Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Patent
1995-11-06
1998-10-20
Brown, Peter Toby
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
257754, 257757, 257763, 257769, 438457, 438715, H01L 2348
Patent
active
058250905
ABSTRACT:
This high-power semiconductor device comprises (a) a disk of refractory metal having flat faces at its opposite sides and (b) two wafers of a semiconductor material having a coefficient of expansion similar to that of the refractory metal, the wafers being alloyed to the faces of the refractory metal disk in substantially aligned relationship to each other to form an assembly of the wafer and the disk with alloyed joints between the wafers and the disk. The alloyed joints are formed at elevated temperatures, and the wafers are of such size and thickness that the tendency of the wafer at one side of the disk to cause bowing of the assembly upon cooling of the assembly following formation of the alloyed joints is counteracted by a substantially equal and opposite tendency of the wafer at the opposite side of the disk to produce a substantially equal and opposite amount of bowing of the assembly, thereby resulting in a substantially flat assembly of the wafers and the disk upon cooling of the assembly following formation of the alloyed joints.
The refractory metal disk is of tungsten or molybdenum, has a diameter of at least 11/2 inches, and has a thickness of at least 5 mils and of such thickness value that if the wafer at one side of the disk were omitted so that a single wafer disk was present, the single wafer assembly would be subject to substantial bowing when it cooled following formation of the alloyed joint between the disk and the remaining wafer.
A method of making this device is also claimed.
REFERENCES:
patent: 3532942 (1970-10-01), Boyer
patent: 3890637 (1975-06-01), Yamamoto
patent: 4826787 (1989-05-01), Muto et al.
patent: 5005069 (1991-04-01), Wasmer et al.
patent: 5173446 (1992-12-01), Asakawa et al.
patent: 5183769 (1993-02-01), Rutter et al.
Brown Peter Toby
Freedman William
Potter Roy
Silicon Power Corporation
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