Patterning scheme to improve euv resist and hard mask selectivity

Abstract

Methods and film stacks for extreme ultraviolet (EUV) lithography are described. The film stack comprises a substrate with a hard mask, bottom layer, middle layer and photoresist. Etching of the photoresist is highly selective to the middle layer and a modification of the middle layer allows for a highly selective etch relative to the bottom layer.

What is claimed is: 
     
         1 . A film stack for EUV patterning, the film stack comprising:
 a low-k dielectric;   a hard mask on the low-k dielectric, the hard mask comprising one or more of titanium nitride (TiN) or tungsten carbide (WC) and having a thickness less than or equal to about 200 Å;   an optional layer comprising silicon oxide having a thickness less than or equal to about 200 Å on the hard mask;   a bottom layer on the optional layer or the hard mask, the bottom layer comprising diamond-like carbon and having a thickness less than or equal to about 300 Å;   a middle layer on the bottom layer, the middle layer having a thickness less than or equal to about 200 Å, the middle layer comprising one or more of a bottom anti-reflective coating (BARC), dielectric anti-reflective coating (DARC), a doped silicon, or doped boron; and   a patterned photoresist on the middle layer, the patterned photoresist comprising an organic resist having a thickness less than or equal to about 280 Å or a metal oxide photoresist with a thickness less than or equal to about 130 Å.   
     
     
         2 . The film stack of  claim 1 , wherein the photoresist comprises an organic resist having a thickness less than or equal to about 280 Å. 
     
     
         3 . The film stack of  claim 1 , wherein the photoresist comprises a metal oxide photoresist with a thickness less than or equal to about 130 Å. 
     
     
         4 . The film stack of  claim 1 , wherein the diamond-like carbon has a density greater than 1.8 g/cc, a modulus greater than 150 GPa, and a stress less than −500 MPa. 
     
     
         5 . The film stack of  claim 1 , wherein the diamond-like carbon has an sp3 carbon content in a range of from 50 percent to 90 percent. 
     
     
         6 . The film stack of  claim 1 , wherein the low-k dielectric comprises SiCOH. 
     
     
         7 . The film stack of  claim 1 , wherein the optional layer is present. 
     
     
         8 . The film stack of  claim 1 , wherein the middle layer has a thickness of less than or equal to above 160 Å. 
     
     
         9 . The film stack of  claim 1 , wherein the doped silicon comprises phosphorus doped silicon. 
     
     
         10 . The film stack of  claim 1 , wherein the middle layer consists essentially of amorphous silicon. 
     
     
         11 . The film stack of  claim 1 , further comprising a modified patterned middle layer. 
     
     
         12 . The film stack of  claim 11 , wherein the modified patterned middle layer comprises silicon oxide. 
     
     
         13 . A film stack for EUV patterning, the film stack comprising:
 a low-k dielectric;   a hard mask on the low-k dielectric, the hard mask comprising one or more of titanium nitride (TiN) or tungsten carbide (WC) and having a thickness less than or equal to about 200 Å;   an optional layer comprising silicon oxide having a thickness less than or equal to about 200 Å on the hard mask;   a bottom layer on the optional layer or the hard mask, the bottom layer comprising diamond-like carbon and having a thickness less than or equal to about 300 Å;   a modified patterned middle layer on the bottom layer, the modified middle layer comprising silicon oxide; and   a patterned photoresist on the modified middle layer, the patterned photoresist comprising an organic resist having a thickness less than or equal to about 280 Å or a metal oxide photoresist with a thickness less than or equal to about 130 Å.   
     
     
         14 . The film stack of  claim 13 , wherein the photoresist comprises an organic resist having a thickness less than or equal to about 280 Å. 
     
     
         15 . The film stack of  claim 13 , wherein the photoresist comprises a metal oxide photoresist with a thickness less than or equal to about 130 Å. 
     
     
         16 . The film stack of  claim 13 , wherein the diamond-like carbon has a density greater than 1.8 g/cc, a modulus greater than 150 GPa, and a stress less than −500 MPa. 
     
     
         17 . The film stack of  claim 13 , wherein the diamond-like carbon has an sp3 carbon content in a range of from 50 percent to 90 percent. 
     
     
         18 . The film stack of  claim 13 , wherein the low-k dielectric comprises SiCOH. 
     
     
         19 . The film stack of  claim 13 , wherein the optional layer is present. 
     
     
         20 . The film stack of  claim 13 , further comprising a middle layer on the bottom layer, the middle layer having a thickness less than or equal to about 200 Å, the middle layer comprising one or more of a bottom anti-reflective coating (BARC), dielectric anti-reflective coating (DARC), a doped silicon, or doped boron.