Quantitative analysis of physical and chemical changes in CMP polyurethane pad surfaces

Polishing pads play a key role in chemical–mechanical polishing (CMP), which has been recognized as a critical step to improve the topography of wafers for semiconductor fabrication. In service, chemical and mechanical changes in a polishing pad are expected to have a significant impact on the padʹs CMP performance. Scanning electron microscopy (SEM) showed changes in the pore geometry on the CMP pad surface after use. The average height of the roughness between the pores of the polishing pad was measured using white light interferometry (WLI). Attenuated total reflectance Fourier Transform Infrared (ATR/FTIR) method was found to provide a novel opportunity for the nondestructive surface analysis of pad materials. Results of an ATR/IR microscopy study that evaluated the extent of chemical degradation of pad materials both before and after polishing cycle are presented. The infrared results identified that the changes in chemical state of used pad materials, specifically for CO and COC infrared stretching bands, were a surface phenomenon.