Resist-pattern transformation studied by x-ray photoelectron spectroscopy after exposure to reactive plasmas. I. Methodology and examples

Abstract

We have used x-ray photoelectron spectroscopy (XPS) to investigate the resist patterns’ transformation after exposure to reactive plasmas and we have correlated the resist modifications with the process performance obtained by scanning electron microscope (SEM) observations. The experimental procedure based on the chemical-topography analysis of resist patterns using XPS has been used to determine the chemical composition and thickness of the reactive layers that are formed both on the tops and sidewalls of the resist features during the plasma process. This method was then applied to a variety of processes used in integrated-circuit fabrication. For all the processes analyzed [resist-trimming process in high-density plasma, bottom-antireflective-coating (BARC) opening process in a medium-density plasma and thin SiO2 hard-mask-opening processes in both plasma sources], we have observed very good correlations between XPS results and the evolution of the resist-patterns’ dimensions during plasma exposure. In this study we show that variations in resist-patterns dimension can be easily generated by reactive plasmas and that they may induce some drastic consequences on plasma processes involved in advanced complementary-metaloxide-semiconductor (CMOS) device fabrication.