We present the results of our development of a deep silicon etching technique, the modified Bosch-type process. Its feasibility was also investigated. This modified Bosch-type process is based on the well known Bosch-type process, but our modified Bosch-type process consists of the etching/passivating time, process transition step, and ion energy control. This modified Bosch-type process has been characterized with respect to ion energy, substrate temperature, and feature size. We found that the etching and deposition characteristics of passivating film were closely related to the resulting deep silicon etch profile. Up to a 40-50 mu m deep silicon structure with vertical and positively sloped profiles was realized by the modified Bosch-type process, depending on a few parameters. In this work, this modified Bosch-type process was applied to silicon mold fabrication used for a structuring microarray and optical power splitter. Replication results confirm that this process is promising for achieving high-yield, reliable microstructures on polymer films. (c) 2005 American Vacuum Society.