Stacked Image Sensor Layout for Low-Noise Pixel Signal Transfer
Find Innovative SolutionsGenerate Solutions
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 it, and insulation layers between the stacks to reduce noise and enhance efficiency.
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 increases 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 formed in a first semiconductor substrate, while pixel circuit components are formed in a second semiconductor substrate, enabling vertical integration that maintains small pixel footprint while preserving functional performance through spatial separation of functions.
Solution Approach 2:
The pixel structure is divided into functionally independent regions across separate semiconductor substrates: the photoelectric conversion region is segmented from the pixel circuit components. This segmentation allows each region to be optimized independently - the photoelectric conversion region can be designed for maximum light sensitivity while the pixel circuit region can be designed for efficient signal processing, thereby maintaining photoelectric conversion efficiency despite small pixel size.
2Area of moving object
If the size of the pixel decreases, then the size of electrical connection components decreases, but noise occurs and photoelectric conversion efficiency deteriorates
Solution Approach 1:
Electrical connections transition from lateral routing within a single substrate to vertical connections through stacked substrates. The pixel circuit components in the second substrate are positioned directly above or adjacent to their corresponding connection points in the first substrate, enabling short vertical connection paths that minimize noise while maintaining compact pixel area.
Solution Approach 2:
Insulation layers are introduced as intermediary structures between the first and second semiconductor substrates. These insulation layers provide electrical isolation that prevents noise coupling between adjacent pixels and circuits, while still allowing controlled signal transfer through designated connection regions, thus reducing noise in the compact pixel structure.
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 with reduced pixel noise and improved conversion efficiency by minimizing the distance between semiconductor substrates and optimizing signal transfer.
Implementation Method 1
a photoelectric conversion region in the first semiconductor substrate
Data Source
Figure 1
Figure 2
Figure 3
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.