CMP characteristics and optical property of ITO thin film by using silica slurry with a variety of process parameters

Surface roughness by peaks, bumps, large particles, and pin-holes on the surface of indium tin oxide (ITO) thin film, which is widely used for a transparent electrode of optoelectronic devices, caused the destruction of color quality and the reduction of device life time. Chemical mechanical polishing (CMP) process was selected to smooth the surface roughness in this study. Some process parameters including polishing time, slurry flow rate, table speed, and slurry temperature were varied to optimize the ITO-CMP process. The removal rate and the non-uniformity were 60.45 nm/min and 5.17% at the condition of appropriate process parameters as follows: head speed, slurry temperature, down force, slurry flow rate, polishing time, and table speed were 60 rpm, 30 °C, 300 gf/cm2, 40 ml/min, 60 s, and 60 rpm, respectively. However, the sufficient non-uniformity below 5.0% was not obtained in all process parameter conditions due to the unequal polishing by the silica slurry. Optical transmittance of ITO thin film was improved from 83.3% to 85.0% after CMP process.