Precision manufacture of optical disc master stampers

Abstract

This paper details a new manufacturing process for compact disc master stamper production. Stamper is an optical disc industry term for the mold used to replicate polymer compact discs (CDs) in an injection molding device. The stamper surface contains a negative image of the CDs more than 1 billion, submicrometer features embossed in a spiral pattern on a 138-mm diameter substrate. In conventional mastering, nickel submaster stampers are generated by electroforming from a glass master. In the proposed process, submaster stampers are not required, and a ceramic master is used directly as a stamper for injection molding. In the new process, ceramic substrates are ion machined through a photoresist mask, resulting in improved productivity, reduced hazardous waste, and lower production costs. All critical process steps have proved feasible in the research reported here. The new stamper production technique replaces the conventional glass master substrate with a tough ceramic and replaces several difficult electrochemical and manual operations with a single precision ion machining step. Processes that precede and follow stamper fabrication remain largely unchanged. In the new process, precision stamper manufacturing (PSM), more than 200 minutes of chemical processing, electroforming, back-polishing, punching, and handling are replaced by fewer than 20 minutes of automatically controlled ion machining. At the same time, PSM eliminates nearly all process steps that produce toxic and hazardous wastes. The process is suitable for production of CD-audio, CD-ROM, and high-density DVD formats. A process flow diagram and a series of proof-of-concept experiments are described.