Dual Optical Microstructures for CMOS Edge-Ray Capture
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Solution Overview
Problem
The wide chief ray angle at the edge of CMOS image sensors (CIS) results in inefficient light reception by photodiodes, leading to poor color performance and image quality in low-light conditions.
Innovation Solution
The optical device incorporates dual optical micro structures with distinct glass transition temperatures and refractive indices, arranged above photoelectric conversion elements, to guide incident light efficiently into the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single optical micro structure is used above photoelectric conversion elements, then the device complexity is low, but the light receiving efficiency is insufficient especially at wide chief ray angles
Solution Approach 1:
The optical structure is divided into two distinct portions: a first portion with higher glass transition temperature and lower refractive index, and a second portion with lower glass transition temperature and higher refractive index. This segmentation allows each portion to perform specialized optical functions - the first portion for light collection and the second portion for light guidance - thereby improving overall light receiving efficiency while maintaining manageable structural complexity through modular design
Solution Approach 2:
The patent employs composite optical structures with different materials having distinct glass transition temperatures and refractive indices. The first portion uses material with Tg1 (70-350°C) and n1 (1.0<n<2.9), while the second portion uses material with Tg2 (50-300°C) and n2 (1.1<n<2.8). This composite approach enables optimization of optical properties for specific functions while utilizing the same fabrication process for both portions
2Reliability
If optical structures with different glass transition temperatures are used, then light guiding performance is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent utilizes parameter changes in glass transition temperature and refractive index to achieve different optical functions. By adjusting Tg and n values within specific ranges for the first and second portions, the structure achieves optimal light guiding performance. The parameter variations are controlled within manufacturable limits, allowing differentiation of optical properties while maintaining compatibility with standard fabrication processes
Solution Approach 2:
The first and second portions are formed in a predetermined sequence during fabrication, with the first portion created first followed by the second portion. This preliminary action approach allows each layer to be optimized for its specific function while ensuring proper integration. The sequential formation process manages manufacturing complexity by breaking down the fabrication into manageable steps with controlled parameters at each stage
3Manufacturing precision
If the first glass transition temperature is higher than the second glass transition temperature, then optical performance at edge fields is improved, but material selection becomes more restricted
Solution Approach 1:
The patent applies local quality by assigning different glass transition temperature ranges and refractive index ranges to different portions of the optical structure. The first portion (with higher Tg) is positioned to collect light from wide angles, while the second portion (with lower Tg) guides the light to the photoelectric conversion element. This localized optimization of material properties ensures consistent optical performance across different fields of view while providing guidance for material selection in each specific region
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 dual optical micro structures enhance light receiving efficiency and reduce cross-talk in the CMOS image sensor, improving image quality in low-light conditions.
Implementation Method 1
The first portion has a refractive index which is lower than or equal to 2.9 and greater than 1. In some embodiments, the second portion has a refractive index which is lower than or equal to 2.8 and greater than 1.1
Implementation Method 2
The first portion has a first glass transition temperature. The second portion has a second glass transition temperature. The first glass transition temperature is higher than the second glass transition temperature
Data Source
AI summary
A method for fabricating an optical device includes providing a substrate, forming a first material having a first glass transition temperature above the substrate, forming a second material having a second glass transition temperature above the substrate, and performing a heating process to form a plurality of optical structures. The first glass transition temperature is higher than the second glass transition temperature.