JPH0377160B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing single crystal wafers, particularly to an improvement in the chamfering method for single crystals such as gadolinium gallium garnet (GGG) and lithium tantalate. The present invention relates to a method of manufacturing these single crystal wafers economically and with a high yield.

(Prior art) It is well known that single crystals of gadolinium gallium garnet (GGG), lithium tantalate, lithium niobate, etc. can be produced by a single crystal pulling method called the Czyochralski method. It is also known that wafers cut from these single crystals are used as materials for various sensors and electronic devices.

However, this type of single-crystal wafer was made by the Czyochralski method, and the end face of the wafer obtained by cutting a single-crystal bar with a constant diameter using cylindrical grinding was roughly ground to adjust the shape. The final product is then wrapped, etched, and then polished. However, this wrapping and etching process involves a large amount of processing loss for the expensive single crystal, so wrapping and etching are performed to minimize processing loss. The method of reducing the amount of etching as much as possible is adopted, but reducing the processing loss due to wrapping and etching has the disadvantage of leaving scratches due to processing distortion remaining on the wafer edge, lowering the product value. Although countermeasures are being considered, this countermeasure has not yet been established.

(Structure of the Invention) The present invention relates to a wafer manufacturing method that is an improved single crystal chamfering method that solves these disadvantages. This method is characterized in that the end faces are roughly ground and then subjected to surface lapping, then a plurality of these wafers are stacked and only the end faces of the wafers are etched, and then the entire surface of each wafer is etched and polished.

That is, as a result of various studies on efficient chamfering methods for single crystals, the inventors of the present invention have found that the surface of a wafer cut from a single crystal is roughly ground and lapped in the usual manner, and then etched.
The amount of etching can be minimized by stacking multiple wafers and etching only their end faces, and then removing the stack and etching the surface of each wafer. The present invention was completed by discovering that it is possible to easily and reliably obtain mirror-finished wafers, since the end faces of the wafers are sufficiently treated by etching during stacking, so that no scratches remain on the end faces. I let it happen.

In the method of the present invention, the single crystal may be cut out to a thickness of 650 to 600 μm using, for example, an internal diamond cutter or a wire saw. When the material is a strong dielectric such as lithium, it is preferable to form it into a single domain before cutting it out. The surface of the wafer cut out in this way is then subjected to rough grinding and lapping processing, but this rough grinding may be done by grinding with fixed diamond abrasive grains or by grinding with aluminum oxide or silicon carbide free abrasive grains. Lapping may also be carried out in a conventional manner using aluminum oxide or silicon carbide abrasive grains.

This wrapped wafer is then commercialized by etching its entire surface, but in the method of the present invention, prior to etching, a plurality of wafers are overlapped and the end surfaces are etched at once. be done. For example, as shown in Fig. 1, this stacking is performed by stacking a plurality of single crystal wafers 1 that have been cut out, roughly ground, and wrapped, and then pressing the top and bottom of the wafers with a Teflon jig 2. If desired, this etching may be performed using hot phosphoric acid only on the end face not covered by the Teflon jig, and the etching width may be approximately 20 μm.

The wafers with only their end faces etched in this way are then removed from the Teflon jig and unstacked, and then either separated one by one, or placed in a cassette etc. and placed in the etching solution at the same time. The surface of the wafer only needs to be etched by about 5 μm, and the wafer thus obtained can easily be made into a mirror-finished wafer with excellent physical properties by polishing the surface using a colloidal silica solution. can do.

The method of the present invention involves etching only the end face of a wafer that has been cut out in accordance with the conventional method, rough-grinding the edges, and wrapping the surface, and then chamfering the surface by etching and polishing the wafer. According to this method, the etching process is performed in two stages: edge treatment and surface treatment, and even if the edge etching process is strengthened to avoid leaving scratches on the edge part, there is no processing loss in the material due to etching. Because there will not be many
The advantage is that this processing can be done economically and with a high yield.

Next, examples of the present invention will be given, and parts in the examples indicate parts by weight.

Example: 29 kg of gadolinium, gallium, and garnet firing raw materials with a purity of 99.99% are placed in an iridium crucible with a diameter of 180 mm and a height of 180 mm, and heated to 1700°C using a high-frequency induction heating device to melt the gadolinium, gallium, and garnet. Immersed single crystal, diameter 106
After pulling a gadolinium gallium garnet single crystal with a diameter of 300 mm and a length of 300 mm, it was cylindrically ground to a diameter of 101 mm using a conventional method. After slicing into wafers, the end faces were roughly ground using a salinder using fixed diamond abrasive grains, and then lapping was performed using aluminum oxide or SiC abrasive grains (average grain size approximately 15 μm).

Next, 100 of these wafers were stacked, Teflon holders were placed on top and bottom of the wafers, and they were tightened with a pressure of 1 kg/cm ² . Only the end faces were etched by about 15 μm with hot phosphoric acid, and then the Teflon holders were removed. When the surface of the gadolinium/gallium/garnet wafer was etched to approximately 5 μm, and then this surface was polished using colloidal silica,
Mirror-polished gadolinium with a diameter of 100.2 mm and a thickness of 500 μm.
A gallium garnet single crystal was obtained, which had no processing defects on either the end face or the surface, and the processing yield in this case was 99%.

However, when we etched the wrapped wafer by approximately 5 μm in an etching device after cutting the wafer without performing the above etching process on the end face, the resulting wafer had scratches on the end face, and the yield was low. It was 10%.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal sectional view of stacking of wafers using a Teflon holding device before etching in the method of the present invention. 1...Wafer, 2...Teflon presser, 3
……End face.

Claims (1)

[Claims] 1. A wafer is created by cutting a single crystal into a predetermined shape, the end face of the wafer is roughly ground and surface lapping is performed, then a plurality of these wafers are stacked and only the end face of the wafer is etched. , a method for producing single crystal wafers, characterized in that the entire surface of each wafer is etched and polished. 2. The method for manufacturing a single crystal wafer according to claim 1, wherein the stacked wafers are fixed with a Teflon jig.