Femtosecond laser micromachining of submicron features

The summary form is given. Femtosecond laser micromachining of variety of materials has been pursued by several research groups for possible improvements due to the extremely short pulse width of the laser. We have used a Spectra Physics 2 mJ laser to explore the micromachining at submicron dimensions. The laser wavelength was 800 nm and was frequency doubled using a LBO crystal. An almost gaussian beam was obtained when the 400 nm wavelength light beam was spatially filtered using a pair of lens and a pinhole. The beam was focused using a microscope objective of 0.85 numerical aperture. The laser beam was scanned on a silicon wafer that was placed on a computer controlled x-y stage. The experiments were conducted in atmospheric air. The laser micromachined wafer was examined using an atomic force microscope (AFM). The laser marked line widths of 390 nm and depth of 200 nm were achieved with optimization of focus position, laser power and scan speed. AFM surface scan of a micromachined line on <100> silicon wafer is viewed. The results of laser beam shape, power, scan speed on micromachined line width; depth, rim formation and debris generation will be discussed. Spectroscopic measurements of the plasma generated during laser ablation process were performed. The achievement of submicron features allows the fabrication of various types of MEMS and optoelectronic devices for sensor and other applications using direct laser writing process.