Precision is deemed the most important aspect of a measurement for process control. This paper discusses the role of accuracy in process control and product quality. Although the discussion is emphasized for CD SEM metrology systems, the idea can be extended to other metrology areas such as thickness measurement where in addition to thickness, material characteristics also play a role. In 1999, the characteristics of accuracy were published in a landmark paper(1). The authors introduced the concept of characteristic slope and offset for the purpose of tool evaluation. Slope and offset were obtained from correlation plots of a measurement tool under test with a reference measurement system. The measurands were features that represent the range of process variations in a line. This paper builds on the ideas put forth in that reference(1) and discusses the impact of measurement accuracy on process control. First, the issue is considered in an abstract sense, by comparison of the measurement method under test to a standard reference method. Then practical implications are discussed in more detail when tools from different suppliers are used in a fab to manufacture products.
