Deep silicon etch for biology MEMS fabrication: review of process parameters influence versus chip design
2013
Micro-system for biology is a growing market, especially for micro-fluidic applications (environment and health). Key
part for the manufacturing of biology MEMS is the deep silicon etching by plasma to create microstructures. Usual
etching process as an alternation of etching and passivation steps is a well-known method for MEMS fabrication,
nowadays used in high volume production for devices like sensors and actuators. MEMS for biology applications are very different in design compared to more common micro-systems like accelerometers for instance. Indeed, their design includes on the same chip structures of very diverse size like narrow pillars, large trenches and wide cavities. This makes biology MEMS fabrication very challenging for DRIE, since each type of feature considered individually would require a specific etch process. Furthermore process parameters suited to match specifications on small size features (vertical profile, low sidewall roughness) induce issues and defects on bigger structures (undercut, micro-masking) and vice versa. Thus the process window is constrained leading to trade-offs in process development. In this paper process parameters such as source and platen powers, pressure, etching and passivation gas flows and steps
duration were investigated to achieve all requirements. As well interactions between those different factors were
characterized at different levels, from individual critical feature up to chip scale and to wafer scale. We will show the
plasma process development and tuning to reach all these specifications. We also compared different chambers
configurations of our ICP tool (source wafer distance, plasma diffusion) in order to obtain a good combination of
hardware and process. With optimized etching we successfully fabricate micro-fluidic devices like micro-pumps.
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