Reliability of MEMS Materials and Components

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9820022BhushanThe objective of the proposed research is to conduct a detailed performance analysis and microtribological study of the mating component surfaces in selected micromotors, microswitches and microgear systems as a function of operating time of the devices, thereby identifying the mechanisms associated with microdevice and component failure during operation. It has been long suspected that failure of MEMS devices occurs due to a drastic change or degradation of tribological properties of the mating surfaces in the device. The effect of device operation on the important tribological parameters associated with mating surfaces such as surface roughness, microscale friction, stiction and mechanical integrity will be studied using an AFM/FFM. Tips of different radii to simulate asperity contacts of different sizes will be developed to study the adhesion and friction of mating surfaces. By using a Nanoscale Kelvin Probe to detect precursors of wear, changes in the structure of the surfaces prior to wear will be studied in order to identify mechanisms associated with degradation of the mating surfaces. Studies to measure device parameters such as start-up current. stopping current etc., which are indicative of device failure, will be conducted and these will be compared with tribological parameters under different operating conditions. This will help to understand the effect of tribological parameters on device failure. Another objective of the study is to identify new materials, lubricants and ultra-thin coatings for use in MEMS devices. Coupons of currently used materials - silicon and polysilicon films will be compared to new candidate materials such as SiC films and other ceramic films. The aim here is to look for materials that exhibit minimum friction/stiction and superior wear performance. Ultra-thin hard amorphous carbon coatings of thicknesses ranging from 10 nm down to 3.5 nm and less will be studied in order to identify the thinnest coatings with the best scratch/wear resistance. By conducting studies on MEMS components made from various potential materials anti coatings, their engineering performance will be studied and their reliability evaluated.The micromotors and other MEMS device will be obtained from research collaborators who will fabricate the devices. Through this study, reliability of the MEMS devices will be better estimated and understanding of failure mechanisms in these devices will be significantly advanced. New materials, coatings and lubricants that are well suited for MEMS devices will also be identified. This study will therefore be of mutual benefit to the fields of both MEMS technology and microtribology science.***