We study the surface dynamics of silica films grown by low pressure chemical vapor deposition. Atomic force microscopy measurements show that the surface reaches a scale invariant stationary state compatible with the Kardar-Parisi-Zhang (KPZ) equation in three dimensions. At intermediate times the surface undergoes an unstable transient due to shadowing effects. By varying growth conditions and using spectroscopic techniques, we determine the physical origin of KPZ scaling to be a low value of the surface sticking probability, related to the surface concentration of reactive groups. We propose a stochastic equation that describes the qualitative behavior of our experimental system.

The growth kinetics of SiO 2 thin films obtained by low-pressure chemical vapor deposition (CVD) from SiH 4 ͞O 2 ͞N 2 gas mixtures has been determined at different temperatures and flow rates. The results show that the film growth is originated by some intermediate species (e.g., SiO x H y ) produced in the gas phase. At low temperatures the deposition rate is limited by some homogeneous reaction with an apparent activation energy of 1.42 eV. Furthermore, the observation of critical limits when total pressure, oxygen/silane flow ratio, and temperature are decreased gives support to a branching-chain mechanism of deposition. Finally, we have observed that the deposition rate shows a hysteresis behavior when varying the temperature within the 300-400 ± C range, which has been attributed to the inhibition of silane oxidation by the Si -OH surface groups of the films grown on the reactor walls.

Hydrogen incorporation into SiO 2 films grown by low-pressure chemical vapor deposition (CVD) from SiH 4 /O 2 mixtures is investigated by means of infrared spectroscopy (IRS), nuclear magnetic resonance (NMR), elastic recoil detection analysis (ERDA), X-ray photoemission spectroscopy (XPS), and nuclear reaction analysis (NRA). We find that hydrogen atoms are preferentially bonded to O atoms, forming bulk SiOH groups, either isolated or clustered, and H 2 O groups, with a minor incorporation of SiH groups, as well as geminal and surface isolated SiOH groups. The proportion of clustered SiOH groups decreases upon increasing the deposition temperature, which has been attributed to the faster dehydroxylation reactions and higher surface mobility of the hydrogenated species involved in the film growth. Using a novel method based on the combination of NRA and ERDA, we verify quantitatively that the predominance of O-H over Si-H bonding implies a slight overstoichiometric character (O/Si atomic ratio > 2) that is accentuated with increasing OH concentration.

We have studied the surface morphology evolution of Si0 2 films grown at 20 nm/min in a low-pressure chemical vapour deposition reactor from SiHi02 mixtures at low (611 K) and high (723 K) temperatures. Films have been deposited for times ranging from 10 min up to 48 hours. It is shown that the SiO, growth at high temperature becomes stable, whereas at low temperature it is unstable (i.e., the surface roughness increases continuously with deposition time). This clear difference is explained on the basis of the different growth mechanisms operating under both experimental conditions. These results are compared with the predictions of the few theoretical works on growth evolution by chemical vapour deposition.

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