Image Sensor Vertical Pillar Charge Transfer
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Solution Overview
Problem
The demand for high-definition image sensing devices requires increasing the number of unit pixels in a limited region, leading to a reduction in photoelectric conversion element size, which deteriorates pixel characteristics.
Innovation Solution
The image sensing device incorporates a photoelectric conversion region and a floating diffusion region with a vertical pillar and switching element, allowing controlled transfer of photocharges without a transfer transistor, enabling the enlargement of the photoelectric conversion element by utilizing space previously allocated for the floating diffusion region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of unit pixels is increased in a limited region, then the resolution is improved, but the photoelectric conversion element size is reduced
Solution Approach 1:
The patent utilizes the vertical dimension by forming the floating diffusion region above the photoelectric conversion region in the depth direction, rather than placing it laterally adjacent. This three-dimensional arrangement allows the photoelectric conversion element to extend horizontally for higher resolution while the floating diffusion occupies vertical space, effectively resolving the area conflict through dimensional transition.
Solution Approach 2:
The patent implements a nested structure where the floating diffusion region is positioned above and overlaps with the photoelectric conversion region in the vertical direction. This nesting arrangement allows both regions to coexist within the same lateral footprint, enabling increased photoelectric conversion element area without expanding the overall pixel area, thus improving resolution while maintaining element size.
2Ease of operation
If a transfer transistor is used to transfer photocharges, then the transfer control is improved, but the device complexity is increased
Solution Approach 1:
The patent extracts and eliminates the transfer transistor from the conventional pixel structure. Instead of using an active transistor component for charge transfer, the invention utilizes the vertical pillar structure and electric field control through the floating diffusion region to achieve transfer functionality, thereby reducing device complexity while maintaining transfer control capability.
Solution Approach 2:
The patent replaces the mechanical/electronic transistor-based charge transfer mechanism with an electric field-based transfer mechanism. By controlling the potential distribution through the floating diffusion region and vertical pillar, photocharges are transferred via electric field guidance rather than transistor switching, simplifying the device structure while preserving transfer control.
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 increases the size of the photoelectric conversion element within a limited region, improving pixel characteristics and reducing dark current leakage, while eliminating the need for a separate transfer transistor, thus enhancing image sensing performance.
Implementation Method 1
a photoelectric conversion region formed in a semiconductor substrate and operable to detect light of a scene to produce photocharges
Implementation Method 2
A depletion region disposed between the photoelectric conversion region and the switching element may be enlarged or reduced in size in response to a control signal applied to the switching element, such that a transfer of the photocharges between the photoelectric conversion region and the floating diffusion (FD) region is controlled
Data Source
AI summary
An image sensing device to control flow of photocharges using a new method is disclosed. The image sensing device includes a photoelectric conversion region formed in a semiconductor substrate, a floating diffusion (FD) region formed apart from the photoelectric conversion region, a vertical pillar formed between the photoelectric conversion region and the floating diffusion region to transfer the photocharges from the photoelectric conversion region to the floating diffusion (FD) region, and a switching element located between the photoelectric conversion region and the floating diffusion (FD) region.