Development of modeling to investigate polyurethane pad hardness in chemical mechanical planarization/polishing (CMP) process

In chemical mechanical polishing (CMP) for IC fabrication, porous pads are critical for achieving extremely consistent throughput in CMP process. The pad hardness, porosity of pad, and pore sizes in the thermoplastic polyurethanes foam fabrication procedure determine the properties of CMP pads. This paper aims to develop a methodology for modeling macro and micro pad hardness. The IC1000 CMP pad has been analyzed with a developed image processing method to determine porosity and pores size. In addition, nano-indentation tests are used to determine physical properties of micro-solid components. For macro hardness analysis, five different sizes of three-dimensional representative volume elements (RVE) have been investigated using the random sequential adsorption technique. Furthermore, simulation of macro pad hardness of RVE models are completed with finite element method. Results of this study not only achieves macro hardness of CMP pad simulation as 3% errors as compared with developed micro-indentation test, but also complete three dimensional porous pad modeling with RVE.