Patent ID: 7855152

Claim:
A method of producing an active matrix substrate in which a plurality of contact holes are formed by a one-mask process so as to reach metal films which are located at different depth positions in an insulating layer, comprising the steps of: performing dry etching using mixed gas of CHF 3 , CF 4 and O 2 to form the plurality of contact holes and to expose the metal films, depositing carbonaceous polymer from the CF 4 on surfaces of the contact holes and on surfaces of the metal films exposed through the contact holes, while the carbonaceous polymer is partially removed by the O 2 in the form of CO 2 ; subjecting the plurality of contact holes to oxygen ashing to further remove the carbonaceous polymer; and forming a transparent conductive film in the plurality of contact holes, wherein the metal films are fluorinated and are not etched by dry etching using a fluorine-containing gas.