DEVELOPMENT OF BILAYER RESISTS FOR DEEP-ULTRAVIOLET AND I-LINE APPLICATION

Bilayer photoresist schemes have the potential of satisfying the many stringent demands associated with the lithographic exposure step. Because the film thickness for this process is quite small, the aspect ratios are increased relative to single layer lithography and hence increased resolution may be obtained. The planarizing layer used in bilayer schemes can also be dyed to avoid reflectivity problems. In this paper the development of a resist for use as the imaging layer in a bilayer resist scheme incorporating oxygen reactive ion etch for image transfer is described. The resist chemistry is based on the coupling reaction(s) of cyclic polyfunctional silanols. The resist is composed of a cyclic silanol, an acid photogenerator, and a phenolic resin. The catalytic nature of the chemistry involved in the resist resulted in high sensitivity during the exposure process. The observed contrast was greater than four for several of the formulations due in part to the unique "bimodal" characteristics of this resist. With sufficient silanol content, high etch resistance was observed and bilayer resist methodology was carried out without loss of film thickness in the exposed regions. Submicron resolution was demonstrated.