Crystalline Perfection of Semiconductor Surfaces by X-Ray Multiple Diffraction
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method, based on a three-beam multiple diffraction (MD) case (incident, primary and secondary beams), to analyze polishing-induced damage in semiconductor surfaces. Here, the effects of mechanical polishing and/or chemical etching on GaAs and Ge (001) surfaces have been investigated using a bidimensional X-ray scanning of the intersection point (hereafter called Tpoint [4]) defined by the condition of simultaneous Bragg diffraction from 002 and 11 1 planes. CRYSTALLINE IMPERFECTIONS AND X-RAY MULTIPLE DIFFRACTION It is well known in X-ray diffraction theory that the crystal perfection determines if the kinematical or the dynamical theory should be used to explain the observed intensities. These theories were formally developed for the ideally imperfect crystal (mosaic crystal) and for the highly perfect one, respectively. An intermediate crystal, between the above ones, is that with large diffracting perfect regions so that their reflectivity undergoes primary extinction [5] and the misorientation is such that coherence among the regions is negligible. Then, corrections in the kinematical reflectivity to take into account its reduction due to dynamical diffraction within the perfect regions had to be considered [6]. Furthermore, a statistical dynamical diffraction theory has been developed [7] to explain diffraction from real crystals and is based on two parameters releted to X-ray phase coherence in short-range and long-range order.
215 Mat. Res. Soc. Symp. Proc. Vol. 355 01995 Materials Research Society
The full width at half maximum (FWHM) of a double-crystal X-ray rocking curve obtained from highly absorbing materials [8] has indicated the existence of crystals diffracting according to the intermediate crystal. In general, for crystals with moderate absorption the one-dimensional character of the rocking curve is not able to either distinguish between primary and secondary [9] extinction effects or give information on the distribution of misorientations in directions other than those normal to diffracting planes. Using triple crystal diffractometry [3], it is possible to separate the diffracted intensity into its dynamical (coherent) and kinematical (incoherent) components [10]. In this sophisticated technique, the rotation angle of highly perfect analyzer crystal adds an extra angular dimension to the diffraction process. However, even in this technique the crystalline perfection is investigated only in the direction normal to the diffracting planes. An extra angular dimension is also added to the diffraction process when the diffraction condition is simultaneously satisfied by two or more atomic planes inside the crystal, as in the
case of multiple diffraction (MD) phenomenon. Under three-beam MD condition, Hij reciprocal vector represents the ij reflection that transfers energy from beam i to beam j. Beam 0 is the incident beam and beams 1 and 2 are generated by the 01 and 02 reflections, respectively. Under this condition, the relationship H0 1=H 0 2+H 2 1 is satisfied. In the chosen three-beam case, th
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