Stacked Image Sensor Structure for Noise-Isolated Small Pixels
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Solution Overview
Problem
As image sensors become more integrated, the small size of pixels leads to noise and decreased photoelectric conversion efficiency due to smaller electrical connection components.
Innovation Solution
A stacked image sensor design with a first semiconductor substrate having a photoelectric conversion region and a floating diffusion region, a second semiconductor substrate with a transmission gate penetrating through, and insulation layers between the stacks to reduce noise and enhance signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the degree of integration of an image sensor increases, then the size of the pixel decreases, but noise occurs and photoelectric conversion efficiency deteriorates
Solution Approach 1:
The patent transitions from a planar pixel structure to a three-dimensional stacked structure with multiple semiconductor substrates stacked vertically. The photoelectric conversion region is positioned in a first substrate while pixel circuit components are positioned in second and third substrates, enabling vertical integration that maintains small pixel footprint while preserving functional performance through spatial separation of noise-sensitive and noise-generating components.
Solution Approach 2:
The pixel structure is segmented into multiple functional regions distributed across different stacked substrates: the photoelectric conversion region is separated from the pixel circuit region, with charges transferred vertically between substrates. This segmentation isolates the noise-sensitive photoelectric conversion function from noise-generating circuit operations, maintaining efficiency despite high integration.
2Area of moving object
If the size of electrical connection components decreases, then the pixel size decreases, but noise occurs and signal transmission quality deteriorates
Solution Approach 1:
An insulation layer is introduced as an intermediary between the first semiconductor substrate containing the photoelectric conversion region and the second semiconductor substrate containing the pixel circuit. This insulation layer acts as a noise barrier that blocks electrical noise from the circuit from reaching the sensitive photoelectric conversion region, enabling small pixel size while maintaining signal quality.
Solution Approach 2:
The patent uses vertical stacking to separate noise sources from sensitive regions in the third dimension. By positioning the photoelectric conversion region in one substrate and circuit components in other substrates with insulation layers between them, the design achieves compact lateral dimensions while using vertical separation to eliminate noise interference.
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 design achieves excellent image quality by reducing pixel noise and maintaining efficient signal conversion even with small pixel sizes, improving the overall performance of the image sensor.
Implementation Method 1
a photoelectric conversion region in the first semiconductor substrate
Implementation Method 2
a floating diffusion region in the first semiconductor substrate, the floating diffusion region being configured to store charges transferred from the photoelectric conversion region
Data Source
AI summary
An image sensor includes: a first stack including: a first semiconductor substrate including a first surface and a second surface opposite to the first surface, a photoelectric conversion region in the first semiconductor substrate, and a floating diffusion region in the first semiconductor substrate, the floating diffusion region being configured to store charges transferred from the photoelectric conversion region; a second stack including: a second semiconductor substrate including a first surface and a second surface opposite the first surface, and a transmission gate penetrating through the second semiconductor substrate and extending into the first stack; and an insulation layer between the first stack and the second stack.