Method for cleaning diffraction gratings

Abstract

A method of cleaning a diffraction grating preferably includes exposing the grating surface to an aqueous base to remove an organic photoresist mask thereon; rinsing the grating surface with de-ionized water; oxidizing acid solution (such as Nanostrip™ or Nanostrip™ 2X) to remove metallic contaminants and residue organic compounds; rinsing the grating surface with de-ionized water; exposing the grating surface to an oxygen plasma ashing process using reactive oxygen species to oxidize and remove fluorinated hydrocarbon residue; exposing the grating surface again to an oxidizing acid solution to remove metallic contaminants and residue organic compounds; and rinsing the grating surface with de-ionized water.

1 . A method of cleaning a diffraction grating comprising:
 exposing the grating surface to an oxidizing acid solution to remove metallic contaminants and residue organic compounds;   rinsing the grating surface with de-ionized water;   exposing the grating surface to an oxygen plasma ashing process using reactive oxygen species to oxidize and remove fluorinated hydrocarbon residue;   exposing the grating surface again to an oxidizing acid solution to remove metallic contaminants and residue organic compounds; and   rinsing the grating surface with de-ionized water.   
   
   
       2 . The method of  claim 1 , further comprising:
 prior to performing the first exposure of the grating surface to an oxidizing acid solution, performing the steps of: exposing a grating surface to an aqueous base to remove an organic photoresist mask thereon, and rinsing the grating surface with de-ionized water.   
   
   
       3 . The method of  claim 2 ,
 wherein the aqueous base is at room temperature.   
   
   
       4 . The method of  claim 2 ,
 wherein during the exposure of the grating surface to the aqueous base, the aqueous base is agitated for about 5 minutes.   
   
   
       5 . The method of  claim 2 ,
 wherein the aqueous base is selected from the group consisting of 5% NaOH solution and RS6 solution.   
   
   
       6 . The method of  claim 1 , further comprising:
 prior to exposing the grating surface to the oxygen plasma ashing process, performing the steps of: exposing the grating surface to a weak tetrymethyl ammonium hydroxide solution to neutralize any remaining acidic residue on the grating surface; and rinsing the grating surface with de-ionized water.   
   
   
       7 . The method of  claim 1 ,
 wherein during at least one of the two exposures of the grating surface to the oxidizing acid solution, the oxidizing acid solution is agitated for about 60 minutes.   
   
   
       8 . The method of  claim 1 ,
 wherein the oxidizing acid solution used in at least one of the two exposures of the grating surface to oxidizing acid solution, is an oxidizing sulfuric acid solution.   
   
   
       9 . The method of  claim 8 ,
 wherein the oxidizing sulfuric acid solution is selected from the group consisting of Nanostrip™ solution and Nanostrip™ 2X solution.   
   
   
       10 . The method of  claim 8 ,
 wherein the oxidizing sulfuric acid solution is self heated to 50-70 C. by periodic addition of water.   
   
   
       11 . The method of  claim 8 ,
 wherein the oxidizing sulfuric acid solution is at room temperature.   
   
   
       12 . The method of  claim 1 ,
 wherein the oxidizing acid solution used is at least one of the two exposures of the grating surface to oxidizing acid solution, is a point-of-use oxidizing acid solution.   
   
   
       13 . The method of  claim 12 ,
 wherein the point-of-use oxidizing acid solution is Piranha solution.   
   
   
       14 . The method of  claim 1 ,
 wherein the reactive oxygen species is generated by RF excitation of an oxygen flow in a vacuum chamber.   
   
   
       15 . The method of  claim 1 ,
 wherein the diffraction grating is a multilayer dielectric (MLD) diffraction grating comprising alternating layers with a grating etched into a top layer.