Traceable Dimension Metrology by AFM for Nanoscale Process Control

Abstract

Your 32nm is different from my 32nm! The paradoxical statement reflects one of the most essential debates in the field of nanoscale dimension metrology for process control in the modern nanoelectronic manufacturing industry. This baffling debate is all about accuracy and traceability of dimension measurement systems used on production floors. As the circuit geometry and density continues to scale to the 45nm node and below, the metrology bias and uncertainty play a more significant role, and the characterization becomes more difficult. This article assesses the capability of atomic force microscope (AFM) as an accurate inline calibration metrology tool and the correlation of AFM measurement to NIST traceable standards. It introduces the methodology of adopting AFM as a traceable reference tool for CD SEM and optical scatterometry used in inline process control. The focus is on height, linewidth, and pitch calibrations due to their critical but challenging roles for process control in today’s nanoelectronic manufacturing. Care must be taken to minimize the impact from factors that affect the traceability and accuracy in the AFM system, including tip width calibration, tip wear, tip shape effect, contamination, and linewidth roughness.