New comprehensive metrics and methodology for metrology tool fleet matching

Measurement matching among metrology tools to the level of the precision specifications in the ITRS is highly desirable. A quantitative measure of this matching should combine single tool precision, tool-to-tool nonlinearities, and tool-to-tool offsets. In this paper we introduce Tool (under test) Matching Precision (TMP) and Fleet Measurement Precision (FMP) as these "bottom-line" metrics. TMP measures a single tool matching performance against a similar benchmark tool, while FMP measures the performance of the entire fleet. The paper describes a technique to diagnose both the tool under test and the fleet of tools when these bottom-line metrics do not meet the required specifications. Additionally, the exercise of assessing the matching of two tools or a fleet of tools requires a methodology that identifies and constructs a set of desirable artifacts, handles measurement induced sample damage, and provides a set of diagnostic metrics to aid in identifying root causes of matching problems. The methodology can be used for many different metrology systems. This case study will revolve around simulated data and actual data acquired from CD SEMs.