Molecular identification of nanoscale defects and ultrathin residues with IR PiFM

Derek Nowak; Padraic O'Reilly; Brian Grennon; Sung Park

doi:10.1117/12.2687329

22 November 2023 Molecular identification of nanoscale defects and ultrathin residues with IR PiFM

Derek Nowak, Padraic O'Reilly, Brian Grennon, Sung Park

Proceedings Volume PC12751, Photomask Technology 2023; PC127510Y (2023) https://doi.org/10.1117/12.2687329
Event: SPIE Photomask Technology + EUV Lithography, 2023, Monterey, California, United States

Conference Poster

Abstract

With film thicknesses approaching a few monolayers in semiconductor processes, the chemical state and the cleanliness of the surfaces become critical in determining the outcome of many semiconductor processes. Currently available molecular analytical techniques with sufficient surface sensitivity such as XPS and ToF-SIMS lack the spatial resolution to analyze nanoscale defects and residues. While electron microscopy-based EDX can identify many atomic elements, they cannot provide chemical bonding information, which is needed to assess more accurately the nature and origin of the defects. In this paper, a relatively new hyperspectral technique called infrared photo-induced force microscopy (IR PiFM), which combines atomic force microscopy (AFM) and infrared (IR) spectroscopy with ~ 5 nm spatial resolution, is introduced. By utilizing a state-of-the-art tunable broadband IR laser, truly nanoscale PiF-IR spectra that agree with bulk FTIR spectra can be acquired without contact, i.e., it is non-contaminating and non-destructive, on films as thin as ~ 1 nm. PiF-IR spectra can be used to search existing IR databases to unambiguously identify the chemical species (both organic and inorganic molecules) of sub-20 nm defects and sub-monolayer residues via their IR signatures. Examples of defects and residues analyzed by IR PiFM system for 8” wafers and standard 6” photomasks are presented. For both types of samples, the system can automatically navigate to defect locations per defect map to acquire both topographical and chemical map images of the defects. PiF-IR spectra acquired on the defects and residue can be searched against Wiley’s KnowItAll IR database for potential matches.

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Derek Nowak, Padraic O'Reilly, Brian Grennon, and Sung Park "Molecular identification of nanoscale defects and ultrathin residues with IR PiFM", Proc. SPIE PC12751, Photomask Technology 2023, PC127510Y (22 November 2023); https://doi.org/10.1117/12.2687329

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