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The rapid shrinking of feature size and introduction of new materials continue to challenge metrology. The 2003 Metrology Roadmap describes the metrology requirements over the next 15 years for traditional CMOS and for emerging devices. As in previous years, the roadmap is divided into sections that reflect process area needs and cross-cut metrology needs. This year the sections are: measurements for processes facing statistical limits and physical structures reaching atomic dimensions; microscopy; lithography metrology; front-end processes metrology; interconnect metrology; materials and contamination characterization; integrated metrology; reference measurement systems; reference materials; and characterization and metrology for emerging devices. In this article, we provide an overview of the 2003 Metrology Roadmap.
In reading the Metrology Roadmap, one will notice that metrology tool requirements are based on measurement precision. Statistical process control (SPC) remains the main approach for keeping processes inside required control specifications. The measurement precision process tolerance ratio metric allows the industry to determine the capability of a metrology tool for maintaining SPC. Although standardized definitions and procedures for metrics are available from standards organizations such as SEMI’s, individualized implementation of metrics such as measurement precision to tolerance P/T) ratio is typical.[1] The P/T ratio for evaluation of automated measurement capability for use in statistical process control relates the measurement variation (precision) of the metrology tool to the product specification limits. Recently, members of the metrology community have become more concerned with the method used to evaluate the P/T ratio. For example, the precision determined using a perfect reference material does not reflect the precision of measuring features on real wafers. One example is the changes in the sidewall angle impact the precision of critical dimension (CD) determination making the true precision larger (worst).
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