Effects of Plasma Processing Parameters on the Surface Reactivity of OH(X2Π) in Tetraethoxysilane/O2 Plasmas during Deposition of SiO2

Abstract

The OH(X2Π) radical in a 20:80 tetraethoxysilane (TEOS)/O2 plasmas has been characterized during deposition of SiO2 using the imaging of radicals interacting with surfaces (IRIS) method. The reactivity of OH at the surface of a growing SiO2 film has been determined as a function of the applied radio-frequency (rf) plasma power (P) and the substrate temperature (TS). The reactivity (R) of OH during deposition of SiO2 on a 300 K Si substrate is 0.41 ± 0.04. R decreases as substrate temperature increases but is unaffected by increasing rf power. Translational and rotational temperatures (ϑT and ϑR, respectively) of the OH radical are also determined. For a 20:80 TEOS/O2 plasma (P = 85 W), ϑT = 912 ± 20 K and ϑR = 450 ± 20 K. ϑT is significantly higher than ϑR and increases with increasing rf power. Using isotopically labeled 18O2 as a precursor, the source of the oxygen in OH is identified as the O2 gas, not oxygen from the ethoxy groups on TEOS. With these data, the role of OH in deposition of SiO2 from TEOS-based plasmas and the effects of plasma deposition parameters on film formation are discussed.