Browse Prior Art Database

Hole Opening in Polysilicon by Selective Doping and Removal Technique

IP.com Disclosure Number: IPCOM000052162D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Bartholomew, RF: AUTHOR [+3]

Abstract

In certain integrated circuit structures a hole in a polysilicon layer has to be opened to an underlying single crystalline silicon layer. Presently, a reactive ion etching step is used for this opening. However, it is extremely difficult to stop etching at the single crystalline surface, and severe overetching of the single crystalline layer can occur.

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Hole Opening in Polysilicon by Selective Doping and Removal Technique

In certain integrated circuit structures a hole in a polysilicon layer has to be opened to an underlying single crystalline silicon layer. Presently, a reactive ion etching step is used for this opening. However, it is extremely difficult to stop etching at the single crystalline surface, and severe overetching of the single crystalline layer can occur.

A method that offers greater control in etch selectivity is as follows: 1) Form desired hole geometry for polysilicon layer 8 on monocrystalline layer 10 using silicon dioxide layer 12 as a mask. Ion implant arsenic into intrinsic polysilicon layer 8 to form N /+/ region 14, as seen in Fig. 1. 2) Anneal to fully form Nregion 15 through the polysilicon layer and remove masking SiO(2) to form the Fig. 2 structure. 3) Ion implant boron into the polysilicon layer to convert the intrinsic polysilicon to Ppolysilicon, except in the N+ region 15, since the Nregion has higher concentration than P+. The N/+/ polysilicon region 15 remains as seen in Fig. 2. 4) The structure Is subjected to hot H(3)PO(4) or any suitable etchant to preferentially remove only Nregions 15 in polysilicon layer and automatically stop at intrinsic or P-type surfaces and the P silicon substrate, as seen in Fig. 3.

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