Deposition of Boron-Doped Thin CVD Diamond Films from Methane-Triethyl Borate-Hydrogen Gas Mixture

At a Glance

Metadata	Details
Publication Date	2020-06-04
Journal	Processes
Authors	N. I. Polushin, Alexander I. Laptev, Б. В. Спицын, A.E. Alexenko, Alexander Mihailovich Polyansky
Institutions	National University of Science and Technology, NPO Energomash (Russia)
Citations	22
Analysis	Full AI Review Included

Technical Documentation & Analysis: Boron-Doped Thin CVD Diamond Films

This document analyzes the research paper “Deposition of Boron-Doped Thin CVD Diamond Films from Methane-Triethyl Borate-Hydrogen Gas Mixture” and outlines how 6CCVD’s advanced MPCVD capabilities can support and scale this critical research in Boron-Doped Diamond (BDD) synthesis for semiconductor and sensor applications.

Executive Summary

This research successfully demonstrates a novel, interruption-free method for synthesizing highly homogeneous, heavily boron-doped single-crystal diamond (SCD) films using Triethyl Borate (TEB).

Innovation in Doping: Triethyl Borate (C₂H₅O)₃B was used as the boron precursor, leveraging its inherent oxygen content to enable simultaneous diamond deposition and surface etching.
Defect Elimination: The in-situ etching process successfully removed polycrystalline diamond defects and incoherent formations, resulting in a defect-free surface morphology on the SCD layers.
High Doping Stability: The resulting monocrystalline films achieved a stable, high boron content of 2.9% mass across independent samples, confirming process stability for heavy doping applications.
Epitaxial Growth Confirmed: Electron Backscatter Diffraction (EBSD) confirmed that the coating maintained the same orientation across investigated areas, verifying single-crystal epitaxial growth.
Mechanical Performance: The synthesized BDD films exhibited high mechanical integrity, with measured hardness ranging from 62 GPa to 117 GPa and elastic modulus between 914 GPa and 1099 GPa.
Application Relevance: This methodology is crucial for reducing production costs and increasing the yield of thick, homogeneous BDD layers required for advanced sensors and power electronics.

Technical Specifications

The following hard data points were extracted from the synthesis and characterization results:

Parameter	Value	Unit	Context
Boron Content (Mass)	2.9	%	Heavily doped SCD layer
Film Thickness	~8	µm	Deposited layer thickness
Growth Rate	4	µm/h	Achieved deposition rate
Hardness (H)	62 to 117	GPa	Measured via Oliver-Farr method
Elastic Modulus (E)	914 to 1099	GPa	Measured via Oliver-Farr method
Substrate Temperature	1100	°C	Optimal synthesis temperature
Reactor Pressure	9.806	kPa	MPCVD operating pressure
Microwave Power	3800	W	Power used for plasma activation
CH₄ Flow Rate	25	cm³/min	Carbon source flow
H₂ Flow Rate	480	cm³/min	Primary carrier gas flow
TEB/H₂ Flow Rate	10	cm³/min	Boron precursor flow

Key Methodologies

The synthesis of the heavily boron-doped single-crystal diamond films relied on the following optimized MPCVD process and precursor delivery system:

Substrate Preparation: Single-crystal diamond substrates were prepared via etching (e.g., in oxygen-hydrogen plasma at >200 nm/min rate) to remove surface defects prior to deposition.
Precursor Selection: Triethyl Borate (C₂H₅O)₃B was selected as the boron source due to its stability and the presence of oxygen atoms, which facilitate in-situ etching.
TEB Delivery System: A saturated solution of boric acid in ethanol was maintained in excess within a bubbler system placed in a thermostat (25 ± 1 °C).
Gas Flow Management: High-purity hydrogen (99.9995%) was split into two streams: one stream (5-15 cm³/min) passed through the TEB bubbler, and the main stream (480 cm³/min) was fed directly to the reactor.
MPCVD Synthesis Parameters: Deposition was carried out at 1100 °C, 9.806 kPa, and 3800 W microwave power, using a CH₄ flow of 25 cm³/min.
In-Situ Etching: The oxygen atoms released from the TEB molecule enabled continuous etching of non-diamond carbon and polycrystalline defects during the 2-hour deposition run, ensuring high structural quality.
Characterization: Films were analyzed using SEM, EDS (confirming 2.9% B content), EBSD (confirming epitaxial growth), and Oliver-Farr nanoindentation (determining mechanical properties).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality materials and customization required to replicate, scale, and advance this BDD research for commercial applications in power electronics and electrochemistry.

Applicable Materials

To achieve the high conductivity and structural integrity demonstrated in this paper, researchers require high-quality, heavily doped single-crystal diamond.

Research Requirement	6CCVD Solution	Technical Advantage
Material Type	Boron-Doped Single Crystal Diamond (BDD SCD)	High crystalline quality necessary for epitaxial growth and high carrier mobility.
Doping Level	Heavy Boron Doped SCD	We can achieve and precisely control doping concentrations to match or exceed the 2.9% mass reported, crucial for low resistivity contacts.
Substrate Quality	High-Purity SCD Substrates (up to 10mm thick)	Provides the ideal template for homoepitaxial growth, minimizing defects and maximizing yield.

Customization Potential

The ability to scale BDD production relies on flexible material dimensions and post-processing capabilities. 6CCVD offers comprehensive customization services far exceeding standard laboratory capabilities.

Large Area Scaling: While the paper utilized small substrates (5 x 5 mm), 6CCVD can supply Polycrystalline Diamond (PCD) wafers up to 125mm in diameter and SCD plates up to 500 µm thick, enabling industrial scaling of BDD devices.
Thickness Control: We offer precise thickness control for both SCD and PCD films, ranging from 0.1 µm (for thin-film sensors) up to 500 µm (for robust power electronics).
Advanced Polishing: Although the in-situ etching provided a defect-free surface, 6CCVD offers ultra-precision polishing services to achieve surface roughness as low as Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, optimizing surface quality for subsequent device fabrication steps (e.g., metalization).
Custom Metalization: For creating ohmic contacts or complex device structures, 6CCVD provides in-house metalization services, including deposition of Ti, Pt, Au, Pd, W, and Cu layers, eliminating the need for external processing steps.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing MPCVD recipes and material selection for demanding applications.

Precursor Optimization: We offer consultation on alternative boron precursors (including TEB and other stable sources) and gas mixture optimization to achieve specific doping profiles (e.g., graded doping or lower B concentration for specific device requirements).
Process Transfer: Our experts can assist researchers and engineers in translating laboratory-scale BDD synthesis parameters (like those detailed in this paper for power electronics and sensor projects) into reliable, high-yield production processes.
Global Logistics: We ensure reliable, global delivery of sensitive diamond materials, offering both DDU (Delivered Duty Unpaid) default and DDP (Delivered Duty Paid) options.

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

View Original Abstract

Boron-doped diamond is a promising semiconductor material that can be used as a sensor and in power electronics. Currently, researchers have obtained thin boron-doped diamond layers due to low film growth rates (2-10 μm/h), with polycrystalline diamond growth on the front and edge planes of thicker crystals, inhomogeneous properties in the growing crystal’s volume, and the presence of different structural defects. One way to reduce structural imperfection is the specification of optimal synthesis conditions, as well as surface etching, to remove diamond polycrystals. Etching can be carried out using various gas compositions, but this operation is conducted with the interruption of the diamond deposition process; therefore, inhomogeneity in the diamond structure appears. The solution to this problem is etching in the process of diamond deposition. To realize this in the present work, we used triethyl borate as a boron-containing substance in the process of boron-doped diamond chemical vapor deposition. Due to the oxygen atoms in the triethyl borate molecule, it became possible to carry out an experiment on simultaneous boron-doped diamond deposition and growing surface etching without the requirement of process interruption for other operations. As a result of the experiments, we obtain highly boron-doped monocrystalline diamond layers with a thickness of about 8 μm and a boron content of 2.9%. Defects in the form of diamond polycrystals were not detected on the surface and around the periphery of the plate.

Tech Support

Original Source

DOI: https://doi.org/10.3390/pr8060666

References

2010 - Effect of B/C ratio on the physical properties of highly boron-doped diamond films [Crossref]
2020 - Voltammetric characterization of boron-doped diamond electrodes for electroanalytical applications [Crossref]
2020 - Preparation of boron-doped diamond foam film for supercapacitor applications [Crossref]
2017 - Evidence of linear Zeeman effect for infrared intracenter transitions in boron doped diamond in high magnetic fields [Crossref]
2016 - Optical and electrical properties of boron doped diamond thin conductive films deposited on fused silica glass substrates [Crossref]
2013 - Electrical properties of the high quality boron-doped synthetic single-crystal diamonds grown by the temperature gradient method [Crossref]
2015 - Properties of boron-doped epitaxial diamond layers grown on (110) oriented single crystal substrates [Crossref]
2017 - Thin CVD diamond film detector for slow neutrons with buried graphitic electrode [Crossref]
2017 - Investigations of the co-doping of boron and lithium into CVD diamond thin films [Crossref]
2015 - Low resistivity p+ diamond (100) films fabricated by hot-filament chemical vapor deposition [Crossref]