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Metal Contacts for Cermet Film Resistors

IP.com Disclosure Number: IPCOM000092421D
Original Publication Date: 1966-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Glang, R: AUTHOR

Abstract

Certain metal contacts, particularly aluminum, have limited thermal stability when used as the contacts for cermet resistors. Silicon monoxide-chromium cermet resistance films of the order of 100 ohms are particularly affected when aluminum contacts are used. The aluminum contact resistance is due to out-diffusion of chromium which enters the adjacent aluminum film. This process leaves the cermet film depleted of its conductive constituent and thus contributes to the additional resistance. To avoid this situation, the out-diffusion from the cermet film must be prevented. The following procedures can be used to prevent out-diffusion.

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Metal Contacts for Cermet Film Resistors

Certain metal contacts, particularly aluminum, have limited thermal stability when used as the contacts for cermet resistors. Silicon monoxide-chromium cermet resistance films of the order of 100 ohms are particularly affected when aluminum contacts are used. The aluminum contact resistance is due to out- diffusion of chromium which enters the adjacent aluminum film. This process leaves the cermet film depleted of its conductive constituent and thus contributes to the additional resistance. To avoid this situation, the out-diffusion from the cermet film must be prevented. The following procedures can be used to prevent out-diffusion.

1. The cermet film is covered with a thin film of chromium before aluminum contacts are deposited.

2. Deposit a chromium-aluminum alloy instead of pure aluminum for the resistor contacts. This deposition can be done by simultaneous evaporation from two sources, by flash evaporation or by sputtering of a suitable alloy.

3. Deposit an intermediate layer of a chromium-aluminum alloy as described in step 2 and continue with a film of pure aluminum.

In every case, the end contacts of aluminum are either presaturated with chromium or can draw chromium out of a reservoir at the interface without depleting the cermet of its conductive constituent.

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