Structure and electrical properties of boron doped hydrogenated mixed-phase silicon films for uncooled microbolometer

Abstract

Boron doped hydrogenated silicon films used as thermo-sensing layers in infrared detectors or uncooled micro-bolometers are prepared by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). In this work, we investigated TCR (higher the better) and sheet resistance, Rsheet (lower the better), which are important factors for thermos-sensing layer used in uncooled microbolometer. The crystalline volume fraction (Xc) of films is controlled to get silicon films that satisfy the characteristics of high TCR and low Rsheet. Through the control, amorphous, mixed- and microcrystalline phases were identified. As a result, the best TCR and Rsheet were obtained in the mixed-phase. For the films, TRC is around 1–3%/K, Rsheet is around 3–61.4 MΩ/□ and Xc is around 7–17%. The 1/f noise is measured for various phases. It is found that 1/f noise of boron doped hydrogenated mixed-phase silicon (BMP-Si:H) is smaller than that of the amorphous phase. The results of BMP-Si:H films show that they are more suitable as thermos-sensing layers than boron doped hydrogenated amorphous silicon films.