Multiple Microlenses Per Pixel Region for 3D Image Sensors
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Solution Overview
Problem
The development of three-dimensional (3D) image sensors with larger pixels increases manufacturing difficulties and production costs due to larger microlenses, which can lower device reliability and efficiency.
Innovation Solution
An image sensor design that applies multiple microlenses to a single pixel, with trench isolation layers and scattering structures to optimize light distribution and reduce the size and complexity of individual lenses, enhancing production efficiency and photoelectric efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel size is increased to enable depth sensing functionality, then the photoelectric efficiency is improved, but the manufacturing difficulty and production cost increase due to larger microlenses
Solution Approach 1:
The pixel is divided into multiple photogates (first photogate and second photogate) that share the pixel region. Each photogate has its own microlens (first microlens and second microlens), allowing the light collection function to be distributed across multiple smaller components rather than requiring a single large microlens. This segmentation enables depth sensing capability while maintaining manageable microlens sizes for manufacturing.
2Use of energy by moving object
If the microlens size is increased to match larger pixels, then the light collection efficiency is improved, but the device reliability decreases due to manufacturing challenges
Solution Approach 1:
Instead of using a single large microlens, the invention employs multiple smaller microlenses (first microlens and second microlens) that collectively cover the pixel region. Each microlens maintains a manageable size that is compatible with existing manufacturing processes, thereby ensuring device reliability while collectively achieving high light collection efficiency through their combined optical gathering capability.
Solution Approach 2:
The multiple microlenses serve dual functions: they individually collect light for their respective photogates while collectively providing depth sensing capability across the entire pixel. This multi-functionality allows the system to achieve both high light collection efficiency and depth measurement capability without requiring any single microlens to be excessively large, thus maintaining manufacturing reliability.
3Productivity
If multiple microlenses are applied to one pixel, then the production efficiency is improved, but the device complexity increases
Solution Approach 1:
The pixel is segmented into multiple photogates with corresponding microlenses, where each component follows a standardized design pattern. This segmentation allows for modular manufacturing processes and simplifies the overall production workflow despite the increased number of components, as each unit can be fabricated using similar techniques and then integrated into the pixel structure.
Solution Approach 2:
Multiple photogates and their corresponding microlenses are merged within a single pixel region, sharing common structural elements such as the substrate, trench isolation layer, and interlayer dielectric layers. This merging approach allows the multiple components to be fabricated simultaneously in a single manufacturing process flow, thereby improving production efficiency while the shared structures help manage the overall device complexity.
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 improves production efficiency and photoelectric efficiency by allowing multiple microlenses to share a pixel, reducing manufacturing challenges and increasing the reliability of 3D image sensors while maintaining high quantum efficiency.
Implementation Method 1
first and second microlenses that share a pixel including the pixel region, are on the second surface, and are configured to pass the incident light toward the first and second photogates
Implementation Method 2
first and second scattering structures that are configured to scatter the incident light in the pixel region
Implementation Method 3
first and second photogates that are on the first surface and are configured to generate electric charge responsive to incident light in the pixel region
Data Source
AI summary
Image sensors are provided. An image sensor includes a substrate that includes a pixel region, a first surface, and a second surface that is opposite the first surface. The image sensor includes first and second photogates that are on the first surface and are configured to generate electric charge responsive to incident light in the pixel region. Moreover, the image sensor includes first and second lenses that are on the second surface and are configured to pass the incident light toward the first and second photogates.