used in the secondary polishing. In this case, preferably, the abrasive supply nozzles 3 are individually provided. FIG. 5 shows another example of the polishing pad according to the present invention.

In this example, the surface of the polishing pad 1 is composed of three regions arranged concentrically. The component 16 on the center side is circular, and the radius of the component 16 is smaller than the diameter of the silicon wafer 5 that is the workpiece. The width of the intermediate ring-shaped component 17 is smaller than the diameter of the silicon wafer 5. A ring-shaped component portion 18 on the outer peripheral side is arranged outside the component portion 17.

In this case, the central component 16 and the intermediate component 17 are used for primary polishing (main polishing), and the outer peripheral component 18 is used for secondary polishing (finish polishing). For this reason, as in the previous example, a relatively low elastic modulus is used for the component 16 on the center side to ensure a high polishing rate, while the component 18 on the outer peripheral side is By using a material having a relatively high elastic modulus, a fine surface roughness after finishing is ensured. The intermediate component 17 is made of a material having a slightly higher elastic modulus than the central component 16.

The reason why the region used for the primary polishing is composed of the two parts having different materials from each other is as follows. That is, in general, the relative speed in the plane of the workpiece tends to be larger at the outer peripheral portion of the workpiece than at the center portion of the workpiece. Also, even when the relative speed in the plane of the workpiece is the same, when comparing the outer peripheral portion of the workpiece and the central portion of the workpiece, it is difficult for the abrasive to enter the central portion of the workpiece, As a result, the polishing rate at the central portion of the workpiece becomes smaller than that at the outer peripheral portion of the workpiece. Due to such factors, the planar accuracy of the workpiece after polishing is impaired. For this reason, the area used for the primary polishing is divided in the radial direction as in the example shown in FIG. 5, and by adjusting the outer polishing rate, the in-plane uniformity of the polishing amount of the workpiece can be improved. Can be improved.

On the basis of the same concept, the surface of the polishing pad is constituted by three or more concentric regions divided in the radial direction, and all the regions (or a part thereof) are formed.
By making the width of the workpiece smaller than the diameter of the workpiece, and individually setting the polishing performance of each component, the difference in the polishing rate between the central part and the outer peripheral part of the workpiece is reduced,
It is also possible to improve the in-plane uniformity of the polishing amount of the workpiece.

[0020]

According to the planar polishing apparatus and the polishing cloth of the present invention, the surface (working surface) of one polishing cloth is divided into a plurality of concentric areas, and the material (for example, By making the elastic moduli different from each other, a plurality of regions having different polishing characteristics can be formed in one polishing cloth. This makes it possible to continuously perform main polishing and finish polishing using the same polishing cloth on the same rotary platen. As a result, the configuration of the planar polishing apparatus is simplified and the number of processed wafers per unit time is increased as compared with the related art.

Further, by arranging a plurality of regions having different polishing characteristics in one polishing cloth, the difference in polishing rate between the central portion and the outer peripheral portion of the workpiece can be reduced,
It is also possible to improve the in-plane uniformity of the polishing amount of the workpiece.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a CMP apparatus using a polishing cloth according to the present invention.

FIG. 2 shows an example of a polishing cloth according to the present invention, (a).
Shows a plan view, and (b) shows a cross-sectional view of AA section.

3A and 3B are diagrams illustrating a method of polishing a silicon wafer using a polishing cloth according to the present invention, wherein FIG. 3A illustrates a state during primary polishing, and FIG. 3B illustrates a state during secondary polishing.

FIG. 4 is a diagram illustrating a relative positional relationship between the polishing cloth and the silicon wafer when polishing a silicon wafer using the polishing cloth according to the present invention.

FIG. 5 is a view showing another example of a polishing cloth according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polishing cloth, 2 ... Rotary platen, 3 ... Abrasive supply nozzle, 5 ... Silicon wafer (workpiece), 6 ... Polishing head, 11, 12, 16, 17 , 18 ... constituent parts.

Claims (9)

[Claims] 1. A polishing cloth which is used by being attached to a surface of a rotating platen when polishing a flat workpiece.
A polishing cloth characterized in that its surface is composed of a plurality of constituent parts made of different materials, and these constituent parts are arranged concentrically adjacent to each other. 2. The polishing cloth according to claim 1, wherein the width of each of the plurality of components is larger than the diameter of the workpiece. 3. The elastic member according to claim 2, wherein the elastic member has a central portion and an outer peripheral portion, and an elastic modulus of the outer peripheral portion is larger than an elastic modulus of the central portion.
The polishing cloth according to 1. 4. The polishing cloth according to claim 3, wherein the component on the outer peripheral side is made of a non-woven fabric, and the component on the central side is made of a one- or two-layer foamed polyurethane. 5. The polishing cloth according to claim 1, wherein a width of at least a part of the plurality of constituent parts is smaller than a diameter of a workpiece. 6. The polishing cloth according to claim 5, wherein an elastic modulus of each component is larger than an elastic modulus of a component adjacent inside. 7. A processing machine comprising: a rotary platen having a polishing cloth adhered to a surface thereof; and a polishing head disposed above the rotary platen so as to face the rotary platen and holding a flat workpiece. In a planar polishing apparatus for polishing a workpiece by pressing a surface of the object against the polishing cloth, the surface of the polishing cloth is composed of a plurality of constituent parts having different materials from each other, and each of these constituent parts is A planar polishing apparatus characterized by being arranged concentrically adjacent to each other. 8. The planar polishing apparatus according to claim 7, wherein the width of each of the plurality of components is larger than the diameter of the workpiece. 9. The planar polishing apparatus according to claim 7, wherein a width of at least a part of the plurality of constituent parts is smaller than a diameter of a workpiece.