The structure and composition of silicon oxides thermally grown in HCI/Oz ambients were investigated for various oxidation conditions. Oxides were grown in 6-10 v/o HCl at I150~for times of 15 rain-6 hr. Transmission electron microscopy in conjunction with x-ray microanalysis has indicated the presence of an additional condensed phase at the oxidesilicon interface, which appears after a certain oxidation time has elapsed. Scanning electron microscopy has shown that after further oxidation, a gaseous compound accumulates at the interface, lifting the oxide from the silicon, and preferentially etching the silicon. A model of the growth mechanisms of HCI oxides, accounting for the additional phase formation, is proposed. * Electrochemical Society Student Member. ** Electrochemical Society Active Member.

The interrelationship which exists between sodium passivation and phase separation in silicon oxides thermally grown in HC1/O2 ambients was investigated using the capacitance-voltage bias temperature stress technique in conjunction with transmission electron microscopy. Oxides were grown in 0, 3, 6, and i0 volume percent (v/o) HCI for various times at ll00 ~ I150 ~ and 1200~ The threshold in passivation characteristic of these oxides was shown to be a steep portion of a continuous, smooth curve, rather than a sharp discontinuity. The microstructural investigation showed that the development of the additional, chlorine-rich phase correlates well with passivation. The development of this phase, characterized by growth and coalescence, is modeled in terms of phase transformation kinetics.

No abstract

The out-diffusion profiles of oxygen from Czochralski grown (Cz) silicon were measured with secondary ion mass spectrometry for several processing conditions. The diffusivity of oxygen was found to be retarded under oxidizing conditions. This effect, however, is eliminated with the addition of 2% HCl to the oxidizing ambient. Both in-diffusing boron and in-diffusing phosphorus enhance the diffusivity of oxygen. These observations are consistent with a vacancy dominant diffusion mechanism for oxygen in silicon. The surface concentration of oxygen Cs varies considerably with processing conditions. An increased concentration of oxygen at the surface was observed under oxidizing conditions. Under inert or reducing conditions, Cs was lower than oxidizing conditions but did not approach as low a value as was expected. The lowest values of Cs were obtained for the phosphorus diffusion, boron diffusion, and for the 10% HCl oxidation.

Fixed charge buildup has been studied in nitrided oxides. Oxides were grown at 1000~ in dry, wet, and HC1 containing ambients. Nitridation was carried out in pure NH:~ at temperatures from 950 ~ to 1150~ for 10, 30, 90, and 240 min. In many cases, thermal nitridation was found to cause fixed positive charge buildup in the films, resulting in negative shifts in flatband voltage. Under appropriate conditions, however, the charge buildup reverses, and VF, approaches prenitridation values as nitridation proceeds. The rates of charge buildup and subsequent relaxation are highly dependent on nitridation conditions and initial oxide thickness, with no significant dependence on oxide growth conditions. The current mode] for positive charge buildup in nitrided oxides, based on dissociation of Si-O bonds caused by hydrogen gas, is found to be incomplete and probably incorrect. Irradiation experiments were performed at doses of 104-10 ~ rad. Thermal nitridation was found to be capable of providing improved resistance to radiation-induced positive charge buildup in some cases.