Microwave plasma assisted sputtering

Abstract

Indium tin oxide (ITO) films were prepared on SiO 2 and on resin coated glass by microwave assisted sputtering and by magnetron dc sputtering using ITO targets. To find out the advantages of the microwave assisted sputtering in comparison to the magnetron sputtering the results of the two methods are compared. At substrate temperatures of 200°C ITO films with a specific resistivity of 133 μΩ cm at a film thickness of 100 nm could be prepared by microwave assisted sputtering, whereas the smallest obtained specific resistivity of the ITO films by the magnetron process was 212 μΩ cm. From Hall measurement it can be seen, that the reduced specific resistivity is mainly caused by the increased carrier density. On resin coated glass substrates the specific resistivity of 100 nm thick ITO films could be reduced by the microwave assisted sputtering process from 226 μΩ cm for the magnetron process to 175 μΩ cm. Also from Hall measurement this reduction in the specific resistivity is affected by an increase of the carrier mobility. Secondary ion mass spectroscopy analyses show, that the higher specific resistivity in the ITO films on resin coated glass in comparison to the films on SiO 2 coated glass is at least partly affected by the larger carbon content in the films. This carbon results from the outgassing of the resin. By the microwave assisted sputtering method the optical properties of ITO films could be improved about 1.5% on resin coated glass substrates. For the SiO 2 coated substrates the maximum transmittance for the two methods was nearly the same.