MEMS devices created within cmos wafers
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A MEMS fabrication process developed by Spanish company Baolab Microsystems allows nanoscale MEMS devices to be created within cmos wafers using standard processes. The approach is said to allow MEMS devices to be created more easily and more quickly than existing techniques. Baolab also claims the cost of MEMS devices can be cut by up to two thirds.
Called NanoEMS, the approach uses the existing metal layers in a cmos wafer to form the MEMS structure using standard mask techniques. The inter metal dielectric is then etched away through the pad openings in the passivation layer using vapour HF. The holes are then sealed and the chip packaged as required. "We have solved the challenge of building MEMS in a completely different way," claimed Dave Doyle, Baolab's ceo. "Existing MEMS technologies are slow, expensive and require specialist equipment. They have to be either built on top of the wafer at a post production stage or into a recess in the wafer. By contrast, NanoEMS enables MEMS devices to be built using standard cmos technologies during the normal flow of the cmos lines."
The company has created MEMS devices using a standard 0.18µm process on 8in wafers with four or more metal layers. Minimum feature sizes of 200nm have been created, said to be an order of magnitude smaller than is currently possible with conventional MEMS processes.
