Antimony, Arsenic, Phosphorus, and Boron Autodoping in Silicon Epitaxy

Abstract

Lateral autodoping is encountered if silicon wafers with heavily doped areas are subjected to silicon epitaxy. The characteristics of the autodoping profile are determined by the pre‐epitaxial bake conditions and by the identity of the impurities. Lateral autodoping originating from arsenic‐ or antimony‐implanted silicon substrates can be suppressed by reduction of the total pressure during the epitaxial process. In contrast, autodoping is enhanced at reduced pressure if boron‐doped buried layers are employed. These phenomena can be accounted for if chemical processes in the gas phase, which involve the dopant, are considered. Thermodynamic computations have been carried out in order to explain the influence of process conditions such as temperature, total pressure, and the presence of chlorine on the autodoping behavior or antimony, arsenic, phosphorus, and boron. Evaporated dopant atoms are converted to stable gaseous compounds such as for antimony, and for arsenic, , , and for phosphorus, and for boron. The reincorporation of the dopant in the epitaxial layer is governed by the partial pressure of monoatomic species in the gas phase. Mass action law describes the influence of total pressure on the efficiency of the autodoping process.