High deposition rates of uniform films in tetramethylsilane-based plasmas generated by elementary microwave sources in matrix configuration

Abstract

Plasma scaling up can be achieved by distributing elementary microwave plasma sources on planar rectangular networks. These so-called matrix plasmas can generate uniform sheets of plasma over a wide argon pressure range, from 7.5 to 750 Pa, with densities between 10 12 and 10 13 cm − 3 . In order to estimate the capabilities of matrix plasmas for PACVD processing in terms of deposition rate and uniformity, SiOCH and SiNCH films were deposited using TMS (tetramethylsilane), as the organic gas precursor of silicon, mixed with oxygen or nitrogen flows. Plasmas of O 2 / TMS and N 2 / TMS gas mixtures can be sustained between 5 and 25 Pa. Variations in the deposition rate as a function of microwave power and nitrogen partial pressure are reported. Thickness uniformity of SiOCH and SiNCH films was measured across a silicon wafer. The obtained deposition rates exceed 1.3 μm/min and the films present a uniformity better than 5% on 75 mm diameter silicon wafers. Composition of the films has also been analyzed by XPS as a function of process parameters: microwave input power, composition of gas mixture, and N 2 partial pressure. In particular, these analyses have shown a very low yield of nitrogen incorporation when using N 2 gas as nitrogen precursor and high Si and Si–Si bonding contents in the films, probably due to a strong fragmentation of the TMS precursor in the high density plasma.