Enhanced Near-Infrared Response CMOS Image Sensors Using High-Resistivity Substrate: Photodiodes Design Impact on Performances

A three-transistor pixel, front-side-illuminated CMOS image sensor is developed and realized using high-resistivity (HR) silicon (N
_a
≈ 10
¹²
cm
^-3
) to enhance its near-infrared response thanks to a large depleted depth. Both TCAD simulations and an analytical model are used to estimate the space-charge region extension of a photodiode. A strong 3-D geometrical variation with pixel design geometry is shown. Punchthrough current measurements in a pixel array are used to demonstrate these variations and their impact. The punchthrough and crosstalk measurements can provide an optimum pixel design on HR silicon. Electrooptical characterization demonstrates excellent quantum efficiency despite slightly degraded crosstalk performances for near-infrared wavelengths.