Basal Plane Bending of Homoepitaxial MPCVD Single-Crystal Diamond

At a Glance

Metadata	Details
Publication Date	2020-10-12
Journal	Materials
Authors	Xiaotong Han, Peng Duan, Yan Peng, Xiwei Wang, Xuejian Xie
Institutions	Shandong University, State Key Laboratory of Crystal Materials
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Basal Plane Bending in MPCVD SCD

Reference Paper: Han et al., “Basal Plane Bending of Homoepitaxial MPCVD Single-Crystal Diamond,” Materials 2020, 13, 4510.

Executive Summary

This research provides critical insights into the structural quality control of Single Crystal Diamond (SCD) grown via Microwave Plasma Chemical Vapor Deposition (MPCVD). The findings directly inform the material specifications required for high-performance diamond semiconductor applications.

Substrate Quality is Paramount: The basal plane bending of the SCD epilayer is primarily determined by the quality and flatness of the initial substrate. High-quality HTHP substrates yielded films 21 times flatter (R = 358.17 m) than films grown on MPCVD substrates (R = 16.78 m).
Thermal Stress is the Root Cause: Basal plane bending is caused by thermal stress resulting from an uneven temperature distribution across the substrate surface (temperature gradients up to 40 °C/mm at 1100 °C).
Growth Parameters Degrade Quality: Increased growth temperature (900 °C to 1150 °C) and extended growth time (4 h to 16 h) monotonically increase basal plane bending severity.
Quantified Degradation: The radius of curvature (R) decreased significantly with increasing temperature, reaching a minimum of 23.40 m at 1150 °C (4 h). Extended growth time further reduced R to 10.20 m (16 h at 1100 °C).
Structural Homogeneity Requirement: To achieve the “ultimate semiconductor” status, SCD used in high-power, high-frequency, and detector applications must utilize ultra-flat substrates and precise thermal management to minimize internal stress and dislocation formation.

Technical Specifications

The following hard data points were extracted from the experimental results detailing growth conditions and resulting material quality.

Parameter	Value	Unit	Context
Growth Method	MPCVD	N/A	ARDIS-300, 2.45 GHz/6 kW reactor
Substrate Orientation	(100)	N/A	Homoepitaxial growth plane
Growth Pressure	275	torr	Constant parameter
Methane Concentration	3.00	%	CH₄/H₂ ratio
Growth Temperature Range	900 to 1150	°C	Parameter varied to study bending
Maximum Growth Time	16	h	Parameter varied to study bending
Temperature Gradient (Max)	40	°C/mm	Measured at 1100 °C across the surface
Curvature Radius (Best Case)	358.17	m	HTHP substrate, 900 °C, 4 h growth
Curvature Radius (Worst Case)	10.20	m	HTHP substrate, 1100 °C, 16 h growth
Measurement Technique	HRXRD	N/A	Bruker D8 Discover, Cu Kα1 radiation

Key Methodologies

The study utilized precise MPCVD growth techniques combined with High-Resolution X-ray Diffraction (HRXRD) mapping to quantify structural defects.

Substrate Selection: (100)-oriented HTHP and MPCVD SCD substrates were used to compare the effect of initial substrate quality on epilayer bending.
MPCVD Setup: Growth was conducted in an ARDIS-300 system (2.45 GHz/6 kW) at a constant pressure of 275 torr and a methane concentration of 3.00% (CH₄/H₂).
Thermal Control: Substrate surface temperature was monitored and maintained via a double interference infrared radiation thermo pyrometer (emissivity 0.1) with self-adjusting microwave power feedback.
Parameter Variation: Experiments systematically varied:
- Growth Temperature (900 °C, 1000 °C, 1100 °C, 1150 °C) over a fixed 4 h period.
- Growth Time (4 h, 8 h, 16 h) at a fixed temperature of 1100 °C.
Bending Measurement: HRXRD was used to measure the relative ω(Δω400) peak positions. The X-ray beam was scanned in 1 mm steps across the diamond plate.
Curvature Calculation: The radius of the basal plane bending (R) was derived from the slope of the rocking curve peak position (ω) as a function of scanning distance (x), confirming the bending was approximately spherical.

6CCVD Solutions & Capabilities

This research underscores the critical need for ultra-high-quality, structurally homogeneous SCD substrates to minimize basal plane bending, which is essential for advanced device fabrication. 6CCVD is uniquely positioned to supply the materials and customization required to replicate and extend this high-level research.

Applicable Materials for Low-Bending Applications

The paper demonstrates that the substrate is the dominant factor in determining final film quality. 6CCVD specializes in providing substrates optimized for minimal inherited stress.

Optical Grade SCD (Single Crystal Diamond): Required for replicating the best-case scenario (R = 358.17 m) and achieving even flatter films. Our SCD is grown and polished to achieve surface roughness Ra < 1nm, ensuring the initial flatness necessary to prevent stress propagation and dislocation formation.
High-Homogeneity PCD (Polycrystalline Diamond): For applications requiring larger areas (e.g., thermal management or large-area detectors), 6CCVD offers PCD plates up to 125mm in diameter with superior structural uniformity and polishing (Ra < 5nm).

Customization Potential for Advanced Research

The study highlights that thermal management (substrate holder design, temperature gradient) is key to mitigating bending, especially during long growth times. 6CCVD offers comprehensive customization to support optimized MPCVD recipes.

Requirement from Paper	6CCVD Customization Capability	Technical Advantage
Ultra-Flat Substrates	SCD polishing to Ra < 1nm	Minimizes inherited basal plane bending and dislocation density.
Large Area Growth	PCD plates up to 125mm diameter	Enables scaling of high-power and high-frequency devices.
Precise Thickness Control	SCD/PCD films from 0.1µm to 500µm	Essential for managing internal stress accumulation during long, high-temperature growth cycles.
Device Integration	Custom Metalization (Au, Pt, Pd, Ti, W, Cu)	Streamlines post-processing for electrodes and contacts in high-voltage/high-frequency electronics.
Custom Substrate Dimensions	Laser cutting and shaping services	Provides precise dimensions and geometries required for specialized pocket holder designs (Figure 9) and optimized thermal profiles.

Engineering Support

The relationship between growth parameters (temperature, time) and structural quality is complex. 6CCVD’s in-house team of PhD material scientists can assist researchers and engineers in selecting the optimal diamond material specifications for projects focused on High-Power Electronics, Deep UV Detectors, or Particle Detectors where structural homogeneity is non-negotiable.

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

View Original Abstract

We report herein high-resolution X-ray diffraction measurements of basal plane bending of homoepitaxial single-crystal diamond (SCD). We define SCD (100) as the base plane. The results revealed that growth parameters such as temperature, growth time, and basal plane bending of the substrate all affect the basal plane bending of SCD. First, the basal plane bending of SCD depends mainly on the substrate and becomes severe with increasing basal plane bending of the substrate. The SCD growth experiments show that the basal plane bending increases with elevated growth temperature and increased growth time. Finally, to understand the mechanism, we investigated the substrate-surface temperature distribution as a function of basal plane bending of SCD fabricated by chemical vapor deposition (CVD). This allowed us to propose a model and understand the origin of basal plane bending. The results indicate that an uneven temperature distribution on the substrate surface is the main cause of the base-plane bending of CVD diamond.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma13204510

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