Image Sensor Pixel Grid Without Metal for Higher Quantum Efficiency
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Solution Overview
Problem
Image sensors face challenges in achieving high quantum efficiency (QE) and preventing stain defects due to the absorption of light by metal layers in grid patterns used for pixel isolation, which also lead to crosstalk between pixels.
Innovation Solution
The use of a metal-free grid pattern with a low refractive index, combined with an anti-reflective layer including a TiO2 layer, which functions as a charge path and prevents stain defects, allowing for improved light transmission and reduced QE loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal grid pattern is used for pixel isolation, then pixel isolation is effective, but quantum efficiency deteriorates due to light absorption by metal layers
Solution Approach 1:
The patent removes the metal layer from the grid pattern entirely, extracting the harmful light-absorbing component while maintaining the grid's isolation function through alternative materials (silicon oxide, silicon nitride, or silicon oxynitride insulating layers), thereby eliminating quantum efficiency loss from metal absorption
Solution Approach 2:
The patent changes the material parameters of the grid pattern from conductive metal materials to insulating materials with appropriate refractive indices, transforming the grid's optical properties to reduce light absorption while maintaining electrical isolation functionality through the insulating nature of the new materials
2Reliability
If a metal grid pattern is used for pixel isolation, then pixel isolation is effective, but stain defects occur due to light absorption
Solution Approach 1:
The patent extracts and removes the metal component that causes stain defects, replacing it with insulating materials that do not exhibit the same light absorption characteristics, thereby preventing stain defect formation while preserving pixel isolation
Solution Approach 2:
The patent converts the potentially harmful metal grid structure into a beneficial metal-free insulating grid structure that eliminates stain defects, turning the problem of metal-induced staining into an opportunity to improve image quality by using materials with superior optical properties
3Reliability
If a metal grid pattern is used for pixel isolation, then pixel isolation is effective, but crosstalk between pixels increases
Solution Approach 1:
The patent introduces insulating materials (silicon oxide, silicon nitride, or silicon oxynitride) as intermediary layers in the grid pattern that provide both optical isolation to prevent crosstalk and electrical isolation, serving as a dual-function mediator between adjacent 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 solution enhances quantum efficiency by eliminating light absorption from metal layers and prevents stain defects, while maintaining effective pixel isolation and reducing crosstalk, thereby improving image sensor performance.
Implementation Method 1
an anti-reflective layer having a first refractive index, the anti-reflective layer being on an upper surface of the first substrate
Implementation Method 2
an anti-reflective layer having a first refractive index, the anti-reflective layer being on an upper surface of the first substrate
Implementation Method 3
a grid pattern on the anti-reflective layer of the pixel area and separating the color filters from each other with a 2-dimensional grid shape, the grid pattern including a single insulating layer that is metal-free and has a low refractive index
Implementation Method 4
an anti-reflective layer including a TiO2 layer... which functions as a charge path and prevents stain defects
Implementation Method 5
Photodiodes may convert light incident thereon into electrical signals
Data Source
AI summary
Provided is an image sensor including a first substrate including a pixel area and a peripheral area adjacent to the pixel area, the pixel area including a plurality of pixels in a 2-dimensional array, a first wiring layer on a lower surface of the first substrate, an anti-reflective layer having a first refractive index, the anti-reflective layer being on an upper surface of the first substrate, and color filters on the anti-reflective layer corresponding to the pixel area and spaced apart from each other by a metal-free grid pattern.