Radiation Hardness Study of Silicon Carbide Sensors under High-Temperature Proton Beam Irradiations

At a Glance

Metadata	Details
Publication Date	2023-01-09
Journal	Micromachines
Authors	Elisabetta Medina, Enrico Sangregorio, Andreo Crnjac, F. Romanò, G. Milluzzo
Institutions	Institute for Microelectronics and Microsystems, University of Catania
Citations	12
Analysis	Full AI Review Included

Executive Summary

This study investigates the radiation hardness of Silicon Carbide (SiC) PIN diode sensors, focusing on the benefits of high-temperature operation and thin membrane geometry in harsh environments (HE).

Core Value Proposition: SiC sensors demonstrate enhanced radiation tolerance when damage is induced at high temperatures (500 °C) compared to room temperature (RT) irradiation, supporting their use in extreme HE applications.
Dynamic Annealing Confirmation: High-temperature irradiation (500 °C) leads to significantly higher Charge Collection Efficiency (CCE) due to dynamic annealing, suppressing the accumulation of radiation-induced point defects.
Performance Retention: Even after the highest fluence irradiation (5 x 10¹³ protons/cm²), the CCE of the high-temperature damaged areas remained robust, generally exceeding 80% at bias voltages above 30 V.
Localized Testing: The Ion Microprobe Chamber was utilized to induce localized damage in small areas (< 100 x 100 µm²) within a single device, minimizing device-to-device variability uncertainties.
Membrane Advantage: Preliminary results suggest that sensors fabricated with ultrathin (20 µm) free-standing SiC membranes exhibit higher radiation hardness (higher CCE) compared to standard bulk regions (370 µm substrate).
Device Structure: The tested sensors are SiC PIN diodes featuring a 20 µm active layer, partially thinned via doping-selective electrochemical etching to create the free-standing membrane.

Technical Specifications

Parameter	Value	Unit	Context
Sensor Type	PIN Diode	N/A	SiC membrane sensor (STLab/SenSiC)
Active Layer Thickness (n^-)	20	µm	Low-doped layer thickness
Substrate Thickness (n⁺)	~370	µm	Bulk region thickness
High Operational Temperature	500	°C	High-temperature irradiation condition
Probing Beam Energy	1	MeV	Proton beam for IBIC (Bragg peak at ~10 µm)
Damaging Beam Energy	3.5	MeV	Proton beam (transmission beam)
Maximum Bias Voltage Tested	-60	V	Safe operating range for I-V characterization
Leakage Current (at -60 V)	< 1	nA	Measured at Room Temperature (RT)
Highest Irradiation Fluence	5 x 10¹³	protons/cm²	Highest dose tested (RT and HT comparison)
Highest Dose (3.5 MeV H⁺)	8.6 x 10⁵	Gy	Corresponding to 5 x 10¹³ protons/cm²
CCE Recovery (Low Fluence, HT)	Up to 90	%	CCE matches pristine values (5 x 10¹² protons/cm²)
CCE Minimum (High Fluence)	> 80	%	CCE above 30 V bias, except for highest fluence
CCE Improvement (HT vs RT)	5 to 20	%	Relative CCE difference between HT- and RT-damaged areas
Ion Microprobe Spot Size	~1	µm	Minimum beam radius for localized damage

Key Methodologies

The radiation hardness study employed the Ion Microprobe Chamber and the Beam-Induced Charge Technique (IBIC) at the Ruđer Bošković Institute (RBI).

Device Fabrication: SiC PIN diodes were fabricated with a 20 µm n^- active layer. Ultrathin free-standing membranes (20 µm) were created in selected areas via doping-selective electrochemical etching.
Experimental Setup: The sensor was mounted on a ceramic PCB in a vacuum chamber, equipped with a resistive heater and a Type K thermocouple to achieve and monitor the 500 °C high-temperature condition.
Localized Damage Induction: A focused 3.5 MeV proton beam (transmission beam, creating homogenous defects) was scanned over small, localized square areas on the sensor surface to induce radiation damage.
Temperature Comparison: Damage was induced in four distinct areas at 500 °C (High Temperature, HT) and four comparable areas at Room Temperature (RT), using fluences ranging from 5 x 10¹² to 5 x 10¹³ protons/cm².
CCE Measurement (IBIC): Charge Collection Efficiency (CCE) was measured at RT using a 1 MeV proton beam (probing beam, Bragg peak located within the 20 µm active layer) scanned over the damaged regions.
Calibration: CCE was calibrated using a reference silicon STIM detector, assuming 100% charge collection for the reference signal.
Geometry Comparison: Additional tests were performed at RT using 3.5 MeV protons to compare CCE degradation between the 20 µm free-standing membrane regions and the 370 µm bulk regions of the sensor.

Commercial Applications

The demonstrated radiation hardness and high-temperature operational stability of SiC membrane sensors make them ideal for several demanding engineering and scientific fields.

Nuclear and Fusion Energy:
- Safety assessment and process monitoring sensors within nuclear facilities.
- In-core monitoring within fusion reactor vessels, where temperatures exceed 500 °C and high radiation doses are unavoidable.
High-Intensity Beam Diagnostics:
- X-ray beam position monitors (BPMs) for synchrotrons and Free-Electron Lasers (FELs), capable of withstanding beam powers > 100 kW/cm².
Advanced Medical Dosimetry:
- Ultra-high-dose-rate electron beam dosimetry for novel radiotherapies, such as FLASH radiotherapy, requiring fast response and high radiation tolerance.
Aerospace and Defense:
- Robust sensing components for space applications (satellites, probes) where devices must operate reliably under high radiation fluxes and extreme thermal cycling.
High-Power Electronics (HPE):
- Integration of robust sensors into HPE systems (e.g., electric vehicles, industrial power grids) where SiC is already the dominant material, ensuring stability under operational heat and potential radiation exposure.

View Original Abstract

Silicon carbide (SiC), thanks to its material properties similar to diamond and its industrial maturity close to silicon, represents an ideal candidate for several harsh-environment sensing applications, where sensors must withstand high particle irradiation and/or high operational temperatures. In this study, to explore the radiation tolerance of SiC sensors to multiple damaging processes, both at room and high temperature, we used the Ion Microprobe Chamber installed at the Ruđer Bošković Institute (Zagreb, Croatia), which made it possible to expose small areas within the same device to different ion beams, thus evaluating and comparing effects within a single device. The sensors tested, developed jointly by STLab and SenSiC, are PIN diodes with ultrathin free-standing membranes, realized by means of a recently developed doping-selective electrochemical etching. In this work, we report on the changes of the charge transport properties, specifically in terms of the charge collection efficiency (CCE), with respect to multiple localized proton irradiations, performed at both room temperature (RT) and 500 °C.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi14010166

References

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