Measurement of Shear Strengths of Cu Films Using Precise Chip Forming

Abstract

The mechanical properties of thin films are under-researched because of the challenges associated with conventional experimental methods. We demonstrate a technique for determining the intrinsic shear strength and strain of thin films using a nano-cutting technique based on an orthogonal cutting model with precise control of the cutting system. In this study, electroplated Cu films with thicknesses of 1.5 μm and 5 μm and a sputtered Cu film with a thickness of 130 nm were fabricated to evaluate the mechanical strength. Experiments revealed a shear strength of approximately 310 MPa with a shear strain of 1.57 for the electroplated Cu film and a shear strength of 389 MPa with a shear strain of 2.03 for the sputtered Cu film. In addition, X-ray diffraction analysis was performed to correlate the experimental results.

Mechanical Property Measurement of Micro/Nanoscale Materials for MEMS: A Review

“…No size effect on the Poisson's ratio of Si has been reported. For a Si(001) [110] thin film specimen, the Poisson's ratio was measured to be 0.069 and 0.35 for in-plane [5,35] and out-of-plane [6,21], respectively, which are almost the same as those ideal values, a strong anisotropy.…”

“…Since single crystal Si possesses a strong anisotropy, its mechanical and electrical characteristics are dependent on the crystal direction. The Young's moduli for Si (001), (110), and (111) are well known as 130, 169, and 187 GPa, respectively, which have been measured in experiment on a micro and nanometer scale [17,22,[58][59][60]. The Young's moduli for poly crystal Si [17] and amorphous Si [61] are measured experimentally to be roughly 160 GPa and 100 GPa, respectively.…”

“…The crack propagation speed in AlSi was roughly 1/10 of that in pure Al. Except for those Al alloys like AlCu [108], various types of metallic film materials on a micro/nm scale have been evaluated so far, such as pure Al [109], Cu [110], Au [111][112][113][114], Ni [115,116], Ti [116], SnAu [117,118], and TiN [6,7], for mechanical reliability investigation as MEMS materials. Electroplated Ni turns on MEMS researchers from the viewpoint of a promising material for a 3D mechanical element made by using UV-LIGA process [21,[119][120][121][122].…”

“…The crack propagation speed in AlSi was roughly 1/10 of that in pure Al. Except for those Al alloys like AlCu [108], various types of metallic film materials on a micro/nm scale have been evaluated so far, such as pure Al [109], Cu [110], Au [111–114], Ni [115,116], Ti [116], SnAu [117,118], and TiN [6,7], for mechanical reliability investigation as MEMS materials.…”