Vertically Stacked Image Sensor Photodiode Fill Factor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Related art horizontal CMOS image sensors face limitations in resolution and sensitivity due to the proximity of photodiodes and transistors, which restricts the fill factor and increases pixel size, making it difficult to achieve ideal production conditions and reducing image quality.
Innovation Solution
The implementation of vertically configured photodiodes with improved physical and electrical contact to circuitry, using a first substrate with circuitry and a photodiode bonded to it, along with a contact plug at the pixel border for electrical connection, and ion implantation regions in a crystalline semiconductor layer to enhance connectivity and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If photodiode and transistor are disposed in mutual horizontal positions and proximity, then device integration is achieved, but fill factor region is reduced and resolution potential is limited
Solution Approach 1:
The patent transitions from a horizontal layout to a vertical stacking architecture, placing the photodiode and transistor in different vertical layers rather than adjacent horizontal positions. This dimensional change allows both components to coexist without occupying the same planar space, thereby increasing the fill factor while maintaining device integration.
2Reliability
If additional space for photodiode is required, then sensitivity is improved, but pixel size must increase reducing resolution
Solution Approach 1:
By stacking the photodiode vertically above the transistor, the patent enables the photodiode to occupy the full pixel area without lateral expansion. This vertical arrangement increases the photodiode area for light detection while maintaining the same pixel footprint, thereby improving sensitivity without compromising resolution.
3Manufacturing precision
If photodiode area is reduced to maintain pixel size, then resolution is maintained, but sensitivity is reduced
Solution Approach 1:
The vertical stacking architecture allows the photodiode to extend vertically rather than laterally, enabling sufficient photodiode area for high sensitivity while maintaining compact pixel dimensions for high resolution. The photodiode's active region is positioned in the vertical dimension above the transistor, decoupling the area requirements of both components.
4Ease of manufacture
If horizontal configuration is used, then manufacturing process is simpler, but ideal production conditions for simultaneous photodiode and transistor production are difficult to attain
Solution Approach 1:
The patent divides the image sensor into separate stacked layers, with the photodiode formed in a first substrate and the transistor formed in a second substrate. This segmentation allows each component to be manufactured independently under its optimal conditions, then bonded together, enabling simultaneous production of photodiodes and transistors without compromising manufacturing simplicity.
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 approach increases the fill factor, minimizes cross-talk between pixels, and improves sensitivity and resolution by ensuring better contact between photodiodes and circuitry, reducing defects and enhancing image sensor performance.
Implementation Method 1
The photodiode may include a first conductive type ion implantation region selectively provided in a crystalline semiconductor layer, and a second conductive type ion implantation region in contact with one side surface of the first conductive type ion implantation region
Implementation Method 2
A photodiode bonded to the first substrate and electrically connected to the circuitry
Data Source
AI summary
Embodiments relate to an image sensor and a method of manufacturing the same. According to embodiments, an image sensor may include a first substrate having circuitry formed thereon. It may further include a photodiode bonded to the first substrate and electrically connected to the circuitry, and a contact plug at a pixel border that may be electrically connected with the circuitry and the photodiode. According to embodiments, the photodiode may include a first conductive type ion implantation region selectively provided in a crystalline semiconductor layer, and a second conductive type ion implantation region in contact with one side surface of the first conductive type ion implantation region.