Electrical Defect Imaging of ITO Coated Glass by Optical Microscope With Microwave Heating

We present a new optical method for the electrical defect inspection for indium tin oxide (ITO) thin film on a glass substrate. The present method is based on the visualization of the microwave heating distribution around an electrical defect from the thermal stress distribution of the glass substrate of ITO-glass. By using a conventional polarized microscope with microwave irradiation (6 ~ 15 GHz), we show that the present method provides a non-contact and non-destructive way to inspect an electrical defect of a transparent conductive thin film with a minimum detectable defect length of 1 mm and a parallel sensing of electrical defects distributed in a 40 mm by 30 mm area. The high resolution and wide field of view of the present method are attractive features for the practical application of this inspection technology.