CMOS Pixel Trench Shielding for Global Shutter Light Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In CMOS image sensors using global electronic shutter mode, light leakage into charge holding portions can cause false signals, degrading image quality due to insufficient light shielding around the charge holding portions.
Innovation Solution
A photoelectric conversion device is designed with a trench structure in the substrate between the photoelectric converter and the charge holding portion, and a metal film covering the charge holding portion to reduce light incidence and prevent false signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding portion is provided to cover the charge holding portion, then light leakage into the charge holding portion is reduced, but the light shielding may not be sufficient when an opening is disposed in the vicinity of the charge holding portion to guide light to the photoelectric converter
Solution Approach 1:
The patent introduces a trench structure that extends vertically into the substrate from the surface, creating a three-dimensional light shielding barrier. This vertical dimension complements the planar light shielding portion, effectively blocking light leakage paths while preserving light guidance to the photoelectric converter through the opening.
Solution Approach 2:
The light shielding function is divided into two separate structures: a planar light shielding portion at the surface level and a vertical trench structure extending into the substrate. This segmentation allows each structure to perform its function optimally - the planar portion blocks surface-level light leakage while the trench blocks deeper light paths, together providing comprehensive shielding without compromising light guidance.
2Reliability
If the charge holding portion is covered with a light shielding portion, then false signal generation is reduced, but image quality may still be degraded due to insufficient light shielding
Solution Approach 1:
The patent combines two different light shielding structures - the planar light shielding portion and the vertical trench structure - into a composite shielding system. This composite approach provides more comprehensive light blocking coverage, effectively preventing false signal generation while ensuring adequate light shielding for high-quality image capture.
3Illumination intensity
If an opening is disposed in the light shielding portion to guide light, then light can reach the photoelectric converter, but light leakage into the charge holding portion occurs
Solution Approach 1:
The trench structure acts as an intermediary light-blocking element positioned between the opening in the light shielding portion and the charge holding portion. It mediates the light paths by allowing light to reach the photoelectric converter through the opening while intercepting and blocking light that would otherwise leak into the charge holding portion, preventing false signal generation.
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
The solution effectively reduces light leakage and false signal generation, thereby improving image quality by ensuring adequate light shielding between the photoelectric converter and the charge holding portion.
Implementation Method 1
a photoelectric converter that accumulates charge generated by an incidence of light
Implementation Method 2
a metal film disposed over a side of a first surface of the substrate so as to cover at least the charge holding portion
Data Source
AI summary
A photoelectric conversion device includes a substrate provided with pixels each including a photoelectric converter that accumulates charge generated by an incidence of light, a charge holding portion that holds charge transferred from the photoelectric converter, and an amplifier unit that includes an input node that receives charge transferred from the charge holding portion, a metal film disposed over a side of a first surface of the substrate so as to cover at least the charge holding portion, and a trench structure provided in the substrate on the side of the first surface of the substrate. The photoelectric conversion device is configured such that the light is incident from the side of the first surface of the substrate. The trench structure is disposed between the photoelectric converter and the charge holding portion of a first pixel.