High-precision machining of silicon surface with intense femtosecond extreme ultraviolet pulses

Femtosecond laser direct writing (LDW), which uses ultraviolet, visible or infrared lasers, is a maskless subtractive manufacturing approach that is widely used for precision surface processing. This is because of the strong spatial confinement of laser energy and minimal collateral damage. Here, we present a conceptual scheme for the high-precision machining of semiconductor materials using LDW with sub-micron-focused extreme ultraviolet (EUV) laser pulses. A proof-of-concept study was conducted at the SACLA free-electron laser facility, which confirmed the feasibility of the machining process by creating reproducible craters with similar geometries in a single EUV femtosecond laser shot, with fixed pulse parameters. Dedicated computer simulations reproduced the experimental trends and provided insight into the ablation mechanism. These results establish the feasibility of controlled and reproducible semiconductor surface machining at micrometer and sub-micrometer length scales, and with further development, femtosecond EUV LDW could provide a route to maskless, high-precision patterning and machining of semiconductors and other technologically relevant materials.