Back-Illuminated Imaging Device Optical Waveguide Integration
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Solution Overview
Problem
Front-illuminated solid-state imaging devices with optical waveguides formed at the same position as the interconnect layer suffer from degraded image quality, making it difficult to improve image quality.
Innovation Solution
A back-illuminated solid-state imaging device is developed with an optical waveguide formed between the semiconductor substrate and the organic photoelectric conversion film, including a lower electrode, through electrode, and interconnect layer, which improves image quality by enhancing sensitivity, shading, and color mixing while reducing parasitic capacitance and random noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an optical waveguide is formed at the same position as the interconnect layer in a front-illuminated imaging device, then the device structure is simplified, but image quality is degraded
Solution Approach 1:
The patent inverts the illumination direction from front-illuminated to back-illuminated configuration. By forming the optical waveguide between the semiconductor substrate and the organic photoelectric conversion film in a back-illuminated structure, light enters from the opposite side, allowing the waveguide to function as an effective light guide without interfering with the interconnect layer positioning, thus resolving the contradiction between structural simplicity and image quality
Solution Approach 2:
The patent repositions the optical waveguide in the vertical stacking direction by implementing a back-illuminated architecture. Instead of placing the waveguide at the same lateral position as the interconnect layer, it is positioned in the depth dimension between the substrate and photoelectric conversion film, enabling both the waveguide and interconnect layer to coexist without spatial conflict while maintaining optimal optical performance
2Ease of manufacture
If light is allowed to enter adjacent pixels, then manufacturing is easier, but color mixing increases and image quality degrades
Solution Approach 1:
The optical waveguide acts as an intermediary structure that channels and confines light propagation. By forming the waveguide between the semiconductor substrate and organic photoelectric conversion film, it serves as a dedicated light transmission pathway that prevents light from straying into adjacent pixels, thereby eliminating color mixing while maintaining manufacturing feasibility through standard waveguide formation techniques
3Reliability
If the distance between the semiconductor substrate and organic photoelectric conversion film is increased, then parasitic capacitance is reduced, but light guidance efficiency decreases
Solution Approach 1:
The optical waveguide ensures continuous and efficient light guidance from the semiconductor substrate to the organic photoelectric conversion film. By maintaining an optimized distance between these components while incorporating the waveguide structure, the system achieves both reduced parasitic capacitance (improved signal-to-noise ratio) and sustained light guidance efficiency, as the waveguide compensates for any potential light loss from the increased spacing
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
The solution effectively improves image quality by preventing light entry into adjacent pixels, increasing sensitivity, and reducing capacitance, thereby enhancing the signal-to-noise ratio and preventing decline in conversion efficiency.
Implementation Method 1
An optical waveguide is formed between the second imaging device and the first imaging device to guide visible light that has transmitted through the second pixels of the second imaging device onto the first pixels of the first imaging device
Implementation Method 2
The second imaging device is stacked over the front surface of the semiconductor substrate, generates a second photoelectric conversion signal by converting infrared light using an organic photoelectric conversion film that absorbs infrared light and transmits visible light
Data Source
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AI summary
To provide a back-illuminated solid-state imaging device that can improve image quality. Provided is a back-illuminated solid-state imaging device that includes at least a semiconductor substrate, an organic photoelectric conversion film, and an optical waveguide. The organic photoelectric conversion film is formed on one of front and back surfaces of the semiconductor substrate. The optical waveguide is formed between the semiconductor substrate and the organic photoelectric conversion film.