Image Sensor Micro-Lens Fabrication with Variable Heights
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Solution Overview
Problem
Conventional image sensors with micro-lenses of the same height suffer from cross talk and poor quantum efficiency.
Innovation Solution
A method of fabricating image sensors with micro-lenses of different heights by using a mask to form first and second groups of micro-lenses with distinct heights on a color filter array, arranged in a checkerboard pattern, to improve quantum efficiency and reduce cross talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If micro-lenses have the same height, then the manufacturing process is simple, but quantum efficiency is poor and cross talk occurs
Solution Approach 1:
The patent applies local quality by creating different micro-lens heights in different regions of the color filter array. Specifically, micro-lenses in the first color filter region have a first height while micro-lenses in the second color filter region have a second height different from the first. This localized variation optimizes light collection and quantum efficiency for different color channels while maintaining a relatively simple single-mask fabrication process.
2Device complexity
If micro-lenses have the same height, then the fabrication process is simple, but cross talk between pixels increases
Solution Approach 1:
The patent implements local quality by varying micro-lens heights according to the specific color filter region. The first group of micro-lenses corresponds to a first group of color filters with a first height, while the second group of micro-lenses corresponds to a second group of color filters with a second height. This localized differentiation reduces optical interference and cross-talk between adjacent pixels while keeping the overall fabrication process relatively simple through single-mask alignment.
3Reliability
If micro-lenses have different heights, then quantum efficiency improves and cross talk is reduced, but fabrication complexity increases
Solution Approach 1:
The patent applies asymmetry by intentionally creating non-uniform micro-lens heights across different color filter regions. The first group of micro-lenses has a first height and the second group has a second height, creating an asymmetric structure that optimizes optical performance. This asymmetric design improves quantum efficiency and reduces cross-talk while the fabrication complexity is managed through careful mask design and alignment procedures.
Solution Approach 2:
The patent implements parameter changes by varying the height parameter of micro-lenses based on their position in the color filter array. By changing the height parameter from a uniform value to multiple distinct values (first height for first color filters, second height for second color filters), the patent optimizes optical performance. The fabrication process incorporates this parameter variation through mask design while maintaining overall process simplicity.
Data Source
AI summary
A method of fabricating an image sensor and an image sensor thereof are provided. The method comprises: providing a mask; utilizing the mask at a first position to form a first group of micro-lenses having a first height on a first group of color filters of a color filter array on a pixel array; shifting the mask from the first position to a second position, wherein a distance between the first position and the second position is substantially equal to a width of a pixel of the pixel array; and utilizing the mask at the second position to form a second group of micro-lenses having a second height, different from the first height, on a second group of color filters of the color filter array.