Fluorocarbon Film Assisted Wafer-Level Sub-100 nm Metal Mold Fabrication for Nanoimprint Lithography

Abstract

Availability of durable molds with nanometer-scale features acts as a bottleneck for nanoimprint lithography and nano-injection molding. Silicon (Si) nanomolds are typically fabricated by electron beam lithography which is very expensive technology and the life time of the Si mold is also short. Nickel molds for nanoimprinting are fabricated by electroforming on Si wafers. After electroforming, Si mold is fully dissolved in KOH to get metal mold. This method is not only time consuming but also results in the loss of costly Si master mold. This thesis demonstrates a very cost effective method for fabrication of wafer level CoNi nanomolds with better residual stress profile and nano features transfer without the consumption of silicon mother mold. For this purpose, 20nm fluorocarbon antistiction film was applied on the silicon mold prior to seed layer deposition and electroplating to ease the separation of metal mold without sacrificing costly mother mold. Chloride bath was used in electroplating of CoNi mold. Step coverage of fluorocarbon film on micro and nano features was found to be dependent on the aspect ratio of nanofeatures. Stress nature and level as well as cobalt content in the electroformed mold were controlled by changing the anode-to-cathode gap in the bath. 6-inch CoNi nanomold was successfully duplicated without consuming the mother mold with this method.