JPH1177515A - Surface polishing device and abrasive cloth used for polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface polishing device by which an even working rate is obtained in the whole body of the surface of a work, and thereby, a polished surface furnishing a high flatness accuracy is obtained. SOLUTION: An abrasive cloth 11 is installed on the upper surface of a turntable 2. A polishing head 4 is set at the upper side of the turntable 2, and it is composed of a main spindle 5, a holding plate 6 opposing to the upper surface of the turntable 2, and the like. A wafer 10 to be the work is held at the lower surface of the holding plate 6. To the abrasive cloth 11, a circular recess 12 is formed at the center, and a ring form of polishing surface 13 is provided around the recess 12. The recess 12 is formed to pass a partial area E along the outer periphery of the work 10 on the recess 12. By setting the size D and the arrangement of the area where the recess 12 is formed, the working rate of the peripheral edge of the work 10 can be regulated. As a result, an even working rate can be obtained in the whole body of the surface of the work 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar polishing apparatus used for polishing a flat workpiece and a polishing cloth used for the polishing apparatus. The present invention relates to a structure suitable for a CMP apparatus used for polishing a workpiece.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, when performing planar polishing of an interlayer insulating film or a metal thin film formed on a silicon substrate, a CMP apparatus (Chemical Mechanical) is used.
l Polishing Machine) is widely used.

FIG. 5 shows an outline of a conventional CMP apparatus.
The turntable 2 is fixed to the upper end of the drive shaft 3, and the polishing pad 1 is adhered to the upper surface of the turntable 2. The polishing head 4 is disposed above the turntable 2 and is connected to a rotating / pressing mechanism (not shown). The main shaft 5 is connected to a lower end of the main shaft 5 so as to face the upper surface of the turntable 2. Etc. The wafer 10 to be processed is held on the lower surface of the holding plate 6. By rotating the turntable 2 and supplying the polishing agent from the polishing agent supply nozzle 7 to the surface of the polishing cloth 1, then, using the polishing head 4, the wafer 10 is pressed against the surface of the polishing cloth 1 while rotating the wafer 10. Then, the wafer 10 is polished.

Generally, a single-layer or two-layer polishing cloth is used as the polishing cloth 1. (Problems of the Prior Art) The abrasive cannot be supplied directly to the surface of the workpiece 10. The abrasive reaches the surface of the workpiece 10 through small irregularities on the surface of the polishing cloth 1 or grooves and holes formed on the surface of the polishing cloth 1.
For this reason, compared with the center part and the peripheral part of the surface of the workpiece 10, the amount of the abrasive supplied to the center part is relatively small. Further, as described below, the relative speed of the polishing pad 1 with respect to the workpiece 10 is generally smaller at the center of the workpiece 10 than at the periphery of the workpiece 10. Due to these effects, the processing rate at the center of the workpiece 10 is lower than the processing rate at the peripheral edge.

FIGS. 6A to 6C show the distribution of the relative speed of the polishing cloth 1 adhered on the turntable 2 to the workpiece 10 to be rotated by the polishing head 4.

First, as shown in FIG. 6A, when the number of revolutions is set so that the angular velocity ωp of the turntable 2 matches the angular velocity ωw of the polishing head 4, the outer peripheral portions A, Assuming that the relative velocities of the polishing pad 1 with respect to B and the center C are Va, Vb, and Vc, respectively, the following relationship is established.

Va = Vc = Vb (ωp = ωw) On the other hand, as shown in FIG. 6B, the rotation speed was set so that the angular velocity ωp of the turntable 2 was higher than the angular velocity ωw of the polishing head 4. In this case, the following relationship holds between the relative speeds Va, Vb, and Vc of the polishing pad 1 with respect to each part of the workpiece 10.

Va <Vc <Vb (ωp> ωw) Also, as shown in FIG. 6C, the rotation speed is set so that the angular velocity ωp of the turntable 2 becomes smaller than the angular velocity ωw of the polishing head 4. In this case, the following relationship holds between the relative speeds Va, Vb, and Vc of the polishing pad 1 with respect to each part of the workpiece 10.

Va>Vc> Vb (ωp <ωw) Comparing the above three cases, when ωp and ωw are equal (FIG. 6A), the relative speed of the polishing cloth 1 with respect to the workpiece 10 is Since the distribution is the same at each position on the surface of the workpiece 10, the polishing rate does not vary due to the difference in the relative speed. On the other hand, when ωp and ωw are different (FIG. 6B or FIG. 6C), the relative speed of the peripheral portion of the workpiece 10 becomes larger than the relative speed of the central portion. As a result, the processing rate increases as approaching the outer peripheral portion.

[0010] By the way, the workpiece 1 using a CMP apparatus.
When performing the polishing of 0, the turntable 2 and the polishing head 4
Are driven at the same rotation speed, the polishing cloth 1 mounted on the turntable 2 and the workpiece 10 held on the holding plate 6 always contact at the same point every rotation. For this reason, a pattern such as a groove or a hole formed in the polishing cloth 1 is transferred to the surface of the workpiece 10 or
When there is a defect on the polishing cloth 1, the influence is not averaged, and a problem such as transfer to the surface of the workpiece 10 occurs.

Therefore, in practice, the turntable 2 and the polishing head 4 are driven at different rotational speeds. Therefore, the processing rate of the workpiece 10 increases as approaching the outer periphery. As a result, the surface of the workpiece 10 is usually polished into a convex shape.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional flat surface polishing apparatus, and an object of the present invention is to provide a method for forming a uniform surface over the entire surface of a workpiece. An object of the present invention is to provide a planar polishing apparatus capable of obtaining a processing rate and, therefore, a surface to be polished with high planar accuracy and a polishing cloth used for the polishing apparatus.

[0013]

A planar polishing apparatus according to the present invention comprises a turntable, a polishing cloth mounted on the turntable, and disposed above the turntable so as to face the turntable. A polishing head that holds the workpiece, and while the abrasive is supplied to the surface of the polishing cloth, the workpiece is rotated by the polishing head and pressed against the surface of the polishing cloth to polish the workpiece. In the planar polishing apparatus, the polishing cloth has a concave portion formed on a surface thereof, around a rotation axis of the turntable, and in a range where a partial area along the outer periphery of the workpiece passes during polishing. It is characterized by being.

According to the planar polishing apparatus of the present invention, by using the polishing cloth having the concave portion formed on the surface around the central portion, a partial area along the outer periphery of the workpiece comes into contact with the polishing cloth. The time is shortened, and the processing rate in the region decreases. Therefore, by appropriately setting the range in which the concave portion is formed on the polishing cloth surface, the processing rate in the vicinity of the peripheral portion of the workpiece can be made closer to the processing rate in the central portion. As a result, the flatness of the polished surface can be improved.

[0015] Preferably, the concave portion is formed in a circular area having a center on the rotation axis of the turntable on the surface of the polishing pad. That is, the concave portion is formed in a circular shape at the center of the polishing cloth, and a ring-shaped polishing surface is formed around the concave portion.

Further, preferably, the concave portion is formed in a circular region having a center at a position slightly off the rotation axis of the turntable on the surface of the polishing pad. That is, the recess is formed at a position slightly eccentric with respect to the center of the polishing cloth. With this configuration, the influence of the edge of the concave portion does not concentrate on a specific location on the surface of the workpiece. Therefore, the flatness of the polished surface can be further improved.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an example of a flat-surface polishing apparatus according to the present invention. FIG. 1 shows an outline of a CMP apparatus according to the present invention. The turntable 2 is fixed to the upper end of the drive shaft 3, and the polishing cloth 11 is mounted on the upper surface of the turntable 2. The polishing head 4 is disposed above the turntable 2 and is connected to a rotating / pressing mechanism (not shown). The main shaft 5 is connected to a lower end of the main shaft 5 so as to face the upper surface of the turntable 2. Etc. The wafer 10 to be processed is held on the lower surface of the holding plate 6. While rotating the turntable 2, the polishing agent is supplied from the polishing agent supply nozzle 7 to the surface of the polishing pad 11, and then the wafer 10 is pressed against the surface of the polishing pad 11 while rotating using the polishing head 4. Then, the wafer 10 is polished.

As shown in FIG. 1, the polishing cloth 11 used in the CMP apparatus according to the present invention has a ring-shaped polishing surface 13 and a circular concave portion 12 is formed at the center thereof. The concave portion 12 is formed such that a part near the periphery of the workpiece 10 passes over the concave portion 12 during polishing. That is, the diameter D of the concave portion 12 is set so that a region having a width E along the outer periphery of the workpiece 10 passes over the concave portion 12.

By using the polishing cloth 11 having such a shape, the contact time with the polishing cloth 11 in the region of the width E of the peripheral portion of the workpiece 10 is reduced, and the peripheral edge of the workpiece 10 is reduced. The processing rate of the part decreases. Therefore, by appropriately setting the dimension of the width E (therefore, the diameter D of the concave portion 12), the processing rate of the peripheral portion of the workpiece 10 can approach the processing rate of the central portion. Thereby, the planarity of the surface to be polished can be improved.

FIG. 2 is an enlarged sectional view of a portion G in FIG.
In this example, the polishing cloth 11 is composed of a first layer 11a in contact with the workpiece 10 and a second layer 11b below the first layer 11a. By hollowing out the center of the first layer 11a, A recess 12 is formed. A linear (FIG. 2A) or curved (FIG.
By performing the chamfering of (b)), occurrence of polishing unevenness due to the edge portion is prevented.

FIG. 3 shows another example of a polishing cloth used in the planar polishing apparatus according to the present invention. This figure is shown in FIG.
It is an expanded sectional view corresponding to G section of. When a single-layer polishing cloth is used as the polishing cloth 11, the lower part of the concave portion 12 at the center of the polishing cloth 11 is closed with a protective sheet 15 made of a nonwoven fabric or a Teflon sheet. As a result, when the polishing cloth 11 is worn and thinned as a result of polishing,
Prevents the workpiece 10 from directly contacting the turntable 2 and damaging the workpiece 10.

FIG. 4 shows another example of a polishing cloth used in the planar polishing apparatus according to the present invention. In this example, the center 22 of the circular recess 12 formed near the center of the polishing pad 11 is located slightly away from the center 21 of the polishing pad 11 (therefore, the rotation axis of the turntable 2 (FIG. 1)). The recess 12 is arranged to come. That is, the center 22 and the center 21 are apart from each other by the distance F. By arranging the region of the concave portion 12 at a position eccentric with respect to the polishing cloth 11 as described above, it is possible to prevent the influence of the edge around the concave portion 12 from being concentrated on a specific portion of the workpiece.
Therefore, the occurrence of polishing unevenness can be effectively prevented, and the planar accuracy of the polished surface can be further improved.

[0023]

According to the planar polishing apparatus of the present invention, by using a polishing cloth having a concave portion formed on the surface around the central portion, the polishing cloth can be formed in a partial area along the outer periphery of the workpiece. The contact time is shortened, and the processing rate near the peripheral edge of the workpiece decreases. Therefore, by appropriately setting the range in which the concave portion is formed on the polishing cloth surface, the processing rate in the vicinity of the peripheral portion of the workpiece can be made closer to the processing rate in the central portion. As a result, the planarity of the polished surface can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a CMP apparatus according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing an example of a polishing cloth used in a CMP apparatus according to the present invention, and (a) and (b) show examples of the shape of a chamfer formed around a concave portion.

FIG. 3 is a partially enlarged cross-sectional view showing another example of the polishing cloth used in the CMP apparatus according to the present invention.

FIG. 4 is a plan view showing another example of the polishing pad used in the CMP apparatus according to the present invention.

FIG. 5 is a diagram showing an outline of a conventional CMP apparatus.

6A and 6B are diagrams for explaining the distribution of the relative speed of the polishing cloth with respect to the workpiece; FIG. 6A shows the case where the angular speed of the turntable is equal to the angular speed of the polishing head; (C) represents the distribution of the relative speed when the angular velocity of the turntable is smaller than the angular velocity of the polishing head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... polishing cloth, 2 ... turntable, 3 ... drive shaft, 4 ... polishing head, 5 ... spindle, 6 ... holding plate, 7 ... abrasive supply nozzle, DESCRIPTION OF SYMBOLS 10 ... Workpiece, 11 ... Polishing cloth, 12 ... Depression, 13 ... Polishing surface, 15 ... Protective sheet, 21 ... Center of polishing cloth (rotary axis of turntable) , 22... The center of the concave area.

Claims (6)

[Claims] A turntable; a polishing cloth mounted on the turntable; and a polishing head disposed above the turntable so as to face the turntable and holding a flat workpiece on a lower surface. A polishing machine that rotates the workpiece with a polishing head and presses the workpiece against the surface of the polishing cloth while supplying an abrasive to the surface of the polishing cloth, thereby polishing the workpiece; A planar polishing apparatus, characterized in that a concave portion is formed around the rotation axis of the turntable and in a range where a partial region along the outer periphery of the workpiece passes during polishing. 2. The polishing apparatus according to claim 1, wherein the polishing cloth has a concave portion formed in a circular area having a center on a rotation axis of the turntable on a surface of the polishing cloth. . 3. The polishing cloth according to claim 1, wherein a concave portion is formed in a circular area having a center at a position off the rotation axis of the turntable on the surface of the polishing cloth. Polishing equipment. 4. A polishing cloth for use in a polishing apparatus, wherein a concave portion is formed around a central axis and in a range where a part of a region along an outer periphery of a workpiece passes during polishing. 5. The polishing pad according to claim 4, wherein the concave portion is formed in a circular region having a center on a central axis of the polishing pad. 6. The polishing cloth according to claim 4, wherein the concave portion is formed in a circular area having a center at a position off the central axis of the polishing cloth.