Fabricating a micromould insert using a novel process

A new method of fabricating micromould inserts that is compatible with semiconductor manufacturing is proposed. Diffusion of phosphorous at a high temperature is first used to increase the electric conductivity of the surface of the silicon wafer to generate a silicon-based seed layer for electroforming. If the process temperature and the duration of doping with phosphorous are controlled, then the electric conductivity of this novel silicon-based seed layer can be expected to equal that of a metal seed layer. Then, a structure layer of amorphous silicon is successfully formed onto the silicon-based seed layer, by plasma enhanced chemical vapor deposition (PECVD). The structure layer has none of the defects that would be present if a metal seed layer were used to replace the silicon-based seed layer. Finally, a silicon-based master microstructure was created by using ICP-RIE to etch the structure layer. The silicon-based master has been demonstrated to be useable in successfully fabricating, by electroforming, a metal micromould insert with a large area and high aspect ratio.