JPH11138427A - Wafer polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization rate of grinding liquid supplied between fixed upper and lower rotary plates and prevent the entry of the grinding liquid into a driving part when polishing a wafer on both faces by performing planetary movement of the wafer between the fixed upper and lower rotary plates. SOLUTION: A carrier 3 is provided between fixed upper and lower rotary plates 1, 2 to hold a wafer 10. An annular grinding liquid pan 11 is mounted on a supporting member 6 for the fixed upper plate 2 so that grinding liquid in the pan can be passed through a grinding liquid supply passage 12 formed in the fixed upper plate 2 and supplied between the fixed plates 1, 2 with negative pressure due to a difference in rotating speed between the fixed upper plate 2 and the carrier 3. The carrier 3 is engaged with a sun gear 7 on the center side and an inner gear 8 on the outer periphery side for planetary movement. The sun gear 7 is integrated with the center of the fixed lower plate 1 to avoid the drainage of the grinding liquid, supplied between the fixed rotary plates 1, 2, to the center side via the fixed upper rotary plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wafer polishing apparatus used for polishing both sides of a semiconductor wafer or the like.

[0002]

2. Description of the Related Art A silicon wafer taken from a silicon single crystal rod is polished to a mirror surface prior to forming a device on the surface. Until now, the mirror polishing of the wafer surface has been performed only on the device forming surface. However, in the case of a wafer having a large diameter of more than 8 inches, for example, 12 inches, the rear surface on which no device is formed is comparable to the mirror polishing. Precision polishing has been required, and accordingly, double-side polishing has been required. The reason for this is that in the process of forming a device on the front surface of the wafer, the front surface is prevented from being contaminated by fine foreign substances adhering to the back surface, and that the surface is affected by irregularities on the back surface during exposure.

When performing double-side polishing of a silicon wafer,
A method in which the wafer performs planetary motion between the upper and lower rotating platens is considered to be promising in terms of the apparatus scale, polishing accuracy, and the like.
2 and 3 show the basic structure of a wafer polishing apparatus of this type.
This will be described below.

[0004] The wafer polishing apparatus of the type in which the wafer performs planetary motion between the upper and lower rotating platens includes an annular lower platen 1 which is horizontally supported, and an annular upper platen 2 which faces the lower platen 1 from above. , And a plurality (usually 3 or 5) of carriers 3, 3, 3 arranged between the upper and lower platens 1, 2. The upper stool 2 is of an elevating type, and is attached to a lower part of a rotary support member 6 suspended via a joint 5 below a cylinder 4 also serving as a pressurizing member.

A plurality of carriers 3, 3, 3 are rotatably supported at equal circumferential positions on the lower platen 1. Each carrier 3 is a so-called planetary gear that meshes with a sun gear 7 provided inside the lower platen 1 and a ring-shaped inner gear 8 provided outside, and at a position eccentric from the center of the carrier 3. The wafer 10 is held.

In order to perform double-side polishing of the wafer 10, the wafer 10 is set on each carrier 3 with the upper platen 2 raised. Next, the lower stool 1 and the sun gear 7 are rotated at a low speed, and the upper stool 2 is lowered. When the pin 17 provided on the upper surface plate 2 and the guide 18 provided on the upper surface of the sun gear 7 mesh with each other, the upper surface plate 2 starts rotating. Then, each wafer 10 is sandwiched between the polishing pads 9 and 9 attached to the opposing surfaces of the upper and lower platens 1 and 2 at a predetermined pressure,
Polishing starts by adjusting to a predetermined number of revolutions.

Each carrier 3 has upper and lower rotating platens 1 and 2
As a result, the wafer 10 eccentrically held by each carrier 3 performs an eccentric rotation and a revolving motion between the polishing pads 9, 9. Both sides will be polished uniformly.

At this time, the polishing liquid is supplied between the upper and lower surface plates 1 and 2 by utilizing a negative pressure caused by a difference in the number of rotations of the upper surface plate 2 and the carrier 3. For this supply, an annular polishing liquid pan 11 is attached to the support member 6 of the upper platen 2, and the polishing liquid in this pan is subjected to a negative pressure due to a rotational speed difference between the upper platen 2 and the carrier 3. As a result, the abrasive fluid supply path 12 formed in the upper surface plate 2
Is supplied to the polishing pads 9, 9 between the platens 1, 2. In order to discharge the used polishing liquid, a drainage path 14 is provided in the support member 13 that supports the lower platen 1, and the support member 1
A drain pan 15 is provided below the outer peripheral portion of 3.

In this type of polishing apparatus, the lower platen 1, the upper platen 2, the sun gear 7, and the inner gear 8 can be rotated. Further, the plurality of carriers 3, 3, 3 can be circulated in synchronization. By such multi-axis driving, the carrier 3 and thus the wafer 10 can perform planetary motions under various conditions.

[0010]

However, such a wafer polishing apparatus of the type in which the wafer 10 makes a planetary motion between the upper and lower platens 1 and 2 has the following problems in relation to the supply of the polishing liquid. There's a problem.

[0011] A plurality of carriers 3,
In order to make the planetary movements of the third and third planets, the lower platen 1 is an annular body, and a sun gear 7 and its drive shaft are provided inside the lower surface plate 1.
It has a structure in which a ring-shaped inner gear 8 is provided on the outside. Due to this structure, gaps exist between the lower stool 1 and the sun gear 7 and between the lower stool 1 and the inner gear 8.

The abrasive fluid supplied between the surface plates 1 and 2 by utilizing the negative pressure due to the rotation speed difference between the surface plates 1 and 2 is directly discharged from the gap on the side of the inner gear 8 to the drainage pan 15. Instead, it is discharged from the gap on the side of the sun gear 7 to the drain pan 15 through the drain path 14. That is, the abrasive fluid supplied between the platens 1 and 2 is discharged in both directions of the center side and the peripheral side. Therefore, the polishing liquid does not sufficiently stay between the platens 1 and 2,
There is a problem that a part of the wastewater goes to a drainage system without being used for polishing, and its utilization rate is reduced.

The abrasive fluid flowing into the gap on the side of the sun gear 7 is concentrated on the lower platen 1
Of the drive unit, and contaminates the shaft and bearings of the drive unit.

An object of the present invention is to provide a wafer polishing apparatus capable of increasing the utilization rate of the polishing liquid supplied between the upper and lower platens and preventing the polishing liquid from entering the driving section. is there.

[0015]

In order to achieve the above object, a wafer polishing apparatus according to the present invention comprises a plurality of carriers holding wafers arranged at predetermined intervals in a rotational direction between upper and lower rotating platens. Each carrier meshes with the sun gear at the center of the surface plate and the inner gear at the periphery of the surface plate, and each carrier performs planetary motion between the upper and lower rotating surface plates, thereby polishing both surfaces of the wafer held by each carrier. In a double-side polishing machine, a plurality of abrasive fluid supply paths for supplying abrasive fluid between upper and lower rotating surface plates are provided on an upper rotating surface plate, and a sun gear is integrated with a central portion of a lower rotating surface plate. is there.

In the wafer polishing apparatus of the present invention, since the sun gear is integrated with the lower rotating platen, the abrasive liquid supplied between the upper and lower rotating platens is separated from the outer inner gear by the lower inner plate. Is discharged only from the gap between the rotary platen. For this reason, the residence time of the polishing liquid between the upper and lower rotating platens becomes longer, the utilization rate of the polishing liquid is improved, and the penetration of the polishing liquid into the drive unit concentrated at the center is avoided. If the polishing liquid is intensively supplied to the center side, the polishing liquid moves to the outer peripheral side by centrifugal force, so that the utilization rate of the polishing liquid is further improved.

When the sun gear is integrated with the lower rotating plate, it is impossible to independently drive the sun gear with respect to the lower rotating plate, and the upper rotating plate is attached to the sun gear. When linked, the upper and lower rotating platens rotate synchronously at a constant speed. However, the planetary movement of the carrier is performed as the sun gear rotates with the lower turntable. Further, suction of the abrasive fluid is also performed by the speed difference between the upper rotating platen and the carrier. In order to make a speed difference between the upper and lower rotating platen,
What is necessary is just to rotate and drive the upper rotating platen independently with respect to the lower rotating platen.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view of a wafer polishing apparatus showing an embodiment of the present invention.

The wafer polishing apparatus according to the present embodiment is different from the conventional wafer polishing apparatus shown in FIGS. 2 and 3 in the structure of the lower platen 1 and the sun gear 7 and the driving form of the upper platen 2. I do. Other configurations are substantially the same as those of the conventional wafer polishing apparatus, and thus detailed description is omitted.

In the wafer polishing apparatus according to the present embodiment, the lower platen 1 is a disk having no through hole at the center as shown in FIG. The lower platen 1 is mounted concentrically on a rotating shaft 16. A sun gear 7 is fixed to the center of the lower stool 1 by bolting. On the other hand, below the lower stool 2, an annular drain pan 15 is provided to receive the abrasive fluid discharged around the lower stool 1. The upper surface plate 2 is driven by a drive mechanism (not shown).
The lower platen 1 is driven independently.

FIGS. 2 and 3 show the abrasive fluid supply system.
In the same manner as in the conventional wafer polishing apparatus shown in FIG. 1, an annular polishing liquid pan 11 is attached to the support member 6 of the upper platen 2, and the polishing liquid in this pan is a rotational difference between the upper platen 2 and the carrier 3. Supply path 12 formed in upper surface plate 2 by negative pressure
And is supplied between the platens 1 and 2 through the plate.

In order to polish the wafer 10 on both sides, the wafer 10 is set on each carrier 3 with the upper platen 2 raised. Next, the lower surface plate 1 and the upper surface plate 2 are rotated at a low speed, and the upper surface plate 2 is lowered, so that the polishing pads 9, 9 adhered to the opposing surfaces of the upper and lower surface plates 1, 2.
The respective wafers 10 are held at a predetermined pressure. Then, the rotation speeds of the lower stool 1 and the upper stool 2 are adjusted to a predetermined speed.

Since the sun gear 7 rotates with the rotation of the lower stool 2, the carriers 3, 3, and 3 between the upper and lower stools 1 and 2 perform a planetary motion of revolving while rotating. The wafer 10 eccentrically held at 3 performs eccentric rotation and orbital movement between the polishing pads 9 and 9. Also, due to the negative pressure due to the rotational speed difference between the upper platen 2 and the carrier 3, the polishing liquid in the polishing liquid pan 11 passes through the polishing liquid supply path 12 formed in the upper platen 2, and Supplied to Thus, both surfaces of the wafer 10 are uniformly polished.

At this time, the abrasive liquid supplied between the upper and lower stools 1 and 2 is stopped by the sun gear 7 screwed on the center of the lower stool 1 so that it is not discharged to the center. All flow only to the outer peripheral side and flow into the drain pan 15. For this reason, the residence time of the abrasive fluid is longer than in the case where the abrasive fluid supplied between the upper and lower platens 1 and 2 is discharged in both the center side and the outer peripheral side, and the utilization rate is improved. . In addition, there is no danger that the rotating shaft 16 that rotates the lower platen 1 is stained by the abrasive liquid. Further, a part of the polishing liquid can be intensively supplied to the center without passing through the upper platen 2.

With respect to the planetary motion of the carriers 3, 3, and 3, the sun gear 7 rotates with the rotation of the lower platen 1, so that
Although independent rotation control of the sun gear 7 is not possible, its planetary motion is possible. Moreover, since the rotation of the inner gear 8 can still be controlled independently and the plurality of carriers 3, 3, 3 can be circulated in synchronization with each other, the planets of the carrier 3 and the wafer 10 under various conditions can be used. Exercise is also possible.

[0026]

As described above, in the wafer polishing apparatus of the present invention, the sun gear for causing the carrier to carry out planetary motion between the upper and lower rotating platens is integrated with the lower rotating platen, so that Since the polishing liquid supplied between the rotary platens is discharged only to the outer peripheral side, the utilization rate of the polishing liquid can be increased. Further, since the abrasive fluid supplied between the upper and lower rotary platens is not discharged to the center side, it is possible to prevent the drive unit concentrated at the central portion from being contaminated by the abrasive fluid.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a wafer polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic side view of a conventional wafer polishing apparatus.

FIG. 3 is a view taken along line AA of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower surface plate 2 Upper surface plate 3 Carrier 7 Sun gear 8 Inner gear 10 Wafer 11 Abrasive liquid pan 12 Abrasive liquid supply path 15 Drain pan 16 Rotation axis

Claims (2)

[Claims] 1. A plurality of carriers holding a wafer are arranged at predetermined intervals in a rotating direction between upper and lower rotating platens, and each carrier meshes with a sun gear at a center side of the platen and an inner gear at a peripheral side of the platen. In a double-side polishing apparatus for polishing both surfaces of a wafer held by each carrier by causing each carrier to perform planetary motion between the upper and lower rotary platens, a plurality of polishing tools for supplying a polishing liquid between the upper and lower rotary platens are provided. A wafer polishing apparatus, wherein a liquid supply path is provided on an upper rotary plate, and a sun gear is integrated with a central portion of the lower rotary plate. 2. The wafer polishing apparatus according to claim 1, wherein the upper rotary plate is driven to rotate independently of the lower rotary plate.