Etch rate behaviour of phosphosilicate glass films chemically vapour deposited in the SiH4PH3O2N2 system at low temperature

Abstract The etch rate behaviour in P-etch solution of phosphosilicate glass (PSG) films chemically vapour deposited in the SiH4PH3O2N2 at low temperatures (400–450°) was investigated as a function of the phosphorus concentration in the films and the subsequent thermal annealings. The experimental results were interpreted in terms of the following: (a) the film density variation vs. the phosphorus content; (b) the chemical states of the phosphorus atoms incorporated in these films; (c) the evolution of the content of the chemical impurities from the PSG films (PH3, H2O and SiOH); (d) the pores detected in the PSF films; (e) the structural changes of the films during annealing. Chemical mechanisms are proposed for the etching reaction of the PSG films: (a) at low phosphorus concentration (0–1 wt.%P) the process is dominated by micropore penetration of the etchant; (b) at high phosphorus concentration (above 8 wt.% P) the process is dominated by the surface reaction at the liquid-film interface due to the catalytic role of phosphorus atoms incorporated in the film.