Flexible polysilicon sensor array modules using "etch-release" packaging scheme

A flexible polysilicon strain gauge array has been designed and fabricated using surface-micromachining with a SiO₂ sacrificial layer. The realized sensor array is mechanically flexible, which can be attached on a non-planar surface. To realize the flexible polysilicon strain gauge array, a new packaging scheme using polysilicon/oxide-based surface-micromachining was developed. The proposed packaging scheme completes the strain sensor and the circuit board on a single process, which eliminates additional assembly and alignment problems. The measured gauge factor shows that it is more sensitive than conventional metal strain gauges. Unlike a single-crystal silicon strain gauge, a crystal direction does not affect its sensitivity in a polysilicon sensor, and this isotropic property makes the realization of an omni-directional strain gauge array possible. The proposed flexible strain sensor array can be used in a measurement of stress distribution of an arbitrary and non-planar surface.