SiGe Epitaxial Growth on Si Substrate Using Al-Ge Paste

Abstract

We investigated the liquid-phase growth of silicon-germanium (SiGe) epitaxial layers formed on Si substrates by a simple and rapid process of screen-printing of Al-Ge paste followed by high temperature annealing. Aluminum (Al) and germanium (Ge) (7:3) mixed paste was prepared, screen-printed on a Si substrate and annealed in an infra-red (IR) furnace at peak temperatures between 800°C to 1000°C. After reaching the Al melting point at 660°C, the melted Al dissolves the Si surface and Ge powder in the paste forming a thick liquid phase of melted Al-Ge-Si layer on the dissolved surface of the Si substrate. During the cooling process, a SiGe layer starts to grow epitaxially at the Si interface. The formed SiGe was observed by scanning electron microscope (SEM), and energy dispersive X-ray spectrometry (EDX) and characterized by X-ray diffraction reciprocal space mapping (XRD-RSM). The thickness of the SiGe layer depended on the peak temperature reaching about 25mm at 1000oC. The results suggest the epitaxially grown SiGe is strain-relaxed with a graded Ge concentration.