On-chip test structure suite for free-standing metal film mechanical property testing, Part I – Analysis

We propose and analyze a notched free-standing thin-film structure subject to a well-defined stress concentration in pure tension for in situ mechanical testing of thin metal films. Load is applied electrostatically, making testing and handling routine and simple. The sensitivity of the notched structure to geometry, residual stress and to electrostatic instability are modeled and discussed. It is found that significant plastic straining can occur in the notch region before electrostatic instability. Coupled with adjacent cantilevers and fixed–fixed beams, this small area test structure suite enables a platform for evaluating linear properties such as Young’s modulus and residual stress, and gaining information on inelastic properties such as plasticity and fatigue. The total area of the suite is much smaller than that of a typical chip, allowing for the possibility that these devices can serve as diagnostic test structures.