Correlation between break-in characteristics and pad surface conditions in silicon wafer polishing

Abstract

The surface properties of a polishing pad play a significant role in chemical mechanical polishing (CMP). The buffing process is able to control the pad surface conditions and ultimately has an effect on polishing characteristics including removal rate and break-in time in the CMP process. In this paper the polishing pad was controlled by the roughening process, which was then investigated for its effect on the material removal characteristics during the silicon wafer polishing process. As a result of this monitoring, the removal rate and wafer to wafer non-uniformity (WTWNU) were influenced by the polishing pad surface conditions, such as roughness. In addition, abnormal signals from friction force and the polishing pad surface temperature were found during polishing process. This phenomenon was named “Break-in delay.” This means that the material on the wafer could not be removed uniformly due to the instability of the polishing consumables. The break-in time was reduced by controlling the pad surface conditions. Therefore, the surface conditions of the polishing pad have a strong correlation with the break-in characteristic in the silicon polishing process.