Selective epitaxial growth of silicon in a barrel reactor

Abstract

Selective epitaxial growth (SEG) of silicon allows isolation among devices to be vastly improved and offers numerous possibilities for novel device structures. In this work, selective epitaxial silicon deposition is carried out in a radiantly heated barrel reactor from SiH 2Cl 2H 2HCl gas mixtures. Substrate temperatures are between 850 and 1000°C while reactor pressures are between 25 and 100 torr. All patterned silicon substrates are 3 in. diameter n-type polished wafers of (100) crystal orientation masked with a thermally grown oxide, 0.08–0.87 μm thick. A new quantity that characterizes several features of silicon SEG in such systems is proposed. This quantity is the ratio of inlet reactor partial pressures P 2 HCl/ P DCS. The SEG rate of silicon is found to decrease monotonically (and almost linearly) with increasing P 2 HCl/ P DCS increases. The apparent activation energy of silicon deposition from SiH 2Cl 2 (DCS) is found to be 33 kcal/mol, while the overall apparent activation energy of silicon SEG is found to be between 50 and 85 kcal/mol for the conditions studied. A detailed mathematical model of SEG in a barrel reactor is also presented. It includes all mass, energy and momentum equations coupled with the special geometry and inlet and exhaust configurations of this reactor. Predictions from the mathematical model developed are shown to be in satisfactory agreement with data obtained in the radiantly heated barrel reactor used.