Photoresist formulation for high aspect ratio plating

Abstract

SU-8 photoresist compositions are modified to improve their adhesion properties by adding 1% to 6% of an adhesion promoter selected from the group consisting of glycidoxypropanetrimethoxysilane, mercatopropyltrimethoxysilane, and aminopropyltrimethoxysilane. SU-8 photoresist compositions are modified to improve their resistance to cracking and film stress by adding 0.5% to 3% of a plasticizer selected from the group consisting of dialkylphthalates, dialkylmalonates, dialkylsebacates, dialkyladipates, and diglycidyl hexahydrophthalates. The improvements can be obtained simultaneously by adding both the adhesion promoter and the plasticizer to SU-8 photoresist compositions.

What is claimed is:  
     
         1 . A photoresist masking material, comprising: 
 a) an octafunctional epoxidized novolac resin;    b) an organic solvent;    c) a photopolymerization initiator;    d) a plasticizer selected from the group consisting of dialkylphthalates, dialkylmalonates, dialkylsebacates, dialkyladipates, and diglycidyl hexahydrophthalates; and    e) an adhesion promoter selected from the group consisting of glycidoxypropanetrimethoxysilane, mercatopropyltrimethoxysilane, and aminopropyltrimethoxysilane.    
     
     
         2 . A photoresist masking material according to  claim 1  wherein said octafunctional epoxidized novolac resin is of the formula:  
       
         
           
           
               
               
           
         
       
     
     
         3 . A photoresist masking material according to  claim 1  wherein said solvent has a boiling point of between 160° C. and 260° C.  
     
     
         4 . A photoresist masking material according to  claim 1  wherein said solvent has a boiling point of between 190° C. and 220° C.  
     
     
         5 . A photoresist masking material according to  claim 1  wherein said solvent has a boiling point of between 200° C. and 210° C.  
     
     
         6 . A photoresist masking material according to  claim 1  wherein said solvent is gamma butyrolactone.  
     
     
         7 . A photoresist masking material according to  claim 1  wherein said solvent is present in an amount ranging between about 15% and about 45%.  
     
     
         8 . A photoresist masking material according to  claim 1  wherein said solvent is present in an amount ranging between about 20% and about 30%.  
     
     
         9 . A photoresist masking material according to  claim 1  wherein said solvent is present in an amount of about 26%.  
     
     
         10 . A photoresist masking material according to  claim 1  wherein said photopolymerization initiator is present in an amount ranging between about 3% and about 10%.  
     
     
         11 . A photoresist masking material according to  claim 1  wherein said photopolymerization initiator is present in an amount ranging between about 5% and about 8%.  
     
     
         12 . A photoresist masking material according to  claim 1  wherein said photopolymerization initiator is present in an amount ranging between about 6% and about 7%.  
     
     
         13 . A photoresist masking material according to  claim 1  wherein said photopolymerization initiator is Cyracure® 6974.  
     
     
         14 . A photoresist masking material according to  claim 1  wherein said plasticizer is present in an amount ranging between about 0.5% and about 3%.  
     
     
         15 . A photoresist masking material according to  claim 1  wherein said plasticizer is present in an amount of about 2%.  
     
     
         16 . A photoresist masking material according to  claim 1  wherein said plasticizer is a dialkylphthalate.  
     
     
         17 . A photoresist masking material according to  claim 1  wherein said dialkylphthalate is dioctylphthalate.  
     
     
         18 . A photoresist masking material according to  claim 1  wherein said adhesion promoter is present in an amount ranging between about 1% and about 6%.  
     
     
         19 . A photoresist masking material according to  claim 1  wherein said adhesion promoter is present in an amount ranging between about 3% and about 4%.  
     
     
         20 . A photoresist masking material according to  claim 1  wherein said adhesion promoter is glycidoxypropanetrimethoxysilane.  
     
     
         21 . A photoresist masking material, comprising: 
 a) 50% to 75% of an octafunctional epoxidized novolac resin of the formula:                          b) 15% to 45% of an organic solvent;    c) 3% to 7% a photopolymerization initiator;    d) 0.5% to 3% of a plasticizer selected from the group consisting of dialkylphthalates, dialkylmalonates, dialkylsebacates, dialkyladipates, and diglycidyl hexahydrophthalates; and    e) 1% to 6% of an adhesion promoter selected from the group consisting of glycidoxypropanetrimethoxysilane, mercatopropyltrimethoxysilane, and aminopropyltrimethoxysilane.    
     
     
         22 . A method of improving the adhesion of an SU-8-based photoresist masking composition, said method comprising the step of including in the composition 0.5% to 3% of a plasticizer selected from the group consisting of dialkylphthalates, dialkylmalonates, dialkylsebacates, dialkyladipates, and diglycidyl hexahydrophthalates.  
     
     
         23 . The method of  claim 21  wherein said plasticizer is a dialkylphthalate.  
     
     
         24 . The method of  claim 21  wherein said plasticizer is dioctylphthalate.  
     
     
         25 . A method of improving the resistance to cracking and film stress of an SU-8-based photoresist masking composition, said method comprising the step of including in the composition 1% to 6% of an adhesion promoter selected from the group consisting of glycidoxypropanetrimethoxysilane, mercatopropyltrimethoxysilane, and aminopropyltrimethoxysilane.  
     
     
         26 . The method of  claim 21  wherein said adhesion promoter is glycidoxypropanetrimethoxysilane.