Study of High Etch Rate Bottom Antireflective Coating and Gap Fill Materials Using Dextrin Derivatives in ArF Lithography

Abstract

In the present paper, we describe a novel class of bottom antireflective coating (BARC) and gap fill materials using dextrin with a-glycoside bonds in a polysaccharide. ArF resist underlayer materials containing a dextrin ester polymer for lithography were studied. Dextrin is a high molecular weight compound with several hydroxyl groups and a low solubility in resist and BARC solvents. Therefore, it is difficult to use dextrin polymers in resist underlayer materials such as BARC and gap fill materials. The main polymer needs to be soluble in propylene glycol monomethylether, propylene glycol monomethylether acetate, and ethyl lactate as common solvents to avoid the issue of defects in the coater cup due to incompatability. The dextrin ester polymer in this study was obtained by the esterification of the hydroxyl groups of dextrin resulting in improved solubility of these organic solvents. The etch rate of the new BARC and gap fill materials of the dextrin ester polymers was more than twofold faster than the etch rate of the ArF resists evaluated under a CF4 gas condition using reactive ion etching. The improved etch performance was also verified by comparison with poly(4-hydroxystyrene) and poly(2-hydroxypropyl methacrylate) as references. In addition to the superior etch performance, these materials showed good resist profiles and via filling performance without voids in via holes. On the basis of our findings, this technology of using the novel dextrin derivatives as sacrificial materials under a resist can be applied in devices of 45 nm node and higher.