Processing, reliability and integration issues in chemical mechanical planarization.

摘要

Global planarization is one of the major demands of the semiconductor industry. Chemical mechanical polishing (CMP) is the planarization method of choice use to achieve the required stringent tolerances essential for successful fabrication of next generation Integrated Circuits (IC). The predominant reason for CMP defects is the shear and normal stresses during polishing to which the material is subjected. Understanding the process of CMP and factor that contribute to overall stress addition during polishing requires an approach that encompasses all the four major categories of variables, namely: (a) machine parameters, (b) material properties, (c) polishing pad characteristics, and (d) polishing slurry performance. In this research, we studied the utilized in-situ technique involving acoustic emission (AE) signal monitoring and coefficient of friction (COF) monitoring using a CETR(TM) Bench Top CMP Tester to evaluate the impact of variation in machine parameters on the CMP process. The mechanical and tribological properties of different candidate materials have been evaluated bring potential challenges in their integration to the fore. The study also involves destructive and non destructive testing of polishing pads performed for characterization and optimization of polishing pad architecture. Finally, the investigation concludes proposing novel nanoparticle CMP slurry which has a predominant chemical component in its polishing mechanism. It was found that the decrease in the mechanical shear and normal loading by: (a) operating the process in the low stress regime, (b) using potential materials that are mechanically stronger, (c) using polishing pads with lesser variation in specific gravity and with a surface that is has its mechanical properties fine tuned to those of the wafer, and (d) deploying polishing slurry with a significant chemical component mechanical removal, are some of the approaches that can be employed to meet the future challenges of the CMP process and reduce the defect associated with it.