Improvement of 4H-SiC selective epitaxial growth by VLS mechanism using Al and Ge-based melts

Al-Si and Ge-Si systems were studied for selective epitaxial growth (SEG) of 4H-SiC by Vapour-Liquid-Solid mechanism. Al-Si and Ge-Si stacking bilayers were deposited on 8 degrees off, Si face, 4H-SiC substrates. After layer patterning, the samples were heated up to 1000 and 1220 degrees C respectively for Al-Si and Ge-Si stackings in order to melt the layers. Propane diluted in Ar was introduced either during the initial heating ramp, before melting of the alloy, or after reaching the temperature plateau. In both cases, SEG of SiC was achieved. However, it was found that the introduction of propane before melting was a key parameter in order to improve the homogeneity of the deposit. This improvement was noticeable with Al-Si and spectacular with Ge-Si. This latter case gave the best results in terms of smoothness and uniformity of the epitaxial deposit on all the pattern sizes and shapes. Some 3C-SiC polycrystalline material appears on the pattern edges and also on the layer itself for long time growth. When H-2 was used instead of Ar as the vector gas, this polycrystal was eliminated at the edges. The thickness of the deposits was determined by mechanical profiling and compared to SIMS measurements. (c) 2006 Elsevier B.V. All rights reserved.