Compact vacuum setup for laser induced plasma etching with optical emission spectrum monitoring

Reactive ion etching and reactive ion beam etching are widely used processes in the semiconductor industry but face challenges due to their high cost, energy demands, and maintenance complexity. Femtosecond laser micromachining has emerged as a versatile and precise method for microfabrication, but it often results in suboptimal surface quality, which requires postprocessing. Laser-induced plasma etching (LIPE) presents a promising solution, achieving low surface roughness and efficient material removal rates. Here, we investigate the LIPE process by utilizing a femtosecond laser setup with optimized optical components and a custom-designed compact vacuum chamber, enabling precise control and monitoring of the reactive gas environment for plasma generation and etching. The effects of numerical aperture, working distance, and laser energy thresholds on plasma ignition and plume formation were examined. Preliminary results demonstrate plasma ignition in air and SF6 gas with laser pulse energy thresholds between 15 and 20 μJ using a 10× magnification microscope objective. The spectral analysis of the plasma generated in the SF6 gas provides insights into plasma dynamics and enables real-time process monitoring. This work establishes foundational parameters for optimizing LIPE setups and advancing precision etching applications.