Improved Thermal Resistance and Electrical Conductivity of a Boron-Doped DLC Film Using RF-PECVD

At a Glance

Metadata	Details
Publication Date	2020-07-07
Journal	Frontiers in Materials
Authors	Wanrong Li, Xing Tan, Yeong Min Park, Dong Chul Shin, Dae Weon Kim
Institutions	Silla University, Pusan National University
Citations	10
Analysis	Full AI Review Included

Technical Analysis and Commercial Solutions: Boron-Doped Diamond-Like Carbon (B-DLC) for High-Performance Applications

Analyzed Research Paper: Improved Thermal Resistance and Electrical Conductivity of a Boron-Doped DLC Film Using RF-PECVD

Executive Summary

This study successfully engineered Boron-Doped Diamond-Like Carbon (B-DLC) films via Radio-Frequency Plasma-Enhanced Chemical Vapor Deposition (RF-PECVD) to achieve concurrent improvements in electrical conductivity and thermal resistance, critical for space-related and high-temperature electronic applications.

Core Achievement: Boron doping effectively reduced internal stress and promoted $sp^2$ bond formation, transitioning the amorphous carbon film toward a pseudo-crystalline structure suitable for p-type semiconductor behavior.
Thermal Stability Peak: The 30 vol% B₂H₆/CH₄ doped film demonstrated the highest thermal resistance, remaining intact and stable up to 460 °C, significantly exceeding the 300 °C stability threshold of undoped DLC.
Electrical Optimization: A B₂H₆/CH₄ ratio of 40 vol% yielded the lowest electrical resistivity (down to < 10⁵ $\Omega$/sq), confirming that increased boron concentration dramatically improves electrical conductivity and enables p-type characteristics.
Structural Trade-off: While boron doping improved critical functional characteristics (thermal/electrical), it resulted in a reduction of Vickers hardness compared to un-doped DLC (1,572 HV down to an average of 1,176.3 HV), due to decreased $sp^3$ fraction.
Mechanism: Boron actively interferes with the normal $sp^3$ bonding combination, driving the formation of a graphitic $sp^2$ network, which in turn facilitates free electron movement and increases thermal resilience.
Material Solution: The findings validate the necessity for highly stable, boron-doped carbon materials (like 6CCVD Boron-Doped Diamond, BDD) where standard amorphous DLC is insufficient due to temperature limitations and poor native conductivity.

Technical Specifications

The following key material and process parameters were derived from the deposition and characterization results.

Parameter	Value	Unit	Context
Deposition Method	RF-PECVD	N/A	Radio-frequency Plasma-Enhanced CVD
Substrate	Si (100) Wafer	N/A	Dimensions: 20 mm x 20 mm
Deposition RF Power	300	W	Standard power for all samples
Working Pressure	2.0 x 10^-2	Torr	Consistent plasma deposition pressure
Pretreatment Plasma	Ar	sccm	30 sccm, 300 W, 30 min
Highest Electrical Conductivity	40 vol%	B₂H₆/CH₄ ratio	Lowest sheet resistance (< 10⁵ $\Omega$/sq)
Highest Thermal Resistance	30 vol%	B₂H₆/CH₄ ratio	Stable up to 460 °C (TGA onset of weight loss)
Undoped DLC Hardness	1,572	HV	Maximum Vickers Hardness
Boron-Doped DLC Hardness (Avg)	1,176.3	HV	Reduced hardness due to $sp^2$ clustering
Deposition Rate (Boron-Doped)	897.6	nm/h	Increased rate compared to undoped (799.6 nm/h)
Heat Treatment Temperatures	300, 350, 400	°C	Evaluated for film delamination (15 min hold time)
Bonding Analysis	$sp^2$ and $sp^3$	N/A	Boron doping promotes $sp^2$ content (graphitization)

Key Methodologies

The B-DLC films were deposited using a highly controlled two-step RF-PECVD process on ultrasonically cleaned Si (100) wafers.

Pretreatment Conditions (Surface Preparation)

Cleaning: Wafers were ultrasonically cleaned sequentially using C₃H₆O (acetone), C₂H₅OH (ethanol), and deionized water for 30 minutes each.
Pre-Cleaning Plasma: Argon (Ar) plasma was sustained for 30 minutes to scavenge negative remnants and stabilize the chamber temperature (“hot starting state”) for stable deposition.

Parameter	Value	Unit	Gas
Ar Flow Rate	30	sccm	Argon
RF Power	300	W	N/A
Duration	30	min	N/A
Working Pressure	2.0 x 10^-2	Torr	N/A

DLC Film Deposition Conditions

Gas Mixture: Methane (CH₄) and Diborane (B₂H₆) were used as precursors. Boron doping was controlled by varying the B₂H₆/CH₄ volumetric ratio from 0% (undoped) up to 40%.
Deposition: The plasma was maintained for 1 hour for all samples.

Parameter	Value	Unit	Conditions
B₂H₆/CH₄ Ratios	0, 10, 20, 30, 40	vol%	Controlled doping concentration
RF Power	300	W	Plasma supply
Duration	1	hour	Operating time
Working Pressure	2.0 x 10^-2	Torr	N/A

Post-Deposition Thermal Treatment (Evaluation of Resistance)

Process: Samples were heated in a muffle furnace at a rate of 10 °C/min.
Hold Times: Samples were held at 300 °C, 350 °C, and 400 °C for 15 minutes before being furnace-cooled to room temperature.

6CCVD Solutions & Capabilities

The findings in this study highlight the critical market demand for carbon-based materials that offer superior electrical conductivity and extreme thermal stability, particularly for high-stress aerospace and advanced electronic applications. While Boron-Doped DLC shows significant promise, 6CCVD provides the next generation material—fully crystalline Boron-Doped Diamond (BDD)—which inherently overcomes the amorphous structure limitations (e.g., lower hardness and structural metastability) seen in B-DLC.

Applicable Materials: Moving Beyond DLC to Crystalline Diamond

For researchers seeking to replicate or exceed the thermal and electrical performance described in this paper, 6CCVD strongly recommends our advanced MPCVD diamond products:

Boron-Doped Diamond (BDD) Wafers: BDD is the ultimate material solution, offering the tunable p-type conductivity demonstrated by the B-DLC films, combined with the extreme hardness, chemical inertness, and stability inherent to diamond ($sp^3$ bonding).
- Advantage: Unlike B-DLC, which is limited to 460 °C, BDD maintains its structural integrity and performance at temperatures exceeding 800 °C, making it ideal for the most demanding high-power and space environments.
Optical Grade Single Crystal Diamond (SCD) Substrates: For integration into thermal management or specialized optical/electronic devices where high crystalline purity is required before customized doping or layer deposition.

Customization Potential for Advanced Research

6CCVD’s unique manufacturing capabilities allow for precise engineering tailored to specific application requirements, ensuring seamless integration into experimental setups.

Research Requirement	6CCVD Customization Service	Specification Range
Material Format/Size	Custom Dimensions and Substrates	Plates/wafers up to 125 mm (PCD/BDD)
Thickness Control	SCD and PCD Growth Layers	SCD/PCD from 0.1 µm up to 500 µm
Doping Precision	Tunable Boron Doping	Precise control of Boron concentration for specific resistivity targets (p-type)
Integration	Custom Metalization Services	Internal capability for Au, Pt, Pd, Ti, W, Cu layers
Surface Finish	Ultra-Low Roughness Polishing	Ra < 1 nm (SCD) or Ra < 5 nm (Inch-size PCD)
Geometry	Laser Cutting and Shaping	Custom shaping for device integration

Engineering Support & Logistics

6CCVD’s in-house PhD team can assist with material selection for similar space-based thermal management and high-temperature electrical switching projects. We offer deep technical consultation to optimize the trade-off between electrical conductivity (doping level) and mechanical properties (crystalline quality).

We facilitate global distribution, handling logistics (DDU default, DDP available) to ensure your custom, high-performance diamond materials arrive safely and quickly, supporting research teams worldwide.

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

View Original Abstract

Diamond-like carbon (DLC) film doped with boron has unique properties and displays higher thermal resistance, lower internal stress, and better electrical conductivity than un-doped DLC film; this makes it is suitable for various applications, especially in outer space. Radio-frequency plasma-enhanced chemical vacuum deposition of boron-doped DLC film was performed to determine the optimal percentage of boron for improving thermal resistance. Additional heat treatment and 40 vol% B2H6/CH4 yielded the best electrical conductivity. X-ray photoelectron spectroscopy, thermal gravimetric analysis, Raman spectroscopy, and the four-point probe method were utilized to analyze the properties of boron-doped DLC film. The boron-doped DLC film displayed outstanding performance in terms of thermal resistance and electrical conductivity.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fmats.2020.00201

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