Pixel Division Structure for Image Sensors With Lower Dark Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image sensors with pixel division structures, electron flow at the boundary between the pixel division structure and the light sensing element generates dark current, which is not effectively captured, leading to increased dark current issues.
Innovation Solution
The pixel division structure includes a core and lateral pattern structure on the sidewall, with the lateral pattern comprising silicon nitride containing carbon, which has a lower etch rate in phosphoric acid, preventing voids or seams and enhancing electron capture, thereby reducing dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lateral pattern is formed on the sidewall of the core to capture electrons, then dark current is reduced, but voids or seams may form in the lateral pattern reducing effectiveness
Solution Approach 1:
The lateral pattern is formed using a composite structure of silicon oxide and silicon nitride containing carbon. The silicon nitride layer provides electron capture capability while the silicon oxide layer ensures complete coverage and prevents void formation. This composite material approach resolves the contradiction by combining materials with complementary properties to achieve both dark current reduction and pattern integrity.
Solution Approach 2:
The invention changes the material composition parameter by incorporating carbon into silicon nitride (forming silicon nitride containing carbon). This parameter change modifies the etching characteristics and deposition behavior, enabling the lateral pattern to be formed completely on the sidewall without voids or seams, thus maintaining pattern integrity while preserving electron capture function.
2Reliability
If silicon nitride is used for the lateral pattern to capture electrons, then dark current is reduced, but the etch rate in phosphoric acid is high causing voids or seams
Solution Approach 1:
The lateral pattern uses a composite of silicon oxide and silicon nitride containing carbon. The silicon nitride component maintains electron capture capability while the modified composition (with carbon) reduces the etch rate in phosphoric acid. This prevents the high etch rate from causing voids or seams during manufacturing, resolving the contradiction between electron capture function and manufacturing ease.
Solution Approach 2:
The lateral pattern is designed with local quality differentiation: the silicon nitride containing carbon portion provides electron capture functionality, while the silicon oxide portion provides structural completeness and resistance to phosphoric acid etching. This local differentiation allows the structure to simultaneously achieve electron capture and avoid manufacturing defects.
3Measurement precision
If a pixel division structure is implemented to define unit pixel regions, then image quality is improved, but electron flow at boundaries generates dark current
Solution Approach 1:
The harmful electron flow at the boundary is extracted and captured by the lateral pattern formed on the sidewall of the core. The lateral pattern acts as an electron capture structure that removes excess electrons generated at the pixel division boundary, preventing them from contributing to dark current while maintaining the pixel division structure's image quality benefits.
Solution Approach 2:
The lateral pattern serves as an intermediary structure between the pixel division structure and the light sensing element. It mediates the electron flow by capturing electrons at the boundary region, preventing direct electron flow that would generate dark current, while allowing the pixel division structure to maintain its function of defining unit pixel regions for image quality.
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 captures electrons, reducing dark current by ensuring no voids or seams are formed in the lateral pattern, thus improving the image sensor's performance.
Implementation Method 1
a negative bias may be applied to a core included in the pixel division structure so that the electron flow may be captured by an impurity region to reduce the dark current
Implementation Method 2
the lateral pattern comprising silicon nitride containing carbon, which has a lower etch rate in phosphoric acid, preventing voids or seams
Data Source
AI summary
An image sensor includes a pixel division structure including a core and a lateral pattern structure on a sidewall of the core, the pixel division structure extending through a substrate in a vertical direction perpendicular to an upper surface of the substrate, the pixel division structure defining unit pixel regions including unit pixels. The image sensor includes a light sensing element in each of the unit pixel regions, a planarization layer on the substrate, a color filter array layer on the planarization layer, the color filter array layer including color filters, and a microlens on the color filter array layer. The lateral pattern structure includes a second lateral pattern on the sidewall of the core and a first lateral pattern on an outer sidewall of the second lateral pattern, the first lateral pattern includes silicon oxide, and the second lateral pattern includes silicon nitride containing carbon.