High termination efficiency using polyimide trench for high voltage diamond Schottky diode

At a Glance

Metadata	Details
Publication Date	2015-07-19
Journal	Diamond and Related Materials
Authors	Houssam Arbess, Karine Isoird, M. Zerarka, Henri Schneider, Marie‐Laure Locatelli
Institutions	Laboratoire Plasma et Conversion d’Energie, Laboratoire d’Analyse et d’Architecture des Systèmes
Citations	3
Analysis	Full AI Review Included

High Termination Efficiency in Diamond Schottky Diodes: 6CCVD Analysis

This technical documentation analyzes the research paper detailing the optimization of high-voltage diamond Schottky diode termination using a polyimide trench architecture, providing actionable material specifications and engineering solutions available through 6CCVD.

Executive Summary

The research successfully demonstrates a novel termination architecture for diamond Schottky diodes (SCDs) optimized for high-voltage power electronics applications, achieving near-ideal performance through simulation.

Core Achievement: Simulation of a 1700 V diamond Schottky diode using a polyimide trench under a field plate (Structure C) yielded a termination efficiency of 97%.
Performance Improvement: This efficiency represents a significant gain over the simple field plate architecture (Structure A), which achieved only 67% efficiency.
Critical Field Reduction: The polyimide trench effectively spreads equipotential lines, drastically reducing the peak electric field at the termination edge, mitigating premature dielectric breakdown.
Optimized E-Field: The maximum electric field peak was minimized to 13.3 MV/cm (for optimum geometry), a value significantly lower than traditional field plate architectures.
Material Focus: The device design relies on precisely controlled P-type SCD layers, requiring both highly doped (P⁺) and lightly doped (P^-) epitaxial structures.
Engineering Relevance: This architecture is essential for realizing the full theoretical breakdown potential of diamond in high-power switching devices.

Technical Specifications

The following critical parameters and performance metrics were extracted from the TCAD simulation and analysis of the optimized polyimide trench diamond Schottky diode (Structure C).

Parameter	Value	Unit	Context
Target Breakdown Voltage (V_BD)	1700	V	Simulated operating voltage
Maximum Termination Efficiency	97	%	Achieved with polyimide trench
P^- Layer (Drift Layer) Thickness	12	µm	MPCVD epitaxial requirement
P^- Layer Boron Doping Concentration	4x10¹⁵	cm^-3	Precision doping requirement
P⁺ Layer Thickness	7	µm	Highly doped contact layer
P⁺ Layer Boron Doping Concentration	3x10²⁰	cm^-3	Ohmic contact layer
Optimized Dielectric (SiO₂) Thickness	2.2	µm	Under field plate extension
Minimum Electric Field Peak	13.3	MV/cm	Optimized geometry (0.5 µm extension length)
Polyimide Critical Electric Field	5	MV/cm	Dielectric limitation
Diamond Intrinsic Bandgap Energy	5.45	eV	Superior thermal stability

Key Methodologies

The study relied on Sentaurus TCAD simulations to optimize the device architecture. The proposed technological realization involves eight key steps focusing on precision material deposition, etching, and planarization.

Diamond Epitaxy: Growth of the P^- (drift) layer on the P⁺ (substrate/contact) layer, defining the essential SCD structure (e.g., 12 µm P^- on 7 µm P⁺).
Diamond Etching: Etching through the P^- layer to expose the P⁺ layer, forming the required trench geometry.
Ohmic Contacts Deposit: Deposition of the Ohmic metal stack onto the exposed P⁺ layer.
Polyimide Deposit & Polymerization: Spin coating and curing of the polyimide layer, acting as a secondary passivation and filling the termination trench.
CMP Process: Chemical Mechanical Polishing (CMP) to planarize the deposited polyimide surface, critical for subsequent precise layer deposition.
Silicon Oxide Deposit: Deposition of the primary dielectric (Silicon Oxide) layer, necessary for the field plate structure.
Schottky Contact Deposit: Deposition of the Schottky metal stack onto the P^- layer surface, defining the diode junction.
Polyimide Etching: Final etching steps to open windows in the polyimide, ensuring access to the interconnected anode contacts.

6CCVD Solutions & Capabilities

The development of advanced high-voltage diamond power devices, such as the optimized Schottky diode presented here, fundamentally relies on the precise material specifications and integration capabilities offered by 6CCVD.

Applicable Materials

The requirements for high-efficiency termination necessitate high-quality, customized diamond epitaxial structures. 6CCVD is uniquely positioned to supply the necessary layers:

Single Crystal Diamond (SCD) Epitaxy: We provide electronic grade SCD wafers up to 125mm (for PCD, suitable as substrates for subsequent SCD growth).
Precision Boron-Doped Diamond (BDD): Successful replication of this device requires tight control over doping densities spanning five orders of magnitude (4x10¹⁵ cm^-3 for the drift layer and 3x10²⁰ cm^-3 for the contact layer). 6CCVD’s MPCVD expertise ensures the high crystalline quality and doping precision required for low ON-resistance and maximized V_BD.
Thickness Control: The simulated device utilizes layers of 12 µm (P^-) and 7 µm (P⁺). 6CCVD routinely delivers SCD thicknesses across the entire research range (0.1 µm - 500 µm), guaranteeing accurate drift layer fabrication.

Customization Potential

Achieving the sub-micron precision necessary for optimum termination (e.g., 0.5 µm field plate extension length) requires exceptional material preparation and post-processing capabilities:

Process Requirement (Paper)	6CCVD Service Offering	Engineering Advantage
Material Base	SCD Plates/Wafers up to 125mm	Provides large-format SCD platforms for industrial scalability and R&D.
Surface Quality	Ultra-Low Roughness Polishing (Ra < 1 nm)	Essential for reliable, defect-free deposition of critical layers like polyimide and silicon oxide, minimizing field peaking due to surface irregularities.
Contact Deposition	Custom Metalization Stacks (Ti/Pt/Au, W/Au, etc.)	Internal capability to deposit and pattern the complex multi-layer metal stacks required for robust Ohmic and Schottky contacts, crucial for high-temperature operation.
Device Definition	Precision Laser Structuring and Cutting	Allows for the creation of small, complex 3mm x 3mm dies with the high lateral precision needed to define the field plate and polyimide trench geometry.

Engineering Support

This research highlights the highly interdisciplinary nature of wide-bandgap device engineering, combining semiconductor growth, dielectric physics, and mechanical planarization (CMP). 6CCVD’s in-house PhD team provides specialized consultation to bridge these domains.

We offer detailed engineering assistance regarding:

Optimal boron doping recipes to match TCAD simulation requirements for high-voltage drift layers.
Surface preparation protocols necessary for successful adhesion and reliability of secondary passivations (like polyimide or BCB) utilized in Deep Trench Termination (DT²) and similar high-voltage termination structures.

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

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.diamond.2015.07.006

References

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2009 - Fabrication of a field plate structure for diamond Schottky barrier diodes [Crossref]
2001 - Design rules for field plate edge termination in SiC Schottky diodes [Crossref]
1993 - Edge terminations for SiC high voltage Schottky rectifiers
1997 - SiC device edge termination using finite area argon implantation [Crossref]
2008 - Edge termination techniques for p-type diamond Schottky barrier diodes [Crossref]
2006 - Termination structures for diamond Schottky barrier diodes