Effects of deposition and annealing temperature on atomic layer-deposited tin dioxide thin films

Abstract

Tin dioxide (SnO₂) is a promising wide-band-gap n-type semiconductor for transparent conducting oxides (TCOs) and oxide-based electronics. In this work, we investigate the effects of deposition and annealing temperatures on the structural and electrical properties of SnO₂ thin films grown by thermal atomic layer deposition (ALD) using tetrakis(dimethylamino)tin (TDMA-Sn) and ozone (O₃). Films were deposited at 150 ℃ and 200 ℃ followed by post-deposition annealing in O₂ between 400 ℃ and 600 ℃. Crystallographic analysis revealed that higher deposition and annealing temperatures promote rutile phase formation and grain growth, improving carrier concentration and mobility. The optimized sample, which was deposited at 200 ℃ and annealed at 600 ℃, achieved a carrier density of 2.54 × 10²² cm⁻³ and Hall mobility of 51.3 cm²/V·s, resulting in a low resistivity of 1.89 × 10⁻⁴ Ω·cm. UV–Vis measurements confirmed high optical transparency (> 80%) in the visible range, supporting TCO applicability. Thickness uniformity and conformality were also demonstrated, achieving step coverage over 96% and wafer-scale thickness uniformity exceeding 98%. While annealing up to 600 ℃ enhanced the film properties, temperatures above 600 ℃ may induce degradation such as interfacial diffusion and grain coarsening. These results highlight that careful optimization of thermal processing conditions enables the fabrication of uniform, highly conductive, and transparent SnO₂ films, suitable for next-generation electronic and optoelectronic devices.