Application of PET plastics in micro-sensor fabrication

Polycrystalline germanium-based thermopiles are fabricated at reduced temperatures on plastic substrate. The Amorphous Ge film, deposited using electron beam evaporation, is post-treated to form a polycrystalline film. The annealing process has been performed at temperatures ranging from 120 to 175°C. The physical characteristics of Ge films have been investigated using XRD and SEM tools confirming the crystallinity of the annealed films. A Seebeck value of 100 μV/°C is extracted for the Ge-Al junctions. A novel ultraviolet assisted micro-machining is presented in which anisotropic etching of PET plastic substrate is achieved. The etching of plastic is performed in a DMF solution and in presence of ultraviolet light illumination with a typical intensity of 15 mW/hr measured at a wavelength of 360 nm. This technique has been applied to realize square membrane, craters, micro-gears and micro-molds.