Growth characteristics and electrical properties of SiO2 thin films prepared using plasma-enhanced atomic layer deposition and chemical vapor deposition with an aminosilane precursor

Abstract

The deposition of high-quality SiO2 films has been achieved through the use of both plasma-enhanced chemical vapor deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) methods using H2Si[N(C2H5)2]2 as a Si precursor. We systematically investigated growth characteristics, chemical compositions, and electrical properties of PE-CVD SiO2 prepared under various deposition conditions. The SiO2 films prepared using PE-CVD showed high purity and good stoichiometry with a dielectric constant of ~4. In addition, the PE-ALD process of the SiO2 films exhibited well-saturated and almost linear growth characteristics of ~1.3 A cycle−1 without notable incubation cycles, producing pure SiO2 films. Electrical characterization of metal-oxide silicon capacitor structures prepared with each SiO2 film showed that PE-ALD SiO2 films had relatively lower leakage currents than PE-CVD SiO2 films. This might be a result of the saturated surface reaction mechanism of PE-ALD, which allows a smooth surface in comparison with PE-CVD method. In addition, the dielectric properties of both SiO2 films were further evaluated in the structures of In–Ga–Zn–O thin-film transistors, and they both showed good device performances in terms of high I on − I off ratios (>108) and low off-currents (<10−11 A). However, based on the negative bias stress reliability test, it was found that PE-ALD SiO2 showed better reliability against a negative V th shift than PE-CVD SiO2, which might also be understood from its smoother channel/insulator interface generation at the interface.