KrF laser epitaxy of silicon germanium alloy layers by irradiation of Si (1-x)Ge x/Si (100) structures

KrF excimer laser pulses at 248 nm were used to irradiate Ge and SiGe films grown on Si (100) by ultrahigh vacuum chemical vapor deposition (CVD) or to assist the CVD growth itself. In both cases the laser energy density was sufficiently high (0.5 J/cm 2) to melt the whole CVD film. The CVD growth either without or with laser assistance, as well as the post-growth irradiation were monitored by online single wavelength ellipsometry, which allowed to follow in real time the modification of the film morphology induced by the laser treatment. Effective smoothing of the surface islands upon laser irradiation was revealed in every case. Particularly, for the laser-assisted CVD growth, the influence of the laser irradiation modality on the surface microroughness during growth was evidenced and the irradiation condition for optimal surface planarization identified. The microstructural properties of the SiGe layers were investigated by high resolution x-ray diffraction and Rutherford backscattering spectrometry. In the case of the laser-assisted CVD growth, the solidification of alloys exhibiting excellent epitaxial quality and graded Ge profiles was attained. The alloys resulted fully strained for Ge content of 5 at %. This growth technique which allows to design the Ge profile inside the alloyed layer, by adjusting precursor gas fluxes and laser irradiation conditions, results particularly attracting for the production of compositionally graded SiGe film, to be applied as buffer layers in SiGe based devices. © 1998 American Vacuum Society.