Image Sensor Isolation Structure for Dark Current Reduction
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Solution Overview
Problem
Existing image sensors face challenges in reducing dark current and white spots, which affect their reliability and performance.
Innovation Solution
The image sensor design includes a semiconductor substrate with specific pad and pixel separation patterns, a through via, and a fixed charge layer to reduce dark current and white spots, featuring a first pad separation pattern with a liner insulation and buried insulation, and a second pad separation pattern with a fixed charge layer and buried insulation, all of which are strategically positioned to enhance electrical signal transformation and isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image sensor structures are used, then manufacturing is simpler, but dark current and white spots increase reducing reliability
Solution Approach 1:
The pad separation pattern is divided into multiple segments extending from both the first surface and second surface of the semiconductor substrate, with each segment containing insulation patterns and charge trapping structures. This segmentation allows for reduced dark current and white spots while maintaining manufacturing feasibility through modular construction
Solution Approach 2:
The pad separation pattern incorporates nested structures where insulation patterns are embedded within the separation pattern, and charge trapping structures are positioned within or adjacent to these insulation regions. This nesting achieves multiple functions (isolation, insulation, charge trapping) within a compact structure, improving reliability without proportionally increasing device complexity
2Object-affected harmful factors
If pad separation patterns with insulation and charge trapping structures are added, then dark current and white spots are reduced, but manufacturing complexity increases
Solution Approach 1:
Insulation patterns and charge trapping structures are formed within the pad separation pattern during the manufacturing process before final device assembly. This preliminary formation of isolation and charge trapping structures ensures reduced dark current and white spots while establishing a systematic manufacturing approach that can be integrated into existing production lines
Solution Approach 2:
The insulation patterns serve as intermediary structures between the pad separation pattern and adjacent pixel regions, providing electrical isolation and charge trapping functionality. These intermediary structures effectively reduce dark current and white spots while maintaining a clear manufacturing process through defined formation steps
3Reliability
If the pad separation pattern extends deeply into the substrate from both surfaces, then isolation and charge trapping are improved, but manufacturing precision requirements increase
Solution Approach 1:
The pad separation pattern employs asymmetric configuration where segments extend from both the first surface and second surface of the substrate, with potentially different depths and configurations on each side. This asymmetric design from dual surfaces achieves effective isolation and charge trapping while distributing manufacturing precision requirements across multiple accessible surfaces, making the deep extension more manufacturable
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 design increases the reliability of the image sensor, decreases dark current, and effectively reduces white spots, leading to improved performance in transforming optical images into electrical signals.
Implementation Method 1
a second pad separation pattern with a fixed charge layer and buried insulation
Implementation Method 2
The photodiode serves to transform incident light into an electrical signal
Data Source
AI summary
Disclosed are image sensors and methods of fabricating the same. The image sensor includes a semiconductor substrate including a pixel zone and a pad zone and having a first surface and a second surface opposing each other, a first pad separation pattern on the pad zone and extending from the first surface of the semiconductor substrate toward the second surface of the semiconductor substrate, a second pad separation pattern extending from the second surface toward the first surface of the semiconductor substrate on the pad zone the second pad and in contact with the first pad separation pattern, and a pixel separation pattern on the pixel zone and extending from the second surface of the semiconductor substrate toward the first surface of the semiconductor substrate.