Investigation of oxide thin films deposited by atomic layer deposition as dopant source for ultra-shallow doping of silicon

Abstract

Atomic layer deposition of solid dopant sources for silicon was carried out by using triethylantimony and ozone, and tris-(dimethylamido)borane and ozone as precursors for antimony or boron containing oxides, respectively. It was proved that homogenous antimony oxide deposition could be achieved on flat silicon wafers and in trench structures. Little growth was found below 100 °C deposition temperature and linear temperature dependence on the growth rate between 100 and 250 °C. The oxide films were not stable above 750 °C and therefore failed to act as dopant source for silicon so far. Boron containing films were only obtained at a deposition temperature of 50 °C. These films were highly instable after exposure to air but degradation could be delayed by thin films of antimony oxide or aluminium oxide that were in situ grown by ALD as well. Only little boron was found by ex-situ chemical analysis. However, rapid thermal annealing of such boron containing dopant source layers resulted in high concentrations of active boron close to the silicon surface. The dependence of the doping results on the thickness of the initial boron containing films could be shown.