Method for etching a molybdenum layer suitable for photomask fabrication

Abstract

Methods for fabricating a photomask are disclosed herein. In one embodiment, a method for fabricating a photomask includes providing a filmstack having a molybdenum layer and a light-shielding layer in a processing chamber, patterning a first resist layer on the light-shielding layer, etching the light-shielding layer using the first resist layer as an etch mask, and etching the molybdenum layer using the patterned light-shielding layer and the patterned first resist layer as a composite mask.

1 . A method of fabricating a photomask, comprising:
 providing a filmstack in a processing chamber, the filmstack having a molybdenum layer, a light-shielding layer and a patterned first resist layer;   etching the light-shielding layer using the first resist layer as an etch mask, the patterned light-shielding layer and patterned first resist layer forming a composite mask;   etching the molybdenum layer using the composite mask as an etch mask; and   patterning a second resist layer on the light-shielding layer to expose the molybdenum layer, wherein at least one opening etched in the molybdenum layer remains filled with the second resist after patterning.   
     
     
         2 . The method of  claim 1 , wherein the light-shielding layer comprises is at least one of chromium or chromium oxide. 
     
     
         3 . The method of  claim 1 , wherein the molybdenum layer comprises is at least one of molybdenum, silicon nitride (SiN) doped with molybdenum (Mo) or molybdenum silicon (MoSi). 
     
     
         4 . The method of  claim 1 , wherein the step of etching the molybdenum layer comprises:
 flowing a fluorine containing gas and a chlorine containing gas into the processing chamber to form a gas mixture; and   forming a plasma from the gas mixture.   
     
     
         5 . The method of  claim 4 , wherein the step of etching the molybdenum layer further comprises:
 flowing an inert gas into the processing chamber.   
     
     
         6 . The method of  claim 4 , wherein the step of flowing the fluorine containing gas further comprises:
 flowing at least a fluorine containing hydrocarbon gases having the general formula C X H Y F Z , wherein x is an integer from 1 to 5 of carbon atoms, y is an integer from 1 to 8 of hydrogen atoms, and z is an integer from 1 to 8 of fluorine atoms.   
     
     
         7 . The method of  claim 4 , wherein the step of flowing the fluorine containing gas further comprises:
 flowing at least a hydrogen-free fluorocarbon gas having from 1 to 5 atoms of carbon and from 4 to 8 atoms of fluorine.   
     
     
         8 . The method of  claim 4 , wherein the step of flowing the chlorine containing gas further comprises:
 flowing chlorine (Cl 2 ), and at least one of carbon tetrachloride (CCl 4 ) or hydrochloric acid (HCl) into the processing chamber.   
     
     
         9 . The method of  claim 1 , wherein the step of etching the molybdenum layer comprises:
 flowing a chlorine (Cl 2 ) gas, trifluoromethane (CHF 3 ), and argon into the processing chamber to form a gas mixture; and   forming a plasma from the gas mixture.   
     
     
         10 . The method of  claim 1  further comprising:
 removing at least a portion of the composite mask. 
 
     
     
         11 . The method of  claim 1 , wherein the step of etching the molybdenum layer exposes an underlying optically transparent silicon based material. 
     
     
         12 . The method of  claim 1 , wherein the optically transparent silicon based material is quartz. 
     
     
         13 . The method of  claim 1  further comprising:
 depositing a protective layer on the first resist layer prior to etching the light-shielding layer. 
 
     
     
         14 . A method of forming a photomask from a film stack having an optically transparent silicon based material having a molybdenum layer, a light-shielding layer and a composite mask having a first photoresist layer, the method comprising:
 providing a film stack in a processing chamber, the film stack having an optically transparent silicon based material having a molybdenum layer, a light-shielding layer and a composite mask having at a first photoresist layer;   plasma etching the molybdenum layer to form a first opening exposing the optically transparent silicon based material using the composite mask;   depositing a second photoresist layer on the light-shielding layer;   patterning the second photoresist layer on a light-shielding layer, wherein the second photoresist layer fills the first opening after patterning; and   plasma etching the light-shielding layer using the second photoresist layer as an etch mask to form a second opening exposing the molybdenum layer.   
     
     
         15 . The method of  claim 14 , wherein the step of patterning the molybdenum layer further comprises:
 deposing a conformal polymer layer on the first resist layer of the composite prior to etching the light-shielding layer.   
     
     
         16 . The method of  claim 14 , wherein the molybdenum layer comprises is at least one of molybdenum, silicon nitride (SiN) doped with molybdenum (Mo) or molybdenum silicon (MoSi); wherein the light-shielding layer comprises chromium, and wherein the optically transparent silicon based material comprises quartz or glass. 
     
     
         17 . The method of  claim 14  further comprising:
 removing the first photoresist layer after patterning the molybdenum layer and before depositing the second photoresist layer. 
 
     
     
         18 . A method of forming a photomask, comprising:
 providing a film stack having a chromium layer, a molybdenum layer, a patterned first photoresist layer and a quartz material layer;   etching the chromium layer using the patterned first photoresist layer as an etch mask;   etching the molybdenum layer to expose the underlying quartz material through an opening defined through the first photoresist layer and the chromium layer;   removing the first photoresist layer in-situ a processing chamber in which at least one of the molybdenum layer or chromium layer is etched;   depositing a second photoresist layer on the chromium layer;   patterning the second photoresist layer; and   etching the chromium layer using the second photoresist layer as an etch mask to expose the molybdenum layer.