Controlled strong excitation of silicon as a step towards processing materials at sub-nanometer precision

Abstract

Interaction of a solid material with focused, intense pulses of high-energy photons or other particles (such as electrons and ions) creates a strong electronic excitation state within an ultra-short time and on ultra-small spatial scales. This offers the possibility to control the response of a material on a spatial scale less than a nanometer—crucial for the next generation of nano-devices. Here we create craters on the surface of a silicon substrate by focusing single femtosecond extreme ultraviolet pulse from the SACLA free-electron laser. We investigate the resulting surface modification in the vicinity of damage thresholds, establishing a connection to microscopic theoretical approaches, and, with their help, illustrating physical mechanisms for damage creation. The cooling during ablation by means of rapid electron and energy transport can suppress undesired hydrodynamical motions, allowing the silicon material to be directly processed with a precision reaching the observable limitation of an atomic force microscope.

Short pulse soft x-ray laser ablation research

“…Figures 1(a) and 1(b) show atomic force microscope (AFM) images of damage structures on the Si surface formed by femtosecond soft x-ray laser pulse irradiations [9]. In the case of the 13.5 nm wavelength irradiation, the first changes of silicon surface appeared around the irradiation fluence of 150-250 mJ/cm 2 .…”

Study on Irradiation Effects by Femtosecond-pulsed Extreme Ultraviolet in Resist Materials

“…The SXFEL shots were attenuated to suitable intensity by using Zr filters having various thicknesses (0.1, 0.2, 0.5, 1.0, and 2.0 µm thickness or these combination). Details of the system have been reported elsewhere [22][23][24].…”

Density functional tight binding approach utilized to study X-ray-induced transitions in solid materials

“…The simulation tool, XTANT can provide transient thermodynamic 32 , 33 and optical parameters 10 , 34 as well as atomic trajectories within irradiated samples. Its reliability has been successfully validated against a number of experimental studies 10 , 34 , 35 . Notably, in Ref.…”