High Resolution Plasma Etch

Abstract

An apparatus for fabrication of microscopic structures that uses a beam process, such as beam-induced decomposition of a precursor, to deposit a mask in a precise pattern and then a selective, plasma beam is applied, comprising the steps of first creating a protective mask upon surface portions of a substrate using a beam process such as an electron beam, focused ion beam (FIB), or laser process, and secondly etching unmasked substrate portions using a selective plasma beam etch process. Optionally, a third step comprising the removal of the protective mask may be performed with a second, materially oppositely selective plasma beam process.

1 . An apparatus for etching a sample substrate to form microscopic structures, comprising;
 a gas injection system;   a first system including a beam generating column for generating a fine beam, the gas injection system positioned to direct a gas toward the sample near the impact point of the beam to deposit a masking material in a pattern on the surface;   a second system including:
 a plasma chamber for generating ions; 
 an ion optical column for receiving ions from the plasma chamber, the ion column including one or more lenses for forming an ion beam by focusing or collimating the ions from the plasma chamber into a beam; and 
 one or more accelerating electrodes, the accelerating electrode being maintained at a voltage to provide the ions with an energy sufficient to react chemically with the unmasked surface but insufficient to sputter the surface. 
   
     
     
         2 . The apparatus of  claim 1  in which the first system comprises an electron beam system or a focused ion beam system. 
     
     
         3 . The apparatus of  claim 1  in which the first system comprises a laser system. 
     
     
         4 . The apparatus of  claim 1  in which the second system comprises an inductively coupled plasma system. 
     
     
         5 . The apparatus of  claim 1  in which the second system produces a beam having a diameter at least an order of magnitude greater than the diameter of the beam from the first system. 
     
     
         6 . The apparatus of  claim 1  in which the second system produces a beam having a diameter less than one half the substrate diameter. 
     
     
         7 . The apparatus of  claim 1  in which the second system produces a beam having a diameter less than one tenth the substrate diameter. 
     
     
         8 . The apparatus of  claim 1  in which the second system produces a beam having a current of between a few picoamps and several milliamps. 
     
     
         9 . The apparatus of  claim 1  in which the second system produces a beam having a current of between one nanoamp and a few microamps. 
     
     
         10 . The apparatus of  claim 1  in which the gas injection system comprises a source of a tungsten precursor and in which the second system comprises a source of SF 6  or XeF 2  for the plasma chamber. 
     
     
         11 . The apparatus of  claim 1  in which the second system further comprises a gas source for the plasma chamber, the gas source providing a gas that, after leaving the plasma chamber, will comprise reactive ions that will react chemically with the unmasked surface. 
     
     
         12 . The apparatus of  claim 1  in which the plasma chamber provides ions of an inert gas to the focusing column and in which the gas injection system provides an etchant precursor that is activated by the ions of the inert gas. 
     
     
         13 . The apparatus of  claim 1  in which the second system comprises differentially pumped chambers between the plasma source and the substrate to remove neutral gas molecules. 
     
     
         14 . The apparatus of  claim 1  in which the substrate is positioned outside of the plasma chamber. 
     
     
         15 . The apparatus of  claim 1  in which the one or more lenses of the ion column provides a collimate beam. 
     
     
         16 . The apparatus of  claim 1  in which the one or more lenses of the ion column provides a convergent beam. 
     
     
         17 . The apparatus of  claim 1  in which the second system provides ionized particles at the sample having an energy in the range of 10 eV and 500 eV. 
     
     
         18 . The apparatus of  claim 1  in which the second system provides a substantially uniform ion flux profile across the unmasked region of the substrate surface. 
     
     
         19 . The apparatus of  claim 1  in which the second system provides a beam that selectively etches the protective mask material more rapidly than the sample substrate material. 
     
     
         20 . The apparatus of  claim 1  in which the second system provides a collimated beam of ions, the average energy of the ions being less than 500 eV.