Si Etching with High Aspect Ratio and Smooth Side Profile for Mold Fabrication

A silicon etching process for imprint mold fabrication is developed. For the imprint mold, an etching profile with a smooth side wall is fabricated in order to obtain good release characteristics. The alternative process using C 4 F 8 plasma and SF 6 +O 2 plasma is applied using an inductively coupled plasma etcher. The relation between the etching profiles and the process parameters is examined under various etching conditions. A vertical etching profile without a side wall scallop can be obtained at 60% O 2 content. A pattern 0.12 µm wide with an aspect ratio of 27 is fabricated. A silicon mold is fabricated by the etching process under good etching conditions. Fine patterns on the mold are transferred to a 2-mm-thick poly(methyl methacrylate) (PMMA) plate by the thermal imprinting. Since a mold pattern with a smooth side wall is used, the mold can be released from the PMMA substrate without difficulty. A fine pattern 0.12 µm in wide is transferred to the PMMA substrate.