Oxidation of Silicon Using Electron Cyclotron Resonance Nitrous Oxide Plasma and Its Application to Polycrystalline Silicon Thin Film Transistors

Abstract

Electron cyclotron resonance nitrous oxide (N2O) plasma oxidation has been investigated as a process to grow thin oxide on polycrystalline silicon and (100), (111), and (110) oriented crystalline silicon. In spite of a low thermal budget, N2O plasma oxidation incorporates nitrogen atoms at the silicon/silicon dioxide interface and forms a nitrogen-rich layer. The incorporated nitrogen atoms are tightly bound to silicon atoms at the interface with N (1s) electron energy of 397.8 eV. The oxidation rate in N2O plasma is less dependent on crystalline orientation in comparison with thermal O-2, and is therefore nearly identical in poly- and single-crystalline-Si. Polysilicon oxide (polyoxide) grown by N2O plasma oxidation exhibits better electrical properties than thermally grown oxides; this is attributed to the smooth interface between the polyoxide and a poly-Si film. Polysilicon thin film transistors fabricated with N2O plasma oxide show improved performance, which is attributed not only to the smooth interface but also to oxygen-and nitrogen-plasma passivation.