Fishing – trapping – and vermin destroying
Patent
1989-08-23
1990-12-11
Hearn, Brian E.
Fishing, trapping, and vermin destroying
437 15, 437228, 437904, H01L 21302
Patent
active
049771078
ABSTRACT:
Rectifiers of excellent characteristics may be more economically fabricated by a process in which a cavity is first etched in a non-epitaxial semiconductor wafer to a depth in the range of typically 15-25 percent of the initial wafer thickness. Simultaneous diffusion of N and P type dopants is used to provide (for an N type substrate) a P+ region in the bottom of the cavity and surrounding surface, and an N+ region on the opposite face of the wafer. A mask is then provided in the cavity bottom and the surrounding wafer regions etched to remove the P+ dopant outside the cavity thereby re-exposing the surrounding region of the original N type substrate. The P+ region may be level with or protrude slightly from the substrate surface. The junction formed between the P+ region in the cavity bottom and the N type substrate has a gradual contour where it intersects the surface thereby providing a more favorable field distribution. Passivation and metallization are provided in the conventional manner. The resulting devices may be fabricated in very thin wafers without significant mechanical breakage loss.
REFERENCES:
patent: 4040084 (1977-08-01), Tanaka et al.
patent: 4524376 (1985-06-01), Cornick
patent: 4636269 (1987-01-01), Boland
Dang Trung
Handy Robert M.
Hearn Brian E.
Motorola Inc.
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