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Inorganic Lift-Off Process

IP.com Disclosure Number: IPCOM000041912D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Raacke, KH: AUTHOR [+2]

Abstract

This article describes a process for patterning using polysilicon as a lift-off mask. Among the advantages of this process over processes using conventional lift-off masks is the elimination of the organic contamination of the depositing insulating film and the film substrate interface, caused by the sputtered impurities of the photoresist. The process includes the following steps described with reference to Figs. 1 - 3: 1. Forming on a semiconductor substrate 10 a layer of an etching barrier material 12, such as, for example, a silicon dioxide or a silicon nitride layer, having a thickness of about 10 nm. 2. Depositing (through a conventional CVD (chemical vapor deposition) or LPCVD (low pressure chemical vapor deposition) process 1.0 to 1.5 mm of intrinsic polysilicon 14. 3.

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Inorganic Lift-Off Process

This article describes a process for patterning using polysilicon as a lift-off mask. Among the advantages of this process over processes using conventional lift-off masks is the elimination of the organic contamination of the depositing insulating film and the film substrate interface, caused by the sputtered impurities of the photoresist. The process includes the following steps described with reference to Figs. 1 - 3: 1. Forming on a semiconductor substrate 10 a layer of an etching barrier material 12, such as, for example, a silicon dioxide or a silicon nitride layer, having a thickness of about 10 nm. 2. Depositing (through a conventional CVD (chemical vapor deposition) or LPCVD (low pressure chemical vapor deposition) process 1.0 to 1.5 mm of intrinsic polysilicon 14. 3. Oxidizing the polysilicon layer 14 to form a layer 16 of 50 to 100 nm of silicon dioxide, or depositing a layer of another material having the appropriate etching selectivity to the underlying polysilicon layer. 4. Applying photoresist layer 17 on layer 16, and then exposing and developing the desired pattern. Etching layer 16 using either a reactive ion etching (RIE) or a wet etching process step, as shown in Fig. 2. 5. Using plasma etching to form a relatively large undercut in the polysilicon layer 14. One recommended process is to use the plasma etch with an etching ambient of 10% SF6 and 90% He which has been found to yield very high etch rate ratios for Si/SO2 structures. 6. Removing photoresist layer 17, and cleaning the structure with an oxygen plasma ash. 7. Forming an opening through the polysilicon layer using a directional dry etch, and completi...