Semiconductor Epitaxial and Nonepitaxial Overgrowth from Solutions
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3 Max-Planck-Institut fdr Metallforschung, Institut fir Physik, and 4 Max-Planck-Institut fir
Festk6rperforschung; both: Heisenbergstr. 1,D - 70569 Stuttgart, Germany
ABSTRACT Having grown semiconductor-on-insulator (SOI) layers by liquid phase epitaxy (LPE) we have investigated their properties by x-ray topography, optical-, atomic force- and high resolution electron microscopy and by etching experiments. A first series of experiments was carried out on (111)-oriented Si substrate wafers which were partially masked by thermal oxide. Area- selective LPE, which was then applied and followed by epitaxial lateral overgrowth (ELO), yielded SOT layers of high quality. Silicon SOl layers had aspect ratios of up to 65 and were typically dislocation-free. These highly perfect SOI structures facilitated studies of the specific processes for semiconductor lateral growth over amorphous layers. Vertical stresses were detected in the substrate-layer systems. They were found to influence the shapes of the SO layers. Our studies suggest that here is a model case for solution growth of thin semiconductor lamellae on dissimilar substrates. Subsequently, a second series of experiments consisted in having SiGe lamellae grown in the same fashion. These experiments confirm that the same morphology is observed for Gecontents up to 2 percent.
INTRODUCTION There have been efforts to produce high-quality semiconductor layers on insulator (SOI) with special emphasis on silicon layers for the past twenty years. Attention now focuses on SIMOX (separation by implanted oxygen [1]) and wafer-bonding techniques [2]. Another technique which operates far below the melting point of the considered semiconductors and which produces highly perfect layers is liquid phase epitaxy (LPE). By this technique silicon or silicon-germanium layers can be grown on silicon oxide by a uniform low-temperature process [3,4]. Characterization by means of optical [5] and electron microscopy [6] and by xray topography [7] and electrical measurements [8] shows the excellent properties of the layers. In the present paper we will discuss the strains which were recently observed in these layers. The strains were found to be closely related with the growth process. A very essential fact was that the layers firmly adhere to the oxide. The strains were detected by means of electron microscopy and x-ray topography and result mainly from an approximately conical curvature of the SOI-layers with radii in the range of a few centimeters. An adhesive force acting during growth was proposed and seems to explain most of the experimental findings. Adhesive forces of this kind may be of general importance for the growth of single crystalline layers on dissimilar substrates. 189 Mat. Res. Soc. Symp. Proc. Vol. 399 @1996 Materials Research Society
GROWTH OFSOI-LA YERS FROMSOLUTION The substrates for our experiments are thermally oxidized (111)-oriented Si wafers which have a misorientation of 8 = 0.33' in the ± [112] direction. Seeding areas for epitaxy are prepared on the wafer by r
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