Terahertz-readable laser engraved marks as a novel solution for product traceability
At a Glance
Section titled âAt a Glanceâ| 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 |
Executive Summary
Section titled âExecutive SummaryâThis research proposes a novel, highly secure method for product traceability using Terahertz (THz)-readable, laser-engraved physical tags, addressing limitations of current anti-counterfeiting solutions (RFIDs, barcodes, PUFs).
- Core Value Proposition: Creation of unique, unclonable, and immutable physical identifiers using rapid, inexpensive femtosecond laser machining, readable non-destructively via far-field THz Time-Domain Spectroscopy (THz-TDS).
- Depth Encoding Validation: A strong linear correlation was established between the physical depth of the laser-engraved mark (controllably set by laser parameters) and the measured THz signal time-of-arrival.
- Resolution and Sensitivity: The method achieved a vertical height measurement resolution of 50 ”m or better, confirming its ability to encode information based on depth variations.
- High-Density Marking: Lateral resolution limitations of far-field THz were mitigated by analyzing multiple reflection valleys within a single THz spot, successfully resolving stripe patterns with feature separations down to 300 ”m.
- Practical Feasibility: The technique was validated for critical applications, demonstrating successful reading of identifiers embedded on the backside of a silicon die and through typical packaging materials.
- Security Advantage: The tags are inherently unclonable due to the complex, non-linear relationship between the vast combination of laser parameters and the resulting physical tag structure.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Laser Type | Femtosecond | N/A | Coherent Monaco 1035 nm 40W system |
| Laser Wavelength | 1035 | nm | Operating wavelength |
| Pulse Width | 257 | fs | Ultrashort pulse duration |
| Max Laser Power | 40 | W | System capability |
| Theoretical Spot Size | 8.5 | ”m | F-Theta lens configuration (70 mm focal length) |
| Engraving Depth Range | 23 to 260 | ”m | Range achieved in silicon trenches (controlled by cycles/power) |
| Laser Repetition Rates (Tested) | 250, 500, 1 | kHz | Parameters used for trench creation |
| THz Reading Method | Time-of-Arrival | N/A | Used to generate height map in reflection mode |
| THz Vertical Resolution | 50 or better | ”m | Resolution for height measurement |
| High-Density Feature Resolution | 300 | ”m | Smallest feature separation resolved using multi-valley THz analysis |
| Sample Material | Silicon | N/A | Wafer samples and die back sides tested |
Key Methodologies
Section titled âKey Methodologiesâ- Tag Creation (Laser Machining): Physical tags were created using a femtosecond laser system (1035 nm, 257 fs pulse width). Tags were formed as trenches or patterns on silicon wafers or the backside of silicon dies.
- Parameter Control: Tags were encoded by varying three primary laser parameters: repetition rate (250 kHz to 1 MHz), number of lasering cycles (20 to 180), and laser power (1W to 6.97W). These variations produced trenches with distinct, controllable average depths.
- Ground Truth Measurement: A confocal height sensor was used to generate a high-resolution height map of the laser-engraved surface, providing the precise average depth (ground truth) for correlation studies.
- Non-Destructive Reading (THz-TDS): Far-field THz Time-Domain Spectroscopy (THz-TDS) in reflection mode was used to scan the tags. The sample was moved using XY stages beneath the THz transmitter/detector setup.
- Depth Retrieval via Time-of-Arrival: The depth of the mark was determined by identifying the time stamp of the lowest valley in the reflected THz signal. Longer arrival times correspond to lower (deeper) surface areas.
- Height Map Leveling: Post-imaging analysis included leveling the raw time-of-arrival data to correct for any sample tilting, ensuring accurate depth measurement across the scanned area.
- High-Information Density Capture: To overcome the low lateral resolution of far-field THz, the system analyzed multiple major valleys in the THz signal (resulting from reflections off different height levels within the wide THz beam spot), allowing a single pixel to capture multiple height values simultaneously.
- Subsurface Validation: Experiments confirmed the methodâs robustness by successfully reading tags embedded on the backside of a silicon die and through layers of packaging material.
Commercial Applications
Section titled âCommercial ApplicationsâThe proposed THz-readable laser-engraved tags are suitable for applications requiring high security, immutability, and passive reading capabilities, particularly in environments where traditional electronic tags fail or are easily compromised.
- Micro-electronics and Semiconductor Traceability:
- Die-level identification and provenance tracking.
- Reading identifiers embedded on the backside of silicon dies or through chip packaging without requiring device power-up.
- High-Security Component Marking:
- Secure identification of critical components in aerospace, defense, and high-reliability industrial machinery.
- Ensuring component integrity against tampering, as any attempt to mutate the physical tag causes destruction of the identifier.
- Pharmaceutical and Medical Device Anti-Counterfeiting:
- Non-destructive verification of product authenticity, potentially reading through non-metallic blister packs or bottles.
- Universal Product Traceability:
- Serving as a standardized, inexpensive, and unclonable alternative to existing traceability methods (RFIDs, barcodes) across diverse manufacturing sectors.