Active Pixel X-Ray Detector Layout for Low-Noise Photon Counting
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Solution Overview
Problem
State-of-the-art photon counting X-ray detectors face increased noise and power consumption due to heterogeneous integration of semiconductor sensors and ASICs, which is exacerbated by direct wire-bonding, leading to suboptimal image quality and higher system complexity and costs.
Innovation Solution
The implementation of active pixel sensors with integrated amplification stages and separate readout circuitry, where each active pixel acts as a passive integrator or uses a bipolar junction transistor to generate output signals, directly coupled to readout circuitry, reducing the impact of detector capacitance and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heterogeneous integration with direct wire-bonding is used, then device functionality is achieved, but noise and power consumption increase
Solution Approach 1:
The detector is divided into separate functional modules: sensor pixels on a semiconductor substrate and readout circuitry on a separate ASIC, connected via trace layers. This segmentation isolates noise-sensitive sensor elements from noisy readout electronics, reducing electronic noise while maintaining full detector functionality.
Solution Approach 2:
Trace layers embedded in interlayer dielectric material serve as intermediaries between the sensor pixels and readout circuitry. These traces transmit signals while being isolated from noise sources, acting as a mediator that reduces harmful electromagnetic coupling between sensor and readout electronics.
2Reliability
If heterogeneous integration with direct wire-bonding is used, then device functionality is achieved, but power consumption increases
Solution Approach 1:
Separating readout circuitry into a dedicated ASIC reduces power consumption by optimizing the readout architecture and minimizing parasitic capacitances associated with wire-bonding. The segmented design allows for lower operating voltages and more efficient signal processing.
Solution Approach 2:
Replacing mechanical wire-bonding connections with planar trace layers reduces parasitic inductance and capacitance, leading to lower power consumption in the readout circuitry while maintaining electrical connectivity.
3Object-generated harmful factors
If separate readout circuitry is used, then noise is reduced, but device complexity increases
Solution Approach 1:
The trace layers and interlayer dielectric material are integrated into a unified planar structure that combines signal transmission and electrical isolation functions. This merging reduces structural complexity compared to three-dimensional wire-bonding arrangements while achieving noise reduction.
Solution Approach 2:
The trace layers serve multiple functions: signal transmission from pixels to readout circuitry, electrical isolation between different circuit nodes, and mechanical support within the layered structure. This multi-functionality reduces the need for separate dedicated components, simplifying the overall device architecture.
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 improves image quality by reducing electronic noise, lowers readout circuitry power consumption, and simplifies the system, resulting in more efficient and cost-effective photon counting detectors for applications like computed tomography.
Implementation Method 1
An X-ray photon is absorbed in a semiconductor material (e.g., cadmium zinc telluride (CZT), silicon, etc.) resulting in generation of photocharge proportional to the X-ray photon energy.
Implementation Method 2
A photodiode or diode, separates the electron-hole pairs and generates a current pulse at its output.
Data Source
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AI summary
A photon counting detector (28) includes a plurality of detector sub-modules (58). Each detector sub-module includes (58) a semiconductor substrate (72). Each detector sub-module (58) also includes a plurality of active pixels (60) configured to act as detector elements disposed on the semiconductor substrate (72). Each detector sub-module (58) further includes a plurality of traces (118) extending from the plurality of active pixels (60) to readout circuitry (120). Each active pixel (60) of the plurality of active pixels (60) is coupled to a respective trace (118) of the plurality of traces (118). Each active pixel (60) includes an amplification stage (116) configured to generate an output signal based on a current pulse output generated by the active pixel (60). The photon counting detector (28) also includes the readout circuitry (120) configured to directly read out the output signals from the plurality of active pixels (60), wherein the readout circuitry (120) is separate from the plurality of detector sub-modules (58).