Image Sensor Global Shutter Mechanism
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Solution Overview
Problem
Conventional image sensors with rolling shutter mechanisms experience image distortion when capturing moving images due to exposure timing differences across pixels, which is not addressed effectively.
Innovation Solution
The design incorporates a global shutter mechanism with a semiconductor layer having a photosensitive device, a charge storage device, a transmission transistor, and a leakage photogenerated charge drain region, along with a blocking layer and drain contact plug to minimize light interference and ensure synchronized exposure across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rolling shutter mechanism is used, then the device complexity is reduced, but image distortion occurs when capturing moving images
Solution Approach 1:
The image sensor is divided into two functional surfaces: a first surface for light incident and charge accumulation (photosensitive device), and a second surface for charge storage and readout (charge storage device). This segmentation allows simultaneous exposure of all pixels while separating the light-sensitive function from the charge storage function, eliminating rolling shutter distortion without requiring complex mechanical shutters.
Solution Approach 2:
The patent transitions from a conventional single-surface architecture to a dual-surface three-dimensional architecture. By stacking the photosensitive device on the first surface and the charge storage device on the second surface, the patent enables global shutter functionality through vertical spatial separation, resolving the image distortion issue without increasing lateral device complexity.
2Manufacturing precision
If a global shutter mechanism is implemented, then image distortion is minimized, but the device complexity increases
Solution Approach 1:
The patent replaces the mechanical moving shutter system with a static dual-surface semiconductor structure. Instead of using mechanical components to control exposure timing, the invention uses fixed photosensitive devices and charge storage devices on opposite surfaces, with electronic control through transmission transistors, thereby achieving global shutter functionality without mechanical complexity.
Solution Approach 2:
The transmission transistor serves multiple functions: it controls charge transfer from the photosensitive device to the charge storage device, enables simultaneous exposure of all pixels, and facilitates the global shutter operation. This multi-functionality reduces the need for additional specialized components, mitigating the increase in device complexity.
3Measurement precision
If light blocking structures are added to prevent light interference, then charge storage accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent uses vertical spatial separation to prevent light interference. By positioning the charge storage device on the second surface beneath the photosensitive device on the first surface, and using the semiconductor substrate thickness to block light, the patent eliminates the need for lateral light blocking structures, maintaining charge storage accuracy without adding structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces image distortion by ensuring all pixels are exposed simultaneously, thereby maintaining image quality even when capturing moving subjects.
Implementation Method 1
a photosensitive device, which is formed in the semiconductor layer in the vicinity of the first surface and accumulates charges based on light incident via the second surface
Implementation Method 2
a blocking layer, which is formed on the second surface of the semiconductor layer and blocks light traveling toward the charge storage device
Data Source
AI summary
Example embodiments relate to an image sensor supporting a global shutter for minimizing image distortion. An example image sensor includes a semiconductor layer having a first surface and a second surface that are opposite to each other; a photosensitive device, which is formed in the semiconductor layer near the first surface and accumulates charges based on light incident via the second surface; a charge storage device, which is formed in the semiconductor layer near the first surface and temporarily stores charges accumulated by the photosensitive device; a first transmission transistor, which transmits charges accumulated by the photosensitive device to the charge storage device and includes a first gate formed on the first surface of the semiconductor layer; and a leakage photogenerated charge drain region, which is formed in the semiconductor layer near the second surface, is apart from the charge storage device, and is arranged above the charge storage device.