SINGLE-LAYER AND MULTILAYER SURFACE-MICROMACHINED PLATFORMS USING ELECTROPLATED SACRIFICIAL LAYERS

The use of electroplated sacrificial layers in the fabrication of surface-micromachined structures is discussed. Electroplated sacrificial layers offer two benefits: first, structures suspended several tens of microns above a substrate can be fabricated due to the ability to deposit relatively thick electroplated layers; secondly, the selective deposition of electroplated material only on conductors allows multi-layer three-dimensional structures to be fabricated in a self-aligned process. Single-layer surface-micromachined bridges and platforms suspended 10 to 50 mum above the surface have been fabricated in this manner. In addition, dual-layer platforms with some portions suspended 2 to 3 mum above the surface and other portions 10 to 50 mum above the surface have also been fabricated. Both structures are demonstrated using copper as the sacrificial layer and polyimide as the structural material, although other material combinations can also be used. Electrostatic actuation of both types of platforms has been achieved.