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Browse Prior Art Database

Thin Metal Film Protection Method for FET Gate Insulator

IP.com Disclosure Number: IPCOM000078071D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Anantha, NG: AUTHOR [+5]

Abstract

A thin metal film, eg., approximately 2,000 Angstroms of aluminum, is denosited over the surface of a field-effect transistor (FET) device wafer immediately following the gate oxide regrowth step, and prior to source and drain contact hole photoresist processing steps. Protection against mobile ion contamination of the gate oxide is afforded, without the need for any phosphosilicate glass gettering layer on the gate oxide.

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Thin Metal Film Protection Method for FET Gate Insulator

A thin metal film, eg., approximately 2,000 Angstroms of aluminum, is denosited over the surface of a field-effect transistor (FET) device wafer immediately following the gate oxide regrowth step, and prior to source and drain contact hole photoresist processing steps. Protection against mobile ion contamination of the gate oxide is afforded, without the need for any phosphosilicate glass gettering layer on the gate oxide.

A conventional process for making FET's includes the steps of initial oxidation of a silicon substrate, photoresist processing steps for defining source and drain diffusion windows, diffusion of the source and drain, and oxidation. Photoresist and etching steps next define the active device region, by stripping the oxide from above and between the source and rain. Gate oxide then is grown over the defined region and a layer of phosphosilicate glass is deposited, to stabilize the gate oxide against existing mobile ion contamination as well as subsequent mobile ion contamination introduced, for example, by subsequent handling and photoresist processing steps.

While the phosphosilicate glass layer is advantageous from the point of view of gettering contaminating mobile ions, the layer tends to introduce objectionable threshold voltage shift of the completed FET device due to polarization of the phosphosilicate glass layer. Additionally, care must be exercised to avoid excess phosphorus in th...