(Invited) Plasma Processes for Emerging Silicon-Based MEMS, NEMS and Packaging Applications

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Plasma processes are important for emerging silicon-based micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS) and packaging applications. Typically every device has a customised process flow but synergies can be found as most are produced using a 2.5D approach comprising sequential deposition, lithography and etch cycles. Plasma processes are critical in enabling reproducible dry deposition and etch steps during the manufacturing flow of MEMS and NEMS devices but individual tools need the flexibility to address multiple different applications and process requirements. Increasingly plasma processes are also being adopted in nano-imprint lithography and bonding process steps. Plasma processes may be divided into the following broad families: chemical vapour deposition (CVD), atomic layer deposition (ALD), physical vapour deposition (PVD), surface functionalisation, etch (physically-driven) and etch (chemically-driven). The merits of each plasma technique and their application to emerging devices are discussed – including silicon etch processes that are at the heart of most MEMS and NEMS devices. Here trends are towards higher aspect ratios for enhanced performance and smaller footprint whilst maintaining throughput. Increasingly, large cavities are also being etched to realise membrane-based devices and in multi-wafer stacks where through silicon vias (TSVs) are emerging as a key technology for interconnect. At the research stage, the integration of ALD into MEMS is becoming more common whilst in NEMS devices are taking advantage novel combinations of processes and materials to realise new functions.