ON THE ROLE OF CHLORINE IN SELECTIVE SILICON EPITAXY BY CHEMICAL-VAPOR-DEPOSITION

Si thermal etching studies have been performed using pure Cl-2 in an u ltrahigh vacuum rapid thermal chemical vapor deposition reactor in the temperature range of 650-850 degrees C and the flow rate range of 1-1 0 seem which corresponds to a pressure range of 0.5-3.5 mTorr. The eff ects of temperature and Cl-2 flow were investigated with thermodynamic equilibrium calculations performed to determine possible reaction pat hways. The effect of adding H-2, up to 500 sccm, on Si etch rates at 8 00 and 850 degrees C was also obtained experimentally. Thermodynamic e quilibrium calculations were used to support the experimental results and determine the reaction by-products. It is proposed that SiCl2 equi librium partial pressure can be used as a means to compare the etching ability, thus the selectivity, of different selective Si processes. T he results from the etching studies were used to explain the behavior of Si epitaxy growth rate from the Si2K6, H-2, and Cl-2 system in the 650-850 degrees C, 22-24 mTorr processing regime. The implications of the etching studies for selective silicon epitaxy with the Si2H6 and C l-2 chemistry are discussed and then extended to the SiH2Cl2 based che mistry.