Filtration of CMP slurry using pleated and depth filters and its impact on product yields

摘要

Filtration of CMP slurry plays a critical role in the CMP process. Without filtration, large particles and agglomerations may be present in the dilute slurry. This may cause microscratches on the surfaces of wafers and ultimately lead to higher wafer defects. There are several filtration product configurations available including pleated and depth filters. The 100% polypropylene melt blown pleated filters rely on surface capture mechanisms for large particle count (LPC) removal. Melt blown depth filters using CoLD fiber technology allow for the capture of agglomerations, gels, and aggregates within its selectively graded pore filter matrix. As the specifications of CMP slurry are becoming more stringent, both filtration technologies are being considered for various locations in a CMP process. When using colloidal silica slurry, specifically Cabot SC- 112, CMPD depth filters have been shown to effectively reduce LPC and increase production yields. This paper evaluates the filtration stage at point of use using Cabot SC-112 slurry. Using metrology and product yield data, a point of use filter is optimized by evaluating a pleated and a depth filter design.