The role of oxygen and surface reactions in the deposition of silicon oxide like films from HMDSO at atmospheric pressure

TL;DR

This study investigates how oxygen and surface reactions influence the deposition of silicon oxide-like films from HMDSO at atmospheric pressure using microplasma jets, highlighting the role of surface reactions in carbon removal and film composition.

Contribution

It demonstrates that oxygen addition enhances film growth and purity, and reveals that surface reactions can enable carbon-free film deposition even without oxygen, using different jet configurations.

Findings

Oxygen increases HMDSO depletion and film growth rate.

Surface reactions are key to carbon removal from films.

Carbon-free films can be deposited without oxygen using coaxial jets.

Abstract

The deposition of thin SiO$_x$C$_y$H$_z$ or SiO$_x$H$_y$ films by means of atmospheric pressure microplasma jets with admixture of Hexamethyldisiloxane (HMDSO) and oxygen and the role of surface reactions in film growth are investigated. Two types of microplasma jets, one with a planar electrodes and operated in helium gas and the other one with a coaxial geometry operated in argon, are used to study the deposition process. The growth rate of the film and the carbon-content in the film are measured as a function of the O$_2$ and HMDSO admixture in the planar jet and are compared to mass spectrometry measurements of the consumption of HMDSO. Additionally, the localized nature of the jet-substrate interaction is utilized to study surface reactions by applying two jets on a rotating substrate. The addition of oxygen into the gas mixture increases HMDSO depletion and the growth rate and results in the deposition of carbon free films. The surface reaction is responsible for the carbon removal from the growing film. Moreover, carbon free films can be deposited even without addition of oxygen, when coaxial jet operated with argon is used for the surface treatment. We hypothesize that ions or excited species (metastables) could be responsible for the observed effect.