JP3091427B2 - Wafer polishing equipment - Google Patents

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 for lapping or polishing silicon wafers, compound semiconductor wafers and the like.

[0002]

2. Description of the Related Art In a polishing apparatus for performing processing such as lapping and polishing on a wafer, the wafer is processed while revolving and rotating a carrier containing the wafer between a lower surface plate and an upper surface plate. The carrier is provided with a plurality of workpiece input holes, each of which has a tooth portion formed on an outer periphery and accommodates a wafer. The carrier is meshed with the sun gear and the internal gear, placed on the lower platen at substantially equal intervals, the wafer is fitted into the work input hole, the upper platen is lowered, and the wafer is sandwiched between the lower platen. During processing, the upper platen, lower platen, sun gear,
Rotate each internal gear. The wafer is
Both surfaces are polished while revolving and rotating. After the processing, the upper platen is raised, and the wafer is taken out from the work input hole of the carrier.

In accordance with the tendency that the demand for wafers increases with the spread of semiconductor devices, various improvements to this type of polishing apparatus have been proposed. For example, Japanese Patent Laid-Open No. 5-2
No. 12670 discloses that, after positioning the carrier with respect to the upper platen, the upper platen is raised, and then the carrier is positioned with respect to the apparatus main body, thereby enabling accurate positioning and automating the processed wafer. Suggest to do. Also, in Japanese Patent Application Laid-Open No. 8-229784,
While holding the wafer on both the front and back surfaces of the polishing plate, holding the wafer between the upper surface plate and the lower surface plate, and rotating the upper and lower surfaces of the polishing plate while rotating and rotating the polishing plate. Has been proposed.

[0004]

In any of the polishing apparatuses, since the upper and lower stools, the sun gear and the internal gear are independently rotated, the power transmission and reduction mechanisms are complicated. Moreover, in the conventional polishing apparatus, since gears are used for the power transmission and the reduction mechanism, a large number of parts machined with high precision are required for each rotating element. As a result, the cost of the entire apparatus increases. In particular, in recent years, in which the diameter of the wafer tends to increase, the size of each component also increases, and the demand for processing accuracy becomes extremely severe. Further, since power is transmitted using gears, generation of vibrations is inevitable, and the working environment may be deteriorated due to noise, and may adversely affect the wafer being processed. Therefore, the present inventor has adopted a method in which power is transmitted to the upper stool, the lower stool, the sun gear, and the internal gear by frictional force instead of the power transmission method using gears.
We developed a polishing machine that does not use expensive gears and has a simplified equipment configuration, and filed a separate application. In the power transmission system using frictional force, the power from the drive motor can be transmitted to the upper stool, the lower stool, the sun gear, and the internal gear without requiring a speed reducer. The present invention is a further improvement of the method of transmitting power by means of this frictional force. By arranging a plurality of drive motors symmetrically with respect to the rotation centers of the upper stool, the lower stool, the sun gear, and the internal gear, a local operation is achieved. It is an object of the present invention to provide a polishing apparatus for rotating the upper platen, the lower platen, the sun gear, and the internal gear smoothly and with high precision by canceling out thermal deformation of the device caused by heating by making the central axis symmetrical.

[0005]

SUMMARY OF THE INVENTION In order to achieve the object, a wafer polishing apparatus according to the present invention has an internal gear in which a gear meshing with a gear portion formed on an outer periphery of a carrier for accommodating a wafer is formed on an inner peripheral surface. , A sun gear in which gears meshing with the gear portion of the carrier are engraved on the outer peripheral surface, a lower stool that mounts the carrier, an upper stool that holds the carrier between the lower stool, an internal gear, a sun gear, and a lower stool. A drive pulley that comes into frictional contact with the power transmission unit of each of the platen and the upper platen, and a drive motor that has the drive pulley directly attached to the output shaft. The drive motors are symmetrically arranged.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a polishing apparatus according to the present invention comprises a bed 10, a motor 21 for driving a lower platen 20, a motor 31 for driving an internal gear 30, and a sun gear 40.
Motor 41 for driving and motor 51 for driving upper surface plate 50
It is equipped with. Each drive motor 21, 31, 41, 5
1 has drive pulleys 23, 33, 4 on their respective output shafts.
3, 53 are directly attached. A column 11 is erected on the bed 10, and a beam 12 extends between the left and right columns 11, 11. An elevating cylinder 13 provided on the beam 12 is connected to an elevating disk 14, and a hanging rod 16 having an upper surface plate hanging tool 15 at a lower end is fixed to the elevating disk 14.

The drive pulley 23 is in frictional contact with a power transmission section 25 of a lower platen support 24. Thus, the lower stool 20 on the lower stool receiver 24 is rotated by the power transmitted from the motor 21 via the drive pulley 23. The drive pulley 33 is in frictional contact with the power transmission section 35 of the internal gear 30. As a result, the internal gear 30
Rotates with the power transmitted from the motor 31 via the drive pulley 33. The drive pulley 43 is in frictional contact with the power transmission section 45 of the sun gear 40. Thus, the sun gear 40 rotates with the power transmitted from the motor 41 via the driving pulley 43. The center of the upper stool 50 is opened in a circular shape, and the upper stool drive shaft 54 faces the opening from below. The lower end of the upper platen drive shaft 54 is a power transmission unit 55, and the drive pulley 53 is in frictional contact. The upper stool 50 is rotated by power transmitted from the motor 51 via the drive pulley 53.

At the upper end of the upper platen driving shaft 54, two notches 56, 56 are formed at axially symmetric positions as shown in FIG. A hook 58 pivotally supported by a hook base 57 fixed to the upper surface plate 50 fits into the notch 56. The upper stool 50 integrated with the upper stool drive shaft 54 by the engagement of the hook 58 with the notch 56 rotates the upper stool 50 with the power transmitted from the motor 51 via the drive pulley 53. I do. A gear portion 66 is formed on the outer periphery of the carrier 65 that accommodates the wafer 60 to be processed. The gear portion 66 meshes with the internal gear 30 and the sun gear 40, and the plurality of carriers 65 are placed on the lower platen 20 at substantially equal intervals, and sandwiched between the upper platen 50. In this state, when the lower platen 20, the upper platen 50, the internal gear 30, and the sun gear 40 are independently rotated while supplying the abrasive, a large number of wafers 65 are polished simultaneously.

As described above, the driving motors 21, 31, 4
As a power transmission means from the power transmission units 1 and 51 to the power transmission units 25, 35, 45 and 55, a friction force is used instead of a conventional gear. For example, the power transmission to the lower platen 20 will be described as an example. As shown in FIG.
The drive pulley 23 directly connected to the lower platen 24 is pressed against the power transmission portion 25 of the lower platen support 24, and the power of the motor 21 is transmitted to the lower platen 20 by frictional force. In order to facilitate power transmission by friction, the drive pulley 23 and the power transmission unit 25 are selected from rubber or metal materials such as butadiene, styrene, isobutylene, nitrile butadiene, silicon, and urethane having a large friction coefficient. . FIG. 4 is an enlarged view of part A of FIG.
As shown in FIG.
Of the motor 21 is transmitted to the lower platen 20 by friction between the two.

When transmitting a large driving force, FIG.
As shown in (1), one or more V-grooves are formed on the side surface of the power transmission unit 25, and a driving pulley 23 having a side surface shape fitted into the V-groove is used. Alternatively, as shown in FIG. 4C, a cocked belt 26 made of an elastic material such as rubber is fixed to the peripheral surface of the power transmission unit 25 by bonding, screwing, or the like, and similarly fixed to the drive pulley 23 side. Cocked belt (not shown)
And transmit power. In this case, a metal gear having a small diameter and low cost can be used for the drive pulley 23 side. In the power transmission system using frictional force, the motor 21 directly rotates the lower platen 20, so that an expensive and space-saving speed reducer is omitted, and the degree of design freedom around the motor 21 is increased. Therefore, the plurality of motors 21, 31, 41, 51 can be symmetrically arranged about the rotation center C of the lower stool 20, the internal gear 30, the sun gear 40, and the upper stool 50. When four drive motors 21 are arranged for rotating the lower platen 20, drive pulleys 23 fixed to the output shaft of each drive motor 21 are arranged at substantially equal intervals as shown in FIG. It contacts the power transmission unit 25 of the lower stool 20.

When the lower stool 20 is rotated in this state, the power transmission section 25 generates heat at four places in contact with the drive pulley 23. Therefore, the temperature of the lower platen 20 and its surroundings increases symmetrically around the rotation center C in the plane direction. Therefore, the thermal deformation caused by the local temperature rise is offset by the axial symmetry, and the smooth rotation of the lower stool 20 is maintained with high accuracy. On the other hand, in the conventional power transmission system, since the speed reducer 21 is used as shown in FIG. 6, the arrangement and the number of the drive motors 21 are restricted. 20 is rotating. for that reason,
The place where the drive motor 21 and the speed reducer 22 are arranged serves as a heat source 27, and causes local thermal deformation of the peripheral device and the bed 10. Such local thermal deformation tends to cause rotational shake on the lower platen 20, resulting in increased vibration and noise, as well as adversely affecting the polishing operation of the wafer 60.

3 to 6, the rotation of the lower platen 20 has been described as an example, but the other internal gear 30, sun gear 4
Similarly, a plurality of drive motors 3
1, 41, 51 are symmetrically arranged around the rotation center C.
Thus, the respective motors 21, 31, 41, 51
To lower platen 20, internal gear 30, sun gear 4
Since the power is transmitted to the upper stool 50 by a friction method, noise is smaller than that of the conventional polishing apparatus, and the equipment configuration is greatly simplified. In addition, a plurality of motor driving motors 2
Since 1, 31, 41, and 51 are symmetrically arranged around the rotation center C, the heat generated when the lower stool 20, the internal gear 30, the sun gear 40, and the upper stool 50 rotate are also symmetric about the rotation center C. There is no locally large temperature distribution that causes thermal deformation. Therefore, rotation blur which causes noise and vibration is prevented, and the wafer 60 sandwiched between the lower surface plate 20 and the upper surface plate 50 is efficiently polished.

[0013]

As described above, the polishing apparatus of the present invention takes advantage of the fact that a speed reducer can be omitted when power is transmitted by frictional force instead of the conventional gear, and the lower platen, the upper platen, and the internal A plurality of drive motors are arranged symmetrically around the rotation center around the gear and sun gear. For this reason, the equipment configuration is simplified, and the noise and vibration due to the rotation blur are suppressed. Further, large power required by a plurality of inexpensive motors can be transmitted to the lower surface plate, the upper surface plate, the internal gear, and the sun gear without requiring an expensive large motor.

[Brief description of the drawings]

FIG. 1 shows a polishing apparatus according to the present invention.

FIG. 2 A lower platen on which a carrier containing a wafer is placed

Fig. 3 Power transmission when lower platen is directly rotated by motor

FIG. 4 shows several examples of a contact state between a driving pulley and a power transmission unit.

FIG. 5 shows a plurality of drive pulleys symmetrically arranged around a power transmission section of a lower stool.

FIG. 6 shows a method of rotating a lower platen through a conventional speed reducer.

[Explanation of symbols]

10: Bed 11: Column 12: Beam 1
3: Lifting cylinder 14: Lifting disk 15: Upper surface plate hanging tool 16: Hanging rod 20: Lower surface plate 21: Lower surface plate driving motor 22:
Reduction gear 23: Drive pulley 24: Lower surface plate receiver
25: Power transmission unit 26: Cocked belt 27: Heat source 30: Internal gear 31: Internal gear drive motor 33: Driving pulley 35: Power transmission unit 40: Sun gear 41: Sun gear drive motor 4
3: Drive pulley 45: Power transmission unit 50: Upper platen 51: Upper platen drive motor 53:
Drive pulley 54: Upper platen drive shaft 55: Power transmission unit 56: Notch 57: Hook table 58: Hook 60: Wafer 65: Carrier 66: Gear part C: Lower platen, upper platen, internal gear, sun gear rotation center

Claims (1)

(57) [Claims] An internal gear in which a gear meshing with a gear portion formed on the outer periphery of a carrier for accommodating a wafer is engraved on an inner peripheral surface, and a sun gear in which a gear meshing with a gear portion of the carrier is engraved on an outer peripheral surface. And a lower surface plate for mounting the carrier, an upper surface plate for holding the carrier between the lower surface plate,
A drive pulley that makes frictional contact with the power transmission section of each of the internal gear, sun gear, lower platen and upper platen, and a drive motor that has the drive pulley directly mounted on the output shaft, are provided with an internal gear, sun gear, lower platen and upper plate. A wafer polishing apparatus in which each drive motor is symmetrically arranged with respect to the center of rotation of the board.