Segmented Light-Receiving Element for Faster Low-Noise X-Ray Readout
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Solution Overview
Problem
Existing X-ray imaging elements face challenges in achieving high frame rates with low noise, due to increased dark current, capacitance, and limited reading speed, particularly in CMOS image sensors with integrated floating diffusion regions.
Innovation Solution
A light-receiving element design with a p-type electrically-conductive region as an anode, a drain region, and a guard ring in an electrically floating state, coupled with an n-type embedded layer, to discharge dark current and improve signal charge movement, reducing capacitance and enhancing reading speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a CMOS image sensor with integrated floating diffusion region is used, then manufacturing simplicity is improved, but dark current increases and reading speed decreases
Solution Approach 1:
The patent segments the electrically-conductive region into multiple functional zones: a first region coupled to the floating diffusion, a second region surrounding it coupled to a different electrode, and a third region in an electrically floating state. This segmentation allows each region to perform its specific function independently, managing dark current while maintaining manufacturing simplicity.
Solution Approach 2:
The third electrically-conductive region acts as an intermediary element between the first and second regions. Being in an electrically floating state, it mediates the interaction between the charged regions, helping to control dark current flow while maintaining the overall structure's manufacturability.
2Ease of manufacture
If a CMOS image sensor with integrated floating diffusion region is used, then manufacturing simplicity is improved, but reading speed decreases
Solution Approach 1:
By segmenting the electrically-conductive region into multiple zones with different electrical couplings, the patent creates optimized charge collection pathways that improve reading speed while keeping the overall structure compatible with standard CMOS manufacturing processes.
Solution Approach 2:
Different regions of the electrically-conductive structure are given different electrical properties: the first region is coupled to the floating diffusion for signal collection, the second region is coupled to another electrode for potential biasing, and the third region is left floating to optimize charge collection. This local differentiation improves reading speed without complicating manufacturing.
3Measurement precision
If the photoelectric conversion region thickness is increased, then sensitivity is improved, but capacitance increases
Solution Approach 1:
The segmented electrically-conductive structure creates multiple zones for charge collection and management. This segmentation allows the system to handle charges from a thicker photoelectric conversion region more efficiently, improving sensitivity while the distributed structure helps manage the associated capacitance increase.
Solution Approach 2:
By changing the electrical parameters of different regions (coupled vs. floating states), the patent optimizes the balance between sensitivity and capacitance. The floating third region, in particular, helps manage the electrical characteristics to handle thicker conversion regions without excessive capacitance penalties.
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
The design effectively prevents dark current from reaching the anode, improves signal charge transfer speed, and enhances resistance to high energy inputs, achieving decreased dark current, reduced capacitance, and improved reading speed.
Implementation Method 1
a semiconductor substrate including a photoelectric conversion region
Data Source
AI summary
A light-receiving element according to an embodiment of the present disclosure includes: a semiconductor substrate (11) including a photoelectric conversion region; a first electrically-conductive region (13A) provided at an interface of one surface of the semiconductor substrate (11) and coupled to a first electrode (16); a second first electrically-conductive region (13B) provided at the interface of the one surface and around the first electrically-conductive region (13A) and coupled to a second electrode (17); and a third first electrically-conductive region (13C) provided at the interface of the one surface and around the second first electrically-conductive region (13B) and being in an electrically floating state.