Shin-etsu Handotai Co., Ltd.

Masao Fukami

Atsuo Uchiyama

Tatsuo Ito

In a method for preparing a substrate for semiconductor device, the substrate is prepared either by directly bonding a bonding wafer to a base wafer or by bonding the bonding wafer to the base wafer with an oxide film formed on at least the bonding surface of the bonding wafer or the bonding surface of the base wafer to make finished semiconductor devices with an SOI structure. Prior to the bonding operation, the bonding wafer and the base wafer are subjected to the steps of (1) making the diameter of the bonding wafer smaller than the diameter of the base wafer, (2) setting the beveling width of the back side (bonding side) of the bonding wafer at 50 microns or less, and (3) beveling the front side of said base wafer so that the bonding surface of the base wafer is equal in size to the bonding surface of the bonding wafer. When the bonding wafer, which has been bonded to the base wafer, is subjected to polishing into a thin film, the peripheral portions of the bonding wafer form a smooth surface of the base wafer. This prevents the peripheral portions from chipping off.

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Nagano, Japan

Masao Fukami