Single microhole per pixel for thin Ge-on-Si complementary metal-oxide semiconductor image sensor with enhanced sensitivity up to 1700 nm

Abstract. We present a germanium “Ge-on-Si” CMOS image sensor with backside illumination for the near-infrared (NIR) electromagnetic waves (wavelength range 300 to 1700 nm) detection essential for optical sensor technology. The microholes help to enhance the optical efficiency and extend the range to the 1.7-μm wavelength. We demonstrate an optimization for the width and depth of the microholes for maximal absorption in the NIR. We show a reduction in the crosstalk by employing thin SiO2 deep trench isolation in between the pixels. Finally, we show a 26 to 50% reduction in the device capacitance with the introduction of a microhole. Such CMOS-compatible Ge-on-Si sensors will enable high-density, ultrafast, and efficient NIR imaging.