Silicon nitride films deposited at substrate temperatures <100 °C in a permanent magnet electron cyclotron resonance plasma

Abstract

Deposition of silicon nitride at low temperatures by plasma-enhanced chemical vapor deposition requires an efficient source of activated precursors and high-current, low-energy ion assist. We report the deposition of silicon nitride at substrate temperatures <100 °C using a permanent magnet electron cyclotron resonance plasma reactor capable of generating uniform plasmas over 300 mm diameters. The effects of gas mixture, silane flow, pressure, and microwave power on the film deposition rate, composition and bonding, index of refraction, stress, and etch rate in buffered oxide etch solution are reported. The N2/SiH4 flow ratio and microwave power both influence the film index and hydrogen content and bonding. For a SiH4 flow of 30 sccm and N2/SiH4 ∼0.75, hydrogen is equally distributed between Si–H and N–H sites and total hydrogen content is minimized. At a deposition rate of 500–600 Å/min, a threshold in microwave power of ∼1100 W exists, above which films with buffered oxide etch rates <150 Å/min result. Near the threshold microwave power compressive stress <400 MPa is observed, with increasing stress at higher microwave powers.