Graphite Membrane Applied for High-Aspect-Ratio Mcirostructures Fabrication

摘要

X-ray mask is the most important component in the X-ray micromachining. Absorber patterns have to forming onto a working mask, then patterns can be transferred into the substrate. Graphite membrane has characteris of low atomic number, electrical conductor, and rigid body suitable for a support diaphragm in a working mask. The treatment of graphite membrane and patterning gold absorber is described in this article. The commercial graphite is a polycrystalline carbon with rough surface (Rt > 5.0 mu m). Rough surface causes pattern defects on the working mask after gold electroplating. The acceptabe roughness is Rt < 1.0 mu m since the absorber thickness requiring 2.0 mu m at least. Thin absorber cannot create enough contrast during exposure and development process. Estimating gold absorber thickness is according to the X-ray dose spectrum penetrating filter materials. The synchrotron radiation at Synchrotron Radiation Research center (SRRC) in Taiwan is used to transfer the absorber patterns. The emitted white light from the bending magnet storage ring has a characteristic wavelength 5.8A at 1.5 GeV. A Beryllium window (125 mu m thick) and aluminum oils are used to adjust topto bottom dose ratio in X-ray exposure. PMMA is used to be the substrate. designed patterns are initially created on photomask, then using UV lithography process to transfer pattrns onto the graphite membrane with certain thickness. Gold electroplating is used to form absorber into the resist mold. Stripping the resist, a working mask is finished for X-ray exposure. The result shows the feasibility of graphite membrane to support gold absorbers in X-ray micromachining.