Characteristics of plasma-enhanced atomic-layer deposited (PEALD) SnO2 thin films

Plasma-enhanced atomic-layer deposition (PEALD) is a promising technique to produce high-purity and high-density metal-oxide thin films at low growth temperatures. Tin-dioxide (SnO2) thin films have been deposited by PEALD on Si (100) substrate by using dibutyl tin diacetate ((CH3CO2)2Sn[(CH2)3-CH3]2) as a precursor. The process parameters were optimized as functions of the substrate temperature, source temperature, purging time, and number of process cycles. Scanning probe microscopic (SPM) images and XRD patterns were used to observe the texture and the annealing effects on the films. The dominant oxygen species for as-deposited films was O2-, but O- was the main species after annealing. The films deposited at 50 - 300 .deg. C source and substrate temperatures for 200 cycles with an 8-s purging time had good morphologies and thus lower RMS roughness values. A correlation between the morphology and the characteristics of the Sn 3d and O 1s XPS spectra of the SnO2 thin films before and after annealing was established and was related to the concentration of the O- species.