Image Sensor Light Blocking Layer for Phase Difference Detection
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Solution Overview
Problem
Existing image sensors face degradation due to optical crosstalk between imaging and phase difference detection pixels, leading to non-uniform brightness and reduced image quality, with trench isolation structures introducing defects that increase dark current and further degrade performance.
Innovation Solution
The implementation of a light blocking layer formed between the photoelectric conversion elements of phase difference detection and imaging pixels, strategically positioned to minimize optical crosstalk, with the trench for the light blocking layer limited to specific regions to reduce defects and enhance image sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light blocking layer is formed between photoelectric conversion elements to reduce optical crosstalk, then image quality and uniformity are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The light blocking layer is selectively formed only in specific regions where optical crosstalk occurs between imaging pixels and phase difference detection pixels, rather than uniformly across the entire sensor. This localized approach reduces optical crosstalk while minimizing additional structural complexity and manufacturing steps.
Solution Approach 2:
The light blocking layer is divided into multiple separate regions corresponding to different pixel boundaries, allowing independent formation and optimization of blocking structures at each interface where crosstalk occurs, rather than requiring a single continuous blocking structure.
2Object-affected harmful factors
If trench isolation structures are used to separate pixels, then optical crosstalk is reduced, but defects increase and dark current rises
Solution Approach 1:
Instead of using continuous trench isolation structures that create extensive defect regions, the light blocking layer is formed only in specific localized areas where optical crosstalk occurs, reducing the total defect density and associated dark current while still providing effective optical isolation.
Solution Approach 2:
The light blocking layer acts as an intermediary structure that provides optical isolation between pixels without requiring deep trench isolation. This intermediate approach achieves crosstalk reduction while avoiding the severe defect introduction associated with full trench isolation.
3Measurement precision
If the open part in phase difference detection pixel is eccentrically located, then phase difference detection capability is improved, but optical crosstalk with adjacent imaging pixels increases
Solution Approach 1:
The light blocking layer is pre-formed at strategic locations to counteract the optical crosstalk that would otherwise occur due to the eccentric positioning of the open part. This preliminary protective measure allows the open part to maintain its optimal eccentric position for phase difference detection while preventing harmful light leakage to adjacent imaging pixels.
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 approach effectively reduces optical crosstalk and associated characteristic degradation, maintaining image quality and minimizing dark current issues, thereby improving the overall performance of the image sensor.
Implementation Method 1
a light blocking layer formed between the first photoelectric conversion element and the second photoelectric conversion element
Implementation Method 2
an image sensor is a device which receives light from an optical image or one or more objects and converts the received light into electrical signals forming an image
Data Source
AI summary
An image sensor may include: a substrate including a plurality of pixels including a first pixel and a second pixel that are located adjacent to each other in a first direction, the first pixel including a first photoelectric conversion element and an open part which is eccentrically located in the first pixel in the first direction and the second pixel including a second photoelectric conversion element; a light-shield pattern that is formed over a part of the first photoelectric conversion element of the first pixel; and a light blocking layer formed between the first photoelectric conversion element and the second photoelectric conversion element.