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Landmark Standards Developed for Microelectro-mechanical Systems

ASTM Task Group 
E08.05.03 on
Structural Films for Microelectromechanical Systems (MEMS) and Electronic Applications is offering the first MEMS standards in the world:

E 2244, Test Method for In-Plane Length Measurements of Thin, Reflecting Films Using an Optical Interferometer,
E 2245, Test Method for Residual Strain Measurements of Thin, Reflecting Films Using an Optical Interferometer, and
E 2246, Test Method for Strain Gradient Measurements of Thin, Reflecting Films Using an Optical Interferometer.

The three standard test methods are for measuring in-plane lengths, residual strain, and strain gradient. The latter two standards are supported by the National Institute of Standards and Technology’s Semiconductor Electronics Division Web site ( test-structures), which was developed by task group member Janet Marshall of NIST. The site facilitates quick and easy calculations.

Task Group E08.05.03 is part of Subcommittee E08.05 on Cyclic Deformation and Fatigue Crack Formation, which is part of ASTM Committee E08 on Fatigue and Fracture.

According to Marshall, principal author of the standards, “The test methods are needed to improve measurements in critical MEMS applications.” Marshall says that these international standards are expected to facilitate international commerce in MEMS technologies.

All three test methods apply to thin films such as those found in MEMS materials, which can be imaged using a non-contact optical interferometer. E 2244 is for in-plane length measurements, such as in-plane deflection measurements or length measurements in an unproven fabrication process. E 2245 shows how to calculate the residual strain from two cosine functions that are used to model the out-of-plane shape of fixed-fixed beams. E 2246 shows how to measure the strain gradient from a circular function that is used to model the out-of-plane shape of cantilevers.

The task group welcomes new task group members to work on the upcoming MEMS terminology and Young’s modulus standards.

For further technical information, contact Janet C. Marshall, NIST, Gaithersburg, Md. (phone: 301/975-2049). Committee E08 meets Nov. 17-20 in Tampa, Fla., and May 17-20, 2004, in Salt Lake City, Utah. For membership or meeting details, contact Jeffrey Adkins, manager, ASTM International (phone: 610/832-9738). //

Copyright 2003, ASTM