Image Sensor Modulation Structures for Longer Optical Paths
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Solution Overview
Problem
Solid-state image sensors face challenges in converting incident light with longer wavelengths due to the short optical path in photoelectric conversion units, resulting in unsatisfactory image signal quality.
Innovation Solution
Incorporating modulation structures within the photoelectric conversion units that change the optical path without increasing the thickness of the conversion element, forming mosaic patterns with varying shapes and sizes, and having different refractive indices to enhance light interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the depletion region of the photoelectric conversion unit is made very deep to sense longer wavelengths, then the photoelectric conversion efficiency is improved, but the optical path length remains insufficient because incident light moves straight up and down
Solution Approach 1:
The patent introduces curved or inclined modulation structures (such as arc-shaped regions or tilted interfaces) within the photoelectric conversion unit that bend the optical path of incident light. This curvature causes light to travel a longer, non-linear path through the depletion region, increasing the interaction length between light and the photoelectric conversion medium without increasing the physical thickness of the sensor element.
Solution Approach 2:
The patent employs modulation structures that introduce lateral or diagonal dimensions to the optical path. Instead of light traveling only vertically through the depletion region, the modulation structures guide light along inclined or three-dimensional trajectories, effectively utilizing additional spatial dimensions to extend the optical path length within the same device footprint.
2Productivity
If the thickness of the photoelectric conversion unit is increased to lengthen the optical path, then the photoelectric conversion efficiency for longer wavelengths is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent embeds modulation structures within the existing photoelectric conversion unit architecture, nesting functional elements inside the depletion region. These internal modulation features (such as graded doping regions, interface structures, or embedded layers) are integrated into the bulk material without requiring additional external components or increasing the overall device thickness, thereby maintaining structural simplicity while enhancing optical path length.
Solution Approach 2:
The patent modifies material or structural parameters within the photoelectric conversion unit, such as doping concentration gradients, refractive index variations, or interface angles, to alter light propagation characteristics. These parameter changes enable the light to follow extended paths through the depletion region without requiring physical thickening of the device, thus avoiding increased manufacturing complexity.
3Reliability
If conventional photoelectric conversion units are used without modulation structures, then the device simplicity is maintained, but the image signal quality for longer wavelengths is unsatisfactory
Solution Approach 1:
The patent applies modulation structures selectively in specific regions within the photoelectric conversion unit, such as at the interface between different material layers or in localized zones of the depletion region. This localized modulation optimizes light interaction precisely where needed for enhanced photoelectric conversion, while leaving other regions unchanged, thus achieving improved signal quality with minimal added structural complexity.
Solution Approach 2:
The patent introduces intermediate modulation structures that act as mediators between incident light and the photoelectric conversion medium. These structures (such as graded doping regions or interface layers) facilitate more effective light trapping and energy transfer, improving image signal quality by enhancing the coupling between optical and electrical domains without requiring fundamental redesign of the entire device architecture.
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 approach improves the quality of the image signal by increasing photoelectric conversion efficiency for longer wavelengths and reducing reflectivity, without thickening the photoelectric conversion units.
Implementation Method 1
the refraction index of the modulation structures is different from the refraction index of the photoelectric conversion units
Implementation Method 2
signal electric charges may be generated according to the amount of light received in the light-sensing portion
Data Source
AI summary
A solid-state image sensor is provided. The solid-state image sensor includes photoelectric conversion units and modulation structures embedded in the photoelectric conversion units. The solid-state image sensor also includes isolation structures disposed between the photoelectric conversion units and a protective layer disposed on the photoelectric conversion units. From the top view of the solid-state image sensor, the photoelectric conversion units and the modulation structures form mosaic patterns, and the ratio of the area of one modulation structure to the area of the corresponding mosaic pattern is between 0.1 and 0.9.