Very high frequency hydrogen plasma treatment of growing surfaces: a study of the p-type amorphous to microcrystalline silicon transition

The deposition of microcrystalline silicon (μc-Si) in a 100 MHz plasma, in condition close to equilibrium between etching and deposition, is studied. Chemical transport in a pure H2 plasma is shown to occur in presence of a lower density, a-Si:H precursor layer, and is used to deposit p-type silicon thin (17.5–40 nm) films with microcrystalline fraction >70% for a 17.5 nm thick film, and up to 90% for thicker films, with dark conductivity up to 0.1 S/cm and much better optically measured homogeneity with respect to 100 MHz plasma deposited samples under high dilution (0.5% silane-to-hydrogen flow ratio). Transmission electron microscopy on the 17.5 nm sample shows that crystalline grains extend to the interface. Within the 2 nm detection limit, no continuous interface amorphous layer is detected.