Precision removal of ITO film by LD-pumped SHG YAG laser

ITO film, which is a kind of transparent conductive film, has been used for LCD, PDP and so on. This film is mostly removed by wet etching method. However, this method needs many chemicals, processes and large-size equipments. On the other hand, laser beam processing can drastically reduces the number of process by achieving the dry process without chemicals. Therefore, selective removal of ITO film of 85nm in thickness on glass substrate by LD-pumped Q-switch SHG YAO laser is experimentally investigated. Electrical 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 on glass material as substrate, since SHG YAG laser of 532nm in wavelength is easy to transmit the glass material. When laser beam is irradiated from ITO film to glass, a non-removed portion of ITO film remains at the bottom of groove under long defocused distance condition. On the other hand, the non-removed portion can be prevented from remaining by backside irradiation, in which laser beam is irradiated to ITO film through glass material. Because absorption of laser beam occurs at the boundary part between ITO film and glass material.