Microstructural Characterization of Si Wafers Processed by Multi-Wire Sawing of Hot Pressed Silicon Powder Based Ingots

The purpose of this work is to verify the possibility to process highly doped Si supporting substrates using a 2-step process: (i) sintering of a low-cost Si powder based ingot using hot pressing and a ELKEM Silgrain material as a feedstock; and (ii) wafering of such ingots using multi-wire sawing technique similar to that, which is used for cast multi-Si or Cz-Si grown ingots. Moreover, the possibility to dope Si powder ingot at sintering temperatures below melting point of Si, using a mixture of Si and boron powders to fabricate highly conductive Si wafers is verified as well. The slurry technique has been chosen for multi-wire sawing of sintered Si powder based ingots. Surface properties of Si powder based substrates as well as their chemical composition have been studied by optical microscopy imaging and energy-dispersive X-ray spectroscopy (EDX). Although the overall concentrations of oxygen, carbon and possibly also metal impurities, which are initially present in a low-cost Si feedstock, are too high to achieve acceptable semiconducting properties, it is concluded, that sintered Si powder based wafers have high enough conductivity (resistivity similar to 0.001 Omega cm) to serve as supporting substrates for low cost Si wafer equivalent structures. (C) 2014 WILEY - VCH Verlag GmbH & Co. KGaA, Weinheim