PDC microfabrication through KOH-etched Si mould casting

The purpose of this project is to fabricate a mould etched by KOH for PDC casting and produce the fist PDC using this method. Casting for PDC is a known process, it has been done with PDMS moulds created from Si masters. Si moulds have also been fabricated with SU-8 or DRIE. The advantages of KOH etching is that the structures are atomically smooth and the side-walls are tilted which would be beneficial forthe production and extraction of the PDC. Prior to the mould fabrication, a mask had to be design and fabricated. It was designed to give interesting and useful shapes after KOH etching for casting. Chips had to been made that could be used for patterning the bottom flat of the moulds by nanoscribing. The fabrication of the mould is a simple process, however, some interesting and unexpected observation were made at the KOH etching step, despite the fact that KOH etching is a well known and established process. It is ineducable the etching rate of KOH may vary due to uncontrollable parameters. Yet, the etching variation between the experimental value that was obtained during the fabrication and the theoretical value provided by the CMi was measured at 35% which was surprisingly high. It has been observed that the KOH etching of the Si plane, is an anisotropic etch. The etching rate vary depending on the area of the plane; at the edges the etching rate is more important than at the center of the membrane. A phenomenon which has been observed on a thin Si film KOH etching are small squared-like pattern perforating the membrane: more investigation need to be performed to understand this phenomenon. The fabrication of the moulds have been re-alised and the PDC have been fabricated with it. The design of the mask need to be improvedto enhance the production success rate of the PDC by reducing the induced stress in the ceramics when they shrunk during the pyrolysis. The firsts PDC microfabrication through KOH-etched Si mould casting have been realised. Yet, further work need to be conducted.