SiO 2 Atomic Layer Deposition Using Tris(dimethylamino)silane and Hydrogen Peroxide Studied by in Situ Transmission FTIR Spectroscopy

The atomic layer deposition (ALD) of silicon dioxide (SiO 2 ) was initially explored using a variety of silicon precursors with H 2 O as the oxidant. The silicon precursors were ( N, N -dimethylamino)trimethylsilane) (CH 3 ) 3 SiN(CH 3 ) 2, vinyltrimethoxysilane CH 2 ═CHSi(OCH 3 ) 3, trivinylmethoxysilane (CH 2 ═CH) 3 SiOCH 3, tetrakis(dimethylamino)silane Si(N(CH 3 ) 2 ) 4, and tris(dimethylamino)silane (TDMAS) SiH(N(CH 3 ) 2 ) 3 . TDMAS was determined to be the most effective of these precursors. However, additional studies determined that SiH* surface species from TDMAS were difficult to remove using only H 2 O. Subsequent studies utilized TDMAS and H 2 O 2 as the oxidant and explored SiO 2 ALD in the temperature range of 150−550 °C. The exposures required for the TDMAS and H 2 O 2 surface reactions to reach completion were monitored using in situ FTIR spectroscopy. The FTIR vibrational spectra following the TDMAS exposures showed a loss of absorbance for O−H stretching vibrations and a gain of absorbance for C−H x and Si−H stretching vibrations. The FTIR vibrational spectra following the H 2 O 2 exposures displayed a loss of absorbance for C−H x and Si−H stretching vibrations and an increase of absorbance for the O−H stretching vibrations. The SiH* surface species were completely removed only at temperatures >450 °C. The bulk vibrational modes of SiO 2 were observed between 1000−1250 cm −1 and grew progressively with number of TDMAS and H 2 O 2 reaction cycles. Transmission electron microscopy (TEM) was performed after 50 TDMAS and H 2 O 2 reaction cycles on ZrO 2 nanoparticles at temperatures between 150−550 °C. The film thickness determined by TEM at each temperature was used to obtain the SiO 2 ALD growth rate. The growth per cycle varied from 0.8 Å/cycle at 150 °C to 1.8 Å/cycle at 550 °C and was correlated with the removal of the SiH* surface species. SiO 2 ALD using TDMAS and H 2 O 2 should be valuable for SiO 2 ALD at temperatures >450 °C.