Bilayer Lithography with Organosilicon Resists

The bottom planarizing layer plays a non-trivial role in the bilayer scheme and thus must satisfy a number of criteria  

Semi-Dry Bilayer Lithography (Wet Development/02 RIE Pattern Transfer) 

Acid-catalyzed silanol condensation to form insoluble networks has been also utilized in the design of aqueous base developable negative resist systems [419]. An aqueous base soluble silicone polymer was synthesized by a sol-gel reaction of a mixture of phenyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane. This polymer contained a high concentration of silanol OH groups and thus was soluble in aqueous base. 

The cleavable Si group as described above has been also incorporated in a polymethacrylate resist for 193 nm bilayer lithography (Fig. 151) [422b]. In a similar fashion 1,3-bis(trimethylsilyl)isopropyl methacrylate was terpolymerized with methacrylic acid and methyl methacrylate with AIBN in THF [428]. The COMA system has been modified to be used as a bilayer positive resist by incorporating norbornenes bearing a passive Si group and an acid-cleavable Si group (Fig. 152) [429]. 

Polysilsesquioxanes have found a use in the design of 193 nm bilayer resist. The phenol structure has been replaced with cyclohexyl carboxylic acid for 

---