International Business Machines Corporation

Korea Advanced Institute of Science and Technology

Byung T Ahn

Wen Yaung Lee

Jeong Nam Lee

Robert B Beyers

Dae G Moon

A method is disclosed for the production of polycrystalline silicon thin films characterized by performing heat treatment of amorphous silicon thin films deposited on a substrate at a relatively low temperature of between 300.degree. and 600.degree. C. under a pressure ranging from 10.sup.-3 to 1 torr. The method can provide polycrystalline silicon thin films having increased grain sizes of about 60-300 .mu.m. In accordance with the method, glass or ceramic substrates can be used instead of an expensive quartz substrate. SiH.sub.4 gas can also be used instead of Si.sub.2 H.sub.6 gas as a source gas. The polycrystalline silicon thin films disclosed have an electron and positive hole mobility closer to that of the level of single crystals, and thus the development of the SOI element having high performance such as TFT for LCD, or TFT for SRAM, and the like may be greatly advanced.

Method of the production of polycrystalline silicon thin films

Improved processes for making thin film and bulk thallium superconductors are described, as well as Tl superconductors having high critical current densities and low surface impedance. An annealing step in a reduced oxygen atmosphere is used to convert compounds containing thallium, calcium, barium and copper to a Tl-2223 superconducting phase or to convert an oxide having the nominal composition Tl.sub.2 Ca.sub.2 Ba.sub.2 Cu.sub.3 O.sub.x to a crystalline Tl-2223 phase. The oxygen pressure during annealing is controlled to be below the thermodynamic stability limit for conversion of Tl-2223 to Tl-2122 and secondary phases. Temperatures less than 880.degree. C. are used, the oxygen pressure being sufficient to prevent excess thallium loss so that the Tl content in the final Tl-2223 phase is Tl.sub.1.6-2.0. Electrical devices including SQUIDs can be made with these improved superconductors.

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Seoul, South Korea

Byung T Ahn