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Laser-Patterned Alumina Mask and Mask-Less Dry Etch of Si for Light Trapping with Photonic Crystal Structures
Jovan Maksimovic1, Haoran Mu1, Daniel Smith1
1Optical Sciences Centre and Australian Research Council (ARC) Industrial Transformation Training Centre in Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn, VIC 3122, Australia.
This study demonstrates using ultra-short laser pulses to create precise holes in alumina etch masks, enabling efficient photonic crystal fabrication for high-efficiency solar cells. Mask-less silicon patterning is proposed for advanced solar cell manufacturing.
Area of Science:
- Materials Science
- Nanotechnology
- Optics
Background:
- Dielectric etch masks are crucial for fabricating photonic crystal (PhC) light-trapping patterns.
- Achieving above-Lambertian performance in high-efficiency solar cells requires advanced light-trapping structures.
- Fabrication of these structures often involves precise patterning of both masks and underlying semiconductor materials.
Purpose of the Study:
- To investigate the laser ablation of thin alumina (Al2O3) dielectric masks using ultra-short laser pulses.
- To understand the effects of laser ablation on sub-surface silicon modifications.
- To propose a mask-less patterning technique for silicon using femtosecond laser direct writing for dry plasma etching.
Main Methods:
- Utilizing ultra-short (230 fs) laser pulses at a 515 nm wavelength, tightly focused to 700 nm spots.
- Opening precise holes (0.4-1 μm) in 20-50 nm thick alumina etch masks.
- Employing plasma etching, numerical modeling, and minority carrier lifetime measurements to analyze laser-induced modifications.
Main Results:
- Successfully demonstrated the controlled ablation of alumina etch masks to create features for PhC fabrication.
- Revealed the conditions for laser ablation and characterized sub-surface silicon modifications.
- Established the feasibility of using femtosecond laser direct writing for mask-less silicon patterning.
Conclusions:
- Ultra-short laser pulses offer a viable method for precise fabrication of dielectric masks for solar cell light-trapping.
- Understanding sub-surface modifications is key to optimizing laser-based fabrication processes.
- Femtosecond laser direct writing presents a promising mask-less approach for advanced silicon solar cell manufacturing.
