Image Sensor Shared Pixel Capacitance Symmetry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors with shared pixel structures face issues due to differences in overlap capacitance or parasitic capacitance among unit pixels, leading to variations in output signals and increased noise during image conversion.
Innovation Solution
The image sensor design incorporates a shared pixel structure with conductive lines of equal length and symmetrical regions to minimize overlap capacitance, ensuring that unit pixels adjacent to each other sense the same color with identical capacitances, thereby preventing signal differences and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If unit pixels are arranged with different conductive line lengths to the floating diffusion, then the layout flexibility is improved, but the overlap capacitance varies among unit pixels causing signal differences and noise
Solution Approach 1:
The patent applies asymmetry in reverse - it deliberately creates symmetry in the conductive line lengths from the floating diffusion to different unit pixels. By making the conductive line lengths equal despite different pixel positions, the patent achieves uniform overlap capacitance values, eliminating signal variations and noise caused by capacitance differences.
Solution Approach 2:
The patent changes the parameter of conductive line length to be equal across all unit pixels connected to the floating diffusion. This parameter change ensures that the overlap capacitance remains constant regardless of the unit pixel's position, thereby maintaining signal uniformity while allowing flexible pixel arrangements.
2Productivity
If more unit pixels share the same floating diffusion to increase integration density, then the productivity is improved, but the parasitic capacitance differences increase causing more noise
Solution Approach 1:
The patent merges multiple unit pixels to share a common floating diffusion node, increasing integration density. By combining multiple pixels around a central floating diffusion with equal-length conductive lines, the patent achieves high integration while maintaining uniform capacitance characteristics across all shared pixels, thereby reducing noise.
3Measurement precision
If the conductive line lengths are made equal to minimize capacitance differences, then the measurement precision is improved, but the device complexity increases due to symmetrical layout constraints
Solution Approach 1:
The patent creates equipotential conditions by ensuring equal conductive line lengths from the floating diffusion to all unit pixels. This equipotential design ensures that all pixels experience the same capacitance environment, achieving signal uniformity and improved measurement precision while the symmetrical layout actually simplifies the design process through standardized patterns.
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 enhances image resolution by ensuring uniform output signals from unit pixels, minimizing errors and noise during image conversion, and allowing for high-density integration of the image sensor.
Implementation Method 1
a photodiode and a transfer transistor, and a floating diffusion, each sharing the same first active region, respectively, the photodiode configured to receive incident light and generate photo charges in response to the received incident light
Data Source
AI summary
Disclosed is an image sensor device including a pixel array in which a plurality of pixel blocks are arranged. Each of the pixel blocks may include: a light receiver comprising a floating diffusion and a plurality of unit pixels and configured to receive incident light and generate photo charges in response to the received incident light, the plurality of unit pixels sharing the floating diffusion; a first driver located at a first side of the light receiver and comprising a driver transistor; a second driver located at a second side of the light receiver and comprising a reset transistor; and a conductive line having a first region coupling the driver transistor to the floating diffusion and a second region coupling the floating diffusion to the reset transistor, wherein the driver transistor and the reset transistor are respectively located the first side and the second side of the light receiver in a diagonal direction.