JPH053438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of manufacturing a lithium tantalate single crystal wafer by chamfering a specific region of the peripheral edge portion of the wafer.

(Prior art) Lithium tantalate single crystals are provided as wafers with polished surfaces for use in various devices such as SAW devices. Conventionally, wafers have been subjected to a polishing process and further to a device fabrication process without being chamfered.

However, the {102} plane of the crystal is a cleavage plane,
Cracks tend to occur at the edges, which tends to cause small pieces to break off, resulting in a low yield.

(Structure of the Invention) The present inventors have chamfered a specific region of the peripheral edge of a lithium tantalate single crystal wafer, thereby significantly reducing the occurrence of cracks and chips in the polishing process and device fabrication. The present invention was completed based on the discovery that the yield was significantly improved.

That is, in the present invention, the peripheral edge portion of a lithium tantalate single crystal wafer is measured from point P to 0.1t≦X≦ on the line between the edge apex P, the point P, and the wafer center point 0 in the cross section in the thickness direction of the wafer. △ Connect point The present invention relates to a method for manufacturing a lithium tantalate single crystal wafer, characterized in that the PXY corresponding portion is chamfered in a direction that does not include the cleavage surface.

A detailed explanation will be given below based on the attached drawings.

FIG. 1 shows a cross section in the thickness direction of a lithium tantalate single crystal wafer. In the figure, P indicates the apex of the circumferential edge portion of the wafer, 0 indicates the wafer center point, and t indicates the wafer thickness. Then, X is on the line connecting point P and wafer center point 0, and is at a distance from point P within the range of 0.1t≦X≦1.5t, and Y is on the line from point P in the wafer thickness direction. 0.1t≦Y≦0.5t from Tekatsu P point
at a distance of The present invention is a specific area where X and Y satisfy such conditions. This is the △PXY part and does not include the cleavage surface. In a lithium tantalate single crystal, for example, in the case of V-axis pulling, this cleavage plane is in the direction of 30 degrees when viewed from the Z plane and 53 degrees when viewed from the Y plane, so the wafer edge portion corresponding to the △PXY portion that does not include that direction It is characterized by chamfering the entire circumference.
In this case, the line segment X-Y may be linear or arcuate (see FIG. 2 below).

FIG. 2 shows a specific example of a chamfered wafer according to the present invention, and FIG.
-The corresponding portion of Y is linear. It is desirable that the bent portions marked with * in Figure 2 be shaved off smoothly. Note that the circumferential edge portions of at least the upper surface or both the upper and lower surfaces of the wafer are chamfered, but the chamfered shapes may be the same or different on both surfaces.

In the present invention, the wafer chamfering process involves slicing a lithium tantalate single crystal using an inner peripheral blade or the like, and then scraping the circumferential edge portion of the wafer using a polishing plate and abrasive grains (GC#1000, etc.). However, other methods may of course be used.

The lithium tantalate single-crystal wafer of the present invention does not cause cracks or chips larger than 0.1 mm during the wrapping process, polishing process, and device manufacturing process such as SAW devices due to the abrasive grains. Therefore, a higher yield can be achieved compared to lithium tantalate single crystal wafers that are not chamfered in the conventional manner.

Next, specific examples will be given.

Example X-axis pulled lithium tantalate single crystal (diameter 3
Wafers are made by slicing 0.7 mm thick (inches) into 0.7 mm thick pieces, and using a 70R polishing plate and GC#1000 abrasive grains, handle lapping and chamfering the wafers to create the cross-sectional shape shown in Figure 2. However, the chamfer direction was 20°.

The wafers chamfered as described above were lapped on both sides using GC#1000 abrasive grains, and then polished on one side using colloidal silica to form lithium tantalate single crystal wafers with a thickness of 0.5 mm. This was used to create a SAW device element. 0.1 in this wrapping process, polishing process, and device element creation process.
There were no chips larger than mm, and compared to when no chamfering was done,
Yield was significantly improved.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a lithium tantalate single crystal wafer in the wafer thickness direction to explain the chamfered portion.
The figure illustrates a partial cross-sectional view of a wafer chamfered according to the present invention.

Claims (1)

[Claims] 1. A peripheral edge portion of a lithium tantalate single crystal wafer, in a cross section in the thickness direction of the wafer,
Edge apex P, point A lithium tantalate single crystal characterized by chamfering in a direction that does not include the cleavage surface at the △PXY equivalent part connecting point Y at a distance within the range of 0.1t≦Y≦0.5t on a line in the horizontal direction. Wafer manufacturing method.