Combined Raman, 29Si NMR and reactivity studies of silica gels indicate that dehydroxylation of the silica surface results in cyclotrisiloxane species with reduced Si-O-Si bond angles and altered acid/base characteristics. XPS experiments indicate that the expected 0.35 eV shifts in Si2p and O1s binding energies due to the reduced bond angles are hidden within broad peaks due to the remaining hydroxyls. Additional Si2P, OlS, and ClS peaks are also observed and are postulated to result from preferential adsorption of extrinsic C-containing species on sites with enhanced acid/base properties.

Detailed electrical characteristics of TiSi2/n+-polysilicon/SiO2/Si MOS capacitors stressed under a variety of high temperature processing conditions is reported. These devices have ˜2000Å TiSi2 formed by a two-step thermal anneal on heavily POCl3doped polysilicon with thicknesses of 6 kÅ and 8 kÅ. These structures were capped with 8 kÅ of SiO2 and stressed in nitrogen at process temperatures in the range of 700° C to 1100° C. The electrical performance was evaluated in terms of I-V, C-V, Fowler-Nordheim tunneling, and SiO2/Si interface characteristics of MOS structures. A systematic degradation of the SiO2/Si interface was observed due to process limitations of TiSi2 at high Lemperatures.

Measurements of film thickness using ellipsometry assume all interfaces to be ideally planar. This approximation works well for films much thicker than the roughness of the interfaces. For very thin films. the interface roughness can cause significant errors in thickness measurements. In this paper, we calculate the effect of interface roughness on oxide thickness measurements and use those calculations to account for some of the observed differences between film thickness measurements of thin oxides (< 200 A) as measured by ellipsometry and transmission electron microscopy.

A new experimental technique to determine Si/SiO2 interface morphology is described. Thermal oxides of silicon are chemically removed, and the resulting surface topography is measured with scanning tunneling microscopy. Interfaces prepared by oxidation of Si (100) and (111) surfaces, followed by post oxidation anneal (POA) at different temperatures, have been characterized. Correlations between interface structure, chemistry, and electrical characteristics are described.

We have studied the oxidation mechanism of SiGe alloys, prepared by UHV/CVD. Ge is found to be completely rejected from the oxide and to pile up at the oxide/substrate interface. In the case of thick SiGe layers, this can give rise to very heavily concentrated layers of SiGe (up to 80% Ge) several hundreds of angstroms thick between the oxide and the substrate. The oxidation of Si then proceeds by Si diffusing though the Ge-rich layer. When only a thin layer of Ge is present on top of Si at the start, it acts as a marker, moving, unchanged, with the SiO2/Si interface. The rate of oxidation is enhanced in this case. The atomic motion and chemical reactions involved in the process are discussed and possible mechanisms are described to explain the data. Oxidation of a SiGeB sample is also discussed and compared with the previous case.

Hexachlorodisilane (Si2Cl6) has been used as an alternative to dichlorosilane and silane for growth of silicon nitride films. The films were grown at a pressure of 0.7 Torr at temperatures between 450° and 850°C. Growth rate data indicates a kinetically controlled deposition with an activation energy of 29.3 kcal/mole. Growth rates are substantially higher than those obtained from SiH2Cl2 under similar conditions, and the physical properties of the films are essentially the same. At the higher growth temperatures stoichiometric Si3N4 films with no detectable chlorine can be obtained when a NH3/Si2Cl6 ratio of 60 or greater is used.

A fast diffusing As species in ion-implanted SiO2 in N2 annealing ambient has been observed for the first time. This As diffuses 20X faster at 1100°C than the slow As found in oxidizing ambients. The activation energy of diffusion of this fast As is 0.71 eV, in sharp contrast to 4.3 and 4.0 eV for the slow As in O2 and O2 /H2O, respectively. The fast species is believed to be As occupying either the O-site or interstitial site in the SiO2 network. By assuming a fast and a slow species coupled together by transitions, we were able to obtain reasonable fits to the SINS diffusion profiles.