SiO2 Atomic Layer Deposition Using Tris(dimethylamino)silane and Hydrogen Peroxide Studied by in Situ Transmission FTIR Spectroscopy

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The atomic layer deposition (ALD) of silicon dioxide (SiO2) was initially explored using a variety of silicon precursors with H2O as the oxidant. The silicon precursors were (N,N-dimethylamino)trimethylsilane) (CH3)3SiN(CH3)2, vinyltrimethoxysilane CH2═CHSi(OCH3)3, trivinylmethoxysilane (CH2═CH)3SiOCH3, tetrakis(dimethylamino)silane Si(N(CH3)2)4, and tris(dimethylamino)silane (TDMAS) SiH(N(CH3)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 H2O. Subsequent studies utilized TDMAS and H2O2 as the oxidant and explored SiO2 ALD in the temperature range of 150−550 °C. The exposures required for the TDMAS and H2O2 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−Hx and Si−H stretching vibrations. The FTIR vibrational spectra following the H2O2 exposures displayed a loss of absorbance for C−Hx 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 SiO2 were observed between 1000−1250 cm−1 and grew progressively with number of TDMAS and H2O2 reaction cycles. Transmission electron microscopy (TEM) was performed after 50 TDMAS and H2O2 reaction cycles on ZrO2 nanoparticles at temperatures between 150−550 °C. The film thickness determined by TEM at each temperature was used to obtain the SiO2 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. SiO2 ALD using TDMAS and H2O2 should be valuable for SiO2 ALD at temperatures >450 °C.