Micro machining of ITO film by LD pumped SHG YAG laser

ITO film, which is a kind of transparent conductive film, has been used for LCD, PDF and so on. This film is mostly removed by wet etching method. However, this method needs many chemicals, numbers of process and large-size equipments. On the other hand, laser beam processing can achieve the dry process without chemicals and drastically reduces the number of process. Therefore, selective removal of ITO film on glass substrate by LD pumped Q-switch SHG YAG laser is experimentally investigated. Electric insulation across machined groove was successful. Better groove shape can be obtained by accurate control of defocused distance and feed rate under a constant average power. Using SHG YAG laser makes it possible to remove only ITO film without any damage to glass material as substrate, since SHG YAG laser of 532 nm in wavelength is easy to transmit the glass material. When laser beam is irradiated from ITO film to glass material, a non-removed portion of ITO film remains at the bottom of groove under long defocused distance condition. On the other hand, backside irradiation method, in which laser beam is irradiated to ITO film through glass material, can prevent from remaining a non-removed portion, since absorption of laser beam occurs from the boundary part between ITO film and glass material.