Pulsed dc magnetron-sputtering of microcrystalline silicon

Nominally undoped silicon films were prepared by pulsed dc magnetron sputtering in a pure Ar atmosphere (without hydrogen dilution) at substrate temperatures in the range of 25-450degreesC. An asymmetrical bipolar pulsed de power generator was operated at pulse frequencies, f, in the range of 50-250 kHz. Crystalline films (muc-Si) were grown at 450degreesC. It is shown that with rising frequency the preferential orientation of the crystallites changes from (110) to (100). In addition, the Ar-content is strongly enhanced and this is connected with an enhancement of disorder in the films. Time-resolved Langmuir probe studies show that increasing the frequency causes an increase of the potential difference between the plasma and the grounded substrate. It is argued therefore that these effects arise from enhanced bombardment of the growing films with Ar+ ions of high energy. (C) 2002 Elsevier Science B.V. All rights reserved.