Method for nanomachining high aspect ratio structures

Abstract

A nanomachining method for producing high-aspect ratio precise nanostructures. The method begins by irradiating a wafer with an energetic charged-particle beam. Next, a layer of patterning material is deposited on one side of the wafer and a layer of etch stop or metal plating base is coated on the other side of the wafer. A desired pattern is generated in the patterning material on the top surface of the irradiated wafer using conventional electron-beam lithography techniques. Lastly, the wafer is placed in an appropriate chemical solution that produces a directional etch of the wafer only in the area from which the resist has been removed by the patterning process. The high mechanical strength of the wafer materials compared to the organic resists used in conventional lithography techniques with allows the transfer of the precise patterns into structures with aspect ratios much larger than those previously achievable.

1 . A method for nanomachining a precise structure by particle-track-guided-etching comprising: 
 irradiating the surface of a wafer with a charged particle beam of suitable energy to form particle tracks capable of discrete etching guided by said particle tracks in said wafer;    depositing a layer of resist material over said irradiated surface of said wafer;    selectively removing portions of said layer of resist material to generate an etching pattern on irradiated surface of said wafer; and    etching said wafer according to said etching pattern;    wherein said etching is guided by said particle tracks.    
   
   
       2 . A method as recited in  claim 1 , wherein said charged particle beam is directed to said surface of said wafer with a predetermined collimation at a desired direction.  
   
   
       3 . A method as recited in  claim 1 , wherein said etched wafer comprises a final nanomachined structure.  
   
   
       4 . A method as recited in  claim 1 , wherein said etched wafer comprises a negative of a final nanomachined structure.  
   
   
       5 . A method as recited in  claim 4 , wherein said final nanomachined structure is formed by electroforming using said negative.  
   
   
       6 . A method as recited in  claim 5 , wherein said electroforming comprises electroplating.  
   
   
       7 . A method as recited in  claim 1 , wherein said wafer comprises a semiconductor material.  
   
   
       8 . A method as recited in  claim 1 , wherein said wafer comprises an insulator material.  
   
   
       9 . A method as recited in  claim 1 , wherein said charged particle beam is produced by removing some or all electrons from neutral atoms by an accelerator or comprises alpha particles emitted from a radioactive source.  
   
   
       10 . A method as recited in  claim 1 , wherein said irradiating of said wafer comprises placing said wafer in said particle beam in a desired direction with respect to the wafer surface.  
   
   
       11 . A method as recited in  claim 10 , wherein said desired direction is perpendicular to the wafer surface.  
   
   
       12 . A method as recited in  claim 10 , wherein said desired direction has an angle of less than ninety degrees with respect to the plane of the wafer surface.  
   
   
       13 . A method as recited in  claim 1 , wherein said particle tracks are substantially parallel to each other.  
   
   
       14 . A method as recited in  claim 1 , wherein said particle tracks are oriented to intercept at a substantially small point if extended.  
   
   
       15 . A method as recited in  claim 1 , wherein said step of depositing a layer of resist material over said irradiated surface of said wafer comprises deposition of a single or multilevel resist layers using spinning or vacuum coating.  
   
   
       16 . A method as recited in  claim 1 , wherein said layer of resist material is suitable for producing said etching pattern and is stable during said etching step.  
   
   
       17 . A method as recited in  claim 1 , wherein said step of selectively removing portions of said layer of resist material to generate an etching pattern on irradiated surface of said wafer comprises writing a pattern on said layer of resist material using an electron beam writing machine and subsequent processing to produce the desired pattern.  
   
   
       18 . A method as recited in  claim 1 , wherein said layer of resist material comprises a single layer of organic resist material.  
   
   
       19 . A method as recited in  claim 1 , wherein said layer of resist material comprises electron beam resist.  
   
   
       20 . A method as recited in  claim 1 , wherein said layer of resist material comprises a multilevel resist structure established for improving the aspect ratio of electron beam lithography.  
   
   
       21 . A method as recited in  claim 17 , wherein said subsequent processing comprises dissolution of selective portions of said layer of resist material using a solvent.  
   
   
       22 . A method as recited in  claim 17:   wherein said layer of resist material comprises sublayers of dissimilar materials; and    wherein said subsequent processing comprises dissolution of selective portions of said layer of resist material using a solvent and plasma based etching.    
   
   
       23 . A method as recited in  claim 1:   wherein said etching of said wafer comprises immersing said wafer in an etching solution;    wherein said etching pattern is partially or completely transferred to the wafer;    wherein said etched portion of said wafer has an aspect ratio substantially greater than one; and    wherein said aspect ratio comprises the ratio of the depth of the etched particle track to the width of the smallest etched portion of said etching pattern.    
   
   
       24 . A method as recited in  claim 23 , wherein said etched wafer comprises a final nanomachined structure.  
   
   
       25 . A method as recited in  claim 23 , wherein said etched wafer comprises a negative of a final nanomachined structure.  
   
   
       26 . A method as recited in  claim 25 , wherein said final nanomachined structure is formed by electroforming using said negative.  
   
   
       27 . A method as recited in  claim 26 , wherein said electroforming comprises electroplating.  
   
   
       28 - 80 . (canceled)