Substrate having thin film and method of thin film formation

A method of thin film formation, the method comprising:

• preparing a substrate;
• forming a thin film above the substrate;
• and
• crystallizing the thin film by irradiating the thin film with a light beam,
• wherein the crystallizing includes steps of:
• (a) crystallizing the thin film in a first region into a first crystalline thin film by irradiating the first region while scanning a first light beam relative to the substrate, the first region including at least one of (i) edge portions of the substrate and (ii) a region through which a cutting line passes when the substrate is cut, the first light beam satisfying a first condition;
• and
• (b) subsequently crystallizing the thin film in a second region into a second crystalline thin film by irradiating at least the second region while scanning a second light beam relative to the substrate, the second region being different from the first region, the second light beam satisfying a second condition different from the first condition, and
• the thin film has a higher absorption ratio of the second light beam than an absorption ratio of the second light beam of the first crystalline thin film.