Stacked Imaging Pixel Structure for NIR Sensitivity Without Color Mixing
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Solution Overview
Problem
Solid-state imaging devices with silicon-based light detection elements face challenges in achieving high sensitivity while maintaining image quality, as increasing the silicon layer thickness leads to color mixing between adjacent pixels, degrading image quality.
Innovation Solution
A solid-state imaging device is designed with a first substrate having a semiconductor substrate with a photoelectric conversion element and a second substrate with a pixel transistor, both featuring uneven structures made of different materials. These structures enhance photoelectric conversion efficiency by diffraction and reflection, reducing light entry into adjacent substrates and minimizing dark current and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the silicon layer is increased to obtain high sensitivity for near-infrared light detection, then the photoelectric conversion efficiency is improved, but color mixing between adjacent pixels increases and image quality deteriorates
Solution Approach 1:
The invention divides the light detection function into two separate silicon layers: a first silicon layer optimized for visible light detection with moderate thickness, and a second silicon layer optimized for near-infrared detection with greater thickness. This segmentation allows each layer to be independently optimized for its specific wavelength range, enabling high sensitivity in both ranges without the color mixing problem that occurs when a single thick silicon layer is used for all wavelengths.
Solution Approach 2:
The invention adds a vertical dimension to the light detection architecture by stacking multiple silicon layers at different depths. The first silicon layer detects visible light at a shallower depth, while the second silicon layer detects near-infrared light at a greater depth. This vertical stratification enables wavelength-specific detection at different depths, resolving the contradiction between sensitivity and image quality by preventing cross-contamination of signals from adjacent pixels.
2Reliability
If the thickness of the silicon layer is increased to enhance sensitivity, then the detection capability for near-infrared light is improved, but dark current and noise increase
Solution Approach 1:
The invention segments the detection function by wavelength and depth, placing the thick second silicon layer specifically for near-infrared detection while keeping the first silicon layer at moderate thickness for visible light. This segmentation confines the dark current and noise generation to specific layers and wavelength ranges, preventing the propagation of noise from the thick near-infrared layer to the visible light detection channels.
Solution Approach 2:
The invention introduces an intermediate structure between the first and second silicon layers that acts as a mediator to manage the interaction between the two layers. This intermediate structure helps isolate the dark current and noise generated in the thick second silicon layer, preventing it from affecting the signal quality in the first silicon layer while still allowing the thick layer to provide high sensitivity for near-infrared detection.
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 enables high-sensitivity detection of near-infrared light while maintaining image quality by improving photoelectric conversion efficiency and reducing noise and dark current, thus addressing the limitations of traditional silicon-based imaging devices.
Implementation Method 1
a plurality of pixels that is provided in the first semiconductor substrate and performs photoelectric conversion
Implementation Method 2
These structures enhance photoelectric conversion efficiency by diffraction and reflection
Implementation Method 3
These structures enhance photoelectric conversion efficiency by diffraction and reflection
Data Source
AI summary
Provided are a solid-state imaging device and an electronic device that have high-sensitivity pixels while curbing deterioration in image quality. A solid-state imaging device according to one aspect of the present disclosure includes a first substrate including a first semiconductor substrate having a first surface and a second surface that is opposite to the first surface and on which light is incident, a plurality of pixels that is provided in the first semiconductor substrate and performs photoelectric conversion, and a first uneven structure that is provided on the first surface of the first semiconductor substrate and includes a material different from a material of the first semiconductor substrate, and a second substrate including a readout circuit that is bonded to the first substrate on the first surface side and outputs a pixel signal based on electric charge output from the plurality of pixels.