Broadband infrared absorber based on a sputter deposited hydrogenated carbon multilayer enhancing MEMS-based CMOS thermopile performance

Abstract

Based on pulsed DC sputter deposition of hydrogenated carbon, an absorber optical coating with maximized broadband infrared absorptance is reported. Enhanced broadband (2.5–20 µm) infrared absorptance ( > 90 % ) with reduced infrared reflection is achieved by combining a low-absorptance antireflective (hydrogenated carbon) overcoat with a broadband-absorptance carbon underlayer (nonhydrogenated). The infrared optical absorptance of sputter deposited carbon with incorporated hydrogen is reduced. As such, hydrogen flow optimization to minimize reflection loss, maximize broadband absorptance, and achieve stress balance is described. Application to complementary metal-oxide-semiconductor (CMOS) produced microelectromechanical systems (MEMS) thermopile device wafers is described. A 220% increase in thermopile output voltage is demonstrated, in agreement with modeled prediction.