This study focuses on the characterization of gap fill materials for advanced ArF lithography process. The gap fill materials have the planarization property on an irregular substrate such as the patterned holes and trenches to increase the depth of focus and resolution. After planarizing the substrate surface, the gap fill materials are used to avoid the dry etching damage in the dielectric materials. In the characterization of gap fill materials with an excellent planarization properties for lithography, two key factors were identified, namely the specific relationship between the cross-link reaction group concentration of the polymers and the via filling performance, and the specific relationship between the solvent used in the polymer solution and the via filling performance.