A thermogravimetric study of the Si-O-N system /

Abstract

A thermogravimetric analyzer was used to study the Si-O-N system. Pure, polished single crystal silicon wafers were heated in the analyzer in an atmosphere of flowing high purity nitrogen or argon. The sample weight was measured continuously over specified temperature ranges. The high affinity of silicon for oxygen made it extremely difficult to form silicon nitride. Zirconium metal strips were placed near the sample to further reduce the local oxygen concentration. Silicon nitride was formed at 1250$sp circ$C with a nitrogen gas with a bulk oxygen concentration of less than 5 ppm. Two distinct modes of formation of silica (SiO$sb2$) were observed. These were active and passive oxidation. Active oxidation involved the evolution of SiO and resulted in a weight loss while passive oxidation resulted in a weight increase. Due to the formation of silicon dioxide, weight measurements were not useful in determining silicon nitride kinetics