Design of MEMS Based Universal Testing Machine for Thin Film Characterization

Abstract

Many materials now a day used in Micro Electromechanical Systems (MEMS) were not considered as mechanical material before. So their mechanical properties are not well known which are very important to predict their specifications like sensitivity, range, and the life which are very important for their reliability. These materials are used in many real time-critical applications where a minor error can cause serious damage just like the accelerometer used for impact detection in automobiles to activate airbags. Thus the mechanical properties should be exactly known then we can define the device characteristics. Similarly, many other applications like in aviation, aerospace, and telecommunication, etc. The mechanical properties of the material used in the MEMS devices should be exactly known for their reliable and safer use. Out of these mechanical properties yield strength of a material has a critical role in the response of a device. There are many challenges in material testing at micron level like the generation of force with such fine resolution, load sensing, adjustment of the specimen, etc. Most of the researchers have used a monolithically fabricated specimen with a testing mechanism that limits the type of test materials. Secondly, for separately fabricated specimens the mounting and collection of specimens to the test structure before and after the test is a challenge. The main objective of this thesis is to design a generalized MEMS-based testing machine that can find the yield strength of different thin films at the MEMS level. The main focus of our work is to make the load application and sensing the more reliable and easier. The biaxial testing mechanism in used with Chevron type electrothermal actuator for force application and gap, an anti-gap capacitive sensor to find the yield strength. The proposed design is validated through FEM analysis on ANSYS.