Improving the quality of silicon carbide wafers
Rapid thermal annealing processes are important for the manufacture of high performance semiconductors used in microelectronic applications. Current practice relies on the use of low energy ion beam implantation before the thermal annealing. Although this allows effective control of the mainstream device processing, lower wafer throughputs may be observed at energies below 1 keV. In order to resolve this problem Flash Lamp Annealing (FLA) processes have been adopted. An alternative approach to the FLA technique is the Flash Lamp Supported Deposition of SiC (FLASiC) that allows the heteroepitaxial growth of thin films of Cubic SiC (3C-SiC). 3C-SiC displays the highest electron mobility of all known SiC polytypes without any of the certain defects that are found in other polytypes. Due to the high quality and low cost of substrate, heteropitaxial growth of 3C-SiC on single crystal Si wafers is very popular. This method can lead to the growth of a thin, low defect density seed layer of SiC on which thicker epitaxial SiC layers may grow. Yet, the 3C-SiC layer involves two regions of different quality that hinders the exploitation of the high quality portion of the 3C-SiC layer to its full potential. Additionally, the rapid melting coupled with the presence of residual defects and thermal stresses may result into buckling phenomena, which lead to the bending and concavely shaping of the substrate. Answering this need, an improved version of the FLASiC process, the so-called inverse FLASiC (i-FLASiC) consists of depositing two layers. Thereby, a catalytic layer of poly-Si is deposited on the epitaxial 3C-SiC film and a capping layer on the former. The i-FLASiC process results into a thin 3C-SiC film of improved quality that could be used as a seed for further epitaxial growth of thick 3C-SiC layers, facilitating the fabrication of bulk 3C-SiC wafers of excellent quality.