JPH03256668A - Mount plate for polishing semiconductor wafer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a mount plate for semiconductor wafer/polishing, and particularly to a mount plate with improved performance in affixing a semiconductor wafer using wax.

[Prior Art] When polishing a semiconductor wafer, a method is generally adopted in which the wafer is stuck on a flat jig, that is, a mount plate.

This was created as a result of emphasizing flatness, and recently there are methods that use wax and methods that do not use wax.

The former is a method of attaching the wafer using wax that is easy to clean, and has very strong adhesive strength, and by making the wax thickness uniform, highly accurate wafer polishing can be expected.

The latter has separate spaces on the surface of the artificial leather,
This is a method of pasting by pressing the wafer to absorb these spaces. This method uses artificial leather, so it is difficult to obtain a surface with good flatness, but it has the advantage of not requiring wax removal after polishing. Therefore, it can be applied to wafers whose flatness accuracy is not strict, and it is expected that productivity will be increased since wax removal after work can be omitted.

Conventionally, in order to mirror-finish a semiconductor wafer such as GaAs, the former method, which exclusively uses wax, has been adopted because highly accurate wafer polishing is required.

FIG. 2 is an overall view showing the schematic structure of a polishing apparatus for polishing wafers using such wax.

A plurality of semiconductor wafers 3 are attached with wax 2 along the circumferential direction on a rotating disk-shaped mount plate 1, and the surfaces of the attached semiconductor wafers 3 are polished while being pressurized. The mounting plate 1 is made of a material that is not chemically attacked and is less deformed over time and under load. It is usually made of ceramic or glass, and has a smooth, flat surface with no irregularities.

FIG. 3 shows a conventional mounting plate 1 with wax 2.
2 is a cross-sectional view showing a state in which a semiconductor wafer is attached via a wafer. As shown in the figure, the wax 2 tends to have an uneven thickness and is attached at an angle. Furthermore, especially when the wafer size becomes large, the molten wax at the center of the wafer cannot be cut out, and the wax thickness at the center tends to increase. As described above, it is difficult to obtain a uniform wax thickness when pasting with wax.

[Problems to be Solved by the Invention] As described above, when polishing a semiconductor wafer by pasting it with wax, there are the following problems.

(1) It is difficult to obtain highly accurate wafers due to uneven wax thickness caused by insufficient correction of wafer warpage.

(2) When attaching a wafer to a mount plate, if foreign matter is present in the wax, a change in the shape of that part will appear on the wafer, and after polishing, it will remain as a mirror surface defect called a dimple.

(3) After mirror polishing, a cleaning process using an organic solvent is required to remove wax remaining on the wafer surface, resulting in increased costs.

(4) When wax is removed using an organic solvent, contamination by melted wax tends to occur, and melted wax on the back surface of the wafer re-adheres to the mirror surface. This redeposited foreign matter cannot be completely removed by subsequent cleaning. The same applies to foreign substances contained in wax. This poses a major obstacle to improving the degree of cleanliness.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and eliminate the effects of uneven wax thickness that occur during wafer attachment, by allowing the molten wax to flow easily when attaching semiconductor wafers. An object of the present invention is to provide a novel mount plate for polishing semiconductor wafers that can realize highly accurate attachment.

[Means for Solving the Problems] The present invention provides a semiconductor wafer polishing mount plate for attaching a semiconductor wafer by applying pressure through wax in order to polish the semiconductor wafer. A portion of the melted wax is flowed to provide unevenness or grooves that uniformly distribute the wax between the wafer and the mount plate, and the flat surface obtained by the apex of the protrusion formed by the unevenness or groove is the surface of the semiconductor wafer. The planar surface roughness is such that it does not impair the flatness required for.

U effect 1: Heat the mount plate above the melting temperature of the wax, melt and apply wax on it, place the semiconductor wafer on the melted wax, and apply pressure uniformly to the semiconductor wafer, the mount plate will melt. Excess wax is extruded from the unevenness or grooves provided on the surface along the direction of the unevenness or grooves. Therefore, the wax near the center, which tends to be trapped, can flow and escape from being trapped.

When the wafer is pressurized until it comes into contact with the protrusions forming the unevenness or grooves, the wax thickness becomes uniform and wax adhesion is minimized.

Further, since foreign matter mixed in the wax gets into the unevenness or grooves, changes in the shape of the wafer can be prevented.

In this way, the semiconductor wafer can be attached with no uneven wax thickness, making it possible to perform mirror polishing with high precision.

[Embodiment] Hereinafter, an embodiment of the present invention will be explained using FIGS. 1 and 4.

As shown in FIG. 1, grooves or grooves 4 are formed on the surface of the mounting plate 1 to a size that allows wax 2 to flow out in a molten state without being trapped in the center. There is.

Further, the plane obtained by the apex of the protrusion 5 formed by the unevenness or the groove 4 is required to have a surface roughness that does not impair the flatness required of the semiconductor wafer 3. For example, as for the surface roughness, it is desirable that the surface has a division value of maximum height Rmax smaller than 6.38.

Furthermore, various shapes of the groove 4 can be considered, as shown in FIG. 4, for example.

A radial type having a large number of grooves 41 extending radially from the center of the mount plate 1 (FIG. 4(a)).

Concentrically or spirally uneven or grooved in the circumferential direction 42.
43 (FIG. 4(b)(C)).

However, in this case, it is necessary to have grooves 41 that reach the edges in the radial direction so as to intersect with the concentric grooves or the spiral grooves (FIG. 4(b)).

In the case of unevenness, it is desirable that the unevenness be uniformly distributed on the surface, such as in a pear-like fabric.

Now, next, the unevenness or grooves 4 (41 to 43) as described above are formed.
) A method of polishing a semiconductor wafer 2 by attaching it to a mount plate l provided on its surface will be explained.

When attaching the semiconductor wafer 3 onto the mount plate I, the mount plate 1 is heated to a temperature higher than the melting temperature of the wax 2. This heating can be performed, for example, using a hot plate (not shown) provided on the lower surface of the mount plate 1. Melted wax or solid wax 2 is melted and applied onto a mount plate 1. Thereafter, the wafer 3 is placed on the wax 2, and pressure is applied uniformly from above the wafer 3 to make the thickness of the wax 2 uniform.

The already mentioned FIG. 1 shows the state in which the wafer 3 is attached on the mount plate 1. As shown in FIG. By applying pressure from above the wafer 3, the wax 2 near the center is pushed out to the periphery through the unevenness or grooves 4, and the wafer 3 comes into contact with the projections 5 formed by the unevenness or grooves 4. By cooling the mount plate 1 in this state, the wax can be applied without uneven thickness.

Thereafter, the attached semiconductor urchin/\3 is polished while being pressurized.

As described above, according to this embodiment, unevenness or grooves 4 are formed on the surface of the mount plate 1 to prevent thickness unevenness when the semiconductor wafer 3 placed on the molten wax 2 is pressurized. The excess wax 2 that causes the wafer 2 is made to flow and be pushed out without being trapped.Even if there is uneven wax thickness caused by the warpage of the wafer 2 not being sufficiently corrected, the excess wax will flow. That will happen.

Therefore, if the wax becomes uneven in thickness and is pasted at an angle, or if the wafer size increases, the melted wax in the center of the wafer cannot be removed, and the wax 2
will not be in a contained state.

Furthermore, even if there are foreign substances in the wax, they will get into the unevenness or grooves 4 during the pressurization process.
There are no mirror defects such as mirror defects caused by foreign substances.

In addition, if the surface roughness of the grooves or grooves 4 formed on the surface of the mount plate 1 is a finished surface with a maximum height Rmax of less than 6.3s, it is important to Highly accurate pasting is possible without damaging the pressure surface shape.

Then, the wafer 3 comes into contact with the protrusions 5 formed by the unevenness or the grooves 4, and the contact surface area becomes very small, so that the wax 2 does not adhere to the surface of the wafer 3 after polishing, and the process of cleaning the wax becomes unnecessary. As a result, it becomes possible to reduce processing costs and eliminate the chlorine-based solvent used in the past.

In addition, although the above embodiment describes the case where the unevenness or the groove has a radial concentric circle or a spiral shape, the present invention is not limited to this. is possible.

[Effects of invention According to the present invention, the following effects are achieved.

(1) The surface of the mount plate is provided with unevenness or grooves to allow the molten wax to flow easily when attaching semiconductor wafers, which eliminates the effects of uneven wax thickness that occurs when attaching wafers. Since foreign matter in the wax is absorbed into the irregularities or grooves, highly accurate pasting can be achieved.

(2) The flatness of the semiconductor wafer is improved by the presence of the unevenness or grooves because the plane obtained by the apex of the protrusion formed by the unevenness or groove is formed with a flatness that does not impair the flatness required of the semiconductor wafer. Moreover, since wax does not adhere to the wafer surface after polishing, there is no need for a wax cleaning process.

[Brief explanation of drawings]

FIG. 1 is a cross section showing the state of wafer attachment according to this embodiment;
FIG. 2 is an explanatory diagram of the entire attachment jig, FIG. 3 is a cross-sectional view showing a conventional wafer attachment state, and FIG. 4 is a plan view of a mount plate showing unevenness or grooves according to this embodiment. 1 is a wafer attachment jig, 2 is wax, 3 is a wafer, 4
5 is an unevenness or groove, and 5 is a protrusion.

Claims (1)

[Scope of Claim] A semiconductor wafer polishing mount plate for attaching a semiconductor wafer by applying pressure through wax in order to polish the semiconductor wafer, wherein the melted wax is applied to the surface of the semiconductor wafer by applying pressure when attaching the semiconductor wafer. Provide unevenness or grooves that allow the wax to flow and evenly distribute the wax between the wafer and the mounting plate, and the flat surface obtained by the apex of the protrusion formed by the unevenness or groove impairs the flatness required of the semiconductor wafer. A mount plate for semiconductor wafer polishing, characterized in that it is formed with no flat surface roughness.