Pulsed-laser deposited TiC coatings for MEMS

Abstract

Titanium carbide (TiC) thin films have very desirable properties that make them ideally suited for applications to MEMS devices. TiC has been one of the preferred coatings for improving the performance of macroscopic moving mechanical components due to its established wear-resistance. Pulsed laser deposition (PLD) has been an excellent method for the deposition of TiC because unlike any other deposition process for TiC, PLD offers the capability of producing high-quality films even at room-temperature. Using a patented PLD technique, especially designed and optimized for the deposition of high-hardness, particulate-free films, we have deposited TiC coatings on a variety of surfaces, including Si and several MEMS compatible film-layers. Our results have demonstrated that TiC coatings also offer a high wear-resistance to Si surfaces. This, together with the excellent chemical and mechanical properties, and thermal stability of our PLD TiC coatings, has led to our application of TiC to moving MEMS devices fabricated from Si. The fabrication of Si MEMS devices is quite well established, however, the reliability and performance of MEMS devices such as microgears, micromotors and microactuators, which involve sliding Si surfaces, remain an open question. The short functional life of these devices is attributed to the excessive wear rate of Si induced by high friction. The work presented here describes a hybrid process whereby PLD is used in conjunction with the Aerospace MEMS fabrication process (AIMMOS) for inserting TiC coatings into critical interfaces in MEMS devices that would involve sliding contact between two Si surfaces. The PLD of TiC, the spectroscopy of the plume, and the properties and applications of PLD-TiC for MEMS will be discussed.