JPS61146799A - Single crystal wafer of lithium tantalate - Google Patents

Abstract

PURPOSE:To reduce cracks and chips formed in a polishing process and in the formation of a device and to improve the yield by chamfering the specified region of the peripheral edge part of a lithium tantalate single crystal wafer. CONSTITUTION:The peripheral edge part of the lithium tantalate single crystal wafer corresponding to DELTAPXY at the cross section of the water in the thickness direction is chamfered. In this case, point P is the vertex of the edge part, and X is in a line linking point P and the central point O of the wafer and at the distance of 0.1t<=X<=1.5t (t is the thickness of the wafer) from the point P. Point Y is on line of the thickness direction and at the distance of 0.1t<=Y<=t/2 from the point P. The cracks and especially chips having >=0.1mm size are never generated in the obtained lithium tantalate single crystal wafer, when the crystal is lapped by abrasive grains and polished or used for the formation of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a lithium tantalate single crystal wafer obtained 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. The wafer is
Conventionally, the material was subjected to the polishing process and further to the device manufacturing process without being chamfered.

However, the (102) plane of the crystal is a cleavage plane.

Cracks tend to occur at the edges, and small pieces tend to break off, resulting in a low yield.

(Structure of the Invention) The present inventors have chamfered a specific region of the peripheral edge portion of a lithium tantalate single crystal wafer to prevent cracks and chips from occurring during the polishing process and during device fabrication. The present invention was completed based on the discovery that the amount was significantly reduced and the yield was significantly improved.

That is, in the present invention, the peripheral edge portion of a lithium tantalate single crystal wafer is separated by 0.1 from point P on the line between the edge apex P, the point P, and the wafer center point ○ in the cross section in the thickness direction of the wafer. t ≦ X ≦ 1.5 with a point X located at a distance within the range of (t: wafer thickness),
A lithium tantalate single crystal characterized by being chamfered at a portion corresponding to ΔPXY connecting point P to point Y located at a distance within the range of 0.1 t≦Y≦t/2 on a line in the thickness direction. It concerns wafers.

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 is the apex of the circumferential edge portion of the wafer, 0 is the center point of the wafer, t is the thickness of the wafer, and X is on the line connecting point P and wafer center point 0, and 0.1 from point
t ≦X≦1.5 The distance is within the range of t, and Y
is on a line in the wafer thickness direction from point P, and is at a distance of 0.1t≦Y≦t/2 from point P.
and ΔPX, where Y is a specific area that satisfies such conditions.
The wafer edge portion corresponding to Y is chamfered over the entire circumference. In this case, the line segment X-Y may be linear or arcuate (see Figures 2 and 3 below).
(see figure).

Figures 2 and 3 show specific examples of chamfered wafers according to the present invention. In Figure 2, the portion corresponding to the line segment It becomes. In Figures 2 and 3, it is desirable to scrape off the bent portions marked with umbrella marks smoothly.Also, at least the circumferential edges of the upper surface or both the upper and lower surfaces of the wafer are chamfered, but this chamfered shape is The shapes may be the same or different on both sides.

In the present invention, chamfering of a wafer is performed by slicing a lithium tantalate single crystal using an inner circumferential blade or the like, and cutting the circumferential edge portion of the wafer using a polishing plate and abrasive grains (a).
C# toooo, etc.), but other methods may of course be used.

The lithium tantalate single crystal wafer of the present invention does not suffer from cracks or chips larger than 0.1 cm due to abrasive grains during the lapping process, polishing process, and device fabrication process such as SAW devices. Therefore, a higher yield can be achieved compared to lithium tantalate single crystal wafers that are not chamfered.

Next, a specific example will be given.

Voice Example I X-axis pulled lithium tantalate single crystal (3 inches in diameter)
A wafer was made by slicing it to a thickness of 0.7 am, and this was subjected to a hunt wrapping chamfering process using a 7OR polishing plate and G C#100G abrasive grains so that it had the cross-sectional shape shown in Figure 2. I strained it.

The wafers chamfered as described above were lapped on both sides using G C111000 abrasive grains, and then polished on one side with colloidal silica to form lithium tantalate single crystal wafers with a thickness of 0.5 m. This was used to fabricate a SAW device element. In this lapping process, polishing process, and device element fabrication process, there were no chips larger than 0.1 mm, and the yield was significantly improved compared to the case where one chamfering process was not performed.

Example 2 A wafer (thickness: 0.5 mm) obtained by slicing in the same manner as in Example 1 was cut into a cross-sectional shape as shown in FIG. 3 using a chamfering machine using fixed abrasive grains (1600). It has been processed to look like this.

The wafer was chamfered in this way.

In the subsequent lapping process, polishing process, and device element fabrication process, no chipping larger than 0.11 occurred, which was excellent.

[Brief explanation of the drawing]

Figure 1 shows a lithium tantalate single crystal wafer.
This is a cross-sectional view in the wafer thickness direction for explaining the chamfered portion, and FIGS. 2 and 3 are partial cross-sectional views of the chamfered wafer according to the present invention. be.

Claims (1)

[Claims] 1. The peripheral edge portion of a lithium tantalate single crystal wafer is measured from point P on the line between the edge apex P and the point P and the center point O of the wafer in a cross section in the thickness direction of the wafer. 1t≦X≦1.5 with a point X located at a distance within the range of (t: wafer thickness),
A lithium tantalate single crystal wafer characterized by being chamfered at a portion corresponding to ΔPXY connecting point P to point Y located at a distance within the range of 0.1t≦Y≦t/2 on a line in the thickness direction. .