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Method of Determining an N+ Area in an N- Environment

IP.com Disclosure Number: IPCOM000041330D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Beck, S: AUTHOR [+3]

Abstract

A method is described which permits marking different concentration areas in an N-doped environment by anodically etching bevelled wafer zones. A control wafer with an N+ subcollector in an N-substrate below an N-epitaxial layer is bevelled. The bevelled zone is etched by means of a 10 percent hydrofluoric acid solution in an etch system at about 5 V for about 1 min. Etching is effected in those areas at the boundary of which the electric field is so strong as to cause an avalanche breakdown. At 5 V, this breakdown occurs in areas with an N+ doping > 2 x 1018 At/cm2 . The etched areas are sharply defined and their expansion can be accurately determined. By suitably selecting the voltage applied, etch marking may also be used for other doping concentrations.

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Method of Determining an N+ Area in an N- Environment

A method is described which permits marking different concentration areas in an N-doped environment by anodically etching bevelled wafer zones. A control wafer with an N+ subcollector in an N-substrate below an N-epitaxial layer is bevelled. The bevelled zone is etched by means of a 10 percent hydrofluoric acid solution in an etch system at about 5 V for about 1 min. Etching is effected in those areas at the boundary of which the electric field is so strong as to cause an avalanche breakdown. At 5 V, this breakdown occurs in areas with an N+ doping > 2 x 1018 At/cm2 . The etched areas are sharply defined and their expansion can be accurately determined. By suitably selecting the voltage applied, etch marking may also be used for other doping concentrations. By means of this method, equiconcentration lines within N-doped areas can be produced in bevelled zones. Compared with existing measuring methods, such as SIMS (secondary ion mass spectrometry) or spreading resistance, the described method has the advantage that it can be implemented without extensive means and expenditure in simple, existing systems.

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