JP2650422B2 - Wafer grinding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a wafer grinding apparatus, a rotating surface of a support plate is controlled while a ground surface of a wafer is measured by a surface roughness measuring means so that an optimum ground surface is always obtained. In order to increase the efficiency of the grinding operation, a multi-axis grinding machine that is driven in rotation and a multi-axis grinding machine that supports a plurality of wafers and that each of the wafers move while facing each other are sequentially ground. As described above, the rotating disk is provided with a holding plate that is driven to rotate, and a surface roughness measuring unit provided to face the ground surface of the wafer, and the rotation speed of the holding plate is controlled by the surface roughness measuring unit. To be configured.

[Industrial applications]

The present invention relates to a wafer grinding apparatus, and more particularly, to a wafer grinding apparatus that controls a rotation speed of a support plate while measuring a ground surface of a wafer by a surface roughness measuring unit.

In recent years, the development of microelectronics has been remarkable, but the development largely depends on the technological innovation of semiconductor devices.

Above all, the scale and integration of integrated circuits using silicon semiconductors have been changing very rapidly, and the number of elements integrated in one chip can be reduced to the number of memory elements. It has expanded four-fold on a yearly basis.

Accordingly, a series of steps from a silicon wafer (hereinafter abbreviated as a wafer) to a device, that is, a so-called wafer process, has been strongly reformed in terms of manufacturing technology.

In addition, mechanical processing steps on wafers performed before and after the wafer process are plain steps, but are regarded as important steps for improving productivity.

In the process before and after this, after the wafer process, that is, the grinding process of grinding the back surface of the wafer after the elements are formed to finish it to a predetermined thickness and ground surface, the added value is maximized Since it is a process for handling a wafer that has been processed, how to perform it efficiently is an important issue.

[Conventional technology]

FIG. 3 is a configuration diagram of a conventional wafer grinding apparatus, and FIG. 4 is a flowchart of a conventional grinding process.

FIG. 3 shows grinding of a wafer 3 by three multi-axis grinding machines 2.
1 shows a wafer grinding apparatus 1 which is sequentially performed.

When the number of the grinding machines 2 is three, for example,
Are placed in three places where the perimeter is divided into four equal parts,
The remaining one position A is a place where the wafer 3 is taken in and out.

Grinding teeth 6 are fixed to the surface of each of the three grinding machines 2.

The grinding teeth 6 are formed by annularly forming and solidifying diamond abrasive powder with a binder, and are also called diamond rings or the like.

The shape of the tip of the grinding tooth 6 is, for example, a prism-shaped protrusion or a triangular-shaped protrusion, and is properly used depending on the purpose.

By the way, in general, a wafer used in a wafer process is considerably thick, for example, 750 μm in order to avoid warping or breakage during the process.

Wafer process is over, this thick wafer 31
At position A, for example, by a vacuum chuck,
It is attached to the holding board 4.

The holding plate 4 has a wafer 3 around the plate, for example,
With a large configuration capable of supporting eight wafers, the supported wafer 3 rotates at a peripheral speed such as to move at a speed of, for example, 100 mm per minute.

And, for example, it spins at 2,000 revolutions per minute. From the first grinder 21 of the three grinders 2 to the second grinder 22, and from the second grinder 22 to the third grinder 23, the thickness is, for example, 500 μm.
It is moved while being ground sequentially so as to have a thickness of.

When the grinding by the third grinder 23 is completed in this way, the wafers 32 having a predetermined thickness and surface roughness are sequentially taken out from the position A.

The speed at which the holding platen 4 is sequentially rotated is called a grinding speed in FIG. 4 and is an important factor that determines the productivity of the grinding process.

In the flow chart of FIG. 7, this grinding speed is usually set at the time of starting the work.

On the other hand, the degree of grinding of the wafer surface is determined based on the quality of the ground surface of the previously grounded lot. If the determination is good, grinding is performed.

 If the determination is no, so-called setup change is performed.

That is, the setup change is to attach a polishing board called a dressing board to a holding board in place of a wafer to be ground and dress the ground teeth.

This dressing removes the binder from the grinding teeth to expose the diamond powder, thereby regenerating the grinding teeth.

Obtaining a regenerating effect similar to that of dressing by using a dummy wafer is called pre-cut, and may be performed as a method of regenerating ground teeth instead of dressing.

When the dressing is completed, the dummy wafer is ground, and if the ground surface is good, the normal grinding operation is restarted.

If the finished state of the ground surface by the dummy wafer is not good, the work flow is returned and the dressing is performed again.

Conventionally, such a series of operations is performed manually, for example, by visually confirming the degree of finish of the ground surface by judging whether or not a face is reflected, or by dressing the grinding teeth which is close to trial and error. Has caused the productivity of the grinding process to be significantly impaired.

[Problems to be solved by the invention]

As described above, the wafer on which elements have been formed by the wafer process is processed to be thicker to prevent the wafer from being warped or damaged during the wafer process.

Therefore, the back side of the wafer on which the element has been formed is ground to a predetermined thickness.

Conventionally, this grinding process is performed regardless of whether the grinding speed is set, the finished state of the ground surface of the wafer is checked, the dressing of the grinding teeth is performed, or the state of the dressing is evaluated using a dummy wafer. , Relying on visual and manual work.

For this reason, in the conventional grinding process, there is a problem that the grinding surface of the wafer is often defective or damaged, which significantly impairs productivity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus that automates monitoring of a ground surface of a wafer and controls a grinding speed based on an evaluation result of the monitoring, thereby improving the efficiency of the grinding process.

[Means for solving the problem]

The problem described above is a multi-axis grinding machine that is rotationally driven, and a plurality of wafers are supported, and the wafers are rotationally driven so that each of the wafers is sequentially ground by the opposing multi-axis grinding machines while moving. A wafer grinding machine having a surface roughness measuring means provided opposite to a grinding surface of the wafer, wherein the rotation speed of the holding disk is controlled by the surface roughness measuring means. Solved by the device.

(Operation)

In the present invention, the grinding surface of the wafer is monitored by the surface roughness measuring means, and the rotational speed of the holding plate supporting the wafer, that is, the grinding time of the wafer is controlled based on the evaluation result.

In other words, when a defect occurs on the ground surface of the wafer, the grinding operation is stopped each time, dressing or pre-cut operation is performed, the quality of the result is checked with a dummy wafer, and then the original operation is restarted. In place of the conventional inefficient grinding process, in the present invention, the ground surface of the wafer is always automatically monitored by the surface roughness measuring means.

And, if the sharpness of the grinding teeth becomes poor and the grinding surface becomes cloudy or tears, causing troubles, the rotation speed of the holding plate, that is, the wafer is multiaxially ground. The speed of sequentially going around the board is automatically reduced to a preset slow speed.

Here, it is not impossible for the surface roughness measuring means to measure the surface roughness while contacting the surface of the wafer being ground, but it is not necessary to use a non-contact type such as an electric micrometer or an air micrometer. Alternatively, an optical surface roughness meter or the like is used.

By reducing the rotation speed of the holding plate, a dressing effect can be given to the grinding teeth of each of the multi-axis grinding machines.

In addition, when a problem occurs on the ground surface, the effect of the dressing need not be checked using the dummy wafer each time, so that the efficiency of the grinding operation can be improved.

〔Example〕

FIG. 1 is an explanatory view of an embodiment of the present invention, and FIG. 2 is a flowchart of a grinding process.

The wafer grinding apparatus 1 according to the present invention shown in FIG.
A holding plate 4 capable of supporting eight wafers 3 by a vacuum chuck was used, and a grinding machine 2 used three axes.

The thickness of the wafer 3 after the grinding is set by the first grinding machine 21.
0.61 mm, second grinder 22 is 0.58 mm, third grinder 23 is 0.52 mm
Thus, the final goal was to enter the range of 0.52 ± 0.05 mm, and the finish of the ground surface to be a mirror surface.

Further, at the position A, the wafers 31 having different thicknesses subjected to thrashing are supported, and the wafers 32 which have been ground are taken out.

On the other hand, the surface roughness measuring means 5 is provided at a position where the wafer 3 after grinding between the position A and the third grinding machine 23 can be measured using a light-section type surface roughness meter.

The peripheral speed is 140 mm per minute, and the same as when the ground surface of the slowly lapping ground wafer 3 is visually confirmed by the conventional visual inspection, the output level of the surface roughness meter when the mirror surface is no longer finished is maintained. The rotation speed of the panel 4 can be controlled by a control system (not shown) so that the peripheral speed is 80 mm per minute.

Thus, the assembled wafer grinding apparatus 1 according to the present invention was operated to evaluate the performance.

As a result, the grinding teeth can be regenerated by the effect equivalent to the dressing without having to perform the conventional grinding and stop the troublesome work of dressing with a dressing board or checking the finish of the ground surface with a dummy wafer. It was confirmed that it was done.

Here, various modifications are possible, such as how many multi-axes the grinding machine has and how many wafers are supported on the holding board.

In addition, the rotation speed of the grinding machine, the peripheral speed of the holding machine, and the like are not values that are determined uniquely, and various modifications are possible.

Furthermore, various non-contact surface roughness meters can be used as the surface roughness measurement means, but a contact surface roughness meter is of course included.

In addition, various modifications are possible as to where and how many are provided.

〔The invention's effect〕

As described above, according to the present invention, the setting of the grinding speed, the confirmation of the finished state of the ground surface of the wafer, the dressing of the grinding teeth, and the condition of the dressing, which were performed in the conventional grinding process, are performed. Various operations such as evaluation using a dummy wafer, and complicated operations that have been performed by relying on visual observation and manual operation can be omitted.

Accordingly, the loss caused by the failure or breakage of the ground surface of the wafer, which has frequently occurred in the conventional grinding process, can be drastically reduced.

Therefore, according to the wafer grinding apparatus of the present invention, there is an effect that the productivity of the grinding process for handling high value-added wafers after the wafer process is greatly improved.

[Brief description of the drawings]

 FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is a flowchart of a grinding process, FIG. 3 is a block diagram of a conventional wafer grinding apparatus, and FIG. is there. In the figure, 1 is a wafer grinding device, 2 is a grinding machine, 3 is a wafer, 4 is a holding plate, 5 is a surface roughness measuring means, and 6 is a grinding tooth.

Claims (1)

(57) [Claims] 1. A multi-axis grinding machine (2) that is driven to rotate and a multi-axis grinding machine (2) that supports a plurality of wafers (3) and faces each of the wafers (3) while moving. And a surface roughness measuring means (5) provided to face the ground surface of the wafer (3) so as to be sequentially ground by (1); (4) The wafer grinding apparatus, wherein the rotation speed is controlled by the surface roughness measuring means (5).