This paper, under the NEDO project, aims at technology development of high-quality, n-type multicrystalline Si wafers. The targets of the technology development are to realize a high minority-carrier lifetime of 1 ms and to apply for a commercial solidification furnace. In particular, real-time observation of the unidirectional solidification process, the effect of quartz crucible quality on the ingots, the quality improvement of n-type Si wafers and evolution to a commercial furnace will be described. (C) 2009 Elsevier B.V. All rights reserved.