Low temperature growth of amorphous and polycrystalline silicon films from a modified inductively coupled plasma

A conventional inductive rf discharge is modified by inserting a discharge antenna in a plasma vessel with magnetic multipole confinement, which gives a high-density (similar to 10(11)cm(-3)) silane plasma at very low pressures (similar to 1 mTorr). This new type of inductively coupled plasma (ICP) enables high-rate deposition (similar to 1 nm/s) of a-Si:H films at low substrate temperatures of similar to 100 degrees C, which have the photoconductivity of 10(-5)-10(-4) S/cm and the dark conductivity of 10(-10)-10(-9) S/cm. Moreover, microcrystalline or polycrystalline silicon films are formed on glass substrates at moderate temperatures of 200-300 degrees C where the dark conductivity becomes comparable to the photoconductivity and the X-ray diffraction pattern shows sharp peaks corresponding to the silicon crystalline surfaces. Mass spectrometric measurements of the highly dissociated silane plasma show unique radical compositions; similar to 90% of ions are hydrogen species (H-3(+), H-2(+), H+) while the density of neutral radicals (SiH3, SiH2, SiH) is lower than that of ionic radicals (SiH3+, SiH2+, SiH+, Si+). Thus, the main precursor of film growth from high-density plasmas may be ionic radicals rather than neutral radicals.