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Browse Prior Art Database

Production of Complementary IGFETs

IP.com Disclosure Number: IPCOM000077978D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Kroell, K: AUTHOR [+2]

Abstract

The present method of producing complementary field-effect transistors (FETs) requires only four photolithographic steps up to metallization. Only one step is needed to produce the source/drain regions for the P and the N channel FETs. The method also permits the formation of self-adjusting gates as the gate dielectric serves as a mask for the source/drain diffusion.

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Production of Complementary IGFETs

The present method of producing complementary field-effect transistors (FETs) requires only four photolithographic steps up to metallization. Only one step is needed to produce the source/drain regions for the P and the N channel FETs. The method also permits the formation of self-adjusting gates as the gate dielectric serves as a mask for the source/drain diffusion.

As is shown in Fig. 1, N- substrate 1 is first coated with SiO(2) layer 2 followed by Si(3)N(4) layer 3. The thickness of layers 2 and 3 is about 1000 Angstroms. Apertures for the source and drain regions of the complementary FETs are etched into these layers in a first photolithographic step. Then the full semiconductor surface is coated with boron-doped oxide layer 4.

The apertures for the P wells of the N channel FETs in layer 4 are produced in.a second photolithographic step (Fig. 2), without Si(3)N(4) layer 3 being affected. P wells 5 are formed by ion implantation. The energy of the implanted boron ions is chosen so that they penetrate the 1000 Angstroms thick layers 2 and 3, extending sufficiently far into substrate 1. No source and drain regions 6 are diffused into p wells 5. During this heat treatment boron from doped oxide layer 4 simultaneously diffuses into substrate 1, leading to P+ source and drain regions 7 of the p channel FETs being formed.

Doped oxide layer 4 is completely etched off. In a third photo-lithographic step, layers 2 and 3 are removed i...