Effect of RF plasma power and deposition temperature on the surface properties of tin oxide deposited by modified plasma enhanced chemical vapor deposition

Lower deposition temperatures for metal oxides are always favorable to prevent damage to substrates and ease of process. In present work, tin oxide thin films were deposited at low temperature (200 °C and 300 °C) by modifying plasma enhanced chemical vapor deposition system. Surface science experiments are important for better fundamental understanding of non-stoichiometric metal oxides and their applications (especially for understanding gas sensing mechanisms). Therefore in this report, a systematic study is presented to investigate the effect of plasma power (RF, 100 to 500 W) on the surface states of SnO₂ thin films. Hydrated SnCl₄ was used as precursor and oxygen (300 sccm) was used as a reactant gas. Fine granular morphology with tetragonal rutile structure is observed at the two deposition temperatures. Higher plasma power resulted in smoother morphology, improved crystallinity; lower sheet resistance values (~0.1 KΩ/ at 300 °C and 250 W, un-doped films). Sn-incorporation is found increasing with plasma power; evident by increased Sn 3d photoelectron peak. Fitting data revealed that Sn is composed of Sn⁴⁺ and O-Sn⁴⁺ only. The suggested deposition method can be of great industrial importance to grow tin oxide at lower temperature.