Embedded spectroscopic reflectometry metrology on FEOL silicon dioxide trench polishing equipment

The aim of the research is to develop a material thickness measurement method to monitor oxide polishing by Chemical-Mechanical Planarization (CMP) during the realization of the Shallow Trench Isolation (STI). The underlying goal is to build a statistical regulation model of the polishing time on a single platen (the two others platens are monitored by an endpoint signal). In addition to the process parameters (head sweep, platen, and head rotation velocity), input and output polished material thicknesses data are essential to build a run-to-run model for CMP. Therefore, stack layer thickness, before and after polishing, needs to be measured fast enough to maintain the acceptable throughput and to accurately control the polishing time wafer by wafer. In this paper, we describe how spectroscopic reflectometry embedded in the polishing equipment, can meet rapidity and capability requirements in setting up a run-to-run control algorithm to maintain the target thickness for STI CMP.