<title>Determining metal interconnect imaging capability</title>

Abstract

This work describes an experimental approach to achieve acceptable manufacturing results for metal interconnect lines through the formulation and optimization of advance i-line photoresist system. The selection of a viable advanced photoresist was preceded by the formulation of several prototypes. The dye loading and PAC (photo-active compound) -to-resin ratio were varied as a means to study the effects of imaging on highly reflective metal. Following the manufacture of the prototypes, the performance characteristics of each prototype were studied. The study documented the photolithographic latitude of each sample via electrical probe analysis. The notching characteristics of the samples were determined via low voltage cross- sectional scanning electron microscope (SEM) analysis. Upon completion the three `best' samples were chosen for further evaluation. The final analysis utilized response surface methodology (RSM) to determine the process window (allowable operating range) of the prototype. This paper addresses both experimental techniques as they apply to developing and optimizing the lithographic performance of the photoresist system. Finally, and most important, this paper documents the main effects that lead to interconnect failure caused by severe reflective notching.