Nanometer-scale ablation using focused, coherent extreme ultraviolet/soft x-ray light

Abstract

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 . Apparatus for nanometer-scale ablation of material from the surface of a sample, comprising in combination: 
 a chamber capable of being evacuated;    pump means for evacuating said chamber to a chosen pressure;    a source of pulsed coherent light having a chosen wavelength in the range between 1 nm and 100 nm, and a chosen fluence, wherein the pulsed light is introduced into said chamber;    a Fresnel zone plate disposed within said chamber for receiving the chosen wavelength of light from said source of light, and for focusing the light; and    means for positioning said sample in the region of the focused light within said chamber such that the focused light is incident on the surface of said sample, whereby material is removed from the surface of said sample.    
     
     
         2 . The apparatus described in  claim 1 , wherein said source of pulsed coherent radiation comprises an extreme ultraviolet/soft x-ray laser.  
     
     
         3 . The apparatus described in  claim 2 , wherein said extreme ultraviolet/soft x-ray laser produces light pulses having picosecond or femtosecond duration.  
     
     
         4 . The apparatus described in  claim 2 , wherein said extreme ultraviolet/soft x-ray laser comprises a capillary discharge x-ray laser, and wherein the chosen wavelength comprises 46.9 nm from the 22.4 eV transition of neon-like Ar ions.  
     
     
         5 . The apparatus described in  claim 4 , wherein the chosen fluence of said source of pulsed laser radiation is controlled by passing the pulsed laser radiation through atoms having a chosen pressure and having an ionization potential less than 26.4 eV.  
     
     
         6 . The apparatus described in  claim 1 , wherein the chosen wavelength has small absorption depth in the material in the surface of said sample.  
     
     
         7 . The apparatus described in  claim 1 , wherein at least one reactive gas is added to said chamber at a chosen pressure such that the ablation is chemically assisted.  
     
     
         8 . The apparatus described in  claim 1 , wherein said sample is located in the vicinity of the third-order focal plane of said Fresnel zone plate.  
     
     
         9 . The apparatus described in  claim 8 , wherein said sample is located at closer to said Fresnel zone plate than the third-order focal plane thereof.  
     
     
         10 . The apparatus described in  claim 1 , further comprising spectroscopic means for analyzing light from the ablation.  
     
     
         11 . The apparatus described in  claim 1 , further comprising mass spectroscopic means for analyzing species emerging from the surface of said sample as a result of said ablation.  
     
     
         12 . 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 in the region of the focused light in the vacuum chamber such that the focused light is incident on the surface of the sample, whereby material is removed from the surface of the sample.    
     
     
         13 . The method described in  claim 12 , wherein the source of coherent light comprises an extreme ultraviolet/soft x-ray laser.  
     
     
         14 . The method as described in  claim 13 , wherein the extreme ultraviolet/soft x-ray laser produces light pulses having picosecond or femtosecond duration.  
     
     
         15 . The method described in  claim 13 , 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.  
     
     
         16 . The method described in  claim 15 , wherein the chosen fluence 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.  
     
     
         17 . The method described in  claim 12 , wherein the chosen wavelength has small absorption depth in the material in the surface of the sample.  
     
     
         18 . The method described in  claim 12 , further comprising the step of adding reactive species to the vacuum chamber such that the ablation is chemically assisted.  
     
     
         19 . The method described in  claim 12 , wherein the sample is positioned in the vicinity of the third-order focal plane of the Fresnel zone plate.  
     
     
         20 . The method described in  claim 19 , wherein the sample is positioned at closer to the Fresnel zone plate than the third-order focal plane thereof.  
     
     
         21 . The method described in  claim 12 , further comprising the step of spectroscopically analyzing light from the ablation.  
     
     
         22 . The method described in  claim 12 , further comprising the step of mass analyzing species emerging from the surface of the sample as a result of the ablation.