Ion and chemical radical effects on the step coverage of plasma enhanced chemical vapor deposition tetraethylorthosilicate films

Abstract

We have compared the step coverage of plasma enhanced chemical vapor deposition tetraethylorthosilicate films of microwave downstream, high frequency radio frequency (rf), and low frequency rf depositions. The microwave-downstream deposition, characterized by bimolecular surface reactions, produces a conformal step coverage. The rf depositions with ion-induced surface reactions produce a low sidewall, high bottom coverage. The chemical radical and the ion effects on the step coverage are discussed.

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

“…2,8 Data from our complementary study of SiO 2 PECVD from TMCTS-and DMDMOS-based plasmas 12 also support the above deposition mechanism. The addition of an oxidant is essential to the deposition of high-quality SiO 2 films, through oxidative removal of hydrocarbon substituents from the precursor in both the gas phase and through gas-surface reactions.…”

Variable-energy positron lifetime study of silicon-oxide films plasma deposited from hexamethyldisiloxane and oxygen mixtures

“…At lower oxygen pressure a more stable film may be formed from neutral HMDSiO molecules adsorbed on the surface and from the active radicals and ions mainly originating from HMDSiO without the participation of a large number of oxygen radicals. 31 The increase of the I 3 with increasing oxygen pressure up to 6.2 Pa may be attributed to the reduction of the power given to HMDSiO. It was observed in a previous study 10 on plasma polymerization of pure HMDSiO at a constant discharge power that, because of the formation of films with less disordered structure, the I 3 systematically increases with increasing HMDSiO pressure.…”

“…Thus, at high oxygen pressure, because of the greater power given to oxygen, the role of oxygen radicals may become important. 31,32 The reaction of oxygen radicals with silicon forms the SiOO bond and oxygen atoms are incorporated in the films. The reaction of oxygen radicals with carbon, however, forms volatile CO and CO 2 , 33 which explains the elimination of carbon atoms and the considerable decline in the deposition rate observed at high oxygen pressures (Figs.…”

“…We relate the formation of such a structure at high oxygen pressure to the etching effect of oxygen radicals. 31,32 It is conceivable that in the presence of a large number of oxygen radicals the growing film is partially decomposed into fragments that may be eliminated or reorganized at a high temperature. The reduction of o-Ps lifetimes upon annealing suggests that the local packing density of the film probed by Ps increases.…”

The chemistry of etching and deposition processes

“…In fact, the deposition mechanism at high temperatures, which has been studied by several authors (see for instance ref. [15][16][17], can hardly be extended at low temperatures, either because the experimental conditions are very different and because the etherogeneous gas-surface interactions, which at high temperature play a very important role, are expected to be less important. The mechanism of a low-temperature deposition process is composed by several steps, whose relative importance depends on the experimental conditions and on the particular film precursors utilized.…”