THIN-FILM TRANSISTOR AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To smooth and highly purify the interface between the polycrystalized silicon thin film, etc., and the gate insulation film of a thin-film transistor, by exposing a polycrystal semiconductor thin film to an active reaction gas to etch and remove its surface layer, and by flattening its surface to remove its surface portions of entrapped matters being segregated therein. SOLUTION: After forming a foundational film 13 on a transparent insulating substrate 1, an amorphous silicon thin film 15 is further formed thereon to subject it to a predetermined pattern processing determined from the arrangement of semiconductor elements on the substrate 1. Then, by projecting a laser beam on the silicon film 15 under the atmosphere of a hydrogen gas, it is fused and solidified to form a polycrystal silicon thin film 2. But, on the top surface of the polyscrystal silicon thin film 2, many protrusive portions 11 are generated, and entrapped matters 12 are segregated in the protrusive portions 11. Therefore, by plasma-exciting the mixed gas of carbon fluoride and oxygen in a vacuum, only activated species having polyatomic charges are led to the surface of the polycrystal silicon thin film 2. Then, the protrusive portions 11 on the surface of the thin film 2 are etched and removed by an active reaction gas to smooth the surface of the thin film 2.