Particulate nanosorting stack

Abstract

Methods and devices for isolating and sorting nanoparticles are disclosed herein. Nanopores of a desired size can be formed in silicon dioxide membranes and used as filters to separate nanoparticles. Devices are also provided herein for sorting nanoparticles with multiple filters having various sized nanopores.

1 . A method for manufacturing a nanopore, said method comprising:
 providing a silicon substrate having a top side and a bottom side;   forming a first nanopillar on the substrate;   oxidizing the nanopillar to form a SiO 2  layer around a silicon core;   removing a portion of the nanopillar from the substrate to expose the silicon core;   selectively removing the silicon core by etching to form a pore in the substrate.   
     
     
         2 . The method of  claim 1 , wherein selectively removing the silicon core comprises:
 providing an oxide layer on the bottom side of the substrate;   etching the oxide layer on the bottom side directly below the first nanopillar to expose the silicon substrate; and   etching the exposed silicon substrate, thereby removing the core and forming a nanopore through the substrate.   
     
     
         3 . The method of  claim 1 , further comprising forming a second nanopillar on the substrate. 
     
     
         4 . The method of  claim 3 , wherein the first nanopillar is about 50 nm from the second nanopillar. 
     
     
         5 . The method of  claim 3 , wherein the first nanopillar and the second nanopillar are about 1 to 100 nm in diameter and about 200 nm to 1 micron in height. 
     
     
         6 . The method of  claim 1 , further comprising forming a plurality of additional nanopillars on the substrate, wherein the additional nanopillars form an array of nanopillars of the same diameter. 
     
     
         7 . The method of  claim 6 , further comprising:
 oxidizing the array of nanopillars to form a SiO 2  layer around a silicon core for each of the additional plurality of nanopillars; and   selectively removing the silicon core of each of the additional plurality of nanopillars to form a corresponding array of nanopores comprising a same diameter.   
     
     
         8 . The method of  claim 1 , further comprising providing a film layer over the SiO 2  layer of the nanopillar subsequent to oxidizing the nanopillar and prior to selectively removing the silicon core. 
     
     
         9 . The method of  claim 1 , wherein oxidizing the nanopillar to form the SiO 2  layer around the silicon core comprises forming a cylinder comprising a concentric silicon core and SiO 2  layer. 
     
     
         10 . The method of  claim 1 , further comprising removing any remaining portion of the nanopillar from the substrate. 
     
     
         11 . The method of  claim 1 , further comprising:
 providing an oxide layer on the bottom side of the substrate; and   etching the oxide layer on the bottom side to form a cavity in fluid communication with the nanopore in the substrate.   
     
     
         12 . The method of  claim 1 , wherein oxidizing the nanopillar comprises a thermal oxidation process. 
     
     
         13 . A method of fabricating an array of nanopores in a substrate, the method comprising:
 forming an array of nanopillars on a first surface of the substrate, wherein each of the nanopillars comprises an oxide outer layer over an un-oxidized inner core;   removing at least a portion of each of the nanopillars from the first surface to expose the un-oxidized inner core; and   selectively etching the un-oxidized inner core of each of the nanopillars to form the array of nanopores in the substrate.   
     
     
         14 . The method of  claim 13 , wherein forming the array of nanopillars comprises:
 providing a patterned hard mask over the first surface of the substrate; and   subsequently etching the substrate using the patterned hard mask to provide an array of un-oxidized nanopillars.   
     
     
         15 . The method of  claim 14 , further comprising oxidizing the un-oxidized array of nanopillars to form the oxide outer layer over the un-oxidized inner core. 
     
     
         16 . The method of  claim 13 , wherein selectively etching the un-oxidized inner core comprises etching through an entire thickness of the substrate to provide an array of nanopores extending through the entire thickness of substrate. 
     
     
         17 . The method of  claim 13 , wherein the substrate and the un-oxidized inner core comprise silicon, and wherein the oxidized outer layer comprises silicon dioxide. 
     
     
         18 . The method of  claim 13 , further comprising etching the substrate to form a plurality of cavities on a second opposing surface of the substrate, wherein each of the plurality of cavities is in fluid communication with a corresponding nanopore of the array of nanopores. 
     
     
         19 . The method of  claim 13 , further comprising:
 forming an oxide layer over a second opposing surface of the substrate;   forming an array of holes in the oxide layer, each of the holes in a position corresponding to the position of a nanopillar in the array of nanopillars on the first surface; and   etching the substrate through the array of holes to form an array of cavities.   
     
     
         20 . The method of  claim 13 , wherein each nanopore of the array of nanopores is 100 nm to 1 micron from an adjacent nanopore from center to center.