THE LASER USER
ISSUE 115 MARCH 2025 ULTRAFAST LASERS
processes for SiC using an MKS Spectra-Physics IceFyre UV picosecond laser. Further, the impact of TimeShift programmable pulse capability for pulse burst tailoring was explored for ablation scribing of 340 μm thick 4H-SiC wafers. Numerous scribes were produced using pulse configurations ranging from single pulses through 12-pulse bursts.
The overall results are displayed in Figure 4. The data clearly shows that with the same or less laser power, scribes are significantly deeper with increased pulse bursts.
Optical microscope images (Figure 5) demonstrate how the scribe quality evolves with single pulse vs. burst processing using 16 W of average power.
Figure 3. SEM images demonstrate that the quality of the inner metal foil improves with burst vs. single pulse processing.
technologies for non-contact scribing and cutting of SiC.
Figure 4. Scribe depths at 25 mm/s net speed increase dramatically with more burst pulses.
Laser-based wafer cutting often relies on “scribe and break” processing – laser surface scribing followed by a mechanical break. The scribe should be deep, narrow, and uniformly smooth along its length, resulting in low cleaving force and smooth die edges. A narrow scribe, along with a low heat-affected zone (HAZ), are also desirable to minimise material waste and allow more devices per wafer. Ultrashort pulse (USP) lasers in the ultraviolet (UV) wavelength should be well-suited for the task as they are known to process hard, brittle materials with excellent quality and precision.
Considering this, experiments were conducted to optimise cutting
The images in Figure 5 show detailed surface quality of scribes machined using single- and burst-pulse processes. All scribes were processed with 16 W and a net processing speed of 25 mm/s. The scribe depths (noted in the figure headings) show that pulse tailoring delivered a threefold increase in scribe depth.
The testing showed that UV picosecond lasers can produce very high quality scribes in SiC. Further, the benefits of TimeShift pulse bursts, for improved quality and higher feed rates were proven. This indicates picosecond burst mode processing of SiC can deliver both the throughput and quality required for cost-effective implementation in production.
Conclusion
USP lasers – with burst mode in particular – significantly enhance key processes for components used in electric vehicle production, providing unmatched combinations of precision, speed and quality. They optimise processing of thin materials like Li-ion battery foils while also enabling the efficient processing of SiC for power electronics. Enhanced features such as burst mode operation empower manufacturers to fully exploit the potential of ultrafast lasers for optimum quality and highest throughputs.
Sources
EV expansion means new prospects for silicon carbide | McKinsey
https://bit.ly/mckinsey_evexpansion
Appnote 70/71 Spectra-Phyics
https://bit.ly/spectraphysics_appnotes
Contact: Jim Bovatsek
Jim.Bovatsek@
mks.com
www.spectra-physics.com
Figure 5. Microscope images show the excellent surface quality achieved with picosecond UV processing in burst mode.
Jim Bovatsek is senior manager of applications engineering at MKS Spectra-Physics’ industrial applications laboratory in Milpitas, California.
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