High aspect ratio 3-d flash memory device

Abstract

Methods of selectively etching tungsten from the surface of a patterned substrate are described. The etch electrically separates vertically arranged tungsten slabs from one another as needed, for example, in the manufacture of vertical flash memory devices. The tungsten etch may selectively remove tungsten relative to films such as silicon, polysilicon, silicon oxide, aluminum oxide, titanium nitride and silicon nitride. The methods include exposing electrically-shorted tungsten slabs to remotely-excited fluorine formed in a capacitively-excited chamber plasma region. The methods then include exposing the tungsten slabs to remotely-excited fluorine formed in an inductively-excited remote plasma system. A low electron temperature is maintained in the substrate processing region during each operation to achieve high etch selectivity.

1 . A 3-D flash memory device comprising:
 a plurality of electrically-isolated tungsten slabs arranged in two adjacent vertical columns, wherein the plurality of electrically-isolated tungsten slabs comprise at least fifty tungsten slabs in the two adjacent vertical columns;   a plurality of dielectric slabs interleaved with the plurality of electrically-isolated tungsten slabs, wherein at least fifty of the plurality of electrically-isolated tungsten slabs are recessed between 1 nm and 7 nm laterally relative to the plurality of dielectric slabs.   
     
     
         2 . The 3-D flash memory device of  claim 1  wherein a height of the two adjacent vertical columns is greater than a gap between the two adjacent vertical columns by a factor of at least ten. 
     
     
         3 . The 3-D flash memory device of  claim 1  wherein the at least fifty of the plurality of electrically-isolated tungsten slabs are recessed within 1 nm of an average recess of the at least fifty of the plurality of electrically-isolated tungsten slabs. 
     
     
         4 . The 3-D flash memory device of  claim 1  wherein each of the at least fifty of the plurality of electrically-isolated tungsten slabs are electrically-isolated from every other of the at least fifty of the plurality of electrically-isolated tungsten slabs. 
     
     
         5 . The 3-D flash memory device of  claim 1  wherein the plurality of electrically-shorted tungsten slabs consist of tungsten and a barrier layer. 
     
     
         6 . The 3-D flash memory device of  claim 1  wherein a trench is disposed between the two adjacent vertical columns. 
     
     
         7 . The 3-D flash memory device of  claim 6  wherein a depth of the trench is greater than one micron. 
     
     
         8 . The 3-D flash memory device of  claim 1  wherein each of the two adjacent vertical columns comprise at least fifty tungsten slabs. 
     
     
         9 . The 3-D flash memory device of  claim 1  wherein the 3-D flash memory device is formed by:
 initially forming a plurality of electrically-shorted tungsten slabs, 
 isotropically etching the plurality of electrically-shorted tungsten slabs, wherein the isotropically etching leaves a tungsten residue at the top of the two adjacent vertical columns, and 
 anisotropically etching additional tungsten material, wherein the anisotropically etching removes the tungsten residue from the top of the two adjacent vertical columns. 
 
     
     
         10 . The 3-D flash memory device of  claim 9  wherein isotropically etching the plurality of electrically-shorted tungsten slabs in combination with anisotropically etching the additional tungsten material electrically isolates the plurality of electrically-shorted tungsten slabs from one another to form the plurality of electrically-isolated tungsten slabs.