Development of the micromilling process for high-aspect-ratio microstructures

At the macroscale, the milling process is very versatile and capable of creating three-dimensional features and structures. Adaptation of this process at the microscale could lead to the rapid and direct fabrication of micromolds and masks to aid in the development of microcomponents. This task has been undertaken, and results of the process indicate it can become an increasingly useful method. The micromilling process is characterized by milling tools that are currently in the range from 22-100 /spl mu/m in diameter and made by the focused-ion beam machining process. The tools are used in a specially designed, high-precision milling machine. Results are comparable to other processes currently used to fabricate mold and mask features. The micromilling process can create trench-like features with nearly vertical sidewalls and good smoothness. External corners are sharp and stepped features can be machined simply by programming those shapes. The process is direct, and therefore dimensional errors do not accumulate as can occur with serial fabrication processes.