Non-Invasive Wide-Field Imaging of Chip Surface Temperature Distribution Based on Ensemble Diamond Nitrogen-Vacancy Centers

At a Glance

Metadata	Details
Publication Date	2025-03-20
Journal	Sensors
Authors	Zhenrong Shi, Ziwen Pan, Qinghua Li, Wei Li
Institutions	Changchun University
Citations	2
Analysis	Full AI Review Included

Executive Summary

This research presents a novel, high-performance system for non-invasive, wide-field temperature imaging of electronic chip surfaces, leveraging ensemble Nitrogen-Vacancy (NV) centers in diamond.

High-Performance Metrics: The system achieves a high sensitivity of 10 mK/Hz^1/2 and a high spatial resolution of 1.3 µm over a wide field of view (500 µm²).
Enhanced Sensitivity via Alignment: Sensitivity was increased by 40% compared to non-aligned configurations by precisely aligning the bias magnetic field with the diamond’s [111] crystal axis, suppressing off-axis lattice strain.
Thermal Diffusion Mitigation: A hybrid device structure—a 200 nm NV-doped diamond layer bonded to a quartz substrate—was engineered to mitigate the high thermal conductivity of bulk diamond, enabling stable, wide-field thermal imaging.
Real-Time Thermal Visualization: The system successfully demonstrated real-time visualization of temperature distribution and thermal diffusion on a Micro-Electromechanical System (MEMS) chip under varying currents (10 mA to 70 mA).
Reliability and Defect Detection: The imaging capability allows for the identification of thermal anomalies and hotspots caused by metal defects or surface scratches, providing a powerful tool for chip quality control and reliability assessment.
Non-Contact and High-Speed: The methodology is non-contact and operates at a high temporal resolution (2.4 s), making it ideal for monitoring dynamic thermal characteristics during chip operation.

Technical Specifications

Parameter	Value	Unit	Context
Temperature Sensitivity	10	mK/Hz^1/2	Achieved performance (B
Spatial Resolution	1.3	µm	Calculated (r = 1.22λ/(2NA))
Field of View (FOV)	500 x 500 (or 500)	µm²	CCD imaging area
Temporal Resolution	2.4	s	Based on 250 FPS CCD frame rate
NV Layer Thickness	200	nm	Final polished thickness on quartz substrate
NV Concentration	~5	ppm	In the active diamond layer
Diamond Crystal Phase	(110)	N/A	Used for the NV center device
Zero-Field Splitting (D)	~2.87	GHz	Ground state energy level
Temperature Coefficient (β_T)	-74	kHz/K	At room temperature
Excitation Laser Wavelength	532	nm	Used for NV center initialization
Fluorescence Wavelength	~670	nm	Emitted red fluorescence
Objective Lens	10x	N/A	Numerical Aperture (NA) = 0.3
Optimal ODMR Linewidth (Δω)	10	MHz	When B
Optimal ODMR Contrast (C)	12	%	When B
Bias Magnetic Field Range	0 to 500	mT	Used for alignment and counteracting stress

Key Methodologies

The system integrates optical, microwave, magnetic field, and control systems to perform Optically Detected Magnetic Resonance (ODMR) thermometry.

1. Hybrid Device Fabrication

Diamond Material: A 3 mm x 3 mm x 1 mm diamond crystal with a (110) crystal phase was used.
NV Layer Creation: Ion implantation was used to generate a high-concentration NV layer approximately 50 nm below the diamond surface.
Layer Thinning: The diamond was polished to retain a 200 nm thick NV-doped layer (concentration ~5 ppm).
Substrate Bonding: The thin NV-doped diamond wafer was bonded to a quartz substrate using crystal bonding wax. Quartz was chosen due to its thermal conductivity being three orders of magnitude lower than diamond, effectively mitigating thermal diffusion for surface imaging.

2. ODMR Setup and Optimization

Optical Initialization: A 532 nm laser, modulated by an Acousto-Optic Modulator (AOM), initializes the NV centers. Fluorescence (~670 nm) is collected by a 10x objective (NA=0.3) and filtered before detection.
Microwave Manipulation: A microwave source generates a signal (~2.87 GHz) amplified to ~30 dBm, transmitted via a horn antenna to manipulate the electron spin states (ms = 0 to ms = ±1).
Magnetic Field Alignment (Critical Innovation): A three-axis adjustable electromagnet is used to align the bias magnetic field precisely parallel to the diamond’s [111] axis. This alignment minimizes off-axis lattice strain, maximizing the linearity of the zero-field splitting (D) shift with temperature (β_T), resulting in a 40% sensitivity gain.

3. Data Acquisition and Processing

Synchronized Scanning: An Arbitrary Waveform Generator (AWG) controls the laser pulse duration and synchronizes the CCD camera (Basler A602f, 250 FPS) with the microwave frequency sweep (2.6 GHz to 2.9 GHz, 0.5 MHz step).
Temperature Calculation: Fluorescence intensity images captured at specific microwave frequencies are processed to generate ODMR spectra. The zero-field splitting value (D) is extracted using Lorentz fitting, and temperature (T) is calculated based on the linear relationship D = D₀ + β_TΔT.
Thermogram Generation: The calculated temperature data is mapped spatially to generate wide-field thermograms (500 µm x 500 µm).

Commercial Applications

This non-invasive, high-resolution thermal imaging technology is critical for industries requiring precise thermal management and quality control of microelectronic devices.

Semiconductor Manufacturing and R&D:
- Chip Reliability Testing: Real-time monitoring of temperature distribution during stress testing (e.g., high current operation) to predict aging and failure points.
- Hotspot Identification: Detecting localized thermal anomalies caused by metal defects, surface scratches, or poor interconnects in MEMS, ASICs, and power electronics.
- Thermal Management Optimization: Validating and optimizing heat dissipation strategies and packaging designs for high-power density chips.
Quantum Sensing and Metrology:
- The optimized NV center alignment technique (B||<111>) is directly applicable to improving the sensitivity of other diamond-based quantum sensors (e.g., magnetometers and strain sensors).
Micro-Electromechanical Systems (MEMS):
- Characterizing the thermal behavior of MEMS devices, which are highly sensitive to temperature fluctuations, ensuring stable operation.
Materials Science Research:
- Non-contact measurement of thermal conductivity and heat flow dynamics in novel materials and thin films at the micro- and nanoscale.

View Original Abstract

With the development of chip technology, the demand for device reliability in various electronic chip industries continues to grow. In recent years, with the advancement of quantum sensors, the solid-state spin (nitrogen-vacancy) NV center temperature measurement system has garnered attention due to its high sensitivity and spatial range. However, NV centers are not only affected by temperature but also by magnetic fields. This article analyzes the impact of magnetic fields on temperature detection. By combining the wide-field imaging platform of optically detected magnetic resonance (ODMR) with a temperature-sensitive structure of thin ensemble diamond overlaid on a quartz substrate, high-sensitivity temperature detection has been achieved. And obtains a sensitivity of approximately 10 mK/Hz1/2. By combining a CCD camera imaging system, it realizes a wide field of view of 500 μm2, a high spatial resolution of 1.3 μm. Ultimately, this study demonstrates the two-dimensional actual temperature distribution on the chip surface under different currents, achieving wide-field, non-contact, high-speed temperature imaging of the chip surface.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s25061947

References

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