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SELF-LIMITING ETCH PROCESS FOR REFRACTORY CONTACTS TO GaAs DEVICES

IP.com Disclosure Number: IPCOM000034836D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Hoh, PD: AUTHOR [+5]

Abstract

Disclosed is a dry etching process for refractory contact metals, such as Ni, Pt, Pd and Mn with acceptable selectivity over GaAs or bilayered GaAs/AlGaAs substrates. These refractory metal films cannot be delineated by a conventional reactive ion etching method using halogen gas plasmas, limiting a choice of refractory metals for electrical contacts of GaAs devices. The present technique opens up this limitation by combining a physical sputtering of refractory metals by Ar plasma and a polymer deposition on GaAs by hydrocarbon or fluorocarbon gas plasmas, such as C2H4 and C2F6 . In a conventional reactive ion etching reactor configuration, argon ions contribute mostly to physical sputtering, while hydrocarbon radicals tend to form a passivation layer on the surface.

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SELF-LIMITING ETCH PROCESS FOR REFRACTORY CONTACTS TO GaAs DEVICES

Disclosed is a dry etching process for refractory contact metals, such as Ni, Pt, Pd and Mn with acceptable selectivity over GaAs or bilayered GaAs/AlGaAs substrates. These refractory metal films cannot be delineated by a conventional reactive ion etching method using halogen gas plasmas, limiting a choice of refractory metals for electrical contacts of GaAs devices. The present technique opens up this limitation by combining a physical sputtering of refractory metals by Ar plasma and a polymer deposition on GaAs by hydrocarbon or fluorocarbon gas plasmas, such as C2H4 and C2F6 . In a conventional reactive ion etching reactor configuration, argon ions contribute mostly to physical sputtering, while hydrocarbon radicals tend to form a passivation layer on the surface. This polymer deposition rate varies from material to material depending on the sticking coefficient of a given radical species. Radicals are chosen which give a polymer deposition rate much slower than argon sputtering rate on the metal, but faster than the sputtering rate on GaAs. Thus, those two competing processes result in an etching of metals to a finite depth and a deposition of a passivating polymer layer on GaAs. Plasma parameters are easily tuned so that a self- limiting etch depth is equal to a thickness of metal film. The feasibility has been demonstrated for NiInW/GaAs contact. Typical thickness of the NiIn contact is 20 nm and can be removed by physical sputtering at a rate of 1 - 2 nm/min by argon plasma at 10 mTorr/200 W. Etch rates are roughly the same for all refractory metals including their composites. To stop the etch at the GaAs l...