6.1 A 3-Stacked Hybrid-Shutter CMOS Image Sensor with Switchable $1.2\mu\mathrm{m}$ -Pitch 50Mpixel Rolling Shutter and $2.4\mu\mathrm{m}$ -Pitch 12.5Mpixel Global Shutter Modes for Mobile Applications

In recent years, the development of CMOS image sensors (CISs), especially for mobile applications, has focused on pixel scaling to achieve ultra-high pixel resolutions of over 50 megapixels (Mp) [1]. In addition, various efforts have been actively devoted to strengthen the functionality of image sensors through advanced stacking process technologies, e.g., rolling shutter (RS) CIS with event vision sensors (EVS) for enhancing imaging quality [2]. A global shutter (GS) CIS is an excellent alternative to overcome the limitations of conventional RS CISs. GS CISs for mobile applications can create value as follows: 1) GS CISs can get distortion-free images when capturing fast-moving objects; 2) GS CISs don't suffer from flicker-related artifacts because all pixels are exposed at the same time, while RS CISs require a tradeoff between a long exposure time such as 1/60 or 1/120 seconds to prevent the flicker phenomena and a short one to avoid image blurring; and 3) Flash banding caused by sudden camera flashes can be avoided. We believe that the aforementioned advantages of GS CISs have the potential to offer a valuable user experience in mobile devices. Despite these features, voltage-domain GS CISs exhibit a higher random noise (RN) level, generated by sampling capacitors, compared to RS CISs, which limits their applicability. Therefore, a hybrid shutter (HS) CIS capable of operating in both modes, RS and GS, is developed to maximize the benefits of each.