Microelectromechanical Materials Testing and Quality 
Assurance System, 18-9170

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Principal Investigators
Stephen J. Hudak Jr
Daniel P. Nicolella
Joseph N. Mitchell
Heather S. Hanson

Inclusive Dates: 11/03/99 - Current

Background - For microelectromechanical systems (MEMS) to develop fully into a thriving nanotechnology, a host of technological problems need to be solved. Although advances in design, manufacturing, and packaging need to continue, these technologies are, in many ways, ahead of other required technologies since they are based on adaptations of preexisting microelectronics technology. One such fundamental barrier is the development of novel methods for accurate and cost-effective measurement of material properties needed in MEMS design. Simply stated, both solids and fluids take on perplexing new properties at the microscopic scale. As the size scale is reduced, surface effects begin to dominate the material response; consequently, bulk properties measured on larger specimens are no longer valid. Properties may also deviate from bulk values as the characteristic size of the device approaches the size scale of material microstructure, for example, the grain size in polycrystalline materials such as silicon. The challenge is to be able to measure these properties at the microscopic scale in a cost-effective manner.

Approach - A multidisciplinary experimental-analytical approach is being employed in pursuit of the following goals: 1) to develop methods for measuring material properties on the microscopic level using atomic force microscopy; 2) to verify computational tools used to design MEMS by comparing computational predictions with microscopic measurements of strain and displacement using stereoimaging measurements (DISMAP) in a scanning electron microscope; 3) to use the above information to develop a laboratory on a chip for cost-effective material property measurements; 4) to verify the utility of the laboratory on a chip by comparing results with independent measurements using the techniques in 1) above; and 5) to define the applicability of these measurements to durability assessment and quality assurance of MEMS.

Accomplishments - A variety of MEMS actuators and test specimens have been designed and fabricated (see photo below of one such device). Improvements in the functionality of these devices, through three design iterations, have been demonstrated. Ongoing efforts are directed at independently validating the measured properties. Software is also being developed to facilitate the analysis of the test specimen and extraction of the measured property. Discussions with MEMS fabricators are underway to define the requirements for these devices to facilitate their application as process optimization and quality control tools. A patent disclosure has been filed.

MEMS device developed by SwRI to study the strength and deformation of thin films on the micro scale. The scratch drive actuator (top photo) moves in a linear motion toward the notched test beam to the right. Upon contact, the test beam can either be deflected or broken, depending on the applied force. High-resolution images of the deformed test specimen (left photo) are also being used to measure deformation in the thin-film microstructure, allowing the strain levels in the material to be determined for validation of MEMS design tools.

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