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Diffusion Using a Ternary Alloy Source

IP.com Disclosure Number: IPCOM000096502D
Original Publication Date: 1963-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Chamberlin, JB: AUTHOR [+4]

Abstract

A highly controllable and reproducible method of diffusing an impurity into semiconductor wafers makes use of a ternary alloy source. Wafers 10 of a material such as germanium are sealed along with ternary alloy source 11 in evacuated quartz capsule 12. Wafers 10 and source 11 are maintained in spaced relation in quartz holder 13 resting within the capsule. Diffusion furnace 14 has zone 15 which is capable of maintaining its temperature within +/-1 degrees C. This in turn assures a uniform diffusion and no erosion of the surface of wafers 10.

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Diffusion Using a Ternary Alloy Source

A highly controllable and reproducible method of diffusing an impurity into semiconductor wafers makes use of a ternary alloy source. Wafers 10 of a material such as germanium are sealed along with ternary alloy source 11 in evacuated quartz capsule 12. Wafers 10 and source 11 are maintained in spaced relation in quartz holder 13 resting within the capsule. Diffusion furnace 14 has zone 15 which is capable of maintaining its temperature within +/-1 degrees C. This in turn assures a uniform diffusion and no erosion of the surface of wafers
10.

Source 11 includes boat 16 made of the same type of germanium and of approximately the same resistivity as wafers 10. It is machined to hold other diffusant materials 17 which consist of electrically inactive tin and an electrically active material or conductivity-determining impurity such as indium. The surface concentration of the indium on the diffused wafers is determined by the amounts of tin and indium in boat 16 and by the diffusing temperature.

Ternary alloy source 11 comprising the germanium of boat 16 and the tin and indium in that boat satisfies the thermo-dynamic equilibrium conditions for the system. Undesired micro-alloying on the wafer surfaces does not result during diffusion of the indium into the wafers. Using this technique, an impurity such as gallium, antimony or tin are also diffused into germanium in lieu of indium.

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