SURFACE PHOTOCHEMICAL-REACTIONS OF DIMETHYLGERMANE, GE(CH3)(2)H-2, AND THEIR APPLICATION TO STEPWISE GE GROWTH

Surface chemical processes of dimethylgermane are investigated by x-ra y photoelectron spectroscopy and thermal desorption spectroscopy. Self -limiting adsorption, in which further adsorption of dimethylgermane i s stopped is found in the exposure range of 3 x 10(5) to 1 x 10(8) Lan gmuir and in the temperature range of 296 to 673 K. By thermal desorpt ion spectroscopy, it is confirmed that this phenomenon operates by met hyl groups terminating in Ge dangling bonds in the adlayer. These meth yl groups in the outermost adlayer are found to be further desorbed by ultraviolet light irradiation. Effective wavelengths for photochemica l decomposition of Me groups in the dimethylgermane adlayer are confir med in the wavelength region below 310 nm. On the basis of these resul ts, the feasibility of photochemical stepwise Ge growth is examined by the repetition of a process sequence that consists of dimethylgermane introduction onto the substrate surface, residual dimethylgermane eva cuation, and photoirradiation. Although one monolayer formation per pr ocess sequence is not achieved in this work, the effectiveness of the photochemical process for Ge growth using dimethylgermane (DMGe) is co nfirmed.