Abstract: Provided is an aromatic hydrocarbon resin with a high carbon concentration and a low oxygen concentration that can be used as a coating agent or a resist resin for semiconductors, as well as a composition for forming an underlayer film for photolithography with excellent etching resistance as an underlayer film for a multilayer resist process, an underlayer film formed from the composition, and a method for forming a pattern using the underlayer film. An aromatic hydrocarbon, an aromatic aldehyde, and a phenol derivative are reacted in the presence of an acidic catalyst to yield an aromatic hydrocarbon resin with a high carbon concentration of 90 to 99.9 mass % and a solubility in propylene glycol monomethyl ether acetate of 10 mass % or more.

Abstract: A composition for forming an underlayer film for lithography for imparting excellent optical characteristics and etching resistance to an underlayer film for lithography, an underlayer film being formed of the composition and having a high refractive index (n) and a low extinction coefficient (k), being transparent, having high etching resistance, containing a significantly small amount of a sublimable component, and a method for forming a pattern using the underlayer film are provided. The composition for forming an underlayer film contains a naphthalene formaldehyde polymer having a specific unit obtained by reacting naphthalene and/or alkylnaphthalene with formaldehyde, and an organic solvent.

Abstract: Provided is an aromatic hydrocarbon resin with a high carbon concentration and a low oxygen concentration that can be used as a coating agent or a resist resin for semiconductors, as well as a composition for forming an underlayer film for photolithography with excellent etching resistance as an underlayer film for a multilayer resist process, an underlayer film formed from the composition, and a method for forming a pattern using the underlayer film. An aromatic hydrocarbon, an aromatic aldehyde, and a phenol derivative are reacted in the presence of an acidic catalyst to yield an aromatic hydrocarbon resin with a high carbon concentration of 90 to 99.9 mass % and a solubility in propylene glycol monomethyl ether acetate of 10 mass % or more.

Abstract: A composition for forming an underlayer film for lithography for imparting excellent optical characteristics and etching resistance to an underlayer film for lithography, an underlayer film being formed of the composition and having a high refractive index (n) and a low extinction coefficient (k), being transparent, having high etching resistance, containing a significantly small amount of a sublimable component, and a method for forming a pattern using the underlayer film are provided. The composition for forming an underlayer film contains a naphthalene formaldehyde polymer having a specific unit obtained by reacting naphthalene and/or alkylnaphthalene with formaldehyde, and an organic solvent.