Reduction the Micro-sized Scratches using Optimal Design of POU Dual Filtration at STI CMP

Shallow Trench Isolation (STI) is a very critical Chemical Mechanical Polishing (CMP) process that requires an exceptional planarization state and reduction of micro-scratches is highly vital [1-2]. Minimizing defects has been a challenging task in STI CMP in both traditionally fumed silica slurry and advanced colloidal silica slurry process [3-4]. Furthermore, the use of ceria (CeO2) slurry in STI CMP heightens this difficulty as ceria slurry tends to agglomerate exceedingly easily in contrast to fumed silica slurry. Additionally, vulnerability to micro-scratches in polished wafers increase exceptionally when ceria (CeO2) slurry is utilized in STI CMP.

In this study it is aimed to determine the optimum filtration methodology for STI CMP, using ceria based slurry (CeO2), at point of use (POU) dual filtration, where it is tested to quantify their effectiveness in removing defects that produces large particles from the slurry. The validation of the consistency of dual filtration is done in mass production setup to confirm its effectiveness and consistency. The introduction of the new split dual design filters, which combines two different sized filters side by side in point-of-use (POU) slurry dispensing at calibrations of 0.2 μm + 0.1 μm filters reduces the micro-scratch level to 30%, and the adoption of dual filter improves the consistency in achieving stable levels of micro-scratch performance and significantly reduces the spikes in the micro-scratches. This work demonstrated the significance of the optimum dual filtration methodology in the performance of it’s the objectives the reduction in micro-sized scratches at STI CMP Process.