Image Sensor Metal Grid Layout to Reduce Light Reflection
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Solution Overview
Problem
The existing metal grid structures in image sensors reflect incident light away from photodetectors due to remnants of the metal grid layer at intersection points, reducing the quantum efficiency (QE) of photodetectors and overall image sensor performance.
Innovation Solution
A method is developed to form a metal grid structure with elongated grid segments intersecting at right angles, preventing remnants of the metal grid layer from extending between adjacent segments, thereby minimizing light reflection and enhancing QE. This is achieved by etching the metal grid structure using a specific masking layer process that ensures rectangular grid openings and reduces light diffraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal grid structure is formed using conventional etching processes, then the grid structure provides electrical connectivity and structural support, but remnants of the metal grid layer extend between adjacent grid segments causing light reflection and reduced quantum efficiency
Solution Approach 1:
The patent applies segmentation by dividing the metal grid layer into discrete, isolated segments. The etching process creates gaps between adjacent grid segments, preventing continuous metal remnants from forming. This segmentation eliminates the harmful light reflection effect while maintaining the electrical connectivity function through the separated grid segments that still provide sufficient structural support and electrical pathways.
2Object-generated harmful factors
If the metal grid layer is completely removed between segments, then light reflection is minimized, but structural support and electrical connectivity may be compromised
Solution Approach 1:
The patent applies local quality by creating different metal layer configurations in different regions. Between adjacent grid segments, the metal layer is completely removed to eliminate light reflection. However, at the grid segment intersections and connection points, the metal layer is maintained to provide structural support and electrical connectivity. This localized differentiation allows simultaneous optimization of optical performance and mechanical/electrical functionality.
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 improved metal grid structure increases the quantum efficiency of photodetectors by minimizing light reflection, leading to enhanced performance of the image sensor.
Implementation Method 1
The existing metal grid structures in image sensors reflect incident light away from photodetectors due to remnants of the metal grid layer at intersection points
Implementation Method 2
Image sensors convert optical images to digital data that may be represented as digital images. An image sensor includes an array of pixel sensors, which are unit devices for the conversion of an optical image into digital data
Data Source
AI summary
Various embodiments of the present disclosure are directed towards an image sensor. The image sensor comprises a plurality of photodetectors disposed within a substrate. A metal grid layer is disposed over the substrate. The metal grid layer comprises a metal grid structure overlying a central pixel region of the substrate. The metal grid layer continuously extends from the central pixel region to a peripheral pixel region of the substrate that laterally encloses the central pixel region. An upper metal structure is disposed over the metal grid layer. The upper metal structure overlies the peripheral pixel region. The upper metal structure is laterally offset from the metal grid structure. A lower surface of the upper metal structure is disposed vertically over an upper surface of the metal grid structure.