Development of Thin-Film Active Device on an Improved Insulating Substrate.

摘要

Single-crystal magnesium aluminate spinel,within the compositional range Mg:1.OAl2O3to MgO:2.5Al2O3,has many advantages over other materials as a substrate material for epitaxial thin films of Si. This material has not previously been available,but as the result of recent preparative research at RCA Laboratories,research quantities of good single crystal can now be grown. The conditions are being optimized for the deposition of epitaxial films of Si on the spinel substrate material. Mobilities were realized in 1.5-microns-thick epitaxial Si films equal to bulk silicon mobilities for hole carrier concentrations greater than 2 x 10to the 16th power/cc. Electrical properties of these films are not significantly changed by the thermal oxidations commonly employed in device processing . Mobilities of both 'as-deposited'and thermally oxidized films are at least twice the mobility of thermally oxidized Si on sapphire with equivalent carrier concentrations. Below the 2 x 10to the 16th power/cc doping level the mobilities are less than bulk and more sensitive to oxidation. MOS structures in Si on spinel have given very promising results,and through-diffused junction diodes have been fabricated. Physical characteristics of the epitaxial Si-spinel composite have been measured by electron scanning microscopy,replica transmission microscopy,and x-ray and electron diffraction. The physical properties are correlated,where possible,with the electrical behavior of the Si films. (Author)