Polysilicon surface micromachined structural entities with continuous hinges and microrivets for assembling three-dimensional MEMS devices

A new polysilicon surface micromachining technique for fabricating and assembling three-dimensional structures has been developed. Single-layer polysilicon elements and laminated polysilicon panels incorporating trapped-glass reinforcement ribs have been successfully fabricated on a silicon substrate with robust and continuous hinges that facilitate out-of-plane rotation and assembly. To realize a stable three-dimensional structure. one of the device's elevatable panel components is terminated with an array of open windows, and the mating rotatable element has a matched set of protruding microrivets with flexible barbs that readily flex to facilitate their joining and assembly. Because the microrivet barb tip-to-barb tip separation is larger than the opening in the mating window, the barbs flex inward as they pass through the open window and then expand to their original shape upon exiting the window, resulting in a permanently latched joint and a three-dimensional structure. Three novel microrivet designs have been micromachined to facilitate the latching process, including a simple arrowhead design, a high-aspect ratio arrowhead variant, and a rivet-like structure with a hemispherical shaped cap and a flexible split shank.