Diamond growth dynamics in a constrained system

At a Glance

Metadata	Details
Publication Date	2024-06-17
Journal	Frontiers in Carbon
Authors	Shengyuan Bai, Ramón D. Díaz, Matthias Muehle, Elias Garratt, Sergey V. Baryshev
Institutions	Michigan State University, Fraunhofer USA
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Growth Dynamics in a Constrained System

This document analyzes the research paper “Diamond growth dynamics in a constrained system” to highlight key scientific achievements and demonstrate how 6CCVD’s advanced MPCVD diamond materials and engineering services are essential for replicating and scaling this breakthrough research.

Executive Summary

Breakthrough in SCD Scaling: The research successfully demonstrated a method to transition Epitaxial Lateral Outgrowth (ELO) of Single Crystal Diamond (SCD) from a constrained exponential decay mode to a constant-rate, linear growth regime.
Geometry Optimization: This transition was achieved by optimizing the constrained system using novel angled pocket holder designs, which directly manipulate methyl radical flux near the growing surface.
Area Quadrupling: Optimized angled pocket geometries (specifically #2 and #4) achieved a lateral-to-vertical growth rate ratio (R_AL/R_V) of 1, resulting in the doubling of the linear size and quadrupling of the useful area of the SCD crystal.
PCD Suppression: The pocket holder design effectively suppressed the parasitic Polycrystalline Diamond (PCD) rim formation, which typically limits the useful lateral area gain.
Industrial Viability: The results indicate that constant-rate ELO via MPACVD could become a self-replicating industrial process for manufacturing 1-2 inch SCD wafers at scale.
Methodology: Experiments utilized high-pressure (240 Torr) Microwave Plasma-Assisted Chemical Vapor Deposition (MPACVD) with H₂/CH₄ gas mixtures and substrate temperatures ranging from 760 °C to 1,020 °C.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on the optimized growth conditions and outcomes.

Parameter	Value	Unit	Context
Reactor Pressure	240	Torr	Standard operating point for MPACVD
Gas Flow (H₂/CH₄)	400/20 or 400/24	sccm	Precursor gas mixture
Substrate Temperature Range	760 to 1,020	°C	Dependent on reactor type and emission coefficient
Vertical Growth Rate (R_V)	12.7 to 27.5	µm/hr	Standard vertical growth rate
Optimal Lateral Growth Rate (R_AL)	Up to 31.10	µm/hr	Achieved in exponential decay mode (SB A)
Linear ELO R_AL/R_V Ratio	1	Dimensionless	Achieved with angled pockets #2 and #4
Maximum Lateral Gain (Single Edge)	1	mm	Achieved after 48-60 hours of growth
Initial Etch Temperature	950	°C	Used for surface cleaning prior to epitaxial growth
Target Wafer Size for Scaling	1-2	inch	Proposed industrial scale goal
Pocket Angle (α) for Linear ELO	37 or 60	°	Used in novel angled pocket designs #2 and #4

Key Methodologies

The research focused on manipulating the gas-to-solid phase transformation kinetics by optimizing the substrate holder geometry within the MPACVD reactor.

Seed Preparation: Type Ib HPHT diamond seeds were rigorously cleaned using a sequence of acids (sulfuric, nitric, hydrochloric) and organic solvents (acetone, methanol, isopropyl alcohol) to ensure contaminant-free surfaces.
Pocket Holder Design: Both traditional box-like pockets and novel angled pocket holders (with fixed angles $\alpha$ of 37° and 60°) were fabricated and tested to systematically vary the substrate-to-wall distance (Gap G).
Chamber Preparation: The CVD chamber was held under high vacuum (~10^-5 Torr) for a minimum of 12 hours prior to deposition.
Initial Etch: A high-power H₂ plasma etch (2.8 kW, 400 sccm H₂, 950 °C) was performed for 10 minutes to 1 hour to obtain a clean, fresh substrate surface, crucial for high-quality homoepitaxy.
MPACVD Growth: Epitaxial growths were conducted in two reactor types (B and C) at 240 Torr, using 2.45 GHz microwave power (2-3 kW) and H₂/CH₄ gas mixtures.
Temperature Control: Substrate temperature was actively regulated via water-cooling to maintain stable growth conditions (760 °C to 1,020 °C).
Kinetic Transition: The angled pocket geometry was shown computationally and experimentally to perturb the methyl radical flux, enabling the transition from exponential decay ELO (L(t) = A(1 - e^-t/$\tau$)) to constant-rate linear growth (R_AL/R_V = 1).

6CCVD Solutions & Capabilities

This research demonstrates the critical need for high-quality, custom-engineered SCD materials and precision fabrication services to advance diamond semiconductor technology. 6CCVD is uniquely positioned to supply the materials and support required to scale ELO into an industrial process.

Applicable Materials

To replicate and extend this research, high-purity, low-dislocation density SCD is mandatory.

Optical Grade Single Crystal Diamond (SCD): Required for the highest quality homoepitaxial growth. 6CCVD provides SCD substrates with dislocation densities $\le$ 10³ cm^-2, matching the quality necessary to achieve the reported linear ELO and large-area expansion.
Thick SCD Epilayers: The paper focuses on achieving thick epilayers (up to 500 µm) to maximize lateral gain. 6CCVD specializes in growing SCD layers up to 500 µm thick, providing the necessary material foundation for industrial-scale ELO.

Customization Potential

The success of this research hinges entirely on the precise geometry of the pocket holder and the quality of the substrate surface. 6CCVD offers comprehensive services to meet these exacting requirements.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Precision Pocket Holder Fabrication	Advanced Laser Cutting and Machining	We can fabricate custom pocket holders (e.g., the complex angled designs #2 and #4) from various materials with high dimensional accuracy, ensuring precise control over the critical Gap G and angle $\alpha$.
Large Area Scaling	Custom Dimensions up to 125mm	While the paper targets 1-2 inch SCD, 6CCVD offers Polycrystalline Diamond (PCD) wafers up to 125mm in diameter, providing a scalable platform for future ELO substrate development.
Surface Quality	Ultra-Precision Polishing Services	SCD substrates polished to Ra < 1nm, guaranteeing the atomically clean, fresh surface required for optimal ELO initiation and minimizing the formation of parasitic PCD/graphitic rims.
Device Integration	Custom Metalization Services	For subsequent device fabrication (e.g., power electronics or quantum applications), 6CCVD offers internal metalization capabilities including Au, Pt, Pd, Ti, W, and Cu deposition.
Substrate Thickness	Custom Substrate Thicknesses	We provide substrates up to 10mm thick, allowing researchers to experiment with deeper pockets and longer growth times, as explored in the ACH series.

Engineering Support

The optimization of ELO kinetics requires deep expertise in plasma chemistry and CVD reactor modeling.

6CCVD’s in-house PhD team specializes in MPCVD growth kinetics and reactor design. We offer consultation and engineering support for projects focused on Epitaxial Lateral Outgrowth (ELO) and large-area SCD wafer manufacturing. Our experts can assist in material selection, process parameter tuning, and custom geometry design to accelerate the transition of this laboratory breakthrough into commercial production.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) to support your research worldwide.

View Original Abstract

Single crystal diamond (SCD) is the most promising future semiconductor. However, it has not been able to make much inroad into the microelectronics industry due to its major disadvantage of the wafer size. Among a few contender technologies, epitaxial lateral outgrowth (ELO) using microwave plasma-assisted chemical vapor deposition (MPACVD) has shown early promise toward lateral area gain during epitaxial growth. While promising, significant wafer area enhancement remains challenging. This study explores the growth dynamics of SCD in a constrained system—a pocket holder—whose effect is twofold: linear dimension and area enhancement and polycrystalline diamond (PCD) edge rim suppression. A series of pocket-type holder designs were introduced that demonstrated that the depth and substrate-to-wall distance are the major means for optimizing and enhancing lateral outgrowth while still suppressing the PCD rim. When taken together with reactor modeling, the pocket effect on the extent of ELO could be understood as directly manipulating and perturbing methyl radical flux near the growing diamond surface, thereby directly manipulating gas-to-solid phase transformation kinetics. Because it was further discovered that simple box-like pockets limit the ELO process to an exponential-decay scenario, a new generation of angled pockets was proposed that allowed boosting ELO to its fullest extent where a constant rate, linear, outgrowth was found. Our results indicate that ELO by MPACVD could become an industrial means of producing SCD at scale.

Tech Support

Original Source

DOI: https://doi.org/10.3389/frcrb.2024.1367715

References

1968 - Growth of diamond seed crystals by vapor deposition [Crossref]
1940 - Kinetics of phase change. II transformation-time relations for random distribution of nuclei [Crossref]
2009 - HPHT growth and x-ray characterization of high-quality type IIa diamond [Crossref]
2017 - Exploring constant substrate temperature and constant high pressure SCD growth using variable pocket holder depths [Crossref]
1961 - Synthesis of diamond
2018 - Progress toward diamond power field-effect transistors [Crossref]
2018 - Theory of diamond chemical vapor deposition [Crossref]
2010 - Modelling of diamond deposition microwave cavity generated plasmas [Crossref]
1983 - Diamond synthesis from gas phase in microwave plasma [Crossref]
2013 - Experimentally defining the safe and efficient, high pressure microwave plasma assisted CVD operating regime for single crystal diamond synthesis [Crossref]