JPH06270052A - Mirror surface polishing device for semiconductor wafer - Google Patents

Abstract

PURPOSE:To set a proper swinging angle according to a wafer diameter by making a distance variable between a connecting point and the swinging center of a swinging arm to swing a pressurizing board where a semiconductor wafer is stuck on an under surface, and making the swinging angle freely adjustable. CONSTITUTION:A mirror surface polishing device l has a lower surface plate 3 where polishing cloth 9 is stuck to an upper surface, and has a head part 6 installed on the upper side of a support shaft 4 erected in the corner of a stand 2 through a support arm 5 and a pressurizing board 7 to make a semiconductor wafer W adsorbable to an under surface. While rotating the wafer W and while swinging it around the axis of a support shaft 4, polishing is carried out by bringing it into pressure contact with the rotating polishing cloth 9. Though the support arm 5 is swung by a swinging mechanism 8, this swinging mechanism 8 has a swinging arm 10 having an arc shape hot guide member 11 on the tip, and one end of a driving arm 13 to move forward and backward by a motor 15 is installed in the guide member 11, so that a swinging angle can be made variable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for polishing a mirror surface of a semiconductor wafer, and more particularly to a semiconductor wafer having various diameters.

[0002]

2. Description of the Related Art Generally, mirror polishing of a semiconductor wafer is
A lower surface plate having an abrasive cloth (hereinafter referred to as a cloth) attached to the upper surface and a pressure plate having a semiconductor wafer attached to the bottom surface are arranged to face each other, and the pressure plate and the lower surface plate are pressed while pressing the wafer against the cloth. It is known to do by rotating.

By the way, when the wafer is polished in this manner, a certain pattern of wear regions is formed on the cross surface, and a step is formed between the wear region and the non-wear region. Then, if the polishing surface of the wafer hits the step due to the difference in the diameter size of the polishing wafer, the flatness of the wafer is impaired, and the polishing accuracy of the wafer deteriorates. Therefore, by using the worn surface of the cloth as a reference surface and performing shape correction dressing for removing and processing an unworn surface higher than the reference surface, the flatness of the cloth surface is ensured and the polishing accuracy of the wafer is maintained.

However, since the dressing for flattening the cloth surface is a removal process, the cloth is worn other than the polishing work, which is not preferable in terms of efficient use of the cloth. In addition, this dressing operation itself is included in the polishing step, which is disadvantageous in terms of the number of steps,
It takes a lot of time to polish many kinds of wafers.

Therefore, when the wafer is polished, the pressure plate to which the wafer is attached is moved toward and away from the center of rotation of the cloth over the radial direction of the cloth, so that the trajectory pattern drawn by the wafer is obtained. There is a mirror-polishing apparatus for semiconductor wafers which is made wide and is uniformly worn over the entire cross surface to prevent a step from being formed on the cross surface.

In such a mirror polishing apparatus, a horizontal lower surface plate is arranged on a pedestal, a supporting shaft is rotatably provided in the vicinity of the lower surface plate, and a pressure plate is provided above the supporting shaft. A head portion is attached via a support arm, and the head portion faces above the lower turn table. The lower platen is rotated by a motor at a constant speed, and a disc-shaped cloth is replaceably attached to the upper surface. The pressure plate is attached to the head portion via a drive shaft, and can be rotated while pressing the pressure plate against the lower platen by a cylinder device or the like built in the head portion. Further, a suction mechanism is provided on the lower surface of the pressure plate so that a semiconductor wafer, which is an object to be polished, can be attached.

Below the support shaft, a swing arm having a base end fixed to the support shaft, a rotary plate driven to rotate by a motor, an eccentric portion of the rotary plate, and a tip of the swing arm. Is provided with a swinging mechanism composed of a drive arm whose ends are pivotally supported. Therefore, by rotating the rotary plate, the drive arm is reciprocated in the direction of the long axis of the arm, and the reciprocating motion is converted into the oscillating motion by the oscillating arm, so that the support shaft is rotatively moved at a constant angle. It has become. As a result, the supporting arm is oscillated horizontally, so that the pressure plate provided at the tip of the supporting arm reciprocates within a certain range in the radial direction of the cross surface. . Therefore, when mirror-polishing a semiconductor wafer, the pressure and lower platen are rotated, and while pressing the platen horizontally, the semiconductor wafer is pressed against the cross surface of the lower platen to polish the entire cross surface. Therefore, it is possible to polish with good accuracy without forming a step.

Further, when the polishing wafers have different diameters, it is necessary to adjust the swing angle for each diameter. This is because, for example, if a small-diameter wafer is polished with this setting after setting a swing angle corresponding to a large-diameter wafer, the wear width of the cross surface due to this small-diameter wafer will be due to the large-diameter wafer. This is because the width becomes narrower than it is, so that a worn area and an unweared area are formed again on the cross surface to form a step, and the flatness of the cross surface is impaired.

For this reason, when the diameter of the wafer to be polished changes, the location where the drive arm is attached to the rotary plate is changed to increase or decrease the distance from the center of rotation of the rotary plate to the eccentric position, thereby reciprocating the drive arm. By increasing or decreasing the amount of exercise, the swing angle was adjusted for each wafer size. Therefore, for example, when changing the wafer size from a large diameter to a small diameter as in the case described above,
The swing angle has been increased by increasing the eccentric distance so as to compensate for the decrease in the diameter size.

[0010]

However, according to the above-mentioned conventional mirror surface polishing apparatus, the swing angle is adjusted by increasing or decreasing the eccentric distance from the center of rotation of the rotary plate, so this distance is slightly changed. Causes a large change in the swing angle, which makes it difficult to finely adjust. This is because the rotating plate rotates and causes the drive arm to reciprocate, so a distance twice the changed distance is reflected as the amount of reciprocating motion, and the swing angle is changed based on this moving distance. Is.

Further, in order to maintain the wafer polishing accuracy, it is necessary to set the pressing force per unit area of the wafer to the same condition during the polishing work. Therefore, when polishing a large-diameter wafer having a wide surface area of the wafer, a pressure plate is used. Also set the pressure force by increasing. Therefore, in the case of a large diameter wafer, the frictional resistance of the wafer becomes large, and a larger force is required to drive the swing arm. Further, in this case, since the swing angle becomes small, the eccentric distance of the rotary plate is set to be small, and similarly, a larger force is required to rotate the rotary plate. As a result, when polishing a large-diameter wafer, the driving force required for rocking increases, so that excessive load is concentrated on the drive arm itself and its joints, and the motor load increases. The burden on the mechanism increases. If the drive arm is made to have a large diameter or a large output motor is used to strengthen the entire mechanism in response to these load loads, the cost of the device itself increases.

Therefore, it is an object of the present invention to provide a mirror polishing apparatus for a semiconductor wafer, which can efficiently polish a plurality of wafers of different diameters and reduce the load on the swing mechanism during the polishing of large diameter wafers.

[0013]

According to a first aspect of the present invention, there is provided a semiconductor wafer mirror polishing apparatus comprising: a lower surface plate having a polishing cloth adhered to an upper surface thereof; and a semiconductor arranged and pressed on the lower surface plate. A pressure plate with a wafer attached to the lower surface, a rotating mechanism that rotates the upper and lower platens, a support arm that supports the pressure plate and has a base end fixed to a support shaft, and a base end on the support shaft. A mirror polishing apparatus comprising a swing arm to which is fixed, and a drive arm having one end connected to the tip of the swing arm and reciprocating by a drive mechanism. A drive arm is connected to a predetermined portion of the guide member that is further away from the center of swing as the diameter of the wafer increases, and the swing angle is adjusted according to the diameter of the wafer. Mirror polishing apparatus according to claim The drive mechanism is configured such that the other end of the drive arm is pivotally attached to an eccentric position of a rotating plate that is rotated by a motor, and a guide member of the swing arm has a rotation axis of the rotating plate as a center. In the mirror polishing apparatus according to the third aspect of the present application, the guide member of the swing arm is a circle centered on the rotation axis of the rotating plate, and the outer shape is outside the circle according to the wafer diameter. It is configured to have a curved shape that is separated toward one side.

[0014]

Therefore, according to the present invention, the guide member is installed by extending the tip of the swing arm, and the drive arm connection point of the guide member can be changed. Since the swing angle is adjusted by adjusting the distance between them, an appropriate swing angle can be set again according to the wafer diameter size, and the swing pattern width drawn on the cross surface by wafers of different diameters can be adjusted. Can always be kept equal to the cross radius.

When the large-diameter wafer is polished to increase the frictional force and the swing angle decreases,
Since the distance between the fulcrums of the swing arm will increase,
The driving force required for rocking can be reduced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in FIGS. As shown in FIG. 1, a mirror polishing apparatus 1 for a semiconductor wafer according to the present embodiment includes a lower surface plate 3 installed on a rectangular parallelepiped base 2 and a support shaft 4 provided upright at a corner of the base 2. A support arm 5 is provided above the support shaft 4.
The head unit 6 is attached via a pressure plate 7, a pressure plate 7 provided on the head unit 6, and a swing mechanism 8 connected to the lower side of the support shaft 4 and arranged in the pedestal 2. There is.

That is, the lower surface plate 3 is formed in a circular shape having a diameter of 3 to 4 times the maximum wafer diameter size to be polished, and is horizontally installed substantially at the center of the gantry 2. The lower surface plate 3 is driven by a motor drive unit in the gantry 2 (not shown).
It is designed to be rotated at a constant speed. Further, a disc-shaped cloth (polishing cloth) 9 having substantially the same diameter is attached to the upper surface of the lower surface plate 3, and the cloth 9 is attached to the lower surface plate 3.
In addition to being firmly fixed to, the worn cloth can be easily replaced with a new one.

Further, the support shaft 4 is formed in a columnar shape, and stands upright at the corner of the pedestal 2. The lower side of the support shaft 4 is located inside the gantry 2 and is rotatably supported. On the upper side of the support shaft 4,
The base end of the horizontally arranged support arm 5 is fixed. On the other hand, a base end of a swing arm 10 of a swing mechanism 8 which is also horizontally arranged is fixed to the lower side of the support shaft 4 located in the mount 2, and the swing arm 10 is mounted on the mount 2. It is provided along the side wall. Therefore, as shown in FIG. 2, the angle between the support arm 5 and the swing arm 10 is fixed, and the swing mechanism 8 described later causes the swing arm 10 to move from a predetermined start point to a predetermined angle. When it is swung to, the support arm 5 is also swung.
In addition, as shown in FIG. 1 again, the support arm 5
A cylindrical head portion 6 is attached to the tip of the.

The head portion 6 has a built-in drive device such as an air cylinder and a motor connected to the control device, and the pressurizing plate 7 is connected via a drive shaft 6a of the built-in device protruding from the lower surface of the head portion 6. Has been done. Therefore, the pressurizing plate 7 can be moved up and down and rotated by this built-in device to rotate the pressurizing plate 7 while pressing it against the lower surface plate 3.

The pressure plate 7 is formed in a disk shape larger than the maximum diameter size of the wafer W to be polished, and has a suction mechanism such as a suction plate on the lower surface. Therefore,
With this suction mechanism, the semiconductor wafer W, which is the object to be polished, can be easily sucked and attached to the lower surface of the pressure plate 7.

As shown in FIG. 2, the swing mechanism 8 has a swing arm 10 whose base end is fixed to the lower side of the support shaft 4 and a guide member 11 having a shape to be described later is provided on the tip side. ,
A drive arm 13 having one end attached to the guide member 11 of the swing arm 10 via a connecting member 12, a rotary plate 14 having the other end of the drive arm 13 connected, and a rotation for rotating the rotary plate 14. A motor 15 and an adjusting motor 17 connected to the connecting member 12 via a slide driving unit 16.
It consists of and.

That is, the rotary plate 14 is formed in a disk shape, and is horizontally arranged in the frame 2 near the corner opposite to the support shaft 4. The center of the rotary plate 14 is connected to the rotary shaft of a rotary motor 15 so that the rotary plate 14 is driven to rotate at a constant speed. Further, one end of the drive arm 13 is pivotally attached to a predetermined eccentric position away from the rotation center Z of the rotary plate 14. The rotary motion of the rotary plate 14 causes the drive arm 13 to reciprocate within a certain range in the longitudinal direction thereof. The other end of the drive arm 13 is pivotally attached to the connecting member 12, and the connecting member 12 is connected to the guide member 11 of the swing arm 10.

The guide member 11 is formed in a predetermined shape, which will be described later, and is provided on the tip side of the swing arm 10. A guide groove 18 is provided along the entire length of the guide member 11, and the connecting member 12 is slidably fitted in the guide groove 18. Therefore, the connecting member 12 can be slid along the shape of the guide member 11. Further, the connecting member 12 is connected to a slide driving unit 16 fixedly provided on the base end side of the swing arm 10 via a bendable joint member 19. The slide driving unit 16 has a spiral gear built therein.
Is driven by the adjusting motor 17. This motor 17
Are connected to the sensors 20a, 20b, 20c provided on the guide member 11 at locations corresponding to the diameter of the wafer through a control device. Therefore, by controlling the drive of the motor 17, the connecting member 12 is moved to the guide member 11
Of the sensors 20a, 2 over the entire length of
0b and 20c can be stopped at a position corresponding to the wafer diameter. That is, the distance between the swing center Y of the swing arm 10 and the connecting member 12 to which the drive arm 13 is connected, in other words, the apparent arm length of the swing arm 10 can be arbitrarily changed. There is.

The mechanism for slidingly moving the connecting member 12 is not limited to the combination of the motor and the slide driving unit 16, and an air cylinder or the like that expands and contracts may be used.
Further, a stepping motor may be used as the adjusting motor 17 to enable finer adjustment with higher accuracy.

The guide member 11 has a linear shape extending along the swing arm 10 up to the connection point of the wafer having the minimum diameter size, and the tip end extending from the guide member 11 serves as the rotary shaft of the rotary plate 14. The curved shape is substantially along the center circle.

This is because the guide member 11 has a linear shape,
When the connection point of the drive arm 13 is moved on this straight line and the distance between the fulcrums is changed, the swing angle according to the wafer diameter can be set, but the swing limit inside the cross cannot be set appropriately. Further, if it is arranged along a circle Z ′ centered on the rotation center Z of the rotating plate 14, the inner limit of the cross of the wafer is always constant, and the wafer diameter cannot be finely handled. This is because, for example, when an arc radius is set with reference to a large-diameter wafer, when a wafer with a smaller diameter is rocked and polished, the wear width drawn on the surface of the cloth 9 is reduced by the smaller-diameter wafer. The diameter of the wafer is smaller than that of the large diameter, and the width becomes narrower. On the other hand, if an arc radius is set with reference to a small-diameter wafer, in the case of a polishing wafer having a larger diameter, the wear width drawn on the cloth 9 by this wafer becomes
The increased radius of the wafer makes it wider than the smaller diameter. Therefore, since the wear areas of the cloth 9 surface generated by the wafers having different diameters do not coincide with each other, a step is formed on the cloth 9 surface, and the polishing wafer surface hits the step, which deteriorates the polishing accuracy. Will end up. That is, not only is the swing angle adjusted according to the wafer diameter size, but also the two swing limits of the swing arm 11, that is, the swing start and end points,
Need to be adjusted.

Therefore, by making the shape of the tip of the guide member 11 a predetermined curved shape, the rocking start and end points thereof are adapted to various wafer diameter sizes. That is, the drive arm 13 is connected to the swing arm 10 after being set to polish a wafer having a minimum diameter size.
When the swing arm 10 is closest to the center X of the cross, the shape of the tip of the guide member 11 is an arc Z ′ about the center Z of rotation of the rotary plate 14 as shown by the solid line in FIG. The curved shape is formed at a distance slightly outside of the. Strictly speaking, this separation distance causes the wafer diameter size to increase and the required swing angle to decrease, so that the swing arm 1
The points b and c where the drive arm 13 is connected to 0 are the swing centers Y
On the line connecting these points b and c and the center of rotation Z of the rotary plate 14, the distance from the arc Z ′ is the distance for swinging the swing arm 10 by the radius size changed from the minimum diameter. . That is, in the above-mentioned state, the distance between the connection points b and c of the swing arm 10 and the rotation center Z of the rotary plate 14 is such that the wafer to be polished has the cross center X.
At the same time as the distance from the connection points b and c to the swing center Y, the distance from this point to the wafers Wb and Wc
Is a distance at which the swing angle is a constant amount of protrusion to the outside of the cloth when the rocking is performed to the outside of the cloth. As described above, when the rocking limit inside the cross is set as the rocking start point, the shape of the guide member 11 of the rocking arm 10 is separated from the arc Z ′ to the outside, and the grinding is performed by this distance. Before the work, the swing arm 10 is swung in advance, and the start point is slid outward from the cross center X by the radius increased as compared with the minimum diameter wafer.

Specifically, in this embodiment, as shown by the three types of lines in the figure, in the case of the smallest 4-inch wafer Wa, the swing arm 10 of the drive arm 13 is shown by the solid line. That is, the connection point to the guide member 11 is a, the swing limit inward of the cross 9 is at the most center, and the swing angle A from this limit is
Is the largest. On the other hand, in the case of the 5 inch and 6 inch wafers Wb and Wc, as shown by the two-dot chain line and the broken line respectively, the connection points are b and c, and the center of the wafer is the radius of the wafer with the increased inward swing limit. Away from. Along with this, the distance between the fulcrums of the swing arm 10 increases, the swing angle decreases by the increased wafer diameter, and the swing angles become B and C.
Therefore, when the diameter size of the wafer to be polished is changed, the adjusting motor 17 is driven and controlled according to these certain diameter sizes, and the connecting member 12 is moved to the guide member 11 having the above shape.
Slide along the sensors 20a, 20b, 2
The drive arm 13 is connected to the swing arm 10 by stopping at a position corresponding to the diameter size by 0c. As a result, the wafer Wa of each of these diameter sizes,
When Wb and Wc swing inward of the cloth 9, the outer peripheral edges of the wafers Wa, Wb and Wc are always in contact with the center of the cloth 9. Further, when swinging outward of the cloth 9, the amount of protrusion of the outer peripheral edges of these wafers Wa, Wb, Wc from the cloth 9 is constantly maintained at, for example, about 10 mm.

Therefore, according to the mirror polishing apparatus of the present embodiment, it is possible to move the portion where the drive arm is connected to the swing arm formed in a predetermined curved shape, and the swing center of the swing arm and the connection point. By adjusting the swing angle by increasing or decreasing the distance between them, the swing width can be set appropriately according to the wafer diameter size, and the swing width drawn by the wafer on the cross surface during polishing is always Since it can be matched with the radius of the cloth, the entire area of the cloth can be efficiently used, and it is possible to prevent a step from being generated on the cloth surface, and improve the polishing accuracy.

When polishing a large diameter wafer, that is,
When the frictional force of the wafer increases and the swing angle decreases, the distance between the fulcrums of the swing arm increases, so the driving force required to swing the swing arm can be reduced,
The load on the rocking mechanism is reduced, and the rocking mechanism can be simplified because the strength of the rocking mechanism is small.

Further, since the entire cross surface is uniformly worn by the polishing work, the number of times of shape correction dressing, which is a removal process required to secure the flatness of the cross surface, can be reduced, and the cloth The thickness is efficiently used for wafer polishing, and the economical efficiency is improved.

Furthermore, since the swing angle is changed by moving and changing the connection position of the swing arm, the swing width can be easily finely adjusted, and even during the actual polishing work. The swing width can be changed and flexible operation becomes possible.

[0033]

As described above, according to the mirror polishing apparatus of the present invention, the swing angle can be adjusted by increasing or decreasing the distance between the swing center of the swing arm and the connection point of the drive arm. Since the width of the swing pattern drawn on the cross surface by each wafer of different diameter size during polishing can always match the cross radius, the generation of cross surface steps due to polishing work is prevented and the wafer polishing accuracy is improved. it can.

When the large-diameter wafer is polished to increase the frictional force and the swing angle decreases,
Since the distance between the fulcrums of the swing arm will increase,
The driving force required for rocking can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a mirror polishing apparatus for a semiconductor wafer according to the present invention.

FIG. 2 is a plan view showing a schematic arrangement of a rocking mechanism according to the mirror polishing device of the present invention.

FIG. 3 is a plan view for explaining the operation of the swing mechanism according to the mirror polishing device of the present invention.

[Explanation of symbols]

 1 Mirror Polishing Device 3 Lower Surface Plate 4 Support Shaft 5 Support Arm 7 Pressurizing Plate 8 Swing Mechanism 9 Cross 10 Swing Arm 13 Drive Arm 14 Rotating Plate 15 Rotating Motor W Semiconductor Wafer Wa 4 Inch Diameter Wafer Wb 5 Inch Diameter Wafer Wc 6 Inch diameter wafer

Claims (3)

[Claims] 1. A lower surface plate having a polishing cloth adhered to the upper surface thereof, a pressure plate having a semiconductor wafer disposed on the lower surface plate and pressed to the lower surface thereof, and the upper and lower surface plates are rotated. A rotation mechanism, a support arm that supports the pressure plate and has a base end fixed to a support shaft, a swing arm having a base end fixed to the support shaft, and a drive mechanism having one end connected to the swing arm tip. In a mirror-polishing device having a drive arm that reciprocates by means of a guide member, the tip of the swing arm is extended to install a guide member, and as the wafer diameter increases, the guide member that is farther from the swing center is provided. A mirror polishing apparatus for a semiconductor wafer, characterized in that a drive arm is connected to a predetermined portion and the swing angle is adjusted according to the diameter of the wafer. 2. The drive mechanism is configured such that the other end of the drive arm is pivotally attached to an eccentric position of a rotary plate rotated by a motor, and the guide member of the swing arm is a rotary shaft of the rotary plate. The mirror-polishing device for a semiconductor wafer according to claim 1, wherein the mirror-polishing device has a curved shape along a circle centered at. 3. The semiconductor device according to claim 2, wherein the guide member of the swing arm has a curved shape that is separated from a circle centered on the rotation axis of the rotary plate according to the diameter of the wafer. Wafer mirror polishing device.