Controlling the Low-Temperature Ionic Purification of a Silicon Surface by Electron Spectroscopy

A comparative study is carried out for etching a surface with negative and positive ions, and the results show completely opposite physical processes occur on a silicon surface. Irradiation with positive ions exhibits oxide removal, while irradiation with negative ions shows an intense oxidation of the sample surface. Technology for low-temperature ion cleaning and the electron-spectrometric control of silicon wafers has been developed. This technology has been shown that only irradiation with caesium ions followed by annealing at 650 °C leads to an atomically clean silicon surface for several minutes, which is dependent on the pressure of residual gases under vacuum. After cleaning in a vacuum of 10-9 Pa, the silicon surface begins to oxidize again within 10 min.

Surface Studies Relevant to the Initial Stages of Diamond Nucleation

ABSTRACTStudies of diamond heteroepitaxy on silicon indicate that C-C surface species act as nucleation precursors. We have investigated the conversion of the Si(100) 2×1 surface to SiC using C2H4 to obtain an understanding of how C-C species may be formed and to determine the effect of an O-adlayer on enhancing or selecting the reaction channel which leads to these species. Under appropriate conditions, the interaction between C2H4 and the clean silicon surface yields both SiC and C-C species. The presence of an O-adlayer significantly reduces the activity of silicon and enhances the formation of sp2 and sp3 C-C species. These results provide key insights into diamond nucleation conditions in conventional growth processes.

UV Laser Processing of Semiconductor Devices

The use of a pulsed UV excimer laser based process for the incorporation of dopant impurities into Si is described. The process can result in high concentration shallow box like profiles suitable for submicron VLSI device fabrication. The process consists of exposure of the clean silicon surface to a doping gas (B2H6, AsH3, PH3) then driving the adsorbed monolayers of dopant into the Si by a melt-regrowth process initiated by a pulsed XeCl excimer laser. Modeling of the process allows prediction of the resulting doping profiles and electrical properties of the doped layers. Excellent crystal quality of the doped layers is found even without a postdoping anneal. Also, recent results indicate that post doping annealing may not be needed for improvement of the electrical characteristics of the doped layers provided certain conditions are met. Detailed descriptions of the process, results, modeling and device fabrication are presented.