Temperature Dependence of Wafer Backside Deposition in Single Wafer CVD Reactor

Abstract

AbstractA quantitative experiment was designed to characterize in detail the backside silicon nodule formation (BSNF) on a single wafer reactor. It is found that there are two BSNF related vapor processes. One is the silicon mass transfer between wafer and wafer susceptor, which is controlled by the temperature difference between wafer and the susceptor. The other is the chemical vapor deposition process due to the presence of precursor (trichlorosilane) at the vicinity of the wafer backside. The contributions of these two processes to BSNF, however, have opposite dependencies on wafer temperatures. The silicon mass transfer from susceptor to wafer backside decreased with increasing wafer temperature. The trichlorosilane deposition increases with increasing wafer temperature. The effects of these two processes are also strongly dependent on susceptor configuration. It is found that having a wafer in direct contact with the susceptor could minimize the trichlorosilane deposition process, but silicon mass transfer is still present at the edge of the wafers. This study demonstrates that careful process control and susceptor design are necessary to eliminate wafer backside deposition.