Issues in deep-UV photoresist technology: Characterization and modeling of bulk and surface imaged resists for 248 and 213 nm lithography

The drive for smaller feature sizes in integrated circuits has necessitated the use of shorter exposure wavelengths and the development of new resist technologies sensitive to the new wavelengths. An examination of chemical and physical mechanisms in resist materials has been made to support the applications of deep-UV lithography as the wavelength is shrunk to 248 nm and below. Resist models for chemically amplified resists and for surface imaging have been proposed and experimentally verified.;Airborne base contamination can significantly alter the lithographic properties of chemically amplified resists as a result of the small quantities of acid generated during the exposure. Techniques for characterizing the effect of contamination on resists and evaluations of the contamination susceptibility of the current available deep UV resists are described. In addition, a technique for estimating airborne contaminant concentration is described. Airborne amine concentrations of 4 to 5 parts per billion were detected in the University of California Microlab.;The use of new light sources has necessitated the development of novel resist materials based on chemical amplification. A fundamental understanding of the chemically amplified resist kinetics is necessary to produce more robust resist materials. Characterization and modeling techniques are described and used to verify a model for the chemically amplified deprotection kinetics in resists. The model proposes specific acid loss mechanisms that previously have been described only generically. In addition, we describe the use of 213 nm exposure wavelengths to characterize photo-acid diffusion in chemically amplified resists. Experimental data obtained to date do not allow a definitive separation of diffusion effects from the chemical kinetics.;Quantitative models for resist profile prediction are discussed for use with exposing wavelengths below 248 nm. A bi-layer surface-imaging resist process suitable for 213 nm exposure is described and demonstrated. Models for selective silylation and plasma etch dry development are proposed and experimentally verified. A methacrylate terpolymer is used as a bulk-imaging resist for 213 nm lithography. Models for the exposure, post-exposure bake and development of methacrylates are described.