<title>Benchmarking of advanced CD-SEMs against the new unified specification for sub-0.18-um lithography</title>

Abstract

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.

Review of current progress in nanometrology with the helium ion microscope

“…Hence, a series of preliminary studies were done to to assess the potential of this technology for these purposes. The work includes (1) the basic imaging configurations to assess signal-to-noise conditions, (2) resist damage section comparing performance of the HIM for two different resist systems currently being used in semiconductor lithography, (3) application of a measure of the apparent beam reporting on a resolution measure that is in common use in the semiconductor industry [34][35][36][37], and (4) an assessment of the HIM for cross section imaging mode.…”

“…But, one must always keep in mind that one sample may work better than another for a particular set of operating conditions or instrument design, so one must be continually vigilant that fair evaluations are made. In order to minimize this issue, the semiconductor manufacturing has adopted the concept of apparent beam width or ABW [34][35][36][37]. ABW represents a rough measure of the edge location uncertainty.…”

“…The idea is to use a typical measurand in semiconductor manufacturing such as a photoresist line (as in these experiments) and determine the edge width using common topographic locations. Providing that the edge profile is vertical or even undercut, the edge has been shown to be a sensitive measure of 'resolution' under imaging conditions appropriate for metrology of that particular material or structure [34][35][36][37]. When the edge profile is not ideal, this measure overestimates the true ABW.…”