LPCVD deposition of silicon nitride assisted by high density plasmas

A low pressure chemical vapour deposition (LPCVD) reactor was transformed i nto an inductively coupled plasma like plasma enhanced chemical vapour depo sition reactor by placing a coil at the inlet side of the tube and applying 13.56 MHz power to it. Silicon nitride films were deposited at 300 degrees C in the plasma region, or at 720 degrees C at the center of the tube, eit her without plasma or with a remote plasma. The films deposited in the plas ma region have a high deposition rate, more than 2.5 times that of the depo sition rate of films deposited without plasma. Their refractive index range s from 1.5-1.8, increasing with the ammonium to dichlorosilane ratio, indic ating a nitrogen rich film. Fourier Transform Infrared Spectroscopy shows t hat at the higher ammonium to dichlorosilane ratios, the number of Si-H bon ds is as low as for stoichiometric silicon nitride. Etching these films in 2% HF results in high etch rates, 2-30 nm/s. The wafers deposited at 720 de grees C with remote plasma show an increased deposition rate, compared to f ilms deposited without plasma, and refractive index of approximately 2.00. (C) 1999 Elsevier Science S.A. All rights reserved.