Deep Trench Isolation Passivation for Lower Dark Current
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Solution Overview
Problem
Existing methods for reducing damage to substrate sidewalls in deep trench isolation structures of image sensors are costly and inefficient, leading to increased dark current and reduced performance in photodetectors.
Innovation Solution
Implementing complementary dipole generating layers with varying oxygen densities in metal oxide and oxide layers to create an electric field that forms a depletion region, capturing dark current carriers and enhancing photodetector performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench isolation structures are used to prevent cross-talk between photodetectors, then isolation between photodetectors is improved, but substrate sidewall damage increases leading to increased dark current
Solution Approach 1:
The patent converts the harmful substrate sidewall damage and dark current generation into a beneficial effect by forming dipole generating layers that create an electric field. This electric field generates positive charge carriers that accumulate in the depletion region, transforming the previously harmful damaged sidewalls into a useful charge generation mechanism that reduces dark current and improves photodetector isolation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the trench interface by introducing dipole generating layers with specific oxygen densities. These layers create electric fields that alter the charge carrier distribution, transforming the interface from a dark current source into a region with enhanced positive charge carrier concentration that actively suppresses dark current.
2Object-generated harmful factors
If existing methods are used to reduce substrate sidewall damage, then dark current is reduced, but manufacturing cost increases and efficiency decreases
Solution Approach 1:
The patent changes the compositional parameters of the trench filling by introducing dipole generating layers with controlled oxygen densities. This approach achieves dark current reduction through a fundamental physical mechanism (electric field generation) rather than relying on expensive or complex processing modifications, thereby maintaining manufacturing efficiency and cost-effectiveness.
Solution Approach 2:
The patent employs composite material structures within the trench, combining dipole generating layers with different oxygen densities (first dipole generating layer with lower oxygen density, second dipole generating layer with higher oxygen density). This composite structure creates optimized electric field distribution that effectively reduces dark current while using standard manufacturing processes.
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 method reduces dark current and improves white pixel performance by increasing the concentration of positive charge carriers in the depletion region, thereby enhancing the photodetector array's performance.
Implementation Method 1
Implementing complementary dipole generating layers with varying oxygen densities in metal oxide and oxide layers to create an electric field that forms a depletion region
Implementation Method 2
create an electric field that forms a depletion region, capturing dark current carriers
Data Source
AI summary
Some embodiments relate to a pixel array, including: a substrate; a plurality of photodetectors within the substrate; a deep trench isolation (DTI) structure with segments extending between photodetectors of the plurality of photodetectors, the DTI structure comprising: a first oxide layer having a first oxygen density; a first metal oxide layer lining inner sidewalls of the first oxide layer and having a second oxygen density greater than the first oxygen density; a second oxide layer lining inner sidewalls of the first metal oxide layer and having a third oxygen density less than the second oxygen density; and a second metal oxide layer lining inner sidewalls of the second oxide layer and having a fourth oxygen density greater than the third oxygen density.