JPS62264858A - Surface grinding method - Google Patents

Abstract

PURPOSE:To improve both efficiency and accuracy for surface grinding of a disc shaped work by feeding a cup shaped grinding stone, the rotating shaft of which is parallel with that of a table mentioned later on, to the radial direction against a work coaxially fixed on the rotating table as a whole in such a way that the depth of cut is made when the same reaches the center thereof. CONSTITUTION:Toward a wafer 3 coaxially mounted on a turning table 4, a cup shaped grinding stone 1 which has a rotating shaft in parallel with that of said table while being held movably up and down to the right and left directions, is lowered down in such a way that a machining allowance from the time of grinding start will be (t1) so as to perform the creep feed grinding with a feed provided to the left direction. And when the grinding stone 1 reaches the center of rotation, a depth of cut (t2) is made, then the grinding stone 1 is lifted up after grinding is over. Accordingly, grinding up-to the machining allowance (t1) can be accomplished for a short period of time only by moving the grinding stone to the center of the wafer, and furthermore grinding is performed while the machining allowance (t2) enables a positional relation between the grinding stone 1 and the wafer 3 to be kept constant thereby providing the satisfactory accuracy of surface shape.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a surface grinding method for a disk-shaped workpiece such as a silicon wafer, and is particularly suitable for efficiently obtaining high precision in planar shape. The present invention relates to a surface grinding method.

[Background of the invention]

For example, as a method for surface grinding a silicon wafer (hereinafter simply referred to as a wafer), Japanese Patent Application Laid-Open No. 57-156157
There is also a method disclosed in Japanese Patent Laid-Open No. 59-187445.

A schematic diagram of the former grinding method is shown in FIG. 2(A).

Shown in (B).

In this method, the cup-shaped grindstone 1 is rotated in the direction of the arrow and moved in a direction parallel to the surface of the wafer 3 fixed to the index table 2 to be processed.

In this method, as shown in FIG. 2(B), the grinding width B changes depending on the grinding position, and the grinding resistance also changes accordingly.

For this reason, the amount of elastic variation of the grinder changes depending on the grinding position, and the grinding surface becomes medium and high in the feeding direction, making it difficult to obtain good planar shape accuracy.

Moreover, a schematic diagram of the latter grinding method is shown in FIG. In this method, the wafer 3 is mounted so that the center of the rotary table 4 substantially coincides with the center of rotation, and the cup-shaped grindstone 1 is arranged so that the center of rotation is located within the grinding surface 5 of the cup-shaped grindstone 1. Then, cup-shaped grindstone 1 and wafer 3
This is a method of grinding by applying a cutting motion to the surface of the wafer 3 to be processed and ground without rotating the wafer 3.

In this method, the positional relationship between the cup-shaped grindstone 1 and the wafer 3 within the grinding surface is always constant, and the grinding width does not change as in the above method, so it is possible to obtain good planar shape accuracy. Yes6 However, since the cutting speed needs to be extremely low, if there are large variations in the wafer thickness before grinding,
There was a problem that the air cutting time increased and the grinding efficiency decreased.

[Purpose of the invention]

An object of the present invention is to provide a surface grinding method that solves the problems of the prior art described above and can achieve high precision and high efficiency at the same time.

[Summary of the invention]

The present invention includes mounting a workpiece on a table that is rotatably held around a rotation axis parallel to the rotation axis of a cup-shaped grindstone so that the center of the workpiece substantially coincides with the rotation center of the table, While rotating the cup-shaped grindstone and the table, a feed operation is applied in a direction perpendicular to the rotation axis to grind the workpiece, and when the cup-shaped grindstone reaches the center of the workpiece, it is parallel to the rotation axis. The cutting motion is applied in a certain direction to perform final grinding of the object to be ground.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIGS. 1(A) to 1(F).

1(A) to (F) are schematic diagrams showing the grinding operation of the present invention, and 1 is a cup-shaped grindstone, which is held so as to be movable in the vertical and horizontal directions in the figure at the same time as the rotational movement; It is arranged so that its axis of rotation is parallel to the axis of rotation of the cup-shaped grindstone 1.

A wafer 3 is mounted so that its center substantially coincides with the rotation center of the rotary table 4. (A) shows the grinding start point, the rotary table 4 rotates, and at the same time the cup-shaped grindstone 1 descends.

When the cup-shaped grindstone 1 reaches the position of the predetermined machining allowance t1, (
As shown in (B), the grinding feed is applied to the left in the figure, and as shown in (C), the wafer 3 is subjected to creep feed grinding while rotating. Since the wafer 3 is rotating, when the cup-shaped grindstone 1 reaches the center of the wafer 3, the grinding of the predetermined machining allowance t1 is completed. At this time, the positional relationship between the cup-shaped grindstone 1 and the wafer 3 is the same as that shown in FIG. In this state, the cup-shaped grindstone 1 is given vertical cutting motion as shown in (D), and after grinding a predetermined machining allowance t2, it rises as shown in (E), and then moves to the right as shown in (F). Move to (A)
The grinding operation is completed by returning to the above state.

According to the present invention, the entire surface of the wafer 3 can be ground by simply moving the cup-shaped grindstone 1 to the center of the wafer 3, so that the entire surface can be ground in half the time compared to the conventional technique shown in FIG. . At this point, the plane accuracy is poor as in the example shown in Fig. 2, but by grinding the machining allowance t2 in steps (D) to (F), it is possible to finish the plane with high precision as in the prior art shown in Fig. 2. .

Since it is sufficient for the value of this machining allowance t2 to be about 0.01 mm, the total grinding time is also about half that of the conventional technique shown in FIG. As described above, according to the present invention, there is an effect that highly accurate grinding can be realized with high efficiency.

〔Effect of the invention〕

As described above, according to the method of the present invention, creep-feed grinding is performed while rotating the wafer, and at the same time, when the cup-shaped grindstone reaches the rotation center of the wafer, vertical cutting motion is applied to the wafer to form a planar shape. Since this method corrects the accuracy, it has the effect of realizing a highly accurate planar shape with high efficiency.

[Brief explanation of drawings]

FIGS. 1(A) to 1(F) are schematic diagrams showing one embodiment of the grinding method according to the present invention. FIGS. 2 and 3 are schematic diagrams showing a conventional surface grinding method. 1...Cup-shaped grindstone, 3...Wafer, 4...Rotary table. Patent Applicant Hitachi Seiko Co., Ltd. Agent Patent Attorney Tadashi Akimoto Figure 1 (C)
(D) DoE,
(F) Figure 2 Figure 3 (25

Claims (1)

[Claims] 1. In a surface grinding method in which a cup-shaped grindstone is used to grind the flat surface of a workpiece, a table, which is held rotatably around a rotation axis parallel to the rotation axis of the cup-shaped grindstone, is placed at the center of rotation of the table. The workpiece is mounted so that the centers of the workpieces substantially coincide with each other, and the cup-shaped grindstone and the table are rotated and fed in a direction perpendicular to the rotation axis to grind the workpiece. A surface grinding method characterized in that when the grinding surface of a shape grindstone reaches the center of the workpiece, finishing grinding is performed by applying a cutting operation in a direction parallel to the rotation axis.