NIST etches MEMS out of diamonds

September 28, 2011 — The National Institute of Standards and Technology (NIST) developed a method to etch diamond crystals, engineering precise microscopic cuts in a diamond surface. These diamond-etched features could lead to better micro electro mechanical system (MEMS) devices.

Diamond withstands extreme conditions, and can vibrate at the highest frequencies required by consumer electronics devices, making it an "ideal substance" for MEMS devices, said Craig McGray, NIST. The harder material could make diamond-based MEMS substantially longer lasting than those fabricated on silicon.

Also read: MEMS applications using diamond thin films

The hard crystal (diamond is a 10 on the Mohs scale of hardness) is difficult to precisely cut. The NIST method creates cavities in the diamon via chemical etch. Diamond crystals are cubic, so slices can be oriented in different ways. Etching speed is dependent on slice orientation: going with cube faces etching is slower, and face planes can create boundaries to etch patterns. The NIST team created diamond cavities 1 to 72┬Ám wide, with vertical, smooth sidewalls and flat bottoms.

Process control still needs to be optimized, noted McGray. The diamond also behaved unexpectedly at some points in the experimental processing. Both of these challenges will be addressed in the team’s next project: creating a prototype diamond MEMS device.

Results are published at: C.D. McGray, R.A. Allen, M. Cangemi and J. Geist. Rectangular scale-similar etch pits in monocrystalline diamond. Diamond and Related Materials. Available online 22 August 2011, ISSN 0925-9635, 10.1016/j.diamond.2011.08.007.

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