Densimetry of Amorphous Silicon Films by Using a Quartz Oscillator

By using a quartz oscillator with one side of the quartz crystal optically polished, both the weight and thickness of the same film can be measured. With this method a film can be deposited on one part of one side of a quartz oscillator; thus, it is necessary to estimate the frequency constant N by Ag and Au films. As a result, N was found to be 1.86±0.10×10 5 Hz·cm, a 12% increase over the nominal frequency constant of an AT-cut quartz oscillator. The density of an amorphous silicon (a-Si) film deposited on an Au film was determined to be 1.71±0.09 g/cm 3 ; the density was 27% less than the density of crystal Si. From the result of high-resolution electron micrographs, it is clear that the cause for the low density is not due to such defects as cracks, pores or voids over 2 nm.