Photosensitive Region Impurity Layout for Stable Charge Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In solid state imaging devices, increasing the length of photoelectric conversion sections in one direction leads to inefficient charge transfer, as the electrical potential gradient in the photosensitive region may not be sufficient to facilitate efficient charge transfer, particularly when the shape of the second impurity region is not optimally designed.
Innovation Solution
The device incorporates a second impurity region with a line-symmetric shape along the photosensitive region's center line, where the width increases gradually in the transfer direction, forming a consistent electrical potential gradient, ensuring efficient charge transfer regardless of the charge generation position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the length of the photoelectric conversion section in the second direction is increased, then the photosensitive region can cover a larger area, but the charge transfer efficiency deteriorates due to insufficient electrical potential gradient
Solution Approach 1:
The patent applies local quality by creating a non-uniform impurity concentration distribution within the photosensitive region. Specifically, a second impurity region with higher impurity concentration is formed in a specific area (with width W2 greater than width W1 in the first direction) to locally enhance the electrical potential gradient where it is most needed for efficient charge transfer, while maintaining larger overall photosensitive region area.
2Productivity
If impurity is additionally implanted to change impurity concentration, then charge transfer efficiency improves, but the complexity of manufacturing increases
Solution Approach 1:
The patent implements local quality through selective impurity implantation. The second impurity region is formed with higher impurity concentration than the first impurity region, creating a localized enhancement of electrical potential gradient. This targeted approach improves charge transfer efficiency while controlling manufacturing complexity by defining specific geometric parameters (width W2 > W1) rather than requiring complex multi-step processes throughout the entire 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
This design enhances charge transfer efficiency by maintaining a consistent electrical potential gradient across the photosensitive region, reducing image lag and improving transfer time compared to conventional designs.
Implementation Method 1
The second impurity region forms an electrical potential gradient, which gradually increases in the transfer direction, in the photosensitive region
Data Source
AI summary
The photosensitive region includes a first impurity region and a second impurity region having a higher impurity concentration than that of the first impurity region. The photosensitive region includes one end positioned away from the transfer section in the second direction and another end positioned closer to the transfer section in the second direction. A shape of the second impurity region in plan view is line-symmetric with respect to a center line of the photosensitive region along the second direction. A width of the second impurity region in the first direction increases in a transfer direction from the one end to the other end. An increase rate of the width of the second impurity region in each of sections, obtained by dividing the photosensitive region into n sections in the second direction, becomes gradually higher in the transfer direction. Here, n is an integer of two or more.