Radiation Detector Pixel Layout for Lower Dark Current
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Solution Overview
Problem
Radiation detectors face degradation due to retained charges in the insulating layer, leading to fluctuated operating points, increased dark current, and deviation from desired sensor outputs, which affects detection sensitivity and image quality.
Innovation Solution
The signal wiring is arranged non-overlapping with the active layer of the amplification transistor and the gate channel region, reducing the electric field and parasitic capacitance, thereby minimizing radiation-induced degradation and improving detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If signal wiring is arranged overlapping with the active layer of the amplification transistor, then device complexity is reduced and manufacturing is easier, but radiation-induced degradation increases due to enhanced electric field and parasitic capacitance
Solution Approach 1:
The patent transitions from a two-dimensional planar layout to a three-dimensional stacked architecture. The signal wiring is moved to a different layer (upper or lower layer) relative to the active layer of the amplification transistor, eliminating overlap in the planar view. This spatial separation in the vertical dimension reduces parasitic capacitance and electric field coupling while maintaining electrical connectivity, thereby improving radiation resistance without compromising manufacturing feasibility.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the signal wiring and the active layer of the amplification transistor. This insulating layer acts as a mediator that electrically isolates the two components, reducing parasitic capacitance and preventing charge leakage. The insulating layer enables the signal wiring to be positioned closer to the active layer while maintaining electrical separation, thus balancing manufacturing ease with radiation resistance.
2Reliability
If signal wiring is arranged non-overlapping with the active layer, then radiation resistance is improved by reducing electric field and parasitic capacitance, but device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent utilizes vertical stacking to achieve non-overlapping arrangement. By positioning the signal wiring in an upper or lower layer relative to the active layer, the design achieves spatial separation without requiring complex lateral routing. This dimensional transition simplifies the overall device architecture compared to alternative approaches that would require intricate wiring patterns to achieve the same isolation effect.
Solution Approach 2:
The insulating layer serves multiple functions simultaneously: it provides electrical isolation between the signal wiring and active layer, acts as a structural support element, and defines the vertical spacing in the stacked architecture. This multi-functionality reduces the need for additional dedicated isolation structures, thereby limiting the increase in device complexity despite the non-overlapping arrangement.
3Ease of manufacture
If signal wiring overlaps with the gate channel region, then manufacturing is simplified, but detection sensitivity deteriorates due to increased dark current and operating point fluctuation
Solution Approach 1:
The patent positions the signal wiring in a different vertical layer from the gate channel region, eliminating planar overlap. This spatial separation prevents the signal wiring from interfering with the gate channel electric field, thereby reducing dark current generation and operating point fluctuation. The vertical stacking maintains manufacturing simplicity by using standard layered fabrication processes.
Solution Approach 2:
An insulating layer is introduced between the signal wiring and the gate channel region to provide electrical isolation. This intermediary prevents charge leakage from the signal wiring into the gate channel, maintaining stable operating points and reducing dark current. The insulating layer is integrated into the existing fabrication process, minimizing the impact on manufacturing complexity.
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 configuration enhances the radiation resistance of the detector, reducing image persistence, fixed pattern noise, and leak current, resulting in improved detection sensitivity and image quality.
Implementation Method 1
a radiation detection element configured to convert radiation into charges
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A radiation detector comprising: a pixel array in which pixels each having a radiation detection element configured to convert radiation into charges and an amplification transistor configured to amplify a signal from the radiation detection element and output the amplified signal are arrayed in a matrix shape; and signal wiring provided for each pixel column, wherein a pixel isolation structure formed to surround the radiation detection element in a plan view is provided, and the amplification transistor is arranged inside a region defined by the pixel isolation structure in a plan view.