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Control of Thin Film Grain Size by Lithographic Methods

IP.com Disclosure Number: IPCOM000053199D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Magerlein, JH: AUTHOR [+2]

Abstract

Thin films made of low melting point metals have been used in superconductive devices. These devices are usually required to withstand temperature changes during fabrication and operation. Thermal contraction mismatch between the film and the substrate introduces strain in the film, particularly in superconductive devices, for which the temperature change is about 300K. For example, for Pb deposited on a Si substrate, the strain introduced upon cooling from 300K to 4.2K is about 0.7%. Most films cannot support the strain elastically, and it is partially relaxed plastically. Such strain relaxation is believed to be a cause of device failures. Thus, it is desirable that the film elastically support the maximum strain upon thermal cycling.

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Control of Thin Film Grain Size by Lithographic Methods

Thin films made of low melting point metals have been used in superconductive devices. These devices are usually required to withstand temperature changes during fabrication and operation. Thermal contraction mismatch between the film and the substrate introduces strain in the film, particularly in superconductive devices, for which the temperature change is about 300K. For example, for Pb deposited on a Si substrate, the strain introduced upon cooling from 300K to 4.2K is about 0.7%. Most films cannot support the strain elastically, and it is partially relaxed plastically. Such strain relaxation is believed to be a cause of device failures. Thus, it is desirable that the film elastically support the maximum strain upon thermal cycling. Strain relaxation can be reduced by using films of reduced thickness and/or finer grain size. There are several techniques to achieve the latter, such as lowering the substrate temperature during film deposition, adding impurities, or evaporation in an O(2) gas atmosphere. However, these ``naturally'' grown grains have a distribution of grain sizes, which could cause undesirable local strain relaxation.

A new technique is proposed to prepare films with uniform fine grains. A pattern is produced on a substrate with features comparable to the grain size desired in the film. A simple set of parallel grooves cut into the substrate, as shown in Fig. 1, may be adequate. A two-dimen...