Image Sensor Inner Light-Condensing Scheme
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Solution Overview
Problem
Conventional image sensors face challenges in controlling the curvature radius of microlenses, leading to degraded light condensing efficiency due to process limitations, which affects the sensitivity and light absorption capabilities.
Innovation Solution
The image sensor design includes a photoelectric conversion layer, a spacer layer with a higher refractive index than the color filter layer but lower than the photoelectric conversion layer, and a first condensing layer with a digital microlens having a single-step or double-step structure, optimized for light condensation and absorption, along with a second condensing layer to enhance light transmission and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the curvature radius of the microlens is controlled to improve light condensing efficiency, then light condensing efficiency is improved, but manufacturing precision deteriorates due to process limits
Solution Approach 1:
The microlens structure is divided into multiple layers: an upper microlens layer and a lower microlens layer with different curvature radii. This segmentation allows each layer to be optimized independently for light condensing efficiency while being manufacturable with existing process capabilities, resolving the contradiction between precision control and ease of manufacture.
Solution Approach 2:
A spacer layer with specific refractive index is introduced between the color filter layer and the photoelectric conversion layer. This intermediary layer acts as a optical mediator that enhances light condensing efficiency by controlling light propagation, providing an alternative approach to achieving high efficiency without relying solely on difficult-to-control microlens curvature.
2Area of moving object
If pixel size is reduced to increase integration density, then integration density is improved, but light condensing efficiency deteriorates
Solution Approach 1:
The microlens is segmented into upper and lower layers with different curvature radii optimized for small pixel dimensions. The upper microlens has a larger curvature radius for effective light collection, while the lower microlens has a smaller curvature radius for precise focusing, enabling high light condensing efficiency in reduced pixel sizes.
Solution Approach 2:
The optical design extends into the vertical dimension by introducing multiple microlens layers at different depths and a spacer layer with specific refractive index. This multi-dimensional approach compensates for the reduced lateral dimensions of small pixels, maintaining light condensing efficiency despite pixel size reduction.
3Device complexity
If a single microlens layer is used to simplify structure, then device complexity is reduced, but light condensing efficiency deteriorates
Solution Approach 1:
The microlens system is segmented into an upper microlens layer and a lower microlens layer, each with optimized curvature radii. This segmentation enables superior light condensing efficiency by combining the light-gathering capability of a larger curvature radius with the focusing precision of a smaller curvature radius, outweighing the increased structural complexity.
Solution Approach 2:
The optical system uses a composite structure combining multiple microlens layers with different optical properties and a spacer layer with specific refractive index. This composite approach achieves high light condensing efficiency by leveraging the complementary strengths of each layer, justifying the increased device complexity.
4Reliability
If the spacer layer refractive index is optimized to prevent light reflection, then sensitivity is improved, but manufacturing precision becomes more difficult
Solution Approach 1:
A spacer layer with intermediate refractive index between the color filter layer and photoelectric conversion layer is introduced as an optical intermediary. This layer reduces light reflection at interfaces by providing a gradual refractive index transition, improving sensitivity while using standard semiconductor materials and processes.
Solution Approach 2:
The refractive index of the spacer layer is optimized as a key parameter to balance light reflection prevention and manufacturing feasibility. By selecting materials with appropriate refractive indices (such as silicon nitride or silicon oxide), the system achieves high sensitivity without requiring difficult-to-control material properties.
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 configuration improves light condensing efficiency and sensitivity by increasing the amount of light absorbed into the photoelectric conversion layer, optimizing quantum efficiency and reducing crosstalk, while allowing for easier focus adjustment and design flexibility.
Implementation Method 1
The microlens may condense incident light
Implementation Method 2
the photo diode may convert light into an electrical signal
Implementation Method 3
a spacer layer formed over the photoelectric conversion layer, and suitable for preventing light reflection while adjusting a focus
Data Source
AI summary
An image sensor may include: a photoelectric conversion layer suitable for converting light into an electrical signal; a spacer layer formed over the photoelectric conversion layer, and suitable for preventing light reflection while adjusting a focus; and a first condensing layer formed at the inner bottom of the spacer layer, and suitable for condensing incident light.