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Method of Producing Defined Edge Profiles in the P+ Polysilicon of a FET Process

IP.com Disclosure Number: IPCOM000052546D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Briska, M: AUTHOR [+2]

Abstract

To obtain a well-defined profile with oblique edges in the P+ doped polysilicon, the desired profile is produced by wet etching a silicon dioxide layer pyrolytically grown on the polysilicon layer, by imaging this profile in the P+ polysilicon layer by arsenic implantation, and by removing the arsenic-doped polysilicon by etching with a mixture of ethylene diamine, pyrocatechol and water.

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Method of Producing Defined Edge Profiles in the P+ Polysilicon of a FET Process

To obtain a well-defined profile with oblique edges in the P+ doped polysilicon, the desired profile is produced by wet etching a silicon dioxide layer pyrolytically grown on the polysilicon layer, by imaging this profile in the P+ polysilicon layer by arsenic implantation, and by removing the arsenic-doped polysilicon by etching with a mixture of ethylene diamine, pyrocatechol and water.

On a silicon wafer 1, on whose surface source and drain regions S and D are defined and on which layers of silicon dioxide 2, silicon nitride 3 and p+ doped polysilicon 4 are arranged, a silicon dioxide layer 5 is pyrolytically grown. Layer 5 is covered with a photoresist layer 6 in which a mask is generated by conventional methods. The desired edge profile 7 is etched into the pyrolytic oxide 5 by means of buffered hydrofluoric acid (Fig. 1). The steepness of the edge profile 7 depends on the hydrofluoric acid content of the buffered etch solution used and on the composition of the oxide layer 5.

After the photoresist 6 has been removed arsenic is implanted over the whole area at a dose of preferably 1 x 10/16/ arsenic atoms over cm/2/. During implantation, edge profile 7 of the pyrolytic silicon dioxide 5 is imaged in the P+ polysilicon layer 4 (Fig. 2). After the pyrolytic oxide 5a has been removed by etching with buffered hydrofluoric acid, the polysilicon layer 4, with the arsenic- implanted re...