Global Shutter Pixel with Vertically Integrated Multi-Phase Charge Transfer

Smart overview of the Invention

An innovative image sensor design integrates a global shutter mechanism with vertically aligned charge transfer regions. Each pixel contains a photodiode (PD) for charge accumulation, a floating diffusion region (FD), and a vertically integrated charge transfer region. This transfer region consists of three distinct phases: P1, P2, and P3, facilitating charge movement from the PD to the FD. The P2 region serves as an in-pixel charge memory, temporarily storing charge during the transfer process, enhancing image capture in global shutter mode.

Technical Context

The image sensor technology is crucial in modern devices like smartphones, cameras, and security systems. Traditional image sensors operate in rolling shutter mode, where pixels are exposed sequentially, leading to potential image distortions. Global shutter mode addresses these issues by synchronizing pixel exposure, capturing the entire image simultaneously. The proposed design enhances global shutter functionality by integrating an in-pixel charge memory, reducing the need for additional memory components and improving image quality, especially in high-speed photography.

Design Features

This sensor design features a pixel array with vertically stacked charge modulation regions. P1, P2, and P3 are strategically placed between the PD and FD, allowing efficient charge transfer. The P2 region acts as a temporary storage for charge, ensuring consistent image capture even when readout is sequential. This configuration minimizes the sensor's footprint and boosts pixel density by integrating memory directly into each pixel.

Component Details

The image sensor is built on a substrate, typically silicon, with each pixel containing a photodiode, floating diffusion, and vertically aligned charge transfer regions. Control signals manage the charge transfer process through gates G1, G2, and G3, which are connected to respective gate contacts. These components are constructed from materials like polysilicon and metal, ensuring robust electrical connectivity and efficient charge handling.

Benefits and Applications

Incorporating an in-pixel charge memory within the global shutter framework offers significant advantages. It enhances image quality by eliminating rolling shutter artifacts, reduces component count, and increases pixel density. This technology is applicable in various fields, including mobile devices, robotics, and surveillance, where high-speed and high-quality image capture are essential.