Characteristics of accuracy for CD metrology

Abstract

The evaluation of a critical dimension (CD) metrology tool foes beyond determining precision. A year ago at this conference, a paper was presented which described the efforts of the SEMATECH metrology group to describe the characteristics of a CD metrology SEM. In that referenced paper there was a description of accuracy, or characteristics of accuracy, that needed evaluation as well. In this paper these characteristics are further developed. Tool evaluation for accuracy requires well characterized artifacts. Constructing these share many of the same hurdles as constructing true standards. Evaluation artifacts must have properties that vary similarly to the products to be measured in the manufacturing line. They also must be characterized by a reference measurement system (RMS) sufficiently well to make the result of an evaluation reflect upon the tool under investigation and not the RMS. This paper details the construction of such an artifact using SEM measurements of cross sections as part of the RMS and the use of this artifact in the evaluation of several CD SEMs. Application of this project to SEMATECH evaluation artifacts currently under construction is also discussed.