JP2645736B2 - Mirror finishing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a surface finishing apparatus for mirror-finishing a processing surface of a processing object such as a semiconductor wafer such as gallium arsenide (GaAs) or silicon or a ceramic substrate. About.

[Prior Art] When the surface to be processed of a workpiece such as a semiconductor wafer is mirror-finished, after the surface to be processed is roughly ground, finish grinding is performed to finish the surface to be processed to a predetermined surface roughness. Is normal.

Of these, in the finish grinding, conventionally, a mirror surface having a predetermined surface roughness that is finally obtained is obtained until a predetermined finishing grinding allowance (for example, 10 μm) is finished. However, they also decided to continue grinding and finish grinding completely to a predetermined grinding allowance.

[Problems to be solved by the invention]

As described above, conventionally, although the mirror surface having a predetermined finish surface roughness is obtained, the finish grinding is continued until the predetermined grinding allowance is finished, so that the mirror surface is obtained. After the grinding, the grinding time was unnecessarily prolonged.

In particular, when the surface of a thin and fragile workpiece such as a compound semiconductor wafer such as GaAs is mirror-finished,
Since the cutting amount (feed amount) of the grinding tool (grinding stone) per unit time in the direction perpendicular to the surface to be processed cannot be increased, the grinding time is long even with a small grinding margin. Therefore, the extra grinding time after the mirror surface is obtained tends to be long.

In view of the above circumstances, the present invention eliminates unnecessary grinding work time after a mirror surface having a predetermined surface roughness is obtained on a surface to be processed, and a mirror finishing device capable of shortening the time required for mirror finishing. It is intended to provide.

[Means for solving the problem]

In order to achieve the above object, in the mirror finishing device according to the present invention, a surface roughness determining means for determining the surface roughness of the surface to be processed during the grinding process is provided, and the mirror surface having a predetermined surface roughness is provided on the surface to be processed. And the grinding of the surface to be processed is finished at the same time.

[Action]

As described above, since the grinding of the surface to be processed is finished at the same time when the mirror surface is obtained on the surface to be processed, an extra grinding operation time after the mirror surface is obtained can be omitted.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The figure shows an outline of a mirror finishing device according to the present invention.

As shown in the figure, the mirror finishing apparatus according to the present invention has a rotatable table 2 for holding a semiconductor wafer (hereinafter simply referred to as a wafer) 1 as a workpiece. The center of the wafer 1 is placed on a table 2 by a so-called back grinding tape (not shown).
And is fixed on the table 2 so as to substantially coincide with the rotation center axis.

Below the table 2, a motor 3 for rotating the table 2 at a predetermined rotation speed is provided. Power for driving the motor 3 is supplied to the motor 3 via a motor drive circuit 5. The motor drive circuit 5 is controlled by a central control circuit 6 including a CPU, a ROM, a RAM, and the like.
Supplies electric power to the motor 3 in response to a command issued by the controller 3.

Above the table 2, a grindstone 7 for grinding the upper surface of the wafer 1 fixed on the table 2 is provided. As the grindstone 7, for example, a diamond grindstone is used, is formed in an annular shape, and the center thereof is arranged to be shifted from the rotation center axis of the table 2. The grindstone 7 is held by a substantially annular holding member 8, and is rotated by a motor 9 together with the holding member 8. The positional relationship between the grindstone 7 and the table 2 is such that the rotation center axis of the table 2 coincides with the outer peripheral end of the grindstone 7. Therefore, the wafer 1 rotates around the outer peripheral end of the grindstone 7, and a portion not covered by the grindstone 7 and the holding member 8 always exists on the upper surface of the wafer 1.

By arranging the table 2 and the grindstone 7 in such a relative positional relationship, while the upper surface of the wafer 1 is being ground by the grindstone 7, the surface roughness of the upper surface of the wafer 1 is measured by a stylus type surface roughness meter described later. It becomes possible to measure. That is, there is always a portion of the upper surface of the wafer 1 that is not covered by the grindstone 7 and the holding member 8 and is exposed, and this portion allows the stylus of the surface roughness meter to contact the upper surface of the wafer 1 being ground. It is secured as a gaining part.

The motor 9 is supplied with electric power for driving the motor 9 via a motor driving circuit 11. The motor drive circuit 11 is controlled by the central control circuit 6 and supplies electric power to the motor 9 according to a command issued by the central control circuit 6. Although not shown, the grindstone 7 is movable in the direction of its rotation center axis, and an elevating means for raising and lowering the grindstone 7 on this rotation center axis is provided. The lifting means is controlled by the central control circuit 6.

Above the table 2, a stylus type surface roughness meter 11 for measuring the surface roughness of the upper surface of the wafer 1 fixed on the table 2 is provided. The surface roughness meter 11 has a stylus 12 that contacts the upper surface of the wafer 1 at the tip. While the stylus 12 is kept in contact with the upper surface of the wafer 1, the wafer 1 is rotated, and the movement of the stylus 12 in the vertical direction (perpendicular to the upper surface of the wafer 1) at this time indicates the surface roughness of the upper surface of the wafer 1. Can be measured. Surface roughness meter
Numeral 11 is provided outside the grindstone 7 so that its stylus 12 always comes into contact with a portion of the upper surface of the wafer 1 which is not covered with the grindstone 7 and the holding member 8. Therefore, the stylus 12 can be constantly brought into contact with the upper surface of the wafer 1 even during the grinding operation. The surface roughness of the upper surface of the wafer 1 measured by the surface roughness meter 11 is converted into an electric signal and input to the central control circuit 6. It is preferable that the surface roughness meter 11 is arranged so as to be able to move in parallel in the radial direction of the wafer 1 while keeping the stylus 12 in contact with the upper surface of the wafer 1. With this arrangement, the surface roughness of the upper surface of the wafer 1 can be measured evenly.

Next, the operation of the above-described mirror finishing device according to the present invention will be described.

First, the roughly ground wafer 1 is fixed on the table 2 and the motors 3 and 9 are driven. At the same time, the surface roughness of the ground surface of the wafer 1 is measured by the surface roughness meter 11. The grindstone 7 is machined at a predetermined feed speed in the direction of the rotation center axis.

The surface roughness meter 11 constantly measures the surface roughness of the upper surface of the wafer 1 while the grinding of the wafer 1 by the grindstone 7 is performed, and inputs the result to the central control circuit 6. The central control circuit 6 determines whether or not the upper surface of the wafer 1 is a mirror surface having a predetermined surface roughness (0.1 μm) or less based on the information on the surface roughness of the upper surface of the wafer 1 input from the surface roughness meter 6. ,
The grinding is continued as long as it is not a mirror surface, and if a mirror surface is obtained, a command to end the grinding is immediately issued.

When there is a command to end the grinding, first, the grindstone 7 is raised by the elevating means, and when the grindstone 7 and the wafer 1 are separated, the power supply to the motors 3 and 9 is cut off, and the rotation of the table 2 and the grindstone 7 is stopped. The operation is stopped, and the mirror finishing work of the wafer 1 is completed.

The grinding allowance that requires grinding before a mirror surface is obtained is about 1-2 μm if the condition of the rough ground surface, the runout of the grindstone, and the accuracy of the table surface are appropriately adjusted.
Usually, a mirror surface is obtained while grinding a grinding allowance of about 2 μm. In the mirror finishing device according to the present invention, as described above, the grinding is finished when the mirror surface is obtained, so that the grinding finish is about 8 μm or more compared to the conventional grinding method in which the grinding allowance of about 10 μm is completely finished. The cost is reduced. Therefore, if the feed speed of the grindstone is 0.8 μm / min, the time required for the mirror finishing work is per wafer
This will be reduced by more than 10 minutes.

〔The invention's effect〕

As described above, in the mirror finishing device according to the present invention, the surface roughness determining means for determining the surface roughness of the surface to be processed during the grinding process is provided, and the mirror surface having the predetermined surface roughness is obtained on the surface to be processed. Since the grinding of the surface to be processed is completed at the same time, the extra grinding work time after the mirror surface is obtained can be omitted, and the time required for the mirror surface finishing can be shortened. Also, the amount of grinding powder (chips) can be eliminated because extra grinding can be omitted.
Is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a surface finishing device according to the present invention. 1 ... Semiconductor wafer, 2 ... Table, 3 ... Motor, 7 ... Whetstone, 9 ... Motor, 11 ... Surface roughness meter, 12
…… a stylus.

Claims (1)

(57) [Claims] 1. A mirror finishing device for mirror-finishing a surface of a workpiece to be processed, said finishing means for grinding said surface to be mirror-finished and said finishing means for polishing said surface to be processed. Surface roughness determining means for determining the surface roughness by contacting the surface to be processed during processing, wherein the surface roughness determination means reduces the surface roughness of the surface to be processed to a predetermined roughness or less. Wherein the finish processing means terminates the processing of the surface to be processed.