[
    {
        "id": "authors:x0aak-j5s42",
        "collection": "authors",
        "collection_id": "x0aak-j5s42",
        "cite_using_url": "https://authors.library.caltech.edu/records/x0aak-j5s42",
        "type": "article",
        "title": "Atomic layer etching of niobium nitride using sequential exposures of O\u2082 and H\u2082/SF\u2086 plasmas",
        "author": [
            {
                "family_name": "Hossain",
                "given_name": "Azmain A.",
                "orcid": "0000-0002-4980-1437",
                "clpid": "Hossain-Azmain-Abrawr"
            },
            {
                "family_name": "Murphy",
                "given_name": "Sela",
                "orcid": "0009-0004-1407-5051"
            },
            {
                "family_name": "Catherall",
                "given_name": "David S.",
                "orcid": "0000-0002-3540-2419",
                "clpid": "Catherall-David-Spencer"
            },
            {
                "family_name": "Ardizzi",
                "given_name": "Anthony J.",
                "orcid": "0000-0001-8667-1208",
                "clpid": "Ardizzi-Anthony-Joseph"
            },
            {
                "family_name": "Minnich",
                "given_name": "Austin J.",
                "orcid": "0000-0002-9671-9540",
                "clpid": "Minnich-A-J"
            }
        ],
        "abstract": "<p>Niobium nitride (NbN) is a metallic superconductor that is widely used for superconducting electronics due to its high transition temperature (T\ua700<span class=\"inline-formula no-formula-id\">\u2060</span>) and kinetic inductance. Processing-induced damage negatively affects the performance of these devices by increasing the microwave surface loss. Atomic layer etching (ALE), with its ability to etch with angstrom-scale control and low damage, has the potential to address these issues, but no ALE process is known for NbN. Here, we report such a process consisting of sequential exposures of O<sub>2</sub>&nbsp;plasma and H<sub>2</sub>/SF<sub>6</sub>&nbsp;plasma. Exposure to O<sub>2</sub>&nbsp;plasma rather than O<sub>2</sub>&nbsp;gas yields a greater fraction of Nb in the +5 oxidation state, which is then volatilized by NbF<sub>5</sub>&nbsp;formation with exposure to an H<sub>2</sub>/SF<sub>6</sub>&nbsp;plasma. The SF<sub>6</sub>:H<sub>2</sub>&nbsp;flow rate ratio is chosen to produce selective etching of Nb<sub>2</sub>O<sub>5</sub>&nbsp;over NbN, enabling self-limiting etching within a cycle. An etch rate of 1.77&thinsp;&Aring;/cycle was measured at 125&thinsp;<span class=\"inline-formula no-formula-id\"> &deg;</span>C using&nbsp;<em>ex situ</em> ellipsometry. The T\ua700 of the ALE-treated film is higher than that of a reactive ion etching-treated film of similar thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of NbN in single-photon detectors and superconducting microresonators.</p>",
        "doi": "10.1116/6.0004548",
        "issn": "0734-2101",
        "publisher": "American Vacuum Society",
        "publication": "Journal of Vacuum Science & Technology A",
        "publication_date": "2025-07",
        "series_number": "4",
        "volume": "43",
        "issue": "4"
    }
]