Surface Reactivity of OH Molecules during Deposition of SiO2 from Siloxane-Based Plasmas

Abstract

The surface interactions of OH(X 2 Π) radicals during SiO 2 deposition from 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS)/oxidant (O 2 or N 2 O) and dimethyldimethoxysilane (DMDMOS)/oxidant (O 2 or N 2 O) plasmas have been measured by using the imaging of radicals interacting with surfaces (IRIS) method. The reactivity of OH at the surface of a growing SiO 2 film has been determined as a function of the applied rf plasma power (P), the precursor-to-oxidant ratio, and the substrate temperature (T s ). For both Si precursors, the surface reactivity (R) of OH during SiO 2 deposition on a 300 K Si substrate is ∼0.60 and is unaffected by changing precursor:oxidant ratio but does increase slightly with P. In contrast, at higher substrate temperatures (T s > 350 K), R decreases to 0.16 ′ 0.10 for 1:10 TMCTS/O 2 plasma (P = 100 W) and to 0.42 ′ 0.03 for 1:10 DMDMOS/O 2 plasma (P = 100 W). The rotational (OR) and translational (Θ T ) temperatures of the OH radicals have also been determined. The formation and role of OH in SiO 2 deposition are discussed and compared with previous results for TEOS/O 2 plasmas.