New Internal Stress Driven on-Chip Micromachines for Extracting Mechanical Properties of Thin Films

TL;DR

This paper introduces a novel on-chip micromachine method utilizing internal stresses to measure the mechanical properties of thin metallic films, specifically aluminum, by analyzing displacement and stress-strain behavior.

Contribution

It presents a new micromachine design that uses internal stress for on-chip mechanical property measurement of thin films, enabling thickness-dependent strength analysis.

Findings

Al thin films show increased strength as thickness decreases.

Displacements measured via SEM enable stress derivation.

Full stress-strain curves are generated for different film thicknesses.

Abstract

A new concept of micromachines has been developed for measuring the mechanical properties of thin metallic films. The actuator is a beam undergoing large internal stresses built up during the deposition process. Al thin films are deposited partly on the actuator beam and on the substrate. By etching the structure, the actuator contracts and pulls the Al film. Full stress strain curves can be generated by designing a set of micromachines with various actuator lengths. In the present study, the displacements have been measured by scanning electronic microscopy. The stress is derived from simple continuum mechanics relationships. The tensile properties of Al films of various thicknesses have been tested. A marked increase of the strength with decreasing film thickness is observed.