Membrane folding by ion implantation induced stress to fabricate three-dimensional nanostructures

We show experimentally that localized ion irradiation into a silicon nitride cantilever creates large stress gradients and folds the cantilever at the irradiated area. The fold angle and radius depend on the thickness of the cantilever, the ion dose and the sputter depth into the silicon nitride. We model the ion implantation with Monte-Carlo simulations and discuss possible stress formation mechanisms. We present experimental results from a fabrication process that allows the ion implantation to be done while the cantilever is held fixed by sacrificial material. The cantilever is then folded upon selective etching. The experimental results indicate that these techniques will provide the means for folding membranes into three-dimensional micro-structures for device fabrication. (c) 2007 Elsevier B.V. All rights reserved.