Vertical Transfer Gate Geometry for Deep-Region Charge Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In CMOS image sensors, the use of vertical gate electrodes for charge transfer in deep regions faces challenges in generating an electric field due to the electrode's uniform potential, leading to inefficient charge transfer, and existing solutions that divide the semiconductor region into multiple regions increase the number of processes.
Innovation Solution
The design features vertical gate electrodes with varying diameters and shapes along the depth of the semiconductor substrate, including tapered, stepped, and polygonal configurations, allowing for controlled electric field generation and enhanced charge transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the length of the vertical gate electrode is extended to reach deep regions, then the reading operation can be performed in deep regions, but it becomes difficult to generate the electric field in the depth direction due to uniform potential
Solution Approach 1:
The patent applies local quality by varying the diameter of the vertical gate electrode along its length. The electrode has a first diameter in a first region and a second diameter different from the first diameter in a second region. This non-uniform structure creates local variations in electrical properties, enabling effective electric field generation in deep regions while maintaining the overall length needed to reach those regions.
2Power
If a plurality of vertical gate electrodes is adopted to increase modulation power, then the modulation power increases, but the device structure becomes more complex
Solution Approach 1:
The patent segments the vertical gate electrode into multiple regions along its length, with each region having a different diameter. This segmentation allows different portions of the electrode to contribute to modulation power while maintaining a single continuous structure, avoiding the complexity of multiple separate electrodes.
Solution Approach 2:
Instead of increasing the number of electrodes (adding elements in the planar dimension), the patent varies the diameter along the depth dimension. This dimensional approach allows multiple functional regions to be achieved within a single electrode structure, increasing modulation power without proportionally increasing device complexity.
3Productivity
If the semiconductor region is divided into a plurality of regions with varying impurity concentrations, then the charge transfer efficiency can be improved, but the number of processes increases
Solution Approach 1:
The patent creates local quality variations in the vertical gate electrode by having different diameters in different regions. This structural variation produces local electrical field differences that enhance charge transfer efficiency without requiring multiple separate manufacturing processes for creating different impurity concentration regions.
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 effectively enhances charge transfer efficiency by generating a stronger electric field in the depth direction, facilitating the transfer of charges from deep regions to shallow regions, while reducing the number of processes required.
Implementation Method 1
a potential such that the charges can be accumulated to a deep region has been formed in some cases. In such a case, a normal transfer gate is not used, but a vertical gate electrode which is inserted into silicon is used, resulting in that to a deep region is modulated to perform the reading operation with a generated electric field.
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
To enhance a charge transfer efficiency in a transfer gate having a vertical gate electrode. A solid-state imaging element includes a photoelectric conversion section, a charge accumulating section, and a transfer gate. The photoelectric conversion section is formed in a depth direction of a semiconductor substrate, and generates charges corresponding to a quantity of received light. The charge accumulating section accumulates the charges generated by the photoelectric conversion section. The transfer gate transfers the charges generated by the photoelectric conversion section to the charge accumulating section. The transfer gate includes a plurality of vertical gate electrodes which is filled to a predetermined depth from an interface of the semiconductor substrate, and at least a part of a diameter is different in the depth direction of the semiconductor substrate.