Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput

Bernard Haochih Liu, Jason R. Osborne, Marc Osborn, Gregory A. Dahlen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

18 Citations (Scopus)

Abstract

As semiconductor and data storage industries apply Critical Dimension Atomic Force Microscopy (CD-AFM) for their metrology needs in research and production, (1) measurement accuracy/repeatability and (2) measurement throughput are the major criteria for acceptance. However, these two requirements are usually contradictory for a metrology instrument. For example, a scatterometer can take a snapshot of a wafer in seconds, but such indirect CD measurements are biased by the availability of library models and uncertainty of computer simulations. Transmission Electron Microscopy (TEM) provides an atomic-scale resolution that is traceable back to the lattice structure of atoms, yet the cross-section data is highly localized and can take days or weeks to acquire. In the case of CD-AFM, since the scanning probe physically interacts with the structure of interest at a close proximity, the determination of sample morphology comes from direct measurements. Therefore, the measurement uncertainty can be attributed to: (1) AFM probe tip shapes and (2) system control and scan algorithms. For the former, past efforts have been mainly focused on improving metrology accuracy and repeatability by reducing the dimensional uncertainty of a tip shape. This approach includes characterizing the probe tip shape periodically. Inevitably, such tip shape calibration procedure takes time (approximately 5 min) and burdens production throughput. In this paper, we introduce several new methods for AFM probe tip shape characterization with different designs of tip shape characterizers. The new tip shape characterizers were designed to address the limitation of current structures. First, a single silicon overhang structure with wear-resistant coatings was used as the characterizer for both tip width and tip shape profile. Tip-to-tip scan repeatability data (0.7 nm 3 Sigma) and measurement statistics suggest an improvement over present state-of-the-art practice. Tip shape profiles of several high aspect ratio (20:1 to 25:1), low lateral stiffness probes were successfully characterized with this method. Furthermore, the use of single characterizer provides an opportunity to shorten tool calibration time, and consequently, increase measurement throughput. In addition, a carbon nanotube characterizer prototype is proposed for CD-AFM. When scanning probe geometry shrinks with semiconductor technology nodes, it has become a challenge to characterize a probe with a few tens of nanometer of width with a micrometer-size characterizer. Using a comparable or smaller size of characterizer for a small (20 to 50 nm) AFM probe not only reduces the dimensional uncertainty, but also expands the 2-D profiling capability of current tip shape characterization. We will discuss limitations of current tip shape profiling techniques, proof-of-concept experiments for new characterizers, implementation of new tip shape characterization methods, and approaches to increasing measurement throughput.

Original languageEnglish
Title of host publicationMetrology, Inspection, and Process Control for Microlithography XXI
EditionPART 3
DOIs
Publication statusPublished - 2007 Oct 15
EventMetrology, Inspection, and Process Control for Microlithography XXI - San Jose, CA, United States
Duration: 2007 Feb 262007 Mar 1

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
NumberPART 3
Volume6518
ISSN (Print)0277-786X

Other

OtherMetrology, Inspection, and Process Control for Microlithography XXI
CountryUnited States
CitySan Jose, CA
Period07-02-2607-03-01

Fingerprint

Atomic Force Microscopy
Critical Dimension
Metrology
metrology
Atomic force microscopy
Throughput
Probe
atomic force microscopy
probes
Repeatability
Profiling
Uncertainty
Semiconductor storage
Scanning
Semiconductors
Calibration
Carbon Nanotubes
Measurement Uncertainty
Silicon
Lattice Structure

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

Cite this

Liu, B. H., Osborne, J. R., Osborn, M., & Dahlen, G. A. (2007). Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput. In Metrology, Inspection, and Process Control for Microlithography XXI (PART 3 ed.). [65183K] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 6518, No. PART 3). https://doi.org/10.1117/12.710437
Liu, Bernard Haochih ; Osborne, Jason R. ; Osborn, Marc ; Dahlen, Gregory A. / Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput. Metrology, Inspection, and Process Control for Microlithography XXI. PART 3. ed. 2007. (Proceedings of SPIE - The International Society for Optical Engineering; PART 3).
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abstract = "As semiconductor and data storage industries apply Critical Dimension Atomic Force Microscopy (CD-AFM) for their metrology needs in research and production, (1) measurement accuracy/repeatability and (2) measurement throughput are the major criteria for acceptance. However, these two requirements are usually contradictory for a metrology instrument. For example, a scatterometer can take a snapshot of a wafer in seconds, but such indirect CD measurements are biased by the availability of library models and uncertainty of computer simulations. Transmission Electron Microscopy (TEM) provides an atomic-scale resolution that is traceable back to the lattice structure of atoms, yet the cross-section data is highly localized and can take days or weeks to acquire. In the case of CD-AFM, since the scanning probe physically interacts with the structure of interest at a close proximity, the determination of sample morphology comes from direct measurements. Therefore, the measurement uncertainty can be attributed to: (1) AFM probe tip shapes and (2) system control and scan algorithms. For the former, past efforts have been mainly focused on improving metrology accuracy and repeatability by reducing the dimensional uncertainty of a tip shape. This approach includes characterizing the probe tip shape periodically. Inevitably, such tip shape calibration procedure takes time (approximately 5 min) and burdens production throughput. In this paper, we introduce several new methods for AFM probe tip shape characterization with different designs of tip shape characterizers. The new tip shape characterizers were designed to address the limitation of current structures. First, a single silicon overhang structure with wear-resistant coatings was used as the characterizer for both tip width and tip shape profile. Tip-to-tip scan repeatability data (0.7 nm 3 Sigma) and measurement statistics suggest an improvement over present state-of-the-art practice. Tip shape profiles of several high aspect ratio (20:1 to 25:1), low lateral stiffness probes were successfully characterized with this method. Furthermore, the use of single characterizer provides an opportunity to shorten tool calibration time, and consequently, increase measurement throughput. In addition, a carbon nanotube characterizer prototype is proposed for CD-AFM. When scanning probe geometry shrinks with semiconductor technology nodes, it has become a challenge to characterize a probe with a few tens of nanometer of width with a micrometer-size characterizer. Using a comparable or smaller size of characterizer for a small (20 to 50 nm) AFM probe not only reduces the dimensional uncertainty, but also expands the 2-D profiling capability of current tip shape characterization. We will discuss limitations of current tip shape profiling techniques, proof-of-concept experiments for new characterizers, implementation of new tip shape characterization methods, and approaches to increasing measurement throughput.",
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Liu, BH, Osborne, JR, Osborn, M & Dahlen, GA 2007, Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput. in Metrology, Inspection, and Process Control for Microlithography XXI. PART 3 edn, 65183K, Proceedings of SPIE - The International Society for Optical Engineering, no. PART 3, vol. 6518, Metrology, Inspection, and Process Control for Microlithography XXI, San Jose, CA, United States, 07-02-26. https://doi.org/10.1117/12.710437

Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput. / Liu, Bernard Haochih; Osborne, Jason R.; Osborn, Marc; Dahlen, Gregory A.

Metrology, Inspection, and Process Control for Microlithography XXI. PART 3. ed. 2007. 65183K (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 6518, No. PART 3).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Liu BH, Osborne JR, Osborn M, Dahlen GA. Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput. In Metrology, Inspection, and Process Control for Microlithography XXI. PART 3 ed. 2007. 65183K. (Proceedings of SPIE - The International Society for Optical Engineering; PART 3). https://doi.org/10.1117/12.710437