Frontside-illuminated image sensor
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Solution Overview
Problem
Current backside-illuminated image sensors have complex manufacturing processes, low yield, limited space for charge storage, and design difficulties due to large photodiode area and interference issues, which are exacerbated by requirements for high dynamic range and global shutter performance.
Innovation Solution
A frontside-illuminated image sensor design featuring a base with charge storage regions, photosensitive units with GaN-based layers for different colors, a color filter unit, and a lens structure, where the photosensitive unit is electrically connected to charge storage regions, and light-shielding structures are used to prevent interference, simplifying the process and increasing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backside-illuminated structure is used, then photoelectric conversion efficiency is improved, but manufacturing complexity increases and yield decreases
Solution Approach 1:
The patent inverts the conventional backside-illuminated structure by placing the photosensitive unit above the base with charge storage regions, and positioning the color filter unit and lens structure above the photosensitive unit. This frontside-illuminated configuration eliminates the need for complex alignment between front-side photodiodes and back-side filter structures, thereby reducing manufacturing complexity while maintaining photoelectric conversion efficiency.
2Quantity of substance
If photodiode area is increased for charge storage, then full well capacity is improved, but space for storage capacitor is reduced
Solution Approach 1:
The patent utilizes the vertical dimension by positioning the color filter unit and lens structure above the photosensitive unit, which is itself above the base with charge storage regions. This three-dimensional arrangement allows the photodiode to occupy sufficient horizontal area for charge storage while the vertical space accommodates other components, effectively resolving the area conflict between charge storage capacity and capacitor space.
3Object-affected harmful factors
If deep trench isolation structure is added to reduce light interference, then adjacent photodiode isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes the complex deep trench isolation structure from the design. Instead, it employs a simplified isolation approach where the base with charge storage regions naturally provides electrical isolation, and the color filter unit with light-shielding structures addresses light interference without requiring additional deep trench isolation, thereby reducing manufacturing complexity.
4Productivity
If frontside-illuminated structure is used, then manufacturing process is simplified and yield increases, but photoelectric conversion efficiency may be reduced
Solution Approach 1:
The patent employs GaN-based composite materials for the photosensitive unit, which inherently possess superior photoelectric conversion properties. This material selection compensates for the potential efficiency reduction associated with frontside illumination, allowing the simplified manufacturing process to maintain high photoelectric conversion efficiency while achieving improved manufacturing yield.
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 simplifies the manufacturing process, increases yield, reduces light interference, and provides sufficient space for charge storage, enhancing high dynamic range and global shutter performance by avoiding backside structure alignment and allowing larger full well capacity.
Implementation Method 1
the photosensitive unit includes photosensitive layers for different colors... generate photosensitive charges based on wavelengths of received light
Data Source
AI summary
The present disclosure provides a frontside-illuminated image sensor, including: a base, a photosensitive unit, a color filter unit and a lens structure. The base has charge storage regions. The photosensitive unit is on the base, the photosensitive unit includes photosensitive layers for different colors, and one of the photosensitive layers is electrically connected to one of the charge storage regions. The color filter unit is at a side of the photosensitive unit away from the base, the color filter unit includes color filter layers for different colors, and one of the color filter layers corresponds to one of the photosensitive layers. The lens structure is at a side of the color filter unit away from the base.