Research of Epitaxial Growth and Electrical Analysis of Si-Ge-C Layer

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Lowering process temperature is important to overcome thermal problems such as interdiffusion between doped layers and autodoping effects. Furthermore, such low temperatures are also required for the growth of strained SiGe or other compound semiconductors based on group IV elements. The introduction of such SiGeC-based heteroepitaxial devices open a new field in the Si technologies.We studied the structural properties of SiGe and SiGeC alloys by ab initio total-energy calculations. It is found from these calculations that the Ge cluster is a stable structure in a SiGe alloy. Furthermore, it is also demonstrated that Vegard's law is valid in a SiGeC system whose C content is less than 3%. The total-energy calculation of the Si0.72Ge0.25C0.03 alloy in which the number of Ge-C bonds around a C atom varies shows that the energy increases on increasing the number of Ge-C bonds. The mechanism of this increase is considered, taking into account the cohesive energy difference of the SiC and G … More eC alloys and the atomic configuration around the C atom.We applied Hot Wire (HW) Cell method to low temperature Si epitaxy. The substrate temperature was 200℃. When the pressure was as low as 5x10ィイD1-4ィエD1 Torr, the film structure was amorphous. By optimizing the pressure during the growth, we obtained epitaxial Si films on Si(100) substrate with film thickness of over 400nm at the pressure of 0.015 Torr. The growth rate was about 0.2mn/s. The film structure changed from epitaxial to polycrystalline by increasing the pressure up to 0.1 Torr. In addition, it was found that the hydrogen was incorporated into the epitaxial Si films from IR spectra measurement. There were absorption peaks at 2150 and 2050 cmィイD1-1ィエD1 originating from Si-H related bondings. X-ray diffraction pattern was also measured, and the peak of the epitaxial Si film was shifted to lower degree compared to the peak of substrate. It indicated that the lattice constant was expanded by the hydrogen atoms which made Si-H-Si configuration in the films. This stress caused the critical thickness for epitaxy and it was about 100nm at the pressure of 0.033 Torr. Less