Shuichi Baba

New inline AFM metrology tool suited for LSI manufacturing at the 45-nm node and beyond

A new inline metrology tool utilizing atomic force microscope (AFM) suited for LSI manufacturing at the 45-nm node and beyond has been developed. The developed AFM is featuring both of high-speed wafer processing (throughput: 30 WPH) and high-precision measurement (static repeatability: 0.5nm in 3σ). Several types of carbon nanotube (CNT) probes specially designed for the AFM have also been developed. The combination of Advanced StepInTM mode and CNT probes realizes high precision measurement for high-aspect-ratio samples such as photoresist patterns. In Advanced StepInTM mode, a probe tip approaches and contacts a sample surface, and then moves away from the surface and toward a new measurement position. A series of these actions is performed in a short time (3.8 ms for single measurement point) full-automatically. Advanced StepInTM mode not only ensures gentle probe tip contact and precise measurement of high aspect ratio samples, but also minimum tip wear. CNT probes can provide long term performance, while eliminating the need for probe exchange. The developed AFM also realizes flatness measurement of 10-nm level in a wide area of 40x40-mm maximum. This performance is sufficient for the evaluation of CMP processes at the 45-nm node.