Capillary jet injection of SiH4 in the high density plasma chemical vapor deposition of SiO2

Abstract

In this article, the authors compare the thickness profiles and OH content of SiO2 films deposited using capillary jet injection of silane in a high density plasma chemical vapor deposition (HDP CVD) system with the results of phenomenological modeling using direct simulation Monte Carlo (DSMC) gas flow calculations. A tube with an internal diameter of 1mm is located vertically at 3cm in front of the substrate surface and is used for the injection of the silane. The deposition plasma is characterized using optical emission spectroscopy (OES) and differentially pumped quadrupole mass spectrometry (QMS). Studying the thickness-normalized OH absorption in the deposited film at various points on the substrate, the authors gain insight into the contribution of the water flux to the OH content in the deposited SiO2 film. Gas flow simulations using the DSMC technique are used to study the fluxes of the species onto the substrate plane. From the results the authors conclude that (i) the flux of the H2O onto the substrate holder is uniform, while the SiH4 flux varies considerably along the substrate holder, which leads to a lower level of hydroxyl incorporated into the deposited film in regions of high deposition rate; (ii) HDP CVD systems cannot be considered as well mixed when using SiH4 because its reaction products have high sticking coefficients and the ground-state molecules have the possibility to be consumed on the surface through reactions with oxygen radicals and ions when depositing SiO2; (iii) the primary beamlike flux of undissociated SiH4 onto the substrate surface has an important influence on the film’s deposition rate; and (iv) the SiH4 reactive sticking coefficient is estimated to be between 0.01 and 0.03.