Novel Device for Tensile Testing of Sub-Micron Scale Freestanding Thin Films

 

This technology is a new experimental method and device for the on-chip, uni-axial tensile testing of freestanding thin films, with virtually no restriction on film thickness (nanometers to micrometers). The method obviates the use of separate gripping mechanisms, ensures virtually perfect specimen alignment, and accurately calibrates loading of the specimen with required force resolution. It also allows measurement of residual stress, creep and fatigue deformation, and crack development and growth, at the micrometer or nanometer scale. Using micro-electronic fabrication processes, this technology drastically reduces the experimental setup size and allows, for the first time, quantitative in situ testing in both SEM and TEM under a wide variety of environmental conditions.

This device is a novel tensile testing instrument that can be used for in situ mechanical characterization of qualitative and quantitative properties of freestanding thin film materials inside scanning and transmission electron microscopes.

The product is a single crystal silicon chip containing the mechanisms for gripping a free-standing specimen, measuring the applied force and corresponding displacement of the specimen, minimizing the misalignment in the specimen, and measuring any residual stress in the specimen.

The device may be cofabricated with electrostatic (microelectromechanical systems) actuators, or it can be set up with commercial actuators to produce the required displacement.

The outputs of the device include the following: (1) mechanical properties of micron- and nanometer-scale thin film materials in uniaxial tension, tension-tension fatigue, and low- and high-temperature creep and (2) in situ qualitative and quantitative descriptions (simultaneous) of material deformation mechanisms for fundamental understanding of the behavior of materials on the micrometer or nanometer scale.

This device was developed to overcome the existing limitations in current methods for studying properties of thin, freestanding films, specifically those of submicron thickness, relevant to microelectronics and micromachines. Before this technology, no method existed that could: (a) ensure perfect gripping and aligning without putting pre-stress in the specimen; (b) apply the required force with required resolution for any film thickness; (c) measure the residual stress without any geometric assumptions; and, (d) perform simultaneous quantitative and qualitative in situ testing of materials in the TEM. All conventional and modern micro-electronic and micromachine materials with size scale ranging from nano- to micro-scale can be tested.

Applications

This device can test any thin film material that can be used in both conventional and modern micro- and nanofabrication techniques. This provides accurate materials properties input to the development of:

  • Microelectronic devices
  • Micro- and nanomachines
  • Advances in fundamental research on nanoscale materials properties.

Benefits

  • Novel, broader use of materials testing equipment: enables testing of ultra-thin (submicron) materials
  • Enhanced measurement accuracy: allows for complete flexibility in required force/displacement resolution for accurate measurement in electron microscopes
  • Time and effort savings: saves testing time via automatic specimen gripping and alignment. Simultaneous qualitative and quantitative measurements save time and effort in comprehensive materials characterization