Film forming material for lithography, composition for film formation for lithography, underlayer film for lithography, and method for forming pattern

An addition polymerization citraconimide resin represented by the following formula (2):

• wherein
• each R2 is independently a group having 0 to 10 carbon atoms and optionally containing a heteroatom;
• each m2 is independently an integer of 0 to 3;
• each m2′ is independently an integer of 0 to 4;
• and
• n is an integer of 1 to 4,
• or the following formula (3):
• wherein
• R3 and R4 are each independently a group having 0 to 10 carbon atoms and optionally containing a heteroatom;
• each m3 is independently an integer of 0 to 4;
• each m4 is independently an integer of 0 to 4;
• and
• n is an integer of 1 to 4.