Backside-Illuminated Image Sensor Isolation for Crosstalk and Dark Current
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Solution Overview
Problem
Backside illuminated image sensors face increased crosstalk and dark current issues due to reduced pixel region sizes and lattice defects at interfaces between pixel and isolation regions, which affect image quality and resolution.
Innovation Solution
The implementation of light isolation patterns formed in trenches around pixel regions, connected in a lattice form, with an anti-reflective layer and light blocking patterns, and the use of bonding pads to apply a negative voltage to these patterns, reducing light leakage and dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel region size is reduced to increase resolution, then image resolution is improved, but crosstalk between pixels increases
Solution Approach 1:
The substrate is divided into pixel regions and isolation regions, with trenches formed between adjacent pixel regions. Light isolation patterns are placed within these trenches to physically segment the light paths between pixels, preventing crosstalk while maintaining high resolution.
Solution Approach 2:
Light isolation patterns serve as intermediary structures between adjacent pixel regions. These patterns block stray light from reaching neighboring pixels, acting as a mediator that prevents harmful light interference while allowing the pixel regions to remain closely spaced for high resolution.
2Object-generated harmful factors
If light isolation patterns are added to reduce crosstalk, then crosstalk is reduced, but device complexity increases
Solution Approach 1:
The light isolation patterns are merged with the trench structure, combining the light blocking function with the physical separation structure. This integration reduces the need for separate isolation components, simplifying the overall device structure while maintaining effective crosstalk reduction.
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
Significantly reduces crosstalk and dark current in backside illuminated image sensors, enhancing image quality and resolution by minimizing light leakage and electron trapping.
Implementation Method 1
an anti-reflective layer formed on the backside surface of the substrate
Implementation Method 2
a light blocking pattern formed on the anti-reflective layer... light isolation patterns formed among the pixel regions
Data Source
AI summary
A backside illuminated image sensor includes a substrate having a frontside surface and a backside surface, pixel regions formed in the substrate, light isolation patterns formed among the pixel regions, first bonding pads electrically connected to the pixel regions, and at least one second bonding pad electrically connected to the light isolation patterns.