Interlayer Lenses in Image Sensors for Sensitivity
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Solution Overview
Problem
The division of photoelectric conversion units in image sensors leads to non-sensitive areas between pixels, reducing sensitivity and degrading the angle of incidence characteristics due to separation regions, which affects the quality of captured images.
Innovation Solution
The integration of interlayer lenses between photoelectric conversion parts and a microlens in the image sensor, formed using a specific manufacturing process involving gray-tone masks and etchback, ensures that light is directed effectively onto the photoelectric conversion parts, minimizing non-sensitive areas and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photoelectric conversion units are divided into multiple parts, then focus detection capability and 3D image generation are improved, but sensitivity and angle of incidence characteristics are degraded due to separation regions
Solution Approach 1:
A light guide layer is introduced as an intermediary component between the divided photoelectric conversion parts and the microlens. This light guide layer redirects light that would otherwise fall into separation regions, channeling it toward the active photoelectric conversion areas, thereby maintaining sensitivity while preserving the divided structure's functionality for focus detection and 3D imaging
Solution Approach 2:
The refractive index of the light guide layer is specifically optimized (higher than surrounding layers) to control light propagation paths. By changing this optical parameter, light is effectively redirected around the separation regions, compensating for the sensitivity loss caused by the divided photoelectric conversion structure
2Device complexity
If photoelectric conversion parts share a common floating diffusion unit, then manufacturing complexity is reduced, but non-sensitive areas increase between divided pixels
Solution Approach 1:
The light guide layer extends horizontally across the separation regions between divided photoelectric conversion parts, utilizing the lateral dimension to redirect light paths. This three-dimensional light routing approach allows the shared floating diffusion structure to function effectively while minimizing the impact of non-sensitive areas on overall pixel performance
3Reliability
If separation regions are eliminated to improve sensitivity, then manufacturing precision requirements increase due to alignment accuracy constraints
Solution Approach 1:
The light guide layer serves as a buffer and redirection medium that decouples the strict alignment requirements. By introducing this intermediary optical element, the system can tolerate greater manufacturing variations while still achieving effective light collection, as the light guide actively redirects straying light toward the photoelectric conversion areas
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 reduces the decrease in pixel sensitivity and improves the angle of incidence characteristics, resulting in improved image capture quality by ensuring that all light is utilized effectively, even when pixels have divided photoelectric conversion units.
Implementation Method 1
a plurality of interlayer lenses formed between the plurality of photoelectric conversion parts and the microlens and integrally formed to correspond to the plurality of photoelectric conversion parts, wherein the plurality of interlayer lenses cause light incident on the plurality of interlayer lenses to enter the corresponding plurality of photoelectric conversion parts
Data Source
AI summary
An image sensor comprising a plurality of pixels, each of at least part of the plurality of pixels comprises: a plurality of photoelectric conversion parts; a microlens; and a plurality of interlayer lenses formed between the plurality of photoelectric conversion parts and the microlens and integrally formed to correspond to the plurality of photoelectric conversion parts. The plurality of interlayer lenses cause light incident on the plurality of interlayer lenses to enter the corresponding plurality of photoelectric conversion parts.