Nanometer-scale ablation using focused, coherent extreme ultraviolet/soft x-ray light
Ablation of holes having diameters as small as 82 nm and having clean walls was obtained in a poly(methyl methacrylate) on a silicon substrate by focusing pulses from a Ne-like Ar, 46.9 nm wavelength, capillary-discharge laser using a freestanding Fresnel zone plate diffracting into third order is described. Spectroscopic analysis of light from the ablation has also been performed. These results demonstrate the use of focused coherent EUV/SXR light for the direct nanoscale patterning of materials.
1. A method for nanometer-scale ablation of material from the surface of a sample, comprising the steps of:
directing pulsed coherent light having a chosen wavelength in the range between 1 nm and 100 nm and a chosen intensity onto a Fresnel zone plate disposed in a vacuum chamber below atmospheric pressure, such that the light is focused; and
positioning the sample closer to the Fresnel zone plate than the third-order focal plane thereof in the vacuum chamber such that the light is focused on the surface of the sample, whereby material is removed from the surface of the sample.
2. The method described in claim 1 , wherein the source of coherent light comprises an extreme ultraviolet/soft x-ray laser.
3. The method as described in claim 2 , wherein the extreme ultraviolet/soft x-ray laser produces light pulses having picosecond or femtosecond duration.
4. The method described in claim 2 , wherein the source of laser radiation comprises a capillary discharge x-ray laser, and wherein the chosen wavelength comprises 46.9 nm from the 26.4 eV transition of neon-like Ar ions.
5. The method described in claim 4 , wherein the chosen intensity of the source of pulsed light is controlled by passing the pulsed light through atoms having a chosen pressure and an ionization potential less than 26.4 eV.
6. The method described in claim 1 , wherein the chosen wavelength has small absorption depth in the material in the surface of the sample.
7. The method described in claim 1 , further comprising the step of adding reactive species to the vacuum chamber such that the ablation is chemically assisted.
8. The method described in claim 1 , further comprising the step of spectroscopically analyzing light from the ablation.
9. The method described in claim 1 , further comprising the step of mass analyzing species emerging from the surface of the sample as a result of the ablation.
10. The method as described in claim 1 , further comprising the step of adjusting the chosen intensity of the pulsed coherent light such that lower intensity concentric rings surrounding a central intensity peak of said pulsed coherent light resulting from focusing by the Fresnel zone plate are incapable of ablating the sample.