Smooth amorphous silicon deposition on silicon dioxide with high deposition rates by rapid thermal chemical vapor deposition using disilane

Abstract

In this paper, we report amorphous silicon (α-Si) deposition on SiO 2 by rapid thermal chemical vapor deposition for the first time at rates compatible with single wafer manufacturing. Depositions were performed using 10% Si 2H 6 in H 2 at 1 Torr in the temperature range 550 to 750 °C. Very high deposition rates are achieved and these rates range from 45 nm/min to as high as 650 nm/min. Analysis of the films by transmission electron microscopy indicates α-Si deposition at temperatures below approximately 600 °C. At temperatures around 625 °C, films with a bilayer amorphous-polycrystalline composite microstructure were obtained which was attributed to a deposition rate greater than the crystallization rate. Analysis of these low temperature films by atomic force microscopy yields rms roughness values, in general, that are less than 1.5 nm and as low as 0.3 nm. The smoothness of the films is comparable to the best α-Si films obtained by conventional low pressure chemical vapor deposition using SiH 4 or Si 2H 6. In summary, by using an efficient source gas, we are able to deposit very smooth Si films by rapid thermal chemical vapor deposition which we believe is a viable option for high quality MOS gate stack formation in a single wafer manufacturing environment.