Three-dimensional structures assembled from polysilicon surface micromachined components containing continuous hinges and microrivets

Abstract

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 arrowheads/microrivets with flexible barbs that readily flex to facilitate their joining and assembly. Because the arrowhead/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 arrowhead/microrivet designs have been micromachined to facilitate the latching process, including a simple arrowhead, a high-aspect ratio arrowhead, and a rivet-like structure with a hemispherical shaped cap and a flexible split shank. To minimize panel breakage after the sacrificial glass release etch process and to facilitate mechanical alignment during assembly, a network of sacrificial electrothermally-actuated mechanical links ('fuses') have been integrated into the MEMS structure designs. © 2001 Elsevier Science B.V. All rights reserved.