Two-layer film and method of forming pattern with the same

Abstract

The invention concerns a lift-off process for patterning layers that are deposited and/or sputtered. The invention provides a two-layer resist and a patterning method using the resist. The patterning method can readily produce burr-free layers on a substrate. The method comprises the steps of: sequentially applying positive radiation-sensitive resin compositions 1 and 2 to form a two-layer laminate; subjecting the two-layer resist to single exposure and development to produce fine patterns having an undercut cross section; depositing and/or sputtering an organic or inorganic thin layer with use of the resist pattern as a mask; and lifting off the resist pattern to leave a pattern of the thin layer in desired shape.

1 . A two-layer laminate comprising: 
 a resist layer (I) formed from a positive radiation-sensitive resin composition  1  which comprises a radical polymer containing a hydroxyl group (A), a quinonediazido group-containing compound (B) and a solvent (C); and    a resist layer (II) formed from a positive radiation-sensitive resin composition  2  which comprises a polymer containing a phenolic hydroxyl group (D), a quinonediazido group-containing compound (E) and a solvent (F),    wherein the radical polymer containing a hydroxyl group (A) comprises repeating unites that result from the cleavage of carbon-carbon double bonds of at least one radically polyerizable compound having a hydroxyl group selected from the group consisting of p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, α-methyl-p-hydroxystyrene, α-methyl-m-hydroxystyrene, α-methyl-o-hydroxystyrene, 4-isopropenylphenol, 2-allylphenol, 4-allylphenol, 2-allyl-6-methylphenol, 2-allyl-6-methoxyphenol, 4-allyl-2-methoxyphenol, 4-allyl-2,6-dimethoxyphenol and 4-allyloxy-2-hydroxybenzophenone.    
   
   
       2 . The two-layer laminate according to  claim 1 , wherein in the positive radiation-sensitive resin composition  1 , the radical polymer (A) is insoluble in water, soluble in an alkaline aqueous solution and insoluble or hardly soluble in the solvent (F).  
   
   
       3 . The two-layer laminate according to  claim 1 , wherein in the positive radiation-sensitive resin composition  2 , the solvent (F) is 2-heptanone.  
   
   
       4 . The two-layer laminate according to  claim 1 , wherein the resist layer (I) has a thickness of 0.1 to 3 μm and the resist layer (II) has a thickness of 1 to 20 μm.  
   
   
       5 . A patterning method comprising a step of forming a two-layer laminate comprising: 
 a resist layer (I) formed from a positive radiation-sensitive resin composition  1  which comprises a radical polymer containing a hydroxyl group (A), a quinonediazido group-containing compound (B) and a solvent (C); and    a resist layer (II) formed from a positive radiation-sensitive resin composition  2  which comprises a polymer containing a phenolic hydroxyl group (D), a quinonediazido group-containing compound (E) and a solvent (F),    wherein the radical polymer containing a hydroxyl group (A) comprises repeating unites that result from the cleavage of carbon-carbon double bonds of at least one radically polymerizable compound having a hydroxyl group selected from the group consisting of p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, α-methyl-p-hydroxystyrene, α-methyl-m-hydroxystyrene, α-methyl-o-hydroxystyrene, 4-isopropenylphenol, 2-allylphenol, 4-allylphenol, 2-allyl-6-methylphenol, 2-allyl-6-methoxyphenol, 4-allyl-2 -methoxyphenol, 4-allyl-2,6-dimethoxyphenol and 4-allyloxy-2-hydroxybenzophenone.    
   
   
       6 . The patterning method according to  claim 5 , comprising the steps of: 
 (a) forming on a substrate a resist layer (I) from the positive radiation-sensitive resin composition  1  and forming on the resist layer (I) a resist layer (II) from the positive radiation-sensitive resin composition  2  to produce a two-layer laminate;    (b) forming a latent pattern in the laminate by UV light exposure and/or electron beam lithography;    (c) developing the laminate to form an undercut resist pattern in which the orifices have a larger size in the bottom than in the top;    (d) depositing and/or sputtering an organic or inorganic thin layer on the resist pattern laminate and on the exposed substrate; and    (e) releasing the laminate together with the overlying thin layer deposited and/or sputtered on the laminate.    
   
   
       7 . The patterning method according to  claim 5 , wherein in the positive radiation-sensitive resin composition  1 , the radical polymer (A) is insoluble in water, soluble in an alkaline aqueous solution and insoluble or hardly soluble in the solvent (F).  
   
   
       8 . The patterning method according  claim 5 , wherein in the positive radiation-sensitive resin composition  2 , the solvent (F) is 2-heptanone.  
   
   
       9 . The patterning method according  claim 5 , wherein the resist layer (I) has a thickness of 0.1 to 3 μm and the resist layer (II) has a thickness of 1 to 20 μm.  
   
   
       10 . The patterning method according to  claim 6 , wherein the substrate in the step (a) is an ABS (air bearing surface) of magnetic head slider and the organic thin layer in the step (d) is a DLC (diamond like carbon) layer.