Plasma-Assisted Atomic Layer Deposition of Low Temperature SiO₂

Abstract

Atomic layer deposition (ALD) was used to deposit SiO 2 films in the temperature range of 50-400 o C. H 2 Si[N(C 2 H 5 ) 2 ] 2 and an O 2 plasma were used as Si precursor and oxidant, respectively. The growth process was characterized in detail, using various in situ diagnostics. Ultrashort precursor doses (~50 ms) were found to be sufficient to reach self-limiting ALD growth with a growth-per-cycle of ~1 Aå. The films exhibited a refractive index of 1.46 ± 0.02, a mass density of 2.0 ± 0.1 g/cm 3 , and an O/Si ratio of 2.1 ± 0.1, virtually independent of the substrate temperature. The results therefore demonstrate an efficient ALD process for the conformal and uniform deposition of SiO 2 at low substrate temperatures. Also the surface chemistry during the plasma ALD process and surface passivation performance of the ALD SiO 2 films on crystalline silicon surfaces are briefly addressed.