The growth temperature dependence of the thin thermally oxidized Si(001)/SiO2 interface width was studied using synchrotron x-ray diffraction. Nine samples with oxide thickness of about 100 Å were studied, with growth temperatures ranging from 800 to 1200 °C. The oxides were prepared by rapid thermal oxidation. We found that interfacial roughness decreases linearly with increasing growth temperature, with a measured interface width of 2.84 Å for the sample grown at 800 °C, and 1.76 Å when grown at 1200 °C.

We describe a novel substrate patterning geometry which can reduce epilayer threading dislocation densities by up to two orders of magnitude in GexSi1−x/Si(100) (x∼0.15–0.20) het- eroepitaxial layers. The basic pattern consists of a two-dimensional array of ∼2 μm diameter oxide pillars which are separated from each other by varying pitch dimensions, and which are staggered slightly from their neighbors with respect to the in-plane 〈011〉 directions. This ensures that a misfit dislocation nucleating at any point within the epilayer must eventually propagate into one of the pillars, where the threading end will be terminated. Prospects for surface planarization and overgrowth of the pillars are discussed.

Traditional techniques for growing Si-Ge layers have centered around low-temperature growth methods such as molecular-beam epitaxy and ultrahigh vacuum chemical vapor deposition in order to achieve strain metastability and good growth control. Recognizing that metastable films are probably undesirable in state-of-the-art devices on the basis of reliability considerations, and that in general, crystal perfection increases with increasing deposition temperatures, we have grown mechanically stable Si-Ge films (i.e., films whose composition and thickness places them on or below the Matthews–Blakeslee mechanical equilibrium curve) at 900 °C by rapid thermal chemical vapor deposition. Although this limits the thickness and the Ge composition range, such films are exactly those required for high-speed heterojunction bipolar transistors and Si/Si-Ge superlattices, for example. The 900 °C films contain three orders of magnitude less oxygen than their limited reaction processing counterparts grown at 625 °C. The films are thermally stable as well, and do not interdiffuse more than about 20 Å after 950 °C for 20 min. Therefore, they can be processed with standard Si techniques. At 900 °C, the films exhibit growth rates of about 15–20 Å/s. We have also demonstrated the growth of graded layers of Si-Ge, and have determined that a strain gradient exists in these layers.

Using x-ray diffraction techniques, we measure the root-mean-square width of the buried crystalline/amorphous Si(001)/SiO2 interface, as a function of oxide thickness. We find that the interface width decreases with increasing oxide thickness; the oxide growth process kinetically smoothens the buried interface. We also find a difference between the rate of smoothing for wet and dry oxides.