Nitrogen Investigation by SIMS in Two Wide Band-Gap Semiconductors - Diamond and Silicon Carbide

At a Glance

Metadata	Details
Publication Date	2022-05-31
Journal	Materials science forum
Authors	Marie Amandine Pinault-Thaury, François Jomard
Institutions	Université Paris-Saclay
Citations	4
Analysis	Full AI Review Included

Nitrogen Detection in Wide Band-Gap Diamond and SiC: A 6CCVD Technical Analysis

This document analyzes the findings of the research paper “Nitrogen Investigation by SIMS in Two Wide Band-Gap Semiconductors: Diamond and Silicon Carbide” and outlines how 6CCVD’s advanced MPCVD diamond materials and customization capabilities directly support and extend this critical research area for power electronics.

Executive Summary

This study validates a robust, non-time-consuming Secondary Ion Mass Spectrometry (SIMS) method using High Mass Resolution (HMR) for quantifying ultra-trace nitrogen (N) impurities in diamond and silicon carbide (SiC). This capability is essential for quality control in wide band-gap semiconductor manufacturing.

Critical Impurity Control: Nitrogen is a key impurity in diamond, used to increase growth rate but requiring strict control (low levels) for high-performance electronic applications.
Validated Methodology: Standard SIMS conditions combined with HMR (M/$\Delta$M $\sim 7500$) successfully separated the target ion ($^{12}C^{14}N^-$) from matrix interference ($^{13}C_2^-$).
Diamond Detection Limit: A Nitrogen Detection Limit ([DL]) of $\sim 2 \times 10^{17}$ at/cm³ was achieved in MPCVD diamond.
SiC Detection Limit: A significantly lower [DL] of $\sim 5 \times 10^{15}$ at/cm³ was achieved in SiC, demonstrating the sensitivity required for lightly doped SiC layers.
Depth Profiling Success: The method enables rapid, deep depth-profiling (3 µm in diamond, 8 µm in SiC) suitable for analyzing multilayer homoepitaxial structures.
6CCVD Relevance: The requirement for ultra-low nitrogen content in diamond directly necessitates 6CCVD’s Electronic Grade Single Crystal Diamond (SCD) materials and precision thickness control for multilayer device fabrication.

Technical Specifications

The following hard data points were extracted from the SIMS analysis and quantification results:

Parameter	Value	Unit	Context
Nitrogen Detection Limit ([DL])	$\sim 2 \times 10^{17}$	at/cm³	MPCVD Diamond
Nitrogen Detection Limit ([DL])	$\sim 5 \times 10^{15}$	at/cm³	Silicon Carbide (SiC)
Relative Sensitivity Factor (RSF)	$3.30 \times 10^{18}$	at/cm³	Diamond (using $^{13}C_2^-$ matrix)
Relative Sensitivity Factor (RSF)	$1.34 \times 10^{18}$	at/cm³	SiC (using $^{13}C_2^-$ matrix)
High Mass Resolution (HMR)	$\sim 7500$	M/$\Delta$M	Required to separate $^{12}C^{14}N^-$ from $^{13}C_2^-$
Primary Ion Beam Energy	10	keV	Cs$^+$ source
Interaction Energy	15	keV	Primary ion interaction
Incidence Angle	23	°	Relative to sample normal
Sputtering Rate (HMR Profile)	$0.55 \pm 0.15$	nm/s	For 3 µm diamond depth profile
Standard Raster Size (Routine)	$150 \times 150$	µm²	Diamond SIMS analysis

Key Methodologies

The determination of the nitrogen detection limit relied on adjusting standard diamond SIMS conditions with High Mass Resolution (HMR) settings and utilizing the Raster Size Method.

Instrument Configuration: Dynamic magnetic sector SIMS (IMS7f-CAMECA) was used, operating in High Mass Resolution (HMR) mode (M/$\Delta$M $\sim 7500$).
Primary Beam Parameters: A Cesium (Cs$^+$) primary ion beam was employed at 10 keV energy, resulting in a 15 keV interaction energy and an incidence angle of 23° relative to the sample normal.
Secondary Ion Detection: Negative secondary ions (M$^-$) were detected by biasing the sample to -5000 V.
Target Ion Selection: The molecular ion $^{12}C^{14}N^-$ (mass $\sim 26$ amu) was chosen for nitrogen detection in both diamond and SiC matrices due to the poor yield of the single negative ion $^{14}N^-$.
Matrix Reference: The ion $^{13}C_2^-$ was used as the matrix element reference for calculating the Relative Sensitivity Factor (RSF) and quantifying the detection limit.
Detection Limit Protocol (Raster Size Method): The detection limit (DL) was determined by systematically reducing the raster size (e.g., $250 \times 250$ µm² down to $100 \times 100$ µm²). The y-intercept of the linear fit of the secondary ion intensity versus primary ion density (Jp) provided the constant background signal, which defines the DL.
Depth Profiling: Multilayer samples were profiled over several micrometers (3 µm in diamond, 8 µm in SiC) using adjusted raster sizes and primary intensities (40-60 nA) to maintain a reasonable sputtering rate ($\sim 0.55$ nm/s).

6CCVD Solutions & Capabilities

The research highlights the critical need for high-purity, low-nitrogen diamond homoepilayers for advanced power electronics. 6CCVD is uniquely positioned to supply the required materials and custom engineering services to replicate and advance this research.

Applicable Materials

Application Requirement	6CCVD Material Recommendation	Rationale
Low-Nitrogen Homoepilayers	Electronic Grade Single Crystal Diamond (SCD)	Our MPCVD growth recipes are optimized to minimize atmospheric contaminants, ensuring N content is controlled well below the $2 \times 10^{17}$ at/cm³ detection limit for critical device layers.
High-Conductivity Doping	Heavy Boron-Doped Diamond (BDD)	For p-type layers or electrodes, we offer BDD films with controlled doping levels, essential for creating complex p-i-n or delta-doped structures referenced in the study.
Large-Area Scaling	Polycrystalline Diamond (PCD) Wafers	For applications where large area is paramount, we provide PCD wafers up to 125mm, enabling scale-up from research-grade SCD to commercial prototypes.

Customization Potential

The ability to analyze multilayer structures via SIMS depth profiling requires precise control over layer thickness, doping interfaces, and substrate quality—all core competencies of 6CCVD.

Customization Service	Relevance to Research	6CCVD Capability
Thickness Control	Required for thick layers ($>20$ µm) and thin layer analysis (depth resolution < 10 nm).	SCD and PCD films available from 0.1 µm up to 500 µm, with precise layer-to-layer thickness control.
Substrate Engineering	Need for high-N substrates (up to $10^{19}$ at/cm³) to contrast with low-N epilayers.	We supply custom diamond substrates up to 10mm thick, tailored for specific doping or orientation requirements.
Surface Preparation	Essential for minimizing SIMS crater edge effects and ensuring accurate depth profiling.	SCD polishing achieves Ra < 1nm; Inch-size PCD polishing achieves Ra < 5nm.
Metalization Services	Although not the focus of this paper, device fabrication requires contacts.	We offer internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu for custom contact schemes.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing MPCVD growth parameters to meet stringent material specifications for power electronics and quantum applications.

Doping Control: We provide expert consultation on achieving and maintaining ultra-low impurity levels, specifically addressing the challenge of controlling nitrogen incorporation below the $10^{16}$ at/cm³ range required for high-quality diamond devices.
Material Selection: Our team assists researchers in selecting the optimal material grade (e.g., Electronic Grade SCD vs. Optical Grade SCD) and orientation for similar wide band-gap semiconductor projects.
Global Logistics: We ensure reliable, global delivery of sensitive materials, offering DDU (default) and DDP shipping options.

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

View Original Abstract

Diamond and Silicon Carbide (SiC) are promising wide band-gap semiconductors for power electronics, SiC being more mature especially in term of large wafer size (200 mm). Nitrogen impurities are often used in both materials for different purpose: increase the diamond growth rate or induce n-type conductivity in SiC. The determination of the nitrogen content by secondary ion mass spectrometry (SIMS) is a difficult task mainly because nitrogen is an atmospheric element for which direct monitoring of N ± ions give no or a weak signal. With our standard diamond SIMS conditions, we investigate 12 C 14 N - secondary ions under cesium primary ions by applying high mass resolution settings. Nitrogen depth-profiling of diamond and SiC (multi-) layers is then possible over several micrometer thick over reasonable time analysis duration. In a simple way and without notably modifying our usual analysis process, we found a nitrogen detection limit of 2x10 17 at/cm 3 in diamond and 5x10 15 at/cm 3 in SiC.

Tech Support

Original Source

DOI: https://doi.org/10.4028/p-684nsi

References

**** - Fundamental research on semiconductor SiC and its applications to power electronics [Crossref]
**** - Single crystal diamond wafers for high power electronics [Crossref]
2006 - Deactivation of nitrogen donors in silicon carbide [Crossref]
2017 - A new model for in situ nitrogen incorporation into 4H-SiC during epitaxy [Crossref]
**** - The Role of Atmospheric Elements in the Wide Band-Gap Semiconductors [Crossref]
**** - The effect of nitrogen addition during high-rate homoepitaxial growth of diamond by microwave plasma CVD [Crossref]
**** - Coupled effect of nitrogen addition and surface temperature on the morphology and the kinetics of thick CVD diamond single crystals [Crossref]
**** - Influence of CVD diamond growth conditions on nitrogen incorporation [Crossref]
**** - Thick and widened high quality heavily boron doped diamond single crystals synthetized with high oxygen flow under high microwave power regime [Crossref]