2012

Precise Chemical Etching Method for Diamond Crystal Components

This technique could help semiconductor makers create key components of long-lasting micro-electromechanical systems for medical implants.

A new method developed at the National Institute of Standards and Technology (NIST) offers a precise way to engineer microscopic cuts in a diamond surface, yielding potential benefits in both measurement and technological fields.*

altBy combining their own observations with background gleaned from materials science, NIST semiconductor researchers have found a way to create unique features in diamond — potentially leading to improvements in nanometrology in short order, as it has allowed the team to make holes of precise shape in one of the hardest known substances. But beyond the creation of virtually indestructible nano rulers, the method could one day lead to the improvement of a class of electronic devices useful in cell phones, gyroscopes, and medical implants.

Well known for making the hugely complex electronic microchips that run our laptops, the semiconductor industry has expanded its portfolio by fabricating tiny devices with moving parts. Constructed with substantially the same techniques as the electronic chips, these “micro-electromechanical systems,” or MEMS, are just a few micrometers in size. They can detect environmental changes such as heat, pressure and acceleration, potentially enabling them to form the basis of tiny sensors and actuators for a host of new devices. But designers must take care that tiny moving parts do not grind to a disastrous halt. One way to make the sliding parts last longer without breaking down is to make them from a tougher material than silicon.

The method uses a chemical etching process to create cavities in the diamond surface. The cubic shape of a diamond crystal can be sliced in several ways — a fact jewelers take advantage of when creating facets on gemstones. The speed of the etching process depends on the orientation of the slice, occurring at a far slower rate in the direction of the cube’s “faces” — think of chopping the cube into smaller cubes — and these face planes can be used as a sort of boundary where etching can be made to stop when desired. In their initial experiments, the team created cavities ranging in width from 1 to 72 micrometers, each with smooth vertical sidewalls and a flat bottom.

On the path to developing a prototype diamond MEMS device, researchers plan to figure out how to optimize control of the process, and also to explore the mysteries behind some of the unexpected ways in which diamond behaved under the conditions.

This technology was done by the National Institute of Standards and Technology, Gaithersberg, MD. For more information, visit http://www.nist.gov.

Reference
* 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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