Deposition of low temperature Si-based insulators by the electron cyclotron resonance plasma method

Abstract

The influence of the gas flow ratio (R) (O-2/SiH4 and N-2/SiH4) and the deposition temperature on the physical properties of SiOy and SiNx:H thin films deposited by the ECR-CVD method is analyzed. Two deposition regimes limited by R = 1, are found for SiOy films. At R < 1, films are very Si-rich in nature, with [O]/[Si] ratios as low as 0.55. At R > 1, the [O]/[Si] ratio varies between 1.69 and 1.88 and the full width at half maximum of the Si-O stretching peak is almost kept constant at 90 cm(-1). The effect of increasing substrate temperatures is mainly to promote a nearest stoichiometric character of the films. The two deposition regimes described agree with the optical diagnosis of the discharge, that present Si related species in those created at R < 1, and OH and O-2(+) species in those created at R > I. A similar trend is observed for the deposition of SiNx:H films, for which the limiting gas flow ratio is also R = I. At R < 1, the films are very Si-rich (x less than or equal to 0.38), meanwhile at R > 1, the composition corresponds to near stoichiometric and N-rich films (x = 0.91-1.49). The main effect of the substrate temperature is to reduce the hydrogen content of the films. Both SiOy and SINx:H films are used in Si-based MIS structures, for those the minimum density of interface states is 3 X 10(11) cm(-2) eV(-1).