Patent · US Expired

Method for manufacturing regions having adjustable uniform doping in silicon crystal wafers by neutron irradiation

US4728371A · kind A · utility

2Cited by

8References

15Claims

0Family size

Assignee

Siemens Aktiengesellschaft · DE

Inventors

Ernst Haas · Buckenhof, DE
Joachim Martin
Heinz Mitlehner · Uttenreuth, DE
Reinhold Kuhnert · Munich, DE

Key dates

Filing date	Mar 11, 1986
Grant date	Mar 1, 1988
Priority date	—
Expiry date	Mar 11, 2006

Classification

Technology area (CPC Y)Emerging Cross-Sectional Technologies
CPC primaryY10S148/165
WIPO fieldSurface technology, coating
WIPO sectorChemistry

Abstract

A method for manufacturing regions having adjustable uniform doping in silicon crystal wafers by neutron irradiation according to the reaction Si.sup.30 (n,.gamma.) Si.sup.31 .beta..sup.- P.sup.31 includes the steps of covering the silicon crystal wafer with neutron-absorbing materials of different thicknesses during the irradiation, and selecting materials having isotopes having a high absorption cross-section which yield stable isotopes in the nuclear reaction having small or short-lived activity. Suitable isotopes are B.sup.10, Cd.sup.113, Sm.sup.149, Gd.sup.155 and Gd.sup.157. The regions are generated photolithographically. By such specific material selection, very small layer thicknesses can be used and microfine surface zones or areas can be doped with high geometrical precision and large penetration depth. The method is particularly suited for manufacturing power thyristors.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.