Optimization Design of MPCVD Single Crystal Diamond Growth Based on Plasma Diagnostics

At a Glance

Metadata	Details
Publication Date	2023-01-01
Journal	Journal of Inorganic Materials
Authors	Yicun LI, Xiaobin Hao, Bing Dai, Dongyue Wen, Jiaqi Zhu
Institutions	Harbin Institute of Technology
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: Optimization Design of MPCVD Single Crystal Diamond Growth Based on Plasma Diagnostics

6CCVD Reference Document: MPCVD-PD-2023-12

Executive Summary

This research presents a systematic, quantitative methodology for optimizing Single Crystal Diamond (SCD) growth via Microwave Plasma Chemical Vapor Deposition (MPCVD) using advanced plasma diagnostics.

Core Achievement: Developed a highly accurate MPCVD process map linking key input parameters (Pressure, MW Power) to critical plasma characteristics (Energy Density, Size, Precursor Concentration) and Substrate Temperature (T).
High Efficiency Growth: Achieved a high SCD growth rate of 8.9 µm/h by operating under conditions that maximized plasma energy density (148.5 W/cm³) at a relatively low input power (2600 W).
Mechanism Verified: Confirmed that high energy density conditions significantly increase the concentration of carbon-containing precursors (C₂ and CH radicals), directly correlating with enhanced growth kinetics.
Predictive Accuracy: The derived process map demonstrated strong predictive capability, with experimental verification showing parameter errors of less than 5% compared to preset targets.
Plasma Control: Methodology allows for precise control over the effective plasma size (major axis up to 54 mm) and shape (eccentricity) necessary for tailoring SCD production to specific area requirements.
Methodology: Utilized quantitative plasma imaging (H_α filter) and Optical Emission Spectroscopy (OES) to diagnose plasma properties in real-time.

Technical Specifications

The following hard data points were extracted from the experimental verification of the optimized MPCVD process.

Parameter	Value	Unit	Context
Maximum Growth Rate	8.9	µm/h	Achieved under optimized conditions (Sample 2)
Maximum Energy Density	148.5	W/cm³	Achieved at 2600 W input power
Input MW Power (Optimized)	2600	W	Lowest power used for high-rate growth
Predicted Pressure (Optimized)	15.6	kPa	Optimized pressure for Sample 2
Preset Growth Temperature	850	°C	Target temperature for all experiments
Actual Growth Temperature Range	835 to 867	°C	Experimentally verified range
Process Map Prediction Error	< 5	%	Accuracy of P, W, and T prediction
Substrate Material	SCD (100)	N/A	CVD Single Crystal Diamond Seed
Substrate Dimensions	5 x 5 x 0.5	mm	Dimensions of the seed crystal
Gas Flow Ratio (H₂:CH₄)	192:8	sccm	Standard precursor gas mixture
Maximum Effective Plasma Size (Major Axis)	54	mm	Observed maximum plasma size

Key Methodologies

The systematic optimization relied on quantitative plasma diagnostics coupled with precise control over the MPCVD reactor environment.

Equipment: Utilized a custom-built 2.45 GHz, 6 kW Microwave Plasma CVD (MPCVD) system (HITLH-2450M) featuring a TM₀₂₁ mode stainless steel resonant cavity.
Substrate Preparation: CVD Single Crystal Diamond (SCD) seeds (5 mm x 5 mm x 0.5 mm) with (100) orientation were used for homoepitaxial growth.
Plasma Diagnostics:
- Imaging: sCMOS camera equipped with an H_α (656 nm) filter was used to capture atomic hydrogen concentration distribution and determine effective plasma size (major axis X_e and minor axis Z_e) using the 1/e intensity boundary.
- Spectroscopy: Optical Emission Spectroscopy (OES, Maya 2000) was used to monitor the intensity of key radical species (H, C₂, CH) in the plasma core.
Process Mapping: Quantitative relationships were established between input parameters (P, W) and plasma characteristics (effective size, eccentricity, volume, energy density) under three matching modes: Uniform Increase, Optimal Absorption, and Saturated Input.
Growth Optimization: Parameters were selected from the derived process map to achieve a target temperature (850 °C) and specific plasma size, prioritizing conditions that yielded high energy density (e.g., 15.6 kPa, 2600 W).
Characterization: Grown samples were analyzed using Optical Microscopy and Raman Spectroscopy to confirm quality and measure growth rate.

6CCVD Solutions & Capabilities

This research successfully demonstrates the critical role of precise plasma control and high energy density in achieving high-rate, high-quality SCD growth. 6CCVD is uniquely positioned to support the replication and industrial scaling of this methodology by providing highly customized diamond materials and engineering services.

Applicable Materials

To replicate or extend the high-quality homoepitaxial growth demonstrated in this paper, 6CCVD recommends the following materials:

Material Grade	Specification	Application Relevance
Optical Grade SCD	High purity, low nitrogen content, (100) orientation.	Ideal for use as high-quality seed crystals for homoepitaxial growth, ensuring low defect incorporation during high-rate deposition.
Electronic Grade SCD	Ultra-low defect density, high thermal conductivity.	Necessary for subsequent device fabrication (e.g., high-frequency communication) where the high-rate material will be used.
Custom Substrates	SCD or PCD up to 10 mm thick.	Provides robust thermal management necessary for maintaining the precise 850 °C substrate temperature required for optimization.

Customization Potential

The research highlights the need to match plasma size (major axis up to 54 mm) and substrate size for optimal deposition area. 6CCVD’s custom fabrication capabilities directly address these requirements:

Custom Dimensions: While the paper used 5x5 mm seeds, 6CCVD can supply custom SCD plates up to 500 µm thick and PCD wafers up to 125 mm in diameter, allowing researchers to scale the optimized growth recipe to larger areas compatible with the observed 54 mm plasma size.
Precision Polishing: Achieving high-quality homoepitaxy requires an atomically smooth surface. 6CCVD offers SCD polishing to Ra < 1 nm and inch-size PCD polishing to Ra < 5 nm, ensuring optimal surface preparation for high-rate growth.
Metalization Services: Although not the focus of the growth phase, subsequent device integration often requires contacts. 6CCVD provides in-house custom metalization (Au, Pt, Pd, Ti, W, Cu) tailored to specific electronic or thermal requirements.

Engineering Support

The development of a predictive process map based on complex plasma physics requires deep material and process expertise.

Process Consultation: 6CCVD’s in-house PhD engineering team specializes in the physics and chemistry of MPCVD. We offer consultation services to assist researchers in selecting optimal material parameters (e.g., substrate thickness, doping levels, surface preparation) to match specific plasma diagnostic recipes.
Material Selection for High Energy Density: We can assist in selecting materials that maintain thermal stability and minimize defect formation under the high energy density (148.5 W/cm³) and high-temperature conditions required for high-rate SCD growth.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research efforts.

Call to Action: For custom specifications or material consultation related to high-rate MPCVD growth or plasma diagnostic projects, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Microwave plasma chemical vapor deposition, MPCVD)技术是制备大尺寸、高品

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Original Source

DOI: https://doi.org/10.15541/jim20230164