Non-destructive roughness analysis of high aspect ratio rectangular grating sidewalls for nanostructured silicon wafer

Dario Loaldi*, Danilo Quagliotti, Matteo Calaon, Ilja Czolkos, Alicia Johansson, Theodor Nielsen, Jørgen Garnæs, Guido Tosello

*Corresponding author for this work

Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

Abstract

The development of nanostructured sample components led to significant interest in metrological solutions and characterization methodologies for features laying on the nanoscale dimensional range. For the specific case of silicon lithography technologies, a well-known case geometry consists of rectangular gratings structures. Among the available equipment, the most commonly employed are Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). For what concerns sidewalls, limited tools and methodologies are available, both for the evaluation of surface roughness and geometrical features. In this study, the use of AFM explores the measurements of surface roughness of rectangular grating sidewalls. The structures under analysis consist of a periodic structure manufactured by of Deep-Ultraviolet-Lithography (DUV) and subsequent dry etching on a silicon wafer, to generate a nominal pitch of 1400 nm (nominal trench size of 700 nm) and a nominal depth of 1130 nm. The resulting structure has a high aspect ratio (ratio between the nominal depth and trench width) of 1.6. The wafer is tilted beneath the microscope on an inclined stage (20°) to access the sidewalls of the grating. The adopted methodology enables the evaluation of surface roughness and geometry of the sidewalls in a non-destructive way. Different sampling lengths and locations are evaluated to investigate the cross-sections of the grating along multiple sidewalls. The results confirm that an isotropic sidewall surface with limited undercut formation along the depth is generated. Considering the variations within the standard deviation, the measured Ra roughness lies below 3 nm on a projected profile length of 650 nm, which corresponds to about 60 % of the total depth of the structure.
Original languageEnglish
Publication date2020
Publication statusPublished - 2020
Event20th International Conference of the european Society for Precision Engineering and Nanotechnology (euspen 20) - Online, Geneva, Switzerland
Duration: 8 Jun 202012 Jun 2020

Conference

Conference20th International Conference of the european Society for Precision Engineering and Nanotechnology (euspen 20)
LocationOnline
Country/TerritorySwitzerland
CityGeneva
Period08/06/202012/06/2020

Keywords

  • Nano Technology
  • Metrology
  • Atomic Force Microscopy (AFM)
  • Wafer

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