KRF LASER EPITAXY OF SILICON-GERMANIUM ALLOY LAYERS BY IRRADIATION OFSI(1-X)GEX 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 ener gy density was sufficiently high (0.5 J/cm(2)) to melt the whole CVD f ilm. The CVD growth either without or with laser assistance, as well a s the post-growth irradiation were monitored by online single waveleng th ellipsometry, which allowed to follow in real time the modification of the film morphology induced by the laser treatment. Effective smoo thing of the surface islands upon laser irradiation was revealed in ev ery case. Particularly, for the laser-assisted CVD growth, the influen ce of the laser irradiation modality on the surface microroughness dur ing growth was evidenced and the irradiation condition for optimal sur face planarization identified. The microstructural properties of the S iGe layers were investigated by high resolution x-ray diffraction and Rutherford backscattering spectrometry. In the case of the laser-assis ted CVD growth, the solidification of alloys exhibiting excellent epit axial 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 partic ularly attracting for the production of compositionally graded SiGe fi lm, to be applied as buffer layers in SiGe based devices. (C) 1998 Ame rican Vacuum Society.