Plasma-Assisted Atomic Layer Deposition of Low Temperature SiO2

Atomic layer deposition (ALD) was used to deposit SiO2 films in the temperature range of 50-400 degrees C. H2Si[N(C2H5)(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 (similar to 50 ms) were found to be sufficient to reach self-limiting ALD growth with a growth-per-cycle of similar to 1 angstrom. 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 SiO2 at low substrate temperatures. Also the surface chemistry during the plasma ALD process and surface passivation performance of the ALD SiO2 films on crystalline silicon surfaces are briefly addressed.