Silicon Photomultiplier Microcell Self-Test Circuitry
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Solution Overview
Problem
Conventional silicon photomultiplier (SiPM) devices face challenges in identifying and isolating noisy microcells with high dark count rates, which are costly and complex to implement, especially in high-volume production, due to non-uniform defect distribution and the need for individual microcell addressing and external controllers.
Innovation Solution
Incorporating self-test circuitry within microcells to detect and disable microcells with high dark count rates, allowing for a self-test procedure at power-on or by command, with a monitor to track and limit the number of disabled microcells to maintain an active threshold, thereby reducing noise and improving overall detector performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional methods (laser pulses or external controllers) are used to identify and disable noisy microcells, then dark count noise can be reduced, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
Each microcell contains self-test circuitry that autonomously measures its own dark count rate and disables itself if the rate exceeds a threshold, eliminating the need for external controllers or complex laser pulse methods to identify and disable noisy microcells
Solution Approach 2:
The SiPM is divided into multiple independent microcells, each with its own self-test circuitry and disablement capability, allowing individual microcells to be independently managed based on their performance characteristics
2Object-affected harmful factors
If individual microcell addressing and static memory cells are implemented to disable noisy microcells, then dark count noise can be managed, but manufacturing cost and device complexity increase
Solution Approach 1:
The self-test circuitry, measurement function, and disablement logic are merged into a single integrated circuit block within each microcell, eliminating the need for separate static memory cells and external addressing systems
Solution Approach 2:
The self-test circuitry within each microcell serves multiple functions: measuring dark count rate, comparing it to a threshold, and controlling the disablement of the microcell, replacing what would otherwise require multiple separate components
3Object-affected harmful factors
If external controllers are used to implement calibration processes, then noisy microcells can be identified and disabled, but device complexity and production efficiency decrease
Solution Approach 1:
The microcells perform their own calibration and self-test autonomously upon power-up, eliminating the need for external controllers to implement calibration processes, thereby significantly improving production efficiency and reducing device 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 approach enhances photon detector performance by managing individual microcells, increasing wafer fabrication yields and reducing manufacturing costs by enabling efficient identification and isolation of noisy microcells without the need for external controllers or complex laser pulse methods.
Implementation Method 1
When a bias voltage applied to the SiPM is above breakdown, a detected photon generates an avalanche, the APD capacitance discharges to a breakdown voltage and the recharging current creates a signal
Implementation Method 2
Photon sensors can be implemented using an array of microcells containing avalanche photo diodes (APD)
Data Source
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Figure 2B
AI summary
A silicon photomultiplier includes a plurality of microcells providing a pulse output in response to an incident radiation, each microcell including circuitry configured to enable and disable the pulse output. Each microcell includes a cell disable switch. The control logic circuit controls the cell disable switch and a self-test circuit. A microcell' s pulse output is disabled when the cell disable switch is in a first state. A method for self-test calibration of microcells includes providing a test enable signal to the microcells, integrating dark current for a predetermined time period, comparing the integrated dark current to a predetermined threshold level, and providing a signal if above the predetermined threshold level.