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The Advanced Metrology Advisory Group (AMAG) comprised of representatives from International SEMATECH consortium member companies and the National Institute of Standards and Technology have joined to develop a new unified specification for an advanced scanning electron microscope critical dimension measurement instrument (CD-SEM). (Ailgair, et al., 1998) This paper describes the results of an effort to benchmark six CD-SEM instruments according to this specification.The consensus among the AMAG metrologists was that many critical areas of performance of CD-SEMs required improvement. Following this assessment this specification for benchmarking was developed. The advanced CD-SEM specification addresses several critical areas for improvement, each with its own a separate section. The critical areas covered are: precision, accuracy, charging and contamination, performance matching, pattern recognition and stage navigation accuracy, throughput, and instrumentation outputs. Each section of the specification contains a concise definition of the respective performance parameter, and wherever appropriate refers to ISO definitions. The test methodology is described, complete with the relevant statistical analysis. Many parameters (including precision, matching, and magnification accuracy) are numerically specified to be consistent with the International Technology Roadmap for Semiconductors (ITRS, 1999). Other parameters, such as charging and linewidth accuracy, are targeted with guidelines for improvement. The test wafers developed for determining the level of compliance with the specification are also discussed.The AMAG circulated this report among the metrology instrument suppliers and conferred with them. Certain components of the specification have already been adopted by some of the manufacturers in their newer metrology instruments. International SEMATECH fabricated the AMAG test wafers described herein. Measurements on six state-of-the-art metrology instruments using the AMAG test wafers have been carried out and the results were processed according to this specification. A review of the results is presented in this paper.

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Automated critical dimension (CD) metrology has long been known to have certain limitations. As a top down imaging technique, retrograde profiles, resist thickness loss and other process issues are difficult to detect with the standard production CD SEMs used throughout the industry. Tilting capability has recently added much needed degrees of freedom to CD SEMs, potentially opening the door to three dimensional metrology. Various methodologies can be used to interpret tilt image information. This paper investigates one particular technique used to extract three dimensional information. Using cross section and/or atomic force microscopy (AFM), one can evaluate the potential benefits and validity of CD SEM tilt capability. Sidewall angle, film thickness and possibly other parameters could possibly become standard calculations the top down CD SEM could perform on a routine basis.Data is reported comparing 3D information generated from top down CD SEM to AFM. Potentially, a couple of different approaches to evaluating 3D information will be compared. Lastly, recommendations for future applications will be discussed.