Thermo-sensing silicon–germanium–boron films prepared by plasma for un-cooled micro-bolometers

Abstract In this work we report a study of silicon–germanium–boron alloys (a-Si x Ge y B z :H) deposited by low frequency plasma enhanced chemical vapor deposition (LF PECVD) at relatively low temperatures, which are compatible with the IC silicon technology for applications as low resistance thermo-sensing films in micro-bolometers. Three values of germanium gas content (Ge y ) were used during the film deposition, Ge y = 0.3, 0.45 and 0.55. Deposition and film properties were compared with a reference intrinsic film (a-Si x Ge y :H) in order to study the Ge y effect on the temperature dependence of conductivity ( σ ( T )) and specifically on the activation energy ( E a ). We observed a variation on the activation energy from E a = 0.34 eV to E a = 0.18 eV and on the room temperature conductivity from σ RT = 6 × 10 −5 (Ω cm) −1 to σ RT = 2.5 × 10 −2 (Ω cm) −1 , for the reference intrinsic film and for the boron alloy with Ge y = 0.55, respectively. The solid phase composition of the films was characterized by SIMS measurements. The effect of patterning the films (μm scale) with photolithography and the deposition on a SiN x micro-bridge on the film electrical properties was also studied.