International SEMATECH (ISMT) and the National Institute of Standards and Technology (NIST) are working together to improve the traceability of atomic force microscope (AFM) dimensional metrology in semiconductor manufacturing. The rapid pace of technological change in the semiconductor industry makes the timely introduction of relevant standards challenging. As a result, the link between the realization of the SI (Systeme International d'Unites, or International System of Units) unit of length -the meter -and measurements on the fab line is not always maintained. To improve this situation, we are using an at-line critical dimension-AFM (CD-AFM) at ISMT as a developmental platform. This tool has been implemented as a Reference Measurement System (RMS) in the facilities at ISMT. However, it is currently being replaced by a next-generation CD-AFM tool. Using the current tool, we have performed measurements needed to establish the traceability chain and developed uncertainty budgets. Specifically, we have developed uncertainty budgets for pitch, height, and critical dimension (CD) measurements. Some evaluations were performed using samples for which a full traceability chain is not available. We expect to improve the uncertainties further for such samples. At present, the standard uncertainties are estimated to be approximately 0.2 % for pitch measurements, 0.4 % for step height measurements, and 5 nm for CD measurements in the sub-micrometer range. Similar budgets will be developed for the new tool once it is installed. We will describe our methodology for RMS implementation and the major applications for which it has been used. These include measurements on new NIST/ISMT linewidth standards, a reference tool for CD-scanning electron microscopes (SEMs), metrology on photo-masks, CD-SEM benchmarking, and 193 nm resist shrinkage measurements.

International SEMATECH (ISMT) and the National Institute of Standards and Technology (NIST) are working together to improve the traceability of AFM dimensional metrology in semiconductor manufacturing. Due to the unique metrology requirements and the rapid change in the semiconductor industry, relevant standards are often not available. Consequently, there is often no traceable linkage between the realization of the SI (Systeme International d'Unites, or International System of Units) unit of length -the meter -and measurements in the fab line. To improve this situation, we have implemented a Reference Measurement System (RMS) using a next-generation critical-dimension atomic force microscope (CD-AFM). We performed measurements needed to establish a traceability chain and developed uncertainty budgets for pitch, height, and critical dimension (CD) measurements. At present, the standard uncertainties are estimated to be approximately 0.2 % for pitch measurements, 0.4 % for step height measurements, and 5 nm for CD measurements in the sub-micrometer range. Further improvement in these uncertainties is expected with the use of newer samples for scale and tip calibration. We will describe our methodology for RMS implementation and the major applications for which it has been used. These include measurements on new NIST/ISMT linewidth standards, a reference tool for CD-scanning electron microscopes (SEMs), metrology on photo-masks, CD-SEM benchmarking, and 193 nm resist shrinkage measurements. As part of the NIST/ISMT linewidth standards project, we are performing an extensive comparison experiment of AFM and TEM (transmission electron microscopy) measurements of linewidth.

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The sidewalls of etched Si lines will be the carrier channel surfaces in FinFET devices. These surfaces must be as smooth as possible for optimal device performance. Thus, the ability to quantitatively measure sidewall roughness is essential to process development. A methodology to quantitatively measure Fin sidewall roughness by AFM is presented. The samples were prepared for measurement by cleaving along the length of the Fins or dense-line test structures and by FIB polishing to bring the edge of the sample close to the sidewall of the etched feature. The cleaved and FIB-polished sample was mounted 17 degrees shy of normal. This exposes the sidewall on the top surface while preventing shadowing of the lower part of the sidewall due to contact between the side of the probe support and the cleaved or polished edge. Quantitative AFM measurements taken by this method show meaningful differences in the sidewall roughness for samples that have seen different sidewall smoothing treatments. The average observed rms roughness values for various surface-smoothing treatments range from 0.8 to 1.8 Å for a 50 nm square area.

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