High-Quality SiO2/O-Terminated Diamond Interface - Band-Gap, Band-Offset and Interfacial Chemistry

At a Glance

Metadata	Details
Publication Date	2022-11-22
Journal	Nanomaterials
Authors	J. Cañas, D.F. Reyes, Alter Zakhtser, Christian Dussarrat, Takashi Teramoto
Institutions	Instituto de Ciencia de Materiales de Sevilla, Centre National de la Recherche Scientifique
Citations	8
Analysis	Full AI Review Included

High-Quality Diamond Dielectrics: Technical Analysis and 6CCVD Solutions

This documentation analyzes the research paper, “High-Quality SiO₂/O-Terminated Diamond Interface: Band-Gap, Band-Offset and Interfacial Chemistry,” focusing on the material requirements and technical achievements relevant to diamond electronics fabrication.

Executive Summary

The study successfully characterized the critical interface between Atomic Layer Deposition (ALD) grown silicon oxide (SiO₂) and oxygen-terminated p-type (100) diamond, validating a robust material stack for advanced diamond MOSFETs.

Core Achievement: Confirmation of a high-quality, low-interface-state density heterojunction suitable for diamond-metal-oxide field effect transistor (MOSFET) gates.
Dielectric Quality: The amorphous SiO₂ layer exhibited a homogeneous, ultra-wide band-gap of 9.4 ± 0.2 eV across the nanometric scale, confirmed by STEM-VEELS.
High Energy Barriers: A straddling band setting was achieved, providing substantial barriers for both holes (Valence Band Offset, VBO = 2.0 eV) and electrons (Conduction Band Offset, CBO = 1.9 eV).
Interfacial Chemistry: XPS analysis confirmed the interface is predominantly characterized by single- and double-carbon-oxygen bonds (C-O, C=O), minimizing detrimental C-Si bonds.
Application Impact: The high VBO and CBO are mandatory for operating diamond MOSFETs in accumulation and inversion regimes without significant leakage currents, paving the way for high-power, normally-off devices.
Material Basis: The research utilized 1 µm thick, boron-doped (100) diamond grown via Microwave Plasma Chemical Vapor Deposition (MPCVD) on HPHT substrates.

Technical Specifications

The following hard data points were extracted from the analysis of the SiO₂/O-terminated diamond heterojunction:

Parameter	Value	Unit	Context
Diamond Orientation	(100)	N/A	p-type, O-terminated
Diamond Layer Thickness	~1	µm	MPCVD grown layer
Nominal Boron Doping	10¹⁶	cm^-3	Required for p-type conductivity
SiO₂ Band-Gap (VEELS)	9.4 ± 0.2	eV	Amorphous phase quality
Valence Band Offset (VBO)	2.0	eV	Barrier height for holes
Conduction Band Offset (CBO)	1.9	eV	Barrier height for electrons
Diamond Band-Gap (Literature)	5.5	eV	Intrinsic diamond value
Dominant Interfacial Bonds	C-O, C=O	N/A	Confirmed by XPS C(1s) deconvolution
C-Si Interfacial Component	15	%	Relative area of C(1s) peak
C-O Interfacial Component	35	%	Relative area of C(1s) peak
C=O Interfacial Component	50	%	Relative area of C(1s) peak

Key Methodologies

The successful fabrication of the high-quality interface relied on precise MPCVD growth and controlled surface termination:

Diamond Epitaxy: p-type diamond layers (1 µm thickness) were grown using MPCVD on (100) HPHT Ib substrates.
Gas Recipe: The process utilized specific gas ratios: CH₄/H₂ = 1%, O₂/H₂ = 0.25%, and B/C = 60 ppm.
Growth Conditions: Growth was performed at 900 °C, 33 Torr pressure, and 240 W microwave power.
Oxygen Termination: The as-grown surface was oxidized using a 120 min ozone plasma treatment at 500 mbar, achieved via a Xenon EXCIMER UV lamp (172 nm).
Dielectric Deposition: SiO₂ layers (2 nm and 40 nm) were deposited via Atomic Layer Deposition (ALD).
Characterization: Interfacial properties were analyzed using high-resolution techniques:
- Scanning Transmission Electron Microscopy (STEM) in Energy Loss Spectroscopy (EELS) mode (60 kV accelerating voltage to minimize Cherenkov effect).
- X-ray Photoelectron Spectroscopy (XPS) using monochromatic Al-Kα radiation (hv = 1486.7 eV).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality, custom diamond materials required to replicate and advance this critical research into diamond MOSFETs. Our MPCVD expertise ensures the precise control over doping, orientation, and surface finish necessary for achieving low-leakage, high-barrier interfaces.

Applicable Materials for High-Power Electronics

Research Requirement	6CCVD Material Solution	Technical Advantage
p-type (100) Doping	Electronic Grade Boron-Doped SCD	Precise control over Boron concentration (10¹⁶ cm^-3 to 10²⁰ cm^-3) and layer thickness (0.1 µm to 500 µm), essential for deep depletion and inversion mode devices.
Large Area Gates	Electronic Grade Boron-Doped PCD	Available in plates/wafers up to 125mm, enabling scale-up of MOSFET fabrication beyond typical SCD limits.
Interface Quality	Ultra-Smooth Polished SCD	Standard polishing achieves Ra < 1nm. This ultra-low roughness is critical for subsequent ALD processes, minimizing interface states and ensuring homogeneous band alignment, as demonstrated in the paper.

Customization Potential for Device Integration

The successful fabrication of diamond MOSFETs requires precise control over dimensions and subsequent processing steps, all available through 6CCVD’s in-house capabilities:

Custom Dimensions: We supply (100)-oriented SCD wafers and PCD plates up to 125mm, allowing researchers to move from small-scale samples to inch-size device fabrication.
Thickness Control: We can grow the required 1 µm p-type layer, or custom layers up to 500 µm, on various substrates (e.g., HPHT Ib or IIa). We also offer thick substrates up to 10mm for robust power device packaging.
Advanced Metalization: The integration of the SiO₂ gate requires subsequent contact formation. 6CCVD offers in-house custom metalization services, including deposition of Au, Pt, Pd, Ti, W, and Cu, tailored for ohmic or Schottky contacts on diamond.
Surface Preparation: While the paper used ozone plasma, 6CCVD can provide materials with specific, controlled surface terminations (H-terminated, O-terminated, or bare polished) ready for immediate ALD or device processing.

Engineering Support

6CCVD’s in-house PhD team specializes in diamond material science and device physics. We offer authoritative professional consultation to assist engineers and scientists in:

Material Selection: Optimizing doping profiles and crystal orientation (e.g., (100) vs. (111)) to maximize carrier mobility and breakdown voltage for specific high-power, high-temperature applications.
Recipe Optimization: Assisting with the selection of appropriate diamond specifications to ensure compatibility with advanced dielectric deposition techniques like ALD, crucial for replicating the high VBO and CBO results reported here.

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

View Original Abstract

Silicon oxide atomic layer deposition synthesis development over the last few years has open the route to its use as a dielectric within diamond electronics. Its great band-gap makes it a promising material for the fabrication of diamond-metal-oxide field effects transistor gates. Having a sufficiently high barrier both for holes and electrons is mandatory to work in accumulation and inversion regimes without leakage currents, and no other oxide can fulfil this requisite due to the wide diamond band-gap. In this work, the heterojunction of atomic-layer-deposited silicon oxide and (100)-oriented p-type oxygen-terminated diamond is studied using scanning transmission electron microscopy in its energy loss spectroscopy mode and X-ray photoelectron spectroscopy. The amorphous phase of silicon oxide was successfully synthesized with a homogeneous band-gap of 9.4 eV. The interface between the oxide and diamond consisted mainly of single- and double-carbon-oxygen bonds with a low density of interface states and a straddling band setting with a 2.0 eV valence band-offset and 1.9 eV conduction band-offset.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano12234125

References

2013 - Figure of merit of diamond power devices based on accurately estimated impact ionization processes [Crossref]
2009 - High hole mobility in boron doped diamond for power device applications [Crossref]
2019 - Diamond power devices: State of the art, modelling, figures of merit and future perspective [Crossref]
2018 - Recent advances in diamond power semiconductor devices [Crossref]
2018 - Vertical-type two-dimensional hole gas diamond metal oxide semiconductor field-effect transistors [Crossref]
2017 - Normally-Off C-H Diamond MOSFETs With Partial C-O Channel Achieving 2-kV Breakdown Voltage [Crossref]
2020 - Charge-carrier mobility in hydrogen-terminated diamond field-effect transistors [Crossref]
2021 - (111) vertical-type two-dimensional hole gas diamond MOSFETs with hexagonal trench structures [Crossref]
2017 - Durability-enhanced two-dimensional hole gas of C-H diamond surface for complementary power inverter applications [Crossref]