STUDY OF SI(111) IMPLANTED WITH AS IONS BY X-RAY-DIFFRACTION AND GRAZING-INCIDENCE METHODS

The Si(111) wafer cut from a bulk single crystal obtained by the Czoch ralski method was implanted with 5 x 10(16) I cm(-2) of As ions of ene rgy 80 keV. The dose applied was chosen above the amorphization limit of the silicon substrate. Two samples, implanted and a reference, were studied by grazing incidence X-ray reflectometry and X-ray diffractio n methods using a high resolution Philips MRD system equipped with a C u source and a channel-cut monochromator. The obtained spectra were co mpared with distributions of ion range and defect production calculate d with TRIM program [1], as well as with theoretical models of reflect ivity [2, 3]. The results of grazing incidence X-ray reflectometry ref lectivity of the implanted sample show well-pronounced oscillations, w hich can be associated with a layer about 50 nm thick, approximately c omparable to the thickness of the defected layer estimated from the TR IM method. Theoretical calculations of reflectivity clearly indicate a n occurrence of a Si layer of electron density lower about 10-15% comp aring to the unimplanted Si sample. This can be due to the vacancy pro duction during ion implantation. A comparison of the spectra with a de nsity distribution profile concluded from the TRIM calculations shows large discrepancies. The results indicate the applicability of grazing incidence X-ray reflectometry method in a study of amorphization proc esses in implanted layers.