Integrated temperature sensor with diamond Schottky diodes using a thermosensitive parameter

At a Glance

Metadata	Details
Publication Date	2017-08-16
Journal	Diamond and Related Materials
Authors	Gaëtan Perez, Gauthier Chicot, Yvan Avenas, Pierre Lefranc, Pierre‐Olivier Jeannin
Institutions	Laboratoire Plasma et Conversion d’Energie, Institut Néel
Citations	37
Analysis	Full AI Review Included

Integrated Diamond Schottky Diode Temperature Sensors: 6CCVD Technical Analysis

This document analyzes the research on monolithically integrated diamond Schottky diode temperature sensors, highlighting the critical material requirements and processing challenges. 6CCVD provides the necessary high-quality MPCVD diamond materials and advanced fabrication services required to replicate, optimize, and scale this technology for next-generation power electronics and active thermal management systems.

Executive Summary

Core Achievement: Successful monolithic integration of a diamond Schottky diode (D_sense) used as a temperature sensor alongside a main power diode (D_power).
Sensing Mechanism: The diode voltage drop (V_sense) at a constant forward bias current is utilized as a reliable thermosensitive electrical parameter (TSEP).
High Sensitivity: The sensor demonstrated excellent linearity (R² > 0.994) and a high sensitivity of -1.6 mV/K to -1.7 mV/K across the 300 K to 440 K operating range.
Material Foundation: Devices were fabricated using homoepitaxial Boron-doped CVD diamond (p⁺/p^- layers) grown on HPHT Ib substrates, confirming the suitability of BDD for high-temperature sensing.
Critical Challenge Identified: Current path overlap between the integrated diodes leads to significant temperature measurement errors (up to 50 K) when D_power is in the ON-state.
Proposed Solution: 3D simulations confirm that implementing deep trench etching to electrically isolate the p⁺ anode regions effectively decouples the current paths, enabling bias-independent, accurate temperature monitoring.
6CCVD Value Proposition: 6CCVD specializes in providing the custom Boron-Doped SCD substrates, precise layer thicknesses, and advanced metalization/etching services required for implementing the optimized, isolated sensor design.

Technical Specifications

The following hard data points were extracted from the experimental results and device structure detailed in the research:

Parameter	Value	Unit	Context
Calibrated Temperature Range	300 to 440	K	Limited by experimental setup
Sensor Sensitivity (S)	-1.6 to -1.7	mV/K	For current densities up to 5 A/cm²
Sensor Linearity (R²)	> 0.994	N/A	Coefficient of determination for linear fit
Sensor Bias Current Density (Linear Range)	0.25 to 5	A/cm²	Ensures operation in exponential regime
Maximum Power Density (Sensor)	5.4	mW/cm²	Negligible self-heating at low bias
Maximum Measurement Error (ΔT_error)	50	K	Observed when D_power is ON-state (unmodified layout)
p^- Layer Thickness	1.3	µm	Doping concentration: 5 * 10¹⁵ cm^-3
p⁺ Layer Thickness	200	nm	Grown on HPHT Ib substrate
Ohmic Contact Stack (Anode)	Ti(20 nm) / Pt(20 nm) / Au(10 nm)	N/A	Common anode contact
Schottky Contact Stack (Cathode)	Zr(30 nm) / Pt(20 nm) / Au(10 nm)	N/A	Isolated cathode contacts
Sensor Diode Area	200 µm x 200 µm	N/A	Calibrated device size

Key Methodologies

The fabrication and characterization relied on precise CVD growth and advanced electrical measurement techniques:

Material Synthesis: Homoepitaxial growth of Boron-doped diamond (BDD) layers via MPCVD. The structure consisted of a 200 nm p⁺ layer followed by a 1.3 µm p^- layer, deposited on an HPHT Ib diamond substrate.
Device Integration: Monolithic integration of multiple large-area power diodes (D_power) and small-area sensor diodes (D_sense) on the same substrate, sharing a common anode contact.
Metalization: Deposition of specific metal stacks for contacts:
- Ohmic Anode: Ti/Pt/Au (20 nm / 20 nm / 10 nm).
- Schottky Cathode: Zr/Pt/Au (30 nm / 20 nm / 10 nm).
Thermal Calibration: The packaged sample (glued to metallized Al₂O₃) was calibrated in a temperature-regulated oven from 300 K (RT) to 440 K, with temperature monitored by a K-type thermocouple.
Pulsed TSEP Measurement: A pulsed current source (1 ms ON time, 50 ms OFF time) was used to bias the sensor diode during calibration. The short pulse time minimized self-heating, ensuring the device temperature matched the oven temperature.
Isolation Strategy (Proposed): 3D Finite Element Analysis (Atlas3D) was used to simulate the effect of adding a deep trench etching step to electrically isolate the p⁺ anode regions, thereby eliminating current path overlap and ensuring bias-independent temperature readings.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-specification diamond materials and custom fabrication services necessary to advance integrated diamond sensor technology, particularly by implementing the critical isolation trench solution.

Applicable Materials

To replicate and optimize the integrated Schottky diode structure, researchers require high-quality, precisely doped diamond layers. 6CCVD recommends:

Boron-Doped Single Crystal Diamond (BDD SCD): Essential for the p-type layers (p⁺ and p^-). We offer precise control over Boron doping concentration (e.g., 5 * 10¹⁵ cm^-3 for the p^- layer) and layer thickness (e.g., 200 nm p⁺ and 1.3 µm p^-).
High Purity SCD Substrates: SCD substrates up to 500 µm thick, or custom substrates up to 10 mm, providing the necessary thermal conductivity and structural integrity for high-power device integration.

Customization Potential

The success of this integrated sensor relies on precise dimensions, layer control, and complex metalization. 6CCVD offers comprehensive customization capabilities:

Research Requirement	6CCVD Capability	Benefit to Project
Layer Thickness	SCD thickness control from 0.1 µm up to 500 µm.	Precise control over the 200 nm p⁺ and 1.3 µm p^- layers.
Device Isolation	Advanced laser cutting and etching services.	Implementation of the critical deep trench etching to electrically isolate p⁺ anode regions, eliminating the 50 K measurement error.
Metalization Stacks	In-house deposition of Au, Pt, Pd, Ti, W, and Cu.	Replication or optimization of the required Ti/Pt/Au (Ohmic) and Zr/Pt/Au (Schottky) contact stacks.
Substrate Size	Plates/wafers up to 125 mm (PCD) and large-area SCD.	Scaling the device from the 4.5 mm x 4.5 mm sample size to commercial power module dimensions.
Surface Finish	Polishing to Ra < 1 nm (SCD).	Ensuring ultra-smooth surfaces critical for high-quality metal-semiconductor interfaces and reliable Schottky barrier formation.

Engineering Support

6CCVD’s in-house PhD team specializes in wide-bandgap semiconductor physics and device fabrication. We can assist researchers and engineers with:

Material Selection: Optimizing BDD doping profiles and layer thicknesses for specific TSEP sensitivity requirements.
Thermal Management Design: Consulting on substrate selection and device layout to maximize thermal coupling between D_power and D_sense while minimizing electrical cross-talk.
Active Parallelization: Providing material solutions and design consultation for projects requiring accurate, real-time temperature monitoring for current balancing in parallel-connected diamond switching cells.

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.2017.08.008

References

2010 - Extreme dielectric strength in boron doped homoepitaxial diamond [Crossref]
2004 - High-voltage diamond Schottky rectifiers [Crossref]
2013 - 1Ω on-resistance diamond vertical-Schottky barrier diode operated at 250°C [Crossref]
2014 - Zr/oxidized diamond interface for high power Schottky diodes [Crossref]
2015 - Power diamond vertical Schottky barrier diode with 10A forward current [Crossref]
2015 - Power high-voltage and fast response Schottky barrier diamond diodes [Crossref]
2012 - High temperature application of diamond power device [Crossref]
2010 - Hall hole mobility in boron-doped homoepitaxial diamond [Crossref]
2017 - Thin large area vertical Schottky barrier diamond diodes with low on-resistance made by ion-beam assisted lift-off technique [Crossref]