To provide an antireflection film compsn., a substrate containing this compsn., and its producing method so as to obtain a resist relief image having a profile in the vertical direction with decreased footing and notching.

This antireflection film compsn. consists of a resin binder, an acid producing agent or thermoreactive acid producing agent, and a photoreactive acid producing agent. The resin binder consists of repeating units of anthracenyl groups. and preferably contains a crosslinking agent such as an amine-based material. It is preferable that the photoreactive acid producing agent produces an acid by exposure to 100 to 300 nm UV rays and is stable for exposure for one or more min at 110 to 175°C. The relief image of the photoresist layer is formed by (i) applying the antireflection compsn. on a substrate, (ii) applying a photoresist compsn. thereon, (iii) exposing the resist layer to produce an acid from the photoreactive acid producing agent of the antireflection compsn., and (iv) developing the resist layer.