Aromatic ring-containing polymer for resist underlayer, resist underlayer composition including the same, and method of patterning device using the same

A resist underlayer composition, comprising:

• (a) an aromatic ring-containing polymer including a unit represented by the following Chemical Formula 1;
• and
• (b) an organic solvent selected from the group of propylene glycol monomethylether acetate, propylene glycol monomethylether, cyclohexanone, ethyl lactate, γ-butyrolactone, and acetyl acetone,
• wherein,
• n is an integer of one or more,
• R1 and R2 are independently hydrogen, a C1 to C10 alkyl group, or an aromatic group,
• A is a functional group derived from an aromatic compound represented by the following Formula 1b,
• R7 and R8 are independently hydrogen, a hydroxy group, an alkoxy group, or a C1-C4 lower alkyl group,
• R9 and R10 are independently hydrogen, a hydroxy group, an alkoxy group, or a C1-C4 lower alkyl group, and
• X is O (oxygen) or S (sulfur).

A resist underlayer, comprising:

• a cross-linked product of an aromatic ring-containing polymer, the aromatic ring-containing polymer including a unit represented by the following Chemical Formula 1:
• wherein,
• n is an integer of one or more,
• R1 and R2 are independently hydrogen, a C1 to C10 alkyl group, or an aromatic group,
• A is a functional group derived from an aromatic compound represented by the following Chemical Formula 1b:
• R7-R10 are independently hydrogen, a hydroxyl group, a C1-C4 lower alkyl group, or an alkoxy group, and
• X is O (oxygen) or S (sulfur).