Silicon film formation by chemical transport in atmospheric-pressure pure hydrogen plasma

Abstract

To prepare polycrystalline silicon (poly-Si) films at low temperatures (<400°C) with high deposition rate, we propose a chemical transport method using atmospheric-pressure pure hydrogen plasma, called the atmospheric-pressure enhanced chemical transport method. In this method, high-pressure (200–760Torr) stable glow plasma of pure hydrogen was generated by a 150MHz very high frequency power between the two parallel electrodes less than 2mm apart. One of the electrodes is composed of the cooled Si solid source and the other the heated substrate (200–400°C). According to the temperature dependence of hydrogen etching rate of Si, SiHx species are mainly generated at the cooled Si solid source by hydrogen atoms. These species are again decomposed in the plasma, transported to the substrate to form Si films. In the present experiments on poly-Si film formation, a high deposition rate of 300nm∕min was achieved at 400°C, and nearly ideal utilization efficiencies (>93%) of Si solid source was realized in every condition. Si grains formed on a (001) Si substrate revealed anisotropic morphology elongated along ⟨110⟩ directions, and most of them had columnar structures epitaxially grown to the thickness of 2μm even at 200°C.