Line-to-line repetitive control of a 6-DoF hexapod stage for overlay measurements using Atomic Force Microscopy

Gert Witvoet, Joost Peters, Stefan Kuiper, Tom Oomen

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

4 Citations (Scopus)


The overlay performance between different layers of semiconductor devices is a key parameter for correct functionality of such devices. With device features getting increasingly smaller, there is a need for novel and more accurate overlay metrology tools. This paper aims to increase the positioning accuracy of such a novel metrology machine below the nanometer by the application of repetitive control. At the heart of the machine is a large stroke 6-DoF hexapod motion stage, carrying a sub-nanometer accurate AFM head, whose positioning accuracy during scanning is a key performance driver. The sample under examination during scanning effectively forms an unknown repetitive disturbance on its feedback loop. For this reason a line-to-line repetitive controller in combination with decentralized feedback has been employed, in which the base harmonic is defined by one full line-scan. Experimental results on the machine with an emulated sample demonstrate a significant performance improvement, achieving nanometer accurate positioning while scanning. This shows that repetitive control in a line-to-line domain is a potential enabler for AFM-based overlay nanometrology.

Original languageEnglish
Title of host publication2019 American Control Conference, ACC 2019
Place of PublicationPiscataway
PublisherInstitute of Electrical and Electronics Engineers
Number of pages6
ISBN (Electronic)978-1-5386-7926-5
Publication statusPublished - 1 Jul 2019
Event2019 American Control Conference (ACC 2019) - Philadelphia, United States
Duration: 10 Jul 201912 Jul 2019


Conference2019 American Control Conference (ACC 2019)
Abbreviated titleACC2019
Country/TerritoryUnited States
Internet address


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