1 New termination architecture for 1700 V diamond schottky diode

At a Glance

Metadata	Details
Publication Date	2015-08-26
Journal	HAL (Le Centre pour la Communication Scientifique Directe)
Authors	Houssam Arbess, Karine Isoird, Saleem Hamady
Institutions	Laboratoire d’Analyse et d’Architecture des Systèmes
Analysis	Full AI Review Included

Technical Analysis & Documentation: High-Voltage Diamond Schottky Diodes

Executive Summary

This documentation analyzes research detailing new field plate termination architectures designed to enhance the breakdown voltage ($V_{BR}$) and manage electric field stress in pseudo vertical diamond Schottky diodes (SCD). This work is crucial for maximizing the performance of diamond in high-power, high-temperature switching applications.

Core Value Proposition: Successful TCAD simulation and optimization of device termination structures, overcoming the critical limitation imposed by the lower breakdown strength of deposited dielectric materials (like SiO₂) compared to diamond.
Performance Improvement: Breakdown Voltage ($V_{BR}$) was significantly improved by 31%, rising from 1632 V (initial architecture) to 2141 V (optimized new architecture) at 700 K.
Electric Field Management: The maximum electric field ($E_{max}$) in the dielectric, which dictates device failure, was successfully reduced from 57 MV/cm to 18 MV/cm using optimized geometry and material selection (Aluminum Oxide, Al₂O₃).
Novel Architecture: Introduces and validates two advanced termination geometries—the Pillars Dielectric Form and the Graduated Dielectric Form—specifically engineered to distribute potential and minimize stress peaks at critical corners.
Material Insight: Confirms the necessity of highly-controlled P-type (Boron-Doped) Single Crystal Diamond (SCD) drift and contact layers for next-generation 1700 V power switching applications.
Temperature Stability: Simulations confirmed stable performance parameters at high temperatures (700 K), demonstrating diamond’s inherent suitability for extreme operational environments.

Technical Specifications

Data extracted from the TCAD simulation results for the optimized diamond Schottky diode termination architectures.

Parameter	Value	Unit	Context
Target Device Operating Voltage	1700	V	Applied reverse bias for E-field analysis
Simulation Temperature	700	K	High-temperature operating condition
Ideal 1D $V_{BR}$ (Theoretical Limit)	2288	V	Used for P^- layer optimization (8 x 10¹⁵ cm^-3)
Initial $V_{BR}$ (Standard Architecture)	1632	V	Before optimization of termination structure
Optimized $V_{BR}$ (New Architecture)	2141	V	Achieved using improved geometry (SiO₂)
Optimized $E_{max}$ in Dielectric (SiO₂)	18	MV/cm	Final result using mixed architecture
Optimal $E_{max}$ in Dielectric (Al₂O₃)	13	MV/cm	Achieved by switching to Aluminum Oxide
P⁺ Layer Doping Concentration	3 x 10²⁰	cm^-3	Highly Boron-Doped Contact Layer
P^- Drift Layer Doping Concentration	8 x 10¹⁵	cm^-3	Lightly Boron-Doped Drift Region
Diamond Layer Thickness (P⁺ & P^-)	7	µm	Thickness of each epitaxially grown layer
Initial Field Plate Dielectric Thickness	0.7	µm	Standard SiO₂ optimization
New Architecture Dielectric Thickness	1.0	µm	Optimized thickness for 2141 V result
Optimized Field Plate Length	10	µm	Lateral dimension of the termination

Key Methodologies

The study utilized Sentaurus TCAD simulations to optimize the junction termination extension (JTE) for the diamond Schottky diode, focusing primarily on dielectric architecture modification.

Baseline Structure Definition: A pseudo vertical Schottky diode consisting of a highly doped P⁺ diamond layer ($3 \times 10^{20}$ cm^-3) and a 7 µm lightly doped P^- drift layer ($8 \times 10^{15}$ cm^-3) was established.
Initial Field Plate Optimization: The standard field plate (FP) architecture, utilizing Silicon Oxide (SiO₂), was optimized for breakdown voltage. The initial best parameters were 10 µm length and 0.7 µm thickness, achieving 1638 V.
New Termination Architecture (Planar Electrode): A novel geometry was introduced where the diamond under the field plate region was replaced with dielectric material, ensuring a flat, corner-free electrode surface to minimize electric field concentration at the diamond/electrode interface. This optimization yielded $V_{BR} = 2141$ V.
Geometrical Stress Mitigation: Two advanced geometries were simulated to increase the number of potential distribution points (corners) in the dielectric path:
- Pillars Dielectric Form: Creation of multiple oxide pillars (optimized to 9 pillars, 0.5 µm width) to reduce $E_{max}$ from 37 MV/cm to 24 MV/cm.
- Graduated Dielectric Form: Use of three varying height steps (graduations) in the oxide to further distribute the potential gradient.
High-k Dielectric Substitution: Dielectric material was changed from low-k SiO₂ to high-k materials (Aluminum Oxide, Al₂O₃) to leverage higher electric permittivity, resulting in a maximum $E_{max}$ of 13 MV/cm.
Final Mixed Architecture: The optimal geometrical form (Pillars/Graduated) was combined with the high-k Al₂O₃ to achieve the lowest overall electric field stress (13-18 MV/cm range), suitable for reliable high-voltage operation.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond materials and engineering services necessary to transition this theoretical 1700 V device architecture into a viable commercial reality. Our capabilities directly address the exacting specifications required for high-performance diamond power electronics.

Applicable Materials

The foundation of the simulated device is high-quality, defect-controlled P-type Single Crystal Diamond. 6CCVD provides the necessary material specifications:

High Purity Single Crystal Diamond (SCD): Required for the critical P^- drift layer (8 x 10¹⁵ cm^-3) to ensure the maximal theoretical breakdown field. Our SCD material guarantees the structural integrity needed for high-voltage operation.
Heavy Boron-Doped Diamond (BDD) Substrates & Layers: Essential for the P⁺ contact layer (3 x 10²⁰ cm^-3). 6CCVD specializes in MPCVD growth of Boron-Doped Diamond (BDD) with precise control over doping levels, achieving the ultra-high concentrations needed for low-resistance Ohmic contacts.
Precise Epitaxial Thickness Control: The device requires exact 7 µm thick layers. 6CCVD offers SCD and PCD epitaxial layers with thickness control ranging from 0.1 µm up to 500 µm, ensuring accurate replication of the optimized 7 µm drift region.

Customization Potential

Replicating the complex termination architectures (Pillars, Graduated Field Plates) necessitates specialized fabrication techniques that 6CCVD offers in-house.

Custom Service	Application in Research Paper	6CCVD Capability
Custom Wafer Dimensions	Device fabrication requires engineering-grade substrates.	Plates/wafers available up to 125 mm (PCD) for large-scale production prototyping.
High-Precision Laser Cutting	Required for defining the 10 µm field plate length, and creating microstructures in the diamond surface before dielectric deposition.	Customized geometries, laser micro-machining, and dicing for complex device layouts.
Advanced Metalization	Schottky and Ohmic contacts are critical for device performance.	Internal capability to deposit and pattern Au, Pt, Pd, Ti, W, and Cu, allowing for high-temperature stable Schottky contacts.
Surface Finish	High-voltage breakdown performance is highly sensitive to surface quality.	Ultra-low roughness polishing available: Ra < 1 nm (SCD), guaranteeing optimal interface quality for dielectric deposition.

Engineering Support

The challenges described in this research—specifically the management of electric field peaks through complex geometries and dielectric material selection (SiO₂ vs. Al₂O₃)—are complex material science problems.

6CCVD’s in-house PhD engineering team offers expert consultation and materials selection assistance for projects focused on High-Voltage Diamond Power Electronics and advanced Junction Termination Extension (JTE) design. We partner with R&D teams to select the appropriate SCD doping profile and substrate specifications required for achieving reliable breakdown performance above 2000 V.

For custom specifications or material consultation regarding high-power BDD devices or specialized epitaxial layer requirements, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

«Diamond», «TCAD simulation», «Schottky diode», «Field plate architecture». New field plate architecture is applied to pseudo vertical diamond Schottky diode. Using several field plate architectures, a TCAD simulation is realized in order to reduce the electric field in the dielectric while maintaining high breakdown voltage. Firstly and after simple variations in the field plate architecture, the breakdown voltage was improved from 1632 V to 2141 V at 700 K. Concerning Emax in the dielectric, we obtained a decreasing of maximum electric field from 57 to 18 MV/cm.

Tech Support

Original Source

DOI: None