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Diffusion Mask for GaAs

IP.com Disclosure Number: IPCOM000075558D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Burkhardt, PJ: AUTHOR [+2]

Abstract

This composite silicon-silicon nitride layer adheres to GaAs during diffusion and provides improved delineation of the impurity region. ABA thin film of silicon nitride on the order of 1000 Angstroms will block the diffusion of zinc into GaAs, but it cannot be applied directly to GaAs as the nitride film will not adhere during the diffusion cycle. When an intermediate layer such as SiO2 is used to bond the silicon nitride to the GaAs, problems are encountered in preventing damage to the exposed surface caused by etchants capable of removing silicon nitride.

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Diffusion Mask for GaAs

This composite silicon-silicon nitride layer adheres to GaAs during diffusion and provides improved delineation of the impurity region. ABA thin film of silicon nitride on the order of 1000 Angstroms will block the diffusion of zinc into GaAs, but it cannot be applied directly to GaAs as the nitride film will not adhere during the diffusion cycle. When an intermediate layer such as SiO2 is used to bond the silicon nitride to the GaAs, problems are encountered in preventing damage to the exposed surface caused by etchants capable of removing silicon nitride.

In this process a metal film, preferably aluminum, having a thickness on the order of 5000 Angstroms is evaporated on the GaAs wafer surface. Using conventional photolithographical techniques the metal is removed everywhere, except in the area to be diffused. Thereafter, a thin silicon layer is deposited by RF sputtering from a silicon target. Initially, argon is used to produce approximately a 700 Angstrom layer of silicon. This is followed by introducing nitrogen into the sputtering chamber and to deposit 800 additional Angstroms of silicon nitride. The silicon-silicon nitride film is deposited directly over the relatively thick metal film. Diffusion openings are then made in the silicon-silicon nitride film by introducing the wafer into an aluminum etch. The aluminum etch attacks the relatively thick metal film along the edges, thereby removing the overlying silicon-silicon nitride f...