AVS 45th International Symposium
    Selected Energy Epitaxy Topical Conference Thursday Sessions
       Session SE-ThM

Invited Paper SE-ThM3
Observation and Nucleation Control of Ge Growth on Si Surfaces using Scanning Reflection Electron Microscopy

Thursday, November 5, 1998, 9:00 am, Room 327

Session: In Situ Characterization and Real-Time Diagnostics of Surface Growth Processes
Presenter: M. Ichikawa, Joint Research Center for Atom Technology, Japan
Correspondent: Click to Email
Scanning reflection electron microscopy (SREM) is one of the useful techniques for studying surface phenomena and also for modifying surfaces through the use of a focused beam. We have developed high-resolution SREMs (2 nm beam diameter) combined with other surface analysis techniques, such as STM, scanning Auger electron microscopy and X-ray photoelectron spectroscopy (XPS), and applied these to study and control surface reaction phenomena. In this study, we mainly show that focused electron beam (EB)-stimulated reactions in ultra-thin SiO@sub 2@ films on Si substrates, are useful for controlling Ge growth on Si surfaces. Ultra-thin Si oxide films less than 1 nm thickness are formed by heating clean Si substrates in oxygen gas at about 700 °C. The thermal oxidation occurs layer-by-layer. The interface between the oxide film and Si substrate becomes atomically abrupt. The oxide film is mainly composed of silicon dioxide (SiO@sub 2@), which is confirmed by XPS. When the samples are annealed at about 750 °C after focused EB irradiation on the SiO@sub 2@ films at room temperature, Si clean surfaces (open windows) are exposed in the oxide films on the substrates due to the EB-stimulated oxygen desorption and selective thermal decomposition of SiO@sub 2@ at the EB irradiated areas. The typical size of these open windows is about 10 nm. After the deposition of Ge on the sample with Si open windows and subsequent annealing, Ge island growth occurs only in the window areas by Ge diffusion from the surrounding areas during the thermal decomposition of SiO@sub 2@ where Ge reacts with SiO@sub 2@ producing volatile SiO and GeO gases. Ge islands with 10-20 nm size can be formed at given areas on the Ge wetting layer by this method. Other Si nanostructures can be also formed by the selective thermal reactions on the patterned ultra-thin SiO@sub 2@. This work is supported by NEDO.