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

Boron doped hydrogenated silicon films used as thereto-sensing layers in infrared detectors or uncooled microbolometers are prepared by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). In this work, we investigated TCR (higher the better) and sheet resistance, R-sheet (lower the better), which are important factors for thermos-sensing layer used in uncooled microbolometer. The crystalline volume fraction (X-c) 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, R-sheet is around 3-61.4 M Omega/square and X-c 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.