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	Rudjer Boskovic Institute, University of Catania
Citations	12
Analysis	Full AI Review Included

Technical Documentation: High-Temperature Radiation Hardness of SiC Sensors

Reference Paper: Medina et al. (2023). Radiation Hardness Study of Silicon Carbide Sensors under High-Temperature Proton Beam Irradiations. Micromachines, 14, 166.

Executive Summary

This documentation analyzes a critical study demonstrating the enhanced radiation tolerance of Silicon Carbide (SiC) PIN diode sensors when operated under high-temperature proton irradiation, a key requirement for harsh environment (HE) applications.

Core Finding: SiC sensors irradiated at 500 °C exhibited significantly higher Charge Collection Efficiency (CCE) compared to those irradiated at Room Temperature (RT), confirming the effect of dynamic annealing in suppressing radiation-induced lattice damage.
Material Context: SiC is positioned as the leading alternative to diamond for HE sensing, balancing industrial maturity (like silicon) with superior radiation hardness (close to diamond).
Device Structure: Testing utilized advanced SiC PIN diodes featuring ultrathin (20 µm) free-standing membranes, fabricated via doping-selective electrochemical etching.
Performance Metric: CCE remained robust, exceeding 80% at bias voltages above 30 V, even after high-fluence proton damage (up to 5 x 10¹³ protons/cm²).
Methodology: Localized damage and subsequent CCE probing were achieved using focused MeV proton beams (1 MeV for probing, 3.5 MeV for damage) within an Ion Microprobe Chamber, enabling localized effect comparison within a single device.
Future Direction: Preliminary results suggest that sensors built on free-standing membranes may offer higher intrinsic radiation hardness compared to standard bulk devices, opening new avenues for ultra-thin SiC sensor design.

Technical Specifications

Parameter	Value	Unit	Context
Active Layer Thickness	20	µm	n^- low-doped layer (Membrane)
Substrate Thickness	~370	µm	n⁺ bulk substrate
p⁺ Doping Concentration	10¹⁸	cm^-3	Highly doped layer (0.3 µm thick)
n^- Doping Concentration	10¹⁴	cm^-3	Active layer
n⁺ Substrate Doping	10¹⁸	cm^-3	Substrate
High Irradiation Temperature	500	°C	Used to induce dynamic annealing
CCE Probing Beam Energy	1	MeV	Proton (H⁺), Bragg peak at ~10 µm depth
Damage Induction Beam Energy	3.5	MeV	Proton (H⁺), Transmission beam (Bragg peak in substrate)
Maximum Fluence Tested (High T/RT)	5 x 10¹³	protons/cm²	Highest damage dose
Maximum Dose Tested (High T/RT)	8.6 x 10⁵	Gy	Corresponding to 5 x 10¹³ protons/cm²
Leakage Current (Safe Bias)	< 1	nA	At -60 V bias (Room Temperature)
Minimum CCE (Damaged)	> 80	%	Achieved above 30 V bias (except highest fluence)
CCE Improvement (High T vs. RT)	5 to 20	%	Higher CCE observed for 500 °C irradiation

Key Methodologies

The study employed the Beam-Induced Charge Technique (IBIC) within an Ion Microprobe Chamber to achieve highly localized irradiation and subsequent charge transport analysis.

Device Preparation: SiC PIN diode sensors were fabricated with a 20 µm free-standing membrane structure using doping-selective electrochemical etching.
Mounting and Heating: The sensor was mounted on a ceramic PCB using high-purity silver paste and placed in the vacuum chamber. A resistive heater and Type K thermocouple enabled precise temperature control up to 500 °C.
Bias Application: Reverse bias (up to -80 V) was applied to achieve “reverse diode operation” for high signal-to-noise ratio.
Damage Induction: A focused 3.5 MeV proton beam (transmission beam) was scanned over selected square areas (below 100 x 100 µm²) to induce radiation damage at specific fluences (up to 5 x 10¹³ protons/cm²). This was performed at both RT and 500 °C.
Charge Collection Efficiency (CCE) Measurement: A lower-energy 1 MeV proton beam (probing ion beam) was used to measure CCE. This beam deposits energy entirely within the 20 µm active layer, allowing for localized charge transport mapping (IBIC maps).
Calibration: CCE was calibrated against a reference silicon STIM detector, assuming 100% charge collection in the reference material.

6CCVD Solutions & Capabilities

The research highlights the critical need for materials that can withstand extreme radiation and high temperatures, positioning SiC as a strong candidate. However, the paper explicitly notes the historic limitations of CVD diamond (high cost, limited size < 1 cm², doping control issues).

6CCVD specializes in overcoming these exact limitations, offering superior diamond materials for applications where SiC performance is insufficient or where ultimate radiation hardness is required.

Applicable Materials for Harsh Environment (HE) Sensing

6CCVD provides MPCVD diamond materials that surpass SiC in key radiation hardness metrics (larger bandgap, higher kick-off energy), making them ideal for extending or replicating this research at even higher radiation doses or temperatures.

6CCVD Material	Description & Application	Relevance to Paper’s Findings
Optical Grade Single Crystal Diamond (SCD)	Highest purity, lowest defect density. Ideal for ultimate radiation hardness, high-speed detection, and high-temperature operation (> 500 °C).	Replaces SiC where maximum CCE stability and minimal radiation damage are required (e.g., fusion reactors, high-intensity synchrotrons).
Polycrystalline Diamond (PCD)	Cost-effective, large-area solution (up to 125mm wafers). Suitable for large-scale HE sensor arrays and dosimetry.	Overcomes the size limitation (< 1 cm²) historically associated with diamond cited in the paper.
Boron-Doped Diamond (BDD)	Highly conductive material used for robust electrodes, ohmic contacts, and electrochemical sensors in HE environments.	Essential for replicating the p⁺/n^- junction structure or creating highly stable, radiation-hard contacts necessary for high-bias operation.

Customization Potential for Advanced Sensor Design

The SiC sensor utilized a complex structure involving specific thicknesses (20 µm membrane, 370 µm bulk) and metal contacts (gold electrodes). 6CCVD’s in-house capabilities directly support the replication and optimization of such advanced sensor geometries using diamond.

Requirement from Paper	6CCVD Capability	Technical Advantage
Thin Active Layers (20 µm membrane)	Custom SCD/PCD thickness control from 0.1 µm up to 500 µm.	Allows precise engineering of active layer thickness to optimize charge collection and minimize diffusion effects, crucial for IBIC/CCE studies.
Large Area Devices	PCD plates/wafers available up to 125 mm diameter.	Enables the fabrication of large-scale sensor arrays for high-flux monitoring, exceeding the limitations of small SCD samples.
Metalization for Contacts	Internal capability for custom metal stacks: Au, Pt, Pd, Ti, W, Cu.	Essential for creating stable, high-temperature ohmic and Schottky contacts, replicating the gold electrodes used in the SiC device setup.
Surface Quality	SCD polishing to Ra < 1 nm; Inch-size PCD polishing to Ra < 5 nm.	Ensures minimal surface defects and low leakage current, critical for high-bias, high-temperature sensor operation.

Engineering Support

The observed dynamic annealing effects in SiC at 500 °C are highly relevant to diamond, which operates stably at even higher temperatures. 6CCVD’s in-house PhD team specializes in material selection and optimization for high-temperature, high-radiation applications, including:

Material Selection: Assisting researchers in choosing the optimal diamond grade (SCD vs. PCD) based on required radiation dose, operating temperature, and cost constraints for Radiation Hardness Studies and Harsh Environment Sensing.
Device Design Consultation: Providing expertise on doping profiles, metal contact stability, and surface preparation to maximize CCE and minimize leakage current in diamond sensors.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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

2022 - High-temperature performance of solid-state sensors up to 500 °C [Crossref]
2000 - Activation of aluminum implanted at high doses in 4H-SiC [Crossref]
2002 - Electrical characteristics of Al+ ion-implanted 4H-SiC [Crossref]
1995 - High temperature ion implantation of silicon carbide [Crossref]
2012 - Effect of high-temperature annealing on ion-implanted silicon solar cells [Crossref]