Fabrication of high-aspect-ratio all-silicon grooves using femtosecond laser irradiation and wet etching

A simple method of fabricating high-aspect-ratio all-silicon grooves using lens-focused femtosecond laser irradiation and wet etching is demonstrated. Firstly femtosecond laser is focused on silicon surface to induce structural changes inside silicon. Then laser-induced structural change regions are selectively removed by hydrofluoric acid (HF) etching to form high-aspect-ratio silicon grooves. Finally, optical microscope and a scanning electronic microscope are employed to characterize the morphology of the grooves, respectively. The dependences of the grooves aspect ratios on the laser irradiation parameters, such as the laser average power, scanning velocity and the lens numerical aperture, are investigated. By optimizing the laser irradiation parameters, grooves with depth of 291 μm and aspect ratio of 25.3 are produced. Compared with microscope objective lens, lens owns longer working distance, which can keep it from being polluted by the debris erupting from specimen during laser irradiation. Besides, lens has the advantages of low cost and large aperture.