As conventional Si based device structures are approaching their physical limits, Ge epitaxial film on Si (100) substrate becomes more attractive for virtual substrates, on which advanced channel engineering techniques to be applied, or integrated Ge photonic devices to be formed. Low threading dislocation density and smooth surface are key features to realize such applications of the Ge/Si virtual substrate. To date, growth methods for Ge epitaxial film on Si (100) substrate involve at least one of thick (micrometer order) Si x Ge 1-x buffer growth process, high temperature annealing steps or Chemical mechanical polishing (CMP) process, any of which could compromise reliability and suitability for production.In this study, feasibility of ultra thin (in the order of 10 nm) Si x Ge 1-x buffer layer for pure Ge epitaxial growth was investigated with regard to Ge layer's crystallinity, threading dislocation density, and surface roughness, as well as suitability for production.As a result, Ge epitaxial film that has low threading dislocation density with very smooth surface (root mean square (RMS) = 0.44 nm) was successfully grown in shorter process time by using SiGe buffer layer 1/1000 thinner than that of previously known methods without using CMP or high temperature annealing.

The SiO2 etch characteristics were investigated using a narrow-gap reactive ion etching (RIE) apparatus. The etch rate was decreased and the selectivity to Si was increased when the upper electrode temperature was increased. However, the etch characteristics were independent of the absolute temperatures of the electrodes. This phenomenon can be explained in terms of the difference in the polymer deposition rate on walls that have different temperatures.

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We report a process for Silicon (Si) nano-crystal dots fabrication using a cold-wall Ultrahigh-Vacuum Chemical Vapor Deposition (UHV-CVD) system. Si2H6 gas was used as the pre-curser and irradiated upon SiO2 film on Si wafer to form Si nano-crystal dots.In our system, nucleation, growth, and coalescence phases of nano-crystal dots on SiO2 were found to be related with the optical pyro-meter's read-out curve.At first, the optimum gas irradiation time which gives the highest dot density without coalescence was decided for every gas irradiation condition by using an optical pyro-meter. Then, the dependence of optimum gas irradiation time, dot diameter and dot density on gas flow rate and wafer temperature were investigated. A decrease of wafer temperature or an increase of gas flow rate during the nucleation and growth phase results in a decrease of dot diameter and an increase of dot density. The optimum gas irradiation time was prolonged by decreasing wafer temperature or gas flow rate.Finally, a reproducible process of forming non-coalesced, small size, and high-density Si nano-crystal dots of about 5.5nm in diameter with density of 1x1012 dots/cm2 were obtained. Typical process time to get such dot formation characteristics was about 10 minutes, which were long enough for ensuring reproducibility.