A novel designed microtensile specimen with electroplated structures is described here. It can be fit into a specially designed microtensile apparatus, which is capable of carrying out a series of tests on sub-micron scale freestanding thin films. Several thin films for microelectromechanical systems (MEMS) applications has been tested here including sputtered copper, gold, gold-chrome and tantalum nitride. All the metal specimens were fabricated by sputtering. For the tantalum nitride film samples, nitrogen gas was introduced into the chamber during the process of sputtering tantalum films on the silicon wafer. We have used copper, gold, 5% gold-chrome alloys and tantalum nitride thin films with thickness of 200-800 nm. The E values of the thin films tested here are consistent with the results from other measurement methods. The test results of metal specimens show the similar trend of the Hall-Petch prediction. However, the values of tantalum nitride thin films do not exhibit any systematic variation with respect to the thickness

This paper presents the results of new microtensile tests conducted to investigate the mechanical properties of submicron-thick freestanding copper films. The method, used in this study, allows the observation of materials response under uniaxial tensile loads with measurements of stress at strain rates up to 5.5 x 10(-4)/s. It also facilitates tension-tension fatigue experiments under a variety of mean stress conditions at cyclic loading frequencies to 20 Hz. The sample processes involve fabrication of a supporting frame with springs and alignment beams all made of electroplated nickel. Electroplating took place on top of a previously deposited sample rather than creating a structure by subtractive fabrication. Tensile sample loading is applied using a piezoelectric actuator. Load was measured using a capacitance gap sensor with a novel mechanical coupling to the sample. Tension-tension fatigue experiments were carried out with feedback to give load control. Fatigue tests were conducted on sputter-deposited 500 and 900 nm copper films with grain sizes similar to 50 nm. Fatigue life reached 10(5) cycles at low mean load, which decreased with an increase in the mean load. The results indicate decreasing plasticity with increasing mean load

The authors describe their design for a paddle-like cantilever beam sample to relieve non-uniform stress distribution in beam-bending tests of the mechanical properties of thin film applications to MEMS. We added the sample to a custom-designed system equipped with an electrostatic panel and optical interferometer. The system overcomes problems associated with using nano-indentation for testing, and reduces errors tied to the amount of contact force required to bend the beam. Accurate paddle cantilever beam deflection was obtained using a four-step phase-shifting process with a Michelson interferometer. Film strain was determined using a simple force equilibrium equation. Residual stresses were measured at -41.3 MPa for 150 nm silver film, -3.2 MPa for 150 nm gold film, and -16.8 MPa for 150 nm copper film. We observed residual stresses for copper films at different thicknesses. The results indicate high tensile stress forms during the early deposition stage for thin copper film due to grain coalescence, and a decrease in stress with an increase in film thickness. In copper films with thicknesses greater than 153 nm, lattice relaxation associated with the surface mobility of metallic atoms changed residual stress from tension to compression

No abstract

A new technique was developed for studying the mechanical behavior of thin films on substrate applications for micro-electro-mechanical system (MEMS). The test structure was designed on novel "paddle" cantilever beam coated thin film specimens with dimensions of a few hundred to 50 nm. This beam has a triangle shape that provides a uniform plane strain distribution. Standard clean room processing was used to prepare the paddle sample. The experiment can be operated using the electrostatic force to deflect the "paddle" cantilever beam and measure the mechanical response of the sample with surface deposited thin film. A capacitance measurement is used to observe the deflection of the cantilever plate on the other side of the sample with respect to the electrostatic force on the one side. The measured strain was then converted through this capacitance measurement to conduct mechanical behavior studies on the coated thin film. Both system performance experiments and calculations were studied to verify the design concepts. The residual thin film stress measurements were performed and compared with the calculated results from three different forces exerted on the "paddle" cantilever beam, including the force due to the film, compliance force, and electrostatic force