engleski

SiOx thin films prepared by magnetron sputtering

Tunable resistivity and optical properties make silicon oxide films excellent material for applications in microelectronic and optoelectronic circuits. While SiOx<2 films is preferred material for passivation layers in MIS devices, "sacrifice" layers in MEMS technology, and as a precursor material for production of crystalline Si nanoclusters in a SiO2 matrix, the stoicihiometric SiO2 is used as insulator in microelectronics, optical coatings and as support for heterogeneous catalysis. Several methods for production of SiOx thin films have been employed so far: vacuum evaporation, laser ablation, sol-gel, CVD and sputtering. The reactive magnetron sputtering is particularly promising in large area deposition. By using different targets (Si, SiO, SiO2), either in single target or codeposition mode, and by variation of oxygen fraction in Ar+O2 plasma a precisely controlled stoichiometry of SiOx films can be achieved. However, beside silicon and oxygen, a various contaminants might be present in magnetron-deposited films: hydrogen, argon and even transition metals from inadvertently sputtered magnetron components, which might hinder a proper functioning of the produced film. Such impurities should be avoided, and we present a few strategies which we have used in KJLC CMS18 sputtering system for preparation of SiOx≈ 2 layers in a multilayer stacks. SiOx≈ 2 layers have been deposited by RF sputtering of pure SiO2 targets onto two kinds of substrates - monocrystalline silicon and fused silica. Three magnetron (target dia 3") geometries were tested: as-received, with protective silica ring inserted, and with dark space shield lip mounted. The working gas (argon) pressure, discharge power, and substrate temperature were varied in order to investigate their influnce upon impurities level in the prepared films. Finally, a fraction of oxygen was added to the argon, in order to improve the stoichiometry of the SiOx≈ 2 by reactive sputtering. A chemical composition (a matter of primary interest here) of the prepared films has been examined by Rutherford backscattering analysis and by Infra Red transmission spectra. The obtained results confirm that the contamination of the SiOx≈ 2 films can be greatly reduced by proper geometry of the magnetron device discharge region, and stoichiometry improved by control of the deposition parameters.

SiOx; thin films; magnetron sputtering

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