Substrate temperature effects on 193 nm photoresist deformation and self-aligned contact hole etching performances

Abstract

The authors managed to accomplish an etching condition for a self-aligned contact (SAC) structure patterned with the 193nm lithography. With lowering the substrate temperature from the previous SAC etching condition optimized for the 248nm lithography, they could minimize the 193nm photoresist deformation. The low-temperature setting is found to form relatively thicker, more uniform, and more carbon-rich fluorocarbon polymer film on the photoresist top and sidewall, which effectively prevents the ion-enhanced selective volatilization of carbonyl groups of the 193nm photoresist [Ling et al. J. Vac. Sci. Technol. B 22, 2594 (2004)]. Along the contact hole, the transmission electron microscope-energy dispersive x-ray spectrometry and field emission-Auger analyses were performed for the two temperature settings. At the low-temperature setting, relatively thinner fluorocarbon film with high fluorine content is observed within the contact hole, which is consistent with the observed etching phenomena of both the decrease in the etching selectivity of SiO2 to Si3N4 and the increase in the etching open strength within the SAC narrow slit. They could maintain the proper Si3N4 etching selectivity even at the low temperature with utilizing a part of the increased etching open strength endowed by decreasing the substrate temperature. They propose a model consistently describing most of all the SAC etching phenomena and surface analysis results observed in this work. The model separates the fluorocarbon radicals into the two groups, the carbon- and fluorine-abundant ones and considers the carbon-abundant radicals much stickier.