Investigation of the Impact of Pad Surface Texture from Different Pad Conditioners on the CMP Performance

Abstract

Chemical mechanical polishing (CMP) is a common method for planarization/polishing materials during integrated circuits (IC) fabrication. Pad conditioning is a critical component of a CMP process. Herein, the impact of surface textures created by different types of pad conditioners (PC) such as coarse, mid-coarse, and fine PC on the solid pads are studied. Additional surface texture parameters such as surface height distribution, skewness, Dale Void Volume are used to determine an optimum surface texture that gives desired CMP performance such as material removal rate and within-wafer non-uniformity. It was determined that an optimum surface texture on a solid CMP pad can be obtained with a mid-coarse disk. It is further demonstrated that by the addition of porosity to the pads, it is possible to recreate an optimum surface texture and desired CMP performance, similar to that obtained with a mid-coarse disk and a solid pad. Tribological mechanisms of the different pad and PC combinations are presented using the coefficient of friction. It is concluded that porous pad and fine PC pairing can tackle the issues of slurry transport limitations, lack of asperity contact, and process stability over pad life.