Performance of different etch chemistries on titanium nitride antireflective coating layers and related selectivity and microloading improvements for submicron geometries obtained with a high-density metal etcher

Abstract

Different chemistries were evaluated in a metal etcher with a high-density plasma source that was used to etch a titanium nitride antireflective coating (ARC). A composite film structure consisting of aluminum (with 0.5%–1% Cu) as the underlying layer, a titanium nitride ARC layer, and titanium nitride as the barrier layer were used for the standard stack, while titanium nitride and aluminum layers alone were used for the initial characterizations of the process. Conventional BCl3/Cl2 chemistry was used initially to etch both the titanium nitride ARC layer and the underlying aluminum layer. The performance of BCl3/Cl2 chemistry on the titanium nitride ARC layer as well as on the composite stack was evaluated. Partial etch measurements were taken to calculate the composite microloading and resist selectivity values. Different etch chemistries were then employed for the ARC layer while keeping conventional BCl3/Cl2 chemistry for the aluminum layer, and the difference in process performances were evaluated. Fluorine additives along with chlorine as the main etchant gave very high etch rate values for the titanium nitride layer. CHF3 was added as the fluorine source for the current study. When the titanium nitride layer was etched with chemistries having faster etch rates, CHF3 added chemistries in the current study, a remarkable improvement in the composite microloading was observed, compared to the microloading values obtained with conventional chemistry. An improved etch rate uniformity was another noticeable performance improvement. Possible mechanisms for these trends are explained in this article. The experimental portion of this article will provide details relating to the etcher and the film structure used for the study. The results and discussion section will give details of the process performance and a comparative evaluation of different titanium nitride chemistries, as well as possible mechanism for the trends observed.