High-Temperature Atomic Layer Deposition of Thermal-Oxide-Quality SiO ₂ Using Methyltrichlorosilane

Continuous scaling of three-dimensional (3D) NAND flash memory requires high-quality, conformal silicon oxide (SiO 2 ) insulating layers that can be deposited at high temperatures. We introduce methyltrichlorosilane (CH 3 SiCl 3 ) as a silicon precursor for atomic layer deposition (ALD) that overcomes the stability-reactivity trade-off of conventional precursors. The objective was to maintain the thermal stability of the thermally robust SiCl 4 molecule while significantly improving its reactivity by replacing its chlorine ligands with other ligands. We selected the CH 3 SiCl 3 precursor via density functional theory (DFT) screening due to its combination of high thermolysis resistance (activation energy of 3.40 eV) and superior surface reactivity, with reaction rates approximately 82 times faster than those of SiCl 4 at 700 °C. Thermal ALD using CH 3 SiCl 3 and O 2 /H 2 exhibits a pure ALD window of up to 750 °C with a low saturation dose of 1.9 × 10 6 L, yielding stoichiometric SiO 2 films with excellent conformality in high-aspect-ratio structures. Electrical characterization revealed that the electrical properties are nearly identical to those of thermal oxide, a leakage current density of 0.22 nA·cm –2 at 2 MV·cm –1 and an oxide-trapped charge density of 0.32 × 10 9 cm –2 . This work demonstrates that high-temperature ALD enabled by CH 3 SiCl 3 is a viable method for the conformal deposition of thermal-oxide-like SiO 2 for advanced semiconductor integration. It also validates a rational, computation-guided approach to identify precursors.