Performance results of MEMS coated with a conformal DLC

A MEMS electrostatic lateral output motor has been successfully coated with a diamond like carbon (DLC) coating to protect against wear. Experiments were performed to characterize coating chemistry and performance. Friction results from accelerated screening tests using a miniature, lightly loaded ball on flat tribometer showed that the DLC coating maintained low friction longer compared to uncoated silicon. DLC on DLC experiments showed the lowest friction, and those that were run in 30% RH showed a much longer lifetime than ones run in dry air. Uniformity of DLC coverage on MEMS was verified by Auger electron spectroscopy (AES), microRaman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Micrographs revealed that there is about a 3:1 ratio of DLC coating for a line of sight deposition region to a non line of sight deposition region. DLC coated MEMS outperformed uncoated MEMS by 16X in air and 300X in vacuum, albeit performance in vacuum was lower than in air. A very clear difference in wear debris was seen between devices run in air and in vacuum. Cylindrical rolls were dominant in the devices that were run in air and platelets were dominant on devices run in vacuum. Ultimately, the DLC coating was found to greatly improve performance over uncoated MEMS.