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Etching PNP Junctions

IP.com Disclosure Number: IPCOM000098720D
Original Publication Date: 1959-Oct-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Beliveau, M: AUTHOR [+3]

Abstract

In the process of forming an alloy junction 10 in a transistor 11, the lead alloy impurity dot 12 becomes molten and spreads out. Upon cooling a skirt 13 forms which undesirably short circuits the junction. To remove the skirt, a thin film 14 of a solution comprising 96 parts of water, 32 parts of glacial acetic acid, and 5 parts of 30% hydrogen peroxide is deposited by an atomizer 15 on the transistor in the region about the dot. Then a current supplied by a source 16, which has its positive terminal connected to the lead 17 embedded in the dot 12 and its negative terminal connected to the base ring 18, is passed through the film 14 to etch away the skirt 13 and create an annular groove 19 as represented in the lower left hand figure.

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Etching PNP Junctions

In the process of forming an alloy junction 10 in a transistor 11, the lead alloy impurity dot 12 becomes molten and spreads out. Upon cooling a skirt 13 forms which undesirably short circuits the junction. To remove the skirt, a thin film 14 of a solution comprising 96 parts of water, 32 parts of glacial acetic acid, and 5 parts of 30% hydrogen peroxide is deposited by an atomizer 15 on the transistor in the region about the dot. Then a current supplied by a source 16, which has its positive terminal connected to the lead 17 embedded in the dot 12 and its negative terminal connected to the base ring 18, is passed through the film 14 to etch away the skirt 13 and create an annular groove 19 as represented in the lower left hand figure. This exposes the periphery 20 of the junction 10 and removes the short circuit without eroding the dot 12 sufficiently to weaken its mechanical support for the lead 17. The magnitude of the etching current and its time of flow are governed by the parameters of the transistor. A current of several milliamperes flowing for several seconds is usually sufficient. It has been found that further electrolytic clean up etching in an alkaline bath by well known techniques now more effectively removes the low-resistance semiconductor material 21 about the periphery 20 of the junction. The removal of this material creates an annular pit 22, represented in the lower right hand figure, and desirably increases the breakdown...