Image Sensor Grid Structure for Uniform Photodiode Energy Distribution
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Solution Overview
Problem
Image sensors face challenges in achieving even energy distribution to photodiodes and reducing the red pixel and clear (white) pixel sensitivity gap, which affects image quality.
Innovation Solution
The image sensor design incorporates a grid layer with shielding portions that partially cover color filters, creating cavities filled with protruding portions from the micro lens or color filter, optimizing the optical characteristics and energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grid layer with shielding portions is added to partially cover color filters, then energy distribution to photodiodes becomes more even and RC gap is reduced, but device complexity increases
Solution Approach 1:
The grid layer is segmented into multiple shielding portions, each extending from the main portion to partially cover specific color filters. This segmentation allows selective coverage of different color filter regions, enabling precise control over light distribution to adjacent photodiodes and achieving more uniform energy distribution while managing structural complexity through modular design
Solution Approach 2:
The shielding portions are strategically positioned to cover only specific regions of color filters based on local requirements. The coverage is not uniform across all color filters but is tailored to each location's need for light distribution control, allowing optimization of energy distribution to photodiodes while minimizing unnecessary structural additions
2Reliability
If shielding portions cover color filters to create cavities, then RC gap is reduced and sensitivity improves, but manufacturing precision requirements increase
Solution Approach 1:
The grid layer with shielding portions is formed before the protruding portions are added. This preliminary structuring establishes the cavity definitions and spatial relationships early in the manufacturing process, allowing subsequent steps to focus on filling the cavities with protruding portions of controlled widths (0.1 to 0.8 pixel size) without needing to simultaneously control all dimensional parameters
Solution Approach 2:
The structure combines multiple materials with different properties: the grid layer material for shielding, the color filter materials for optical filtering, and the protruding portion materials (either color filter material or micro lens material) for light focusing. This composite approach allows each material to be optimized for its specific function while working together to achieve improved sensitivity and reduced RC gap
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 enhances even energy distribution to photodiodes, reducing the red pixel and clear pixel sensitivity gap, thereby improving image sensor performance and quality.
Implementation Method 1
a first micro lens disposed on the first color filter and the first grid
Implementation Method 2
a first color filter disposed on a first photodiode
Implementation Method 3
photoelectric transducers such as photodiodes for converting light into electric charges
Implementation Method 4
a first shielding portion extended from the first main portion. The first shielding portion partially covers the first color filter
Data Source
AI summary
An image sensor includes a first color filter disposed on a first photodiode, a first grid, and a first micro lens disposed on the first color filter and the first grid. The first grid includes a first main portion and a first shielding portion extended from the first main portion. The first main portion surrounds the first color filter and the first shielding portion partially covers the first color filter such that a first cavity defined by the first shielding portion is configured over the first color filter. The first color filter or the first micro lens includes a first protruding portion filled in the first cavity, and a width of the first protruding portion is in a range from 0.1 pixel size to 0.8 pixel size. A manufacturing method of an image sensor is also disclosed.