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

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 Å 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.