Electrodeposited Metal Structures in High Aspect Ratio Cavities using Vapor Deposited Polymer Molds and Laser Micromachining

This paper reports a laser-assisted fabrication scheme for three-dimensional (3-D) electrodeposited metal structures into high aspect ratio trenches. A polymer (parylene C) is conformally deposited onto a highly nonplanar surface, selectively laser ablated, and used as an electroplating mold to fabricate metallic structures. Laser ablation of high-resolution (< 10 mum) features is performed using a 248 nm KrF Excimer laser. The ablation parameters for the parylene layer have been characterized for various film thicknesses. Metal lines of 2 mum thickness, and 2.5 mum width have been electroplated into 300 mum deep silicon trenches. The minimum resolution achieved is less than 5 mum. This process can potentially be applied toward the fabrication of embedded inductors, high density electrodes, buried interconnects or high voltage circuitry in CMOS and MEMS devices.