Intrinsic stress in hydrogenated amorphous silicon deposited with a remote hydrogen plasma

Abstract

In hydrogenated amorphous silicon it is demonstrated that the maximum compressive intrinsic stress correlates with the optimum electronic properties. Undoped films were deposited over a range of temperatures in a remote hydrogen plasma (RHP) reactor and, for comparison, in a rf glow discharge (GD) system. The dependence of the stress on deposition temperature is qualitatively identical for the two reactors. Quantitatively, both the maximum compressive stress and the optimized electronic properties (e.g., minimum defect density) are obtained at 400 °C for the RHP films and near 250 °C for the GD films. Additionally, it is demonstrated that the transition from amorphous to microcrystalline silicon, induced by high hydrogen dilution, is accompanied by a reduction in compressive stress. Formation of compressive stress during RHP growth is ascribed to the insertion of hydrogen into the rigid silicon network immediately beneath the growing surface.