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Heterostructures With Self-Aligned Trenches

IP.com Disclosure Number: IPCOM000062470D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Frank, DJ: AUTHOR [+3]

Abstract

Self-aligned isolation trenches may be formed, separating specific regions in a semiconductor layer, by providing a reactive ion etch (RIE) resistant pattern above the layer and an RIE resistant layer on the surface of the semiconductor layer. The composite is then etched in an ambient that will not etch the surface protection layer, but will etch the pattern layer slowly and the semiconductor rapidly. When the semiconductor is GaAs, the pattern layer may be Mo, the surface protection layer may be formed when FREON 14* and oxygen are used to etch the Mo, and the trench forming etch may be FREON 12 and helium. An RIE resistant layer, such as AlGaAs, may also be used between the semiconductor layer and the substrate, if desired. The structure is shown in Fig 1.

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Heterostructures With Self-Aligned Trenches

Self-aligned isolation trenches may be formed, separating specific regions in a semiconductor layer, by providing a reactive ion etch (RIE) resistant pattern above the layer and an RIE resistant layer on the surface of the semiconductor layer. The composite is then etched in an ambient that will not etch the surface protection layer, but will etch the pattern layer slowly and the semiconductor rapidly. When the semiconductor is GaAs, the pattern layer may be Mo, the surface protection layer may be formed when FREON 14* and oxygen are used to etch the Mo, and the trench forming etch may be FREON 12 and helium. An RIE resistant layer, such as AlGaAs, may also be used between the semiconductor layer and the substrate, if desired. The structure is shown in Fig
1. As an alternative, the RIE processing is to pattern the molybdenum film with photoresist (PR) and then plasma oxidize the surface of the molybdenum. In this, the oxide acts as an etch inhibitor. Next, the molybdenum film is etched in FREON 14 and oxygen for the time required to reach the underlying GaAs surface. A trench is formed at the interface of the photoresist and the molybdenum film which conforms to a mask design. The photoresist is then removed and the GaAs that is exposed through the trench in the molybdenum is etched in a FREON 12 and helium ambient for the length of time required to stop at the AlGaAs surface. The slit in the molybdenum would then contr...