Deep Sub-Electron Read Noise in Image Sensors Using a Multigate-Source-Follower

As the in-pixel source-follower (SF) gate size scales down in CMOS image sensors (CISs) and quanta image sensors (QISs), the pixel conversion gain (CG) increases at the cost of more 1/<inline-formula> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> noise. In this article, a multigate SF (MGSF) is proposed to simultaneously increase pixel CG and reduce 1/<inline-formula> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> noise. The MGSF improves the tradeoff between 1/<inline-formula> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> noise and CG that exists for pixels with conventional SFs, leading to reduced input-referred read noise at deep sub-electron levels.