Terahertz-readable laser engraved marks as a novel solution for product traceability

At a Glance

Metadata	Details
Publication Date	2023-08-01
Journal	Scientific Reports
Authors	Pouria Hoveida, Adrian Phoulady, Hongbin Choi, Nicholas May, Sina Shahbazmohamadi
Institutions	University of Connecticut
Citations	16
Analysis	Full AI Review Included

Terahertz-Readable Laser Engraved Marks for Product Traceability: A 6CCVD Analysis

This technical documentation analyzes the feasibility and methodology presented in the research paper, “Terahertz-readable laser engraved marks as a novel solution for product traceability,” and aligns the requirements of this advanced anti-counterfeiting technique with the capabilities of 6CCVD’s MPCVD diamond materials.

Executive Summary

The research demonstrates a novel, highly secure method for product traceability using laser-engraved physical tags read non-destructively by Terahertz (THz) spectroscopy.

Core Value Proposition: Creation of unique, unclonable, and immutable physical identifiers using ultrashort pulsed laser ablation, overcoming limitations of traditional barcodes and RFIDs.
Methodology: Tags are created by varying trench depth (23 µm to 260 µm) using precise femtosecond laser parameters (1035 nm, 257 fs pulse width).
Reading Mechanism: Far-field THz Time-Domain Spectroscopy (THz-TDS) measures the time-of-arrival signal, which correlates linearly with the engraved depth.
Depth Indexing: A strong linear correlation between engraved depth and THz time-of-arrival allows the depth value to serve as a reliable, retrievable information index.
Resolution & Feasibility: The THz reading method achieved a vertical height resolution of 50 µm or better, and successfully demonstrated reading tags through packaging material and on the backside of microelectronic dies.
Application Focus: The solution is highly relevant for die-level traceability in microelectronics, requiring materials with high precision and durability, such as MPCVD diamond.

Technical Specifications

The following hard data points were extracted from the experimental setup and results:

Parameter	Value	Unit	Context
Laser Wavelength	1035	nm	Femtosecond machining system (Coherent Monaco)
Laser Pulse Width	257	fs	Ultrashort pulsed laser source
Theoretical Laser Spot Size	8.5	µm	Achieved via F-Theta lens (70 mm effective focal length)
Engraved Trench Size (Test)	4 x 4	mm	Size of individual test trenches
Measured Average Depth Range	23 to 260	µm	Range of depths used for unique identifiers (Table 2)
THz Vertical Height Resolution	50 or better	µm	Resolution achieved by THz-TDS time-of-arrival analysis
Maximum Time of Arrival Measured	~1400	ps	Corresponds to the deepest engraved trenches
Laser Power Range (Engraving)	1 to 6.97	W	Power range used to control ablation depth
Repetition Rate Range	250 kHz, 500 kHz, 1	MHz	Repetition rates used for recipe variation

Key Methodologies

The experiment relied on precise control of femtosecond laser ablation parameters on silicon substrates, followed by non-destructive THz-TDS analysis.

Substrate Preparation: Silicon wafers (3 cm x 3 cm) were used as the base material for laser engraving tests.
Femtosecond Laser Machining: A Coherent Monaco 1035 nm, 40W laser with a 257 fs pulse width was used. The beam was expanded and focused via a fused silica F-Theta lens to achieve an 8.5 µm theoretical spot size.
Parameter Variation: 81 unique combinations of engraving parameters were tested to achieve varying depths, including:
- Repetition Rates: 250 kHz, 500 kHz, and 1 MHz.
- Number of Lasering Cycles: Varied between 20 and 180.
- Laser Power: Varied between 1W and 6.97W.
Reference Measurement: A Keyence confocal height sensor (CL-P070) was used to measure the actual average depth of the trenches with high micrometer resolution for correlation.
THz Reading Setup: THz reflection-mode imaging (THz-TDS) was used, employing two stages for X-Y scanning of the sample.
Data Retrieval: Time-of-arrival analysis of the lowest valley in the THz signal was used to generate a height map, demonstrating a linear relationship between arrival time (ps) and engraved depth (µm).
Application Testing: Tags were successfully read when covered by packaging material and when engraved on the backside of a microelectronic die.

6CCVD Solutions & Capabilities

The research demonstrates the viability of high-precision, depth-indexed physical tags for microelectronics traceability. Diamond, with its superior thermal, mechanical, and optical properties, is the ideal material to transition this technology from silicon to high-reliability, high-performance applications. 6CCVD provides the necessary MPCVD diamond substrates and customization services to replicate and advance this research.

Requirement from Paper/Application	6CCVD Solution & Value Proposition
Applicable Materials	Optical Grade SCD & High-Quality PCD: Diamond is the ultimate tamper-proof substrate. We recommend Optical Grade SCD for high-purity applications requiring maximum THz transparency and High-Quality PCD for cost-effective, large-area scaling (up to 125 mm).
Precision Depth Control for Indexing	Custom Thickness SCD/PCD: The research utilized depths up to 260 µm. 6CCVD offers SCD and PCD plates with precise thickness control from 0.1 µm up to 500 µm, enabling the creation of complex, multi-layer subsurface tags and deep-engraved identifiers.
Scaling to Production/Large Area	Large Format PCD Wafers: We supply Polycrystalline Diamond (PCD) plates up to 125 mm in diameter, supporting the scaling of this THz-readable tagging methodology for industrial traceability and large component integration.
Surface Quality for Optimal THz/Laser Interaction	Ultra-Smooth Polishing: Achieving precise laser ablation and reliable THz reflection requires exceptional surface quality. 6CCVD guarantees surface roughness (Ra) < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ensuring minimal signal scattering and high fidelity in both engraving and reading.
Integration into Microelectronic Packages	Custom Metalization Services: For die-level integration, the tags require robust electrical contacts or bonding layers. 6CCVD offers internal metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu, tailored to specific packaging requirements (e.g., creating a Ti/Pt/Au stack).
Engineering Support	Expert Consultation: 6CCVD’s in-house PhD team can assist researchers and engineers in optimizing laser parameters for diamond substrates and selecting the appropriate material grade (SCD vs. PCD) for similar THz-readable security tag and die-level traceability projects.

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

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-023-39586-5