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Reducing Intrinsic Tensile Stress in Thin Films of Niobium Tantalum and Other BCC Metals

IP.com Disclosure Number: IPCOM000075456D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Berry, BS: AUTHOR [+2]

Abstract

Reduction of internal stress is described for certain metallic thin films. It is well known that vacuum deposited thin films of the refractory metals are subject to extremely large intrinsic tensile stresses ~200,000 psi. Stresses of this magnitude impose a limit on the thickness of the film that can be deposited, before substrate cracking or film peeling takes place. Where an appreciable interstitial solubility exists, such as for oxygen in niobium, a substantial reduction of the stress can be obtained by heat treatments which cause the gaseous element to dissolve in the film. The reduction of the stress is achieved by the increase in the unrestrained lattice parameter, which accompanies the formation of the solid solution.

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Reducing Intrinsic Tensile Stress in Thin Films of Niobium Tantalum and Other BCC Metals

Reduction of internal stress is described for certain metallic thin films. It is well known that vacuum deposited thin films of the refractory metals are subject to extremely large intrinsic tensile stresses ~200,000 psi. Stresses of this magnitude impose a limit on the thickness of the film that can be deposited, before substrate cracking or film peeling takes place. Where an appreciable interstitial solubility exists, such as for oxygen in niobium, a substantial reduction of the stress can be obtained by heat treatments which cause the gaseous element to dissolve in the film. The reduction of the stress is achieved by the increase in the unrestrained lattice parameter, which accompanies the formation of the solid solution. The magnitude of the stress relief obtainable with a given solute level can both be calculated and checked experimentally. Tests performed with Nb films, show a marked factor of 2 reduction in stress by oxygen solution.

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