R. J. Jaccodine

A DIFFUSIONAL MODEL FOR THE OXIDATION BEHAVIOR OF SI1-XGEX ALLOYS

We have developed a kinetic model to describe the oxidation behavior of Si1−xGex alloys during Ge segregation, which compares the Deal–Grove flux of oxidant diffusing through the oxide to the maximum flux of Si diffusing through the Ge-rich layer. This is motivated by thermal oxidation experiments on Si1−xGex alloys (x<0.17) using a fluorine-containing ambient (O2 and 200 ppm of NF3). The fluorine is known to modify point defect generation during oxidation of pure Si toward vacancy production, which is also the case for Ge in Si. We demonstrate that fluorinated oxidation of Si1−xGex enhances the oxidation rate by 25%–40% in the temperature range of 700–800 °C. Oxides formed at these temperatures were SiO2, while those formed at 600 °C exhibited a transition from SiO2 to mixed oxide growth at some point during the very early phase of oxidation, depending on the alloy composition. Consideration of these data suggests that other factors in addition to oxidation temperature must be considered in predicting wh...

Fluorine‐Enhanced Oxidation of Silicon Effects of Fluorine on Oxide Stress and Growth Kinetics

The influence of fluorine on film stress as well as on oxide growth kinetics for oxide films grown by fluorine-enhanced thermal oxidation of silicon using NF3 as fluorine source is reported. The effect of NF3 concentration and oxidation temperature on the measured stress has been studied and compared to kinetics effects. A marked stress reduction while the oxidation rate is greatly enhanced can be observed in fluorinated oxides with respect to dry ones grown at the same temperature. This suggests a fluorine-related mechanism for stress relaxation. Moreover, a saturation of the stress relaxation with increasing fluorine exposure is observed which seems to be correlated with the saturation that we observe for the oxidation rate enhancement.

Influence of in situ applied stress during thermal oxidation of (111)Si on Pb interface defects

The results of a series of experiments are reported in which constant, controlled levels of in-plane stress were applied in situ to oxidizing (111) silicon substrates. Electron spin resonance measurements show that the properties of inherently incorporated electrically active Pb defects at the (111)Si/SiO2 interface are affected; among others, tensile stresses decrease the number of Pbs, while compressive stresses have the opposite effect. The results are in agreement with the generally accepted relationship between Pb-defect generation and interfacial mismatch (stress).

Enhanced tail diffusion of ion implanted boron in silicon

The enhanced diffusion tail of implanted boron in Si was studied using conventional furnace annealing. Surface layer stripping was applied to remove part of the sample before annealing in order to distinguish the effect of the defect‐rich surface region from the tail region on the enhanced diffusion of boron. The boron concentration profiles were obtained with secondary ion mass spectrometry (SIMS). Spreading resistance profiles were also measured to compare with the SIMS profiles. The results show that implantation‐induced damage in the surface region is responsible for the enhanced boron diffusion. Channeled boron in the tail of the implantation profile becomes activated during annealing and has little effect on the tail redistribution during annealing.

Stress effects in the oxidation of planar silicon substrates

We report here on the results of a series of experiments in which constant, controlled levels of in-plane stress were applied to oxidizing silicon substrates. The results indicate that compressive stresses tend to retard the growth of the oxide layer, while tensile stresses have an uncertain effect. These results are at variance with the predictions of a widely held model for the effect of stress upon the oxidation of silicon.

Interface State Density Reduction and Effect of Oxidation Temperature on Fluorine Incorporation and Profiling for Fluorinated Metal Oxide Semiconductor Capacitors

The effect of fluorine incorporation on the as‐grown interface state density of the system was investigated using MOS capacitors with fluorinated oxide dielectrics grown by oxidation as test structures. A clear reduction of the interface trap density, attributed to fluorine‐induced passivation of interfacial dangling bonds, weak bonds, and weak interactions, was shown for additions in the parts‐per‐million range as compared to dry oxides. Fluorine incorporation in the oxide was investigated with SIMS profiling. The application of a pulsed oxidation process in which the fluorine source is added to the oxidant in intervals within the total oxidation time demonstrated that the variation of oxidation processing parameters strongly influences the resulting fluorine profile. A two‐peak pattern of the fluorine profile, with one peak in the interfacial area and the other corresponding to the oxide area grown during the step, was observed. This pattern was strongly dependent on the oxidation temperature, with the interfacial fluorine accumulation more pronounced with increasing temperature. The pronounced influence of the oxidation temperature on the fluorine profile resulting from oxidation was ascribed to a thermally activated replacement reaction of bonded fluorine by oxygen.

Effect of fluorine on the diffusion of through‐oxide implanted boron in silicon

Annealing of boron through‐oxide implanted silicon has been known to induce an incubated, oxygen‐precipitation enhanced boron diffusion. In this letter, it is shown that annealing the ‘‘through‐oxide’’ implants in a NF3‐containing N2 ambient effectively reduces the incubated enhanced diffusion. The effect of fluorine is further demonstrated for boron plus fluorine through‐oxide implants with pure N2 annealing. Comparing the boron diffusion between boron plus fluorine and boron plus neon implants suggests that fluorine does not have a chemical effect on capturing the point defects that cause the enhanced diffusion. Rather, fluorine is believed to be incorporated in the oxygen precipitates, which alters the point defect generation.

Silicon‐fluorine bonding and fluorine profiling in SiO2 films grown by NF3‐enhanced oxidation

The incorporation and chemical bonding of fluorine introduced in SiO2 thin films by NF3‐enhanced oxidation of silicon has been studied by means of x‐ray photoelectron spectroscopy and secondary ion mass spectrometry depth profiling. Fluorine bonding in the oxide network is observed, indicated to occur in the area of the oxidizing interface and resulting in depth profiles which reflect the manner of the exposure of the growing oxide to the NF3 fluorine source during oxidation.

The Effect of Fluorine Additions to the Oxidation of Silicon

Experiments were carried out to study the effects of fluorine additions to a dry oxidation ambient. Two distinct classes of fluorine sources, liquid dichlorofluoroethane (C 2 H 3 Cl 2 F), and gaseous nitrogen trifluoride (NF 3 ), were investigated. We experimentally found that small fluorine additions caused large enhancements in oxidation kinetics. The oxidation kinetics data were analyzed by both the power of time and linear-parabolic models as a function of fluorine addition, temperature, and the type of fluorine additive

Oxygen content of heavily doped silicon

We have determined the oxygen content of heavily doped n‐ and p‐type silicon using charged particle activation analysis. Specifically, when crystals are grown using the Czochralski technique and keeping growth parameters constant, the oxygen content does not vary with dopant additions for p− and n+ crystals but does seem to increase for p+ crystals.