Progress on implementation of a reference measurement system based on a critical-dimension atomic force microscope

Abstract

The National Institute of Standards and Technology (NIST) and SEMATECH are working to address traceability issues in semiconductor dimensional metrology. In semiconductor manufacturing, many of the measurements made in the fab are not traceable to the SI unit of length. This is because a greater emphasis is often placed on precision and tool matching than on accuracy. Furthermore, the fast pace of development in the industry makes it difficult to introduce suitable traceable standard artifacts in a timely manner. To address this issue, NIST and SEMATECH implemented a critical-dimension atomic-force-microscope-based reference measurement system (RMS). The system is calibrated for height, pitch, and width, and has traceability to the SI definition of length in all three axes. Because the RMS is expected to function at a higher level of performance than inline tools, the level of characterization and handling of uncertain sources is on a level usually seen in instruments at national measurement institutes. In this work, we discuss recent progress in reducing the uncertainty of the instrument as well as details of a newly implemented performance monitoring system. We also present an example of how the RMS concept can be used in a semiconductor manufacturing environment.