JPH09300210A - Wafer polishing device and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To polish a wafer into highly accurate flatness by making uniform the gap between the inside face of a retainer ring and the outer circumferential edge of a wafer. SOLUTION: A dummy 7 is inserted into a gap between the inside face 6a of a retainer ring 6 and a cutout part 1a of a wafer 1. The dummy 7 is made of Si or SiO similar to the wafer 1, or polytetrafluoroethylene resin of difficult polishing material. By inserting the dummy 7 into the gap between the inside face 6a and the cutout part 1a of the wafer 1, the gap between the inside face 6a and the outer circumferential edge of the wafer 1 becomes uniform even at the cutout part 1a, a polishing head 3 in the vicinity of the outer circumferential edge of the wafer 1 is prevented from swelling, and the swelling quantity can be reduced. Consequently, the wafer 1 can be polished into highly accurate flatness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus and a wafer polishing method, and more particularly to a wafer polishing apparatus and a wafer polishing method for polishing a wafer to a highly accurate flatness.

[0002]

2. Description of the Related Art A wafer is provided with a notch 1a such as an orientation flat or a notch on its outer periphery as shown in FIGS. Has been. By the way, in the process of manufacturing a semiconductor device, the main surface of the wafer 1 on which the circuit pattern is formed is mechanically and chemically polished to be highly accurately flattened. Hereinafter, a wafer polishing apparatus for polishing the wafer 1 having the cutout portion 1a will be described with reference to FIGS. 6 to 7.

FIG. 6 is a schematic side sectional view of a wafer polishing apparatus, FIG. 7 (a) is a schematic enlarged view of a portion A in FIG. 6, and FIG. 7 (b) shows a state of a wafer 1 after polishing. It is a schematic plan view. Polishing surface plate 2 Polishing pad 3 attached to the upper surface
The wafer 1, which is fixed to the pressure contact head 4 and surrounded by a retainer ring 6 which is a circular ring, is suction-held on the backing pad 5. This retainer ring 6
Is provided in order to prevent the wafer 1 from popping out or being displaced, and the inner diameter thereof is 1 to more than the outer diameter of the wafer 1 so that the wafer 1 having a processing tolerance can be stored.
It is about 2 mm large. Then, the polishing pad 3 is rotated by the rotation of the polishing platen 2, the wafer 1 is rotated by the rotation of the pressure contact head 4, and the droplets are dropped from the nozzle 8 onto the polishing pad 3 near the center of rotation and diffused onto the polishing pad 3. The wafer 1 is polished by the interposition of the slurry 9.

By the way, when the wafer 1 is pressed against the polishing pad 3, the vicinity of the outer peripheral edge of the wafer 1 of the polishing pad 3 rises, and due to this rising, the pressure contact stress at the outer peripheral edge of the wafer 1 becomes larger than that at the central portion of the wafer 1, The polishing rate tends to be high. In particular, as shown in FIG. 7A, in the notch 1a where the gap between the retainer ring 6 and the inner surface 6a is large, the amount of swelling of the polishing pad 3 is large, and the pressure contact stress is larger. Therefore, FIG.
As shown in FIG. 3, there is a possibility that the large polishing rate portion 1b having a large polishing rate may be formed in the notch portion 1a of the wafer 1 after polishing.

As a concrete example, the retainer ring 6 accommodates an 8-inch wafer 1 having a notch 1a,
The polishing amount when mechanical chemical polishing is performed under the following conditions is shown. Polishing pad material Hard polyurethane Polishing slurry Silica particles + KOH solution Polishing plate rotation speed 20 rpm Wafer holder rotation speed 20 rpm Pressing force to press the wafer against the polishing pad 4.9 × 10 ⁴ Pa Wafer polishing surface SiO ₂ film

As a result, the average of the central portion of the wafer 1 is 660.
While the polishing amount was nm, the average of the outer peripheral portion of the wafer 1 (at 5 mm from the outer edge) excluding the cutout portion 1a was 69.
The polishing amount is 0 nm and is 73 in the cutout portion 1a.
The range of the polishing amount of 0 nm extends from 10 to 15 mm from the outer edge, and the polishing amount of 757 nm is 3 mm from the outer edge. Therefore, in the cutout portion 1a of the wafer 1, a portion having particularly poor flatness is formed, which is one of the major factors that make it impossible to increase the number of semiconductor devices manufactured per wafer.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer polishing apparatus and a wafer polishing method for polishing a wafer to a highly accurate flatness.

[0008]

In order to solve the above problems, in the wafer polishing apparatus of the invention of claim 1, a polishing pad adhered to a polishing platen, a retainer ring for surrounding and holding a wafer, In a wafer polishing apparatus having a pressure contact head for fixing a retainer ring and polishing the wafer by bringing the wafer into pressure contact with a polishing pad and relatively moving the wafer, a uniform gap between the inner surface of the retainer ring and the outer peripheral edge of the wafer is provided. It is characterized by doing.

According to a second aspect of the present invention, there is provided a wafer polishing method including a step of inserting a wafer into a retainer ring fixed to a pressure contact head, wherein the wafer inserting step aligns the cutouts of the wafer. Step, step of storing wafer in opening recess of storage case with uniform gap between outer peripheral edge of wafer, and step of inserting wafer accommodated in opening recess into retainer ring with uniform gap between outer peripheral edge of wafer And a process.

According to the above-mentioned means, the gap between the outer peripheral edge of the wafer including the cutout portion and the inner side surface of the retainer ring becomes uniform, and the swelling of the polishing pad in the cutout portion of the wafer can be reduced. Therefore, the pressure contact stress can be made uniform over the entire polishing surface of the wafer, and the polishing rate can be made uniform. Further, if a storage case having an opening concave portion with a uniform gap with the outer peripheral edge of the wafer is used,
The wafer can be easily inserted into the retainer ring.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Note that components in the figure that have the same structure as the conventional technology are denoted by the same reference numerals. Further, regarding the schematic configuration of the wafer polishing apparatus, FIG.
Since it is similar to the case described with reference to, the description thereof will be omitted.

The wafer polishing apparatus of the present invention makes the gap between the inner side surface 6a of the retainer ring 6 and the outer peripheral edge of the wafer 1 including the cutout portion 1a uniform. This will be described with reference to FIGS.

FIG. 1A is a schematic diagram of FIG.
7 is a schematic enlarged view of a portion A in FIG. 6, similar to FIG.
A dummy 7 is inserted in the gap between the inner surface 6a of the retainer ring 6 and the cutout portion 1a. FIG. 1 (b)
FIG. 4 is a schematic plan view showing a state where the wafer 1 is held in a retainer ring 6 having a dummy 7 inserted therein. As shown in FIGS. 1A and 1B, the retainer ring 6 has substantially the same shape as the planar shape formed in the gap between the inner surface 6 a of the retainer ring 6 and the cutout portion 1 a of the wafer 1, and the retainer. A dummy 7 having a thickness that is substantially flush with the surface of the ring 6 facing the polishing pad 3 is inserted. This dummy 7
The material is made of Si or SiO ₂ which is the same as that of the wafer 1, or polytetrafluoroethylene resin which is a hard-to-polish material.

By inserting the dummy 7 into the gap between the inner side surface 6a and the cutout portion 1a of the wafer 1, the gap between the inner side surface 6a and the outer peripheral edge of the wafer 1 becomes uniform even in the cutout portion 1a. It is possible to prevent the polishing pad 3 from rising in the vicinity of the outer peripheral edge of the wafer 1 and reduce the amount of rising. Therefore, the polishing rate in the cutout portion 1a is substantially the same as that of the other portions, and the wafer polishing apparatus can polish the wafer 1 with high accuracy and flatness.

As a concrete example, the polishing amount when the dummy 7 of the above-mentioned case is inserted and the 8-inch wafer 1 having the notch 1a is mechanically and chemically polished under the following conditions is shown. Polishing Pad Material Hard Polyurethane Polishing Slurry Silica Particles + KOH Solution Polishing Plate Rotation Speed 20 rpm Wafer Holder Rotation Speed 20 rpm Pressing force to press wafer against polishing pad 4.9 × 10 ⁴ Pa Wafer polishing surface SiO ₂ film Dummy material Polytetrafluoroethylene

As a result, the average of the central portion of the wafer 1 is 600.
While the polishing amount was nm, the average of the outer peripheral portion of the wafer 1 (at 5 mm from the outer edge) excluding the cutout portion 1a was 56.
Polishing amount of 0 nm, 5 from the outer edge in the cutout portion 1a
The polishing amount was 555 nm at mm. Therefore, the dummy 7 is formed on the inner surface 6a and the cutout portion 1a of the wafer 1.
The wafer 1 was able to be polished to a highly accurate flatness by inserting the wafer 1 in the gap between and.

FIG. 2 shows the dummy 7 integrally formed with the retainer ring 6. Similar to FIG. 1A, FIG. 2A is a schematic enlarged view of a portion A in FIG. 6A referred to in the related art, and FIG. 2B shows the wafer 1 inserted in a retainer ring 6. It is a schematic plan view showing a worn state. The following is the same as the case described with reference to FIG.

The process of inserting the wafer 1 into the retainer ring 6 fixed to the pressure contact head 4 in the wafer polishing apparatus of the case described with reference to FIGS. 1 and 2 will be described below with reference to FIGS. Will be described with reference to. 3A to 3C are schematic flow charts, and FIG. 4A is a schematic perspective view of a storage case 13 for storing the wafer 1.
FIG. 4B is a schematic side sectional view showing a state where the wafer 1 is stored in the storage case 13.

As shown in FIG. 3A, a table 12a for adsorbing the wafer 1 is provided at one end of the rotary shaft from which both ends of the motor 12 are projected, and the wafer 1 is not shown at the other end.
An air exhaust port is provided to adsorb. Also,
A light source 10 such as a laser is arranged on one side near the outer edge of the wafer 1 in the thickness direction of the wafer 1, and a light receiving element 11 is arranged on the other side. Then, first, the motor 12 is rotated and the wafer 1 is rotated to rotate the light receiving element 11
Thus, feedback control is performed until the cutout portion 1a of the wafer 1 is detected. When the cutout 1a is detected, the rotation of the motor is turned off, and the cutout 1a of the wafer 1 is positioned in a predetermined direction. As the motor 12 used in such feedback control, it is desirable to use a stepping motor that does not need a position holding means for the rotating shaft.

Next, the motor 12 with the cutout portion 1a of the wafer 1 positioned in a predetermined direction is moved to a place where the container case 13 is installed, and air suction is turned off.
Then, the wafer 1 is stored in the opening recess 13 a of the storage case 13. As shown in FIG. 4A, the opening recess 13a has a planar shape that is slightly larger than the outer dimension of the wafer 1 including the cutout portion 1a, and as shown in FIG. As shown, the upper surface of the wafer 1 projects by about 0.5 mm when the wafer 1 is housed in the opening recess 13a. Since the wafer 1 stored in the opening recess 13a does not rotate, the storage case 13
The position of the notch 1a with respect to is always maintained.

Next, the container case 13 accommodating the wafer 1 is moved to the pressure contact head 4 of the wafer polishing apparatus,
The pressure contact head 4 is lowered. At this time, the retainer ring 6 of the press contact head 4 is of the case described with reference to FIG. 1 or FIG. 2 (here, the case of using the dummy 7 is shown in the case described with reference to FIG. 1). But the opening recess 13a
If the position of the cutout portion 1a of the wafer 1 housed in the wafer 1 and the position of the dummy 7 are matched, the outer peripheral edge of the wafer 1 including the cutout portion 1a and the inner surface 6 as shown in FIG.
It can be easily inserted and attached so that the gap with a is uniform.

[0022]

According to the wafer polishing apparatus of the present invention, since it is possible to polish the entire surface of the wafer to be polished with high accuracy, it is possible to increase the number of semiconductor chips manufactured from one wafer. can do. Further, according to the wafer polishing method of the present invention, a wafer having a cutout portion such as an orientation flat or a notch can be easily attached to a retainer ring corresponding to the wafer shape.

[Brief description of drawings]

1A and 1B show an example of an embodiment using a dummy in the present invention, FIG. 1A is a schematic enlarged view of part A in FIG. 6, and FIG. 1B is a wafer inserted into an opening hole of a retainer ring. It is a schematic plan view of a state.

2A and 2B show an example of an embodiment in which a retainer ring is integrally molded in the present invention, FIG. 2A is a schematic enlarged view of a portion A in FIG. 6, and FIG. It is a schematic plan view of the worn state.

FIG. 3 illustrates the steps of the present invention, (a)
(C) is a schematic flowchart.

FIG. 4 illustrates the steps of the present invention, (a)
FIG. 4A is a schematic perspective view of a storage case, and FIG. 6B is a schematic side cross-sectional view of a state in which a wafer is stored in an opening recess of the storage case.

5A is a schematic plan view of a wafer having an orientation flat, and FIG. 5B is a schematic plan view of a wafer having a notch.

FIG. 6 is a schematic side sectional view of a wafer polishing apparatus showing a conventional example.

FIG. 7 shows a conventional example, (a) is a schematic enlarged view of a portion A in FIG. 6, and (b) is a schematic plan view showing a state of a wafer after polishing.

[Explanation of symbols]

1 ... Wafer, 1a ... Notch, 1b ... Large polishing rate, 2 ... Polishing platen, 3 ... Polishing pad, 4 ... Press head,
5 ... backing pad, 6 ... retainer ring, 6a ... inner surface, 7 ... dummy, 8 ... nozzle, 9 ... polishing slurry, 10
... light source, 11 ... light receiving element, 12 ... motor, 12a ... table, 13 ... storage case, 13a ... opening recess

Claims (2)

[Claims] 1. A polishing platen, a polishing pad attached to the polishing platen, a wafer pressed against the polishing pad, a retainer ring surrounding and holding the wafer, and the retainer ring fixedly. In a wafer polishing apparatus having a pressure contact head, the wafer is pressed against the polishing pad and relatively moved, and polishing the wafer, a gap between the inner surface of the retainer ring and the outer peripheral edge of the wafer is uniform. A wafer polishing apparatus characterized by: 2. A step of inserting a wafer into a retainer ring fixed to a pressure contact head, and a step of bringing the wafer into pressure contact with a polishing pad attached to a polishing surface plate and relatively moving the wafer to polish the wafer. In the method of polishing a wafer, the step of inserting the wafer includes the step of aligning the cutout portion of the wafer having the cutout portion, and the opening for forming a uniform gap between the wafer and the outer peripheral edge of the wafer. A step of accommodating the opening recess of the accommodating case having a recess, and a step of inserting the wafer accommodated in the opening recess into a retainer ring having a uniform gap with the outer peripheral edge of the wafer. A characteristic wafer polishing method.