Negative Charge in Plasma Oxidized SiO2 Layers

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    Silicon dioxide (SiO2) gate dielectric layers (4-60 nm thick) were deposited (0.6 nm/min) on n-type Si by inductively-coupled plasmaenhanced chemical vapor deposition (ICPECVD) in strongly diluted silane plasmas at 150°C . In contrast to the well-accepted positive charge for thermally grown SiO2, the net oxide charge was negative and a function of the layer thickness. Our experiments suggested that the negative charge was created due to unavoidable oxidation of the silicon surface by plasma species, and the CVD component adding a positive space charge to the deposited oxide. The net charge was negative under process conditions where plasma oxidation played a major role. Such conditions included low deposition rates and relatively thin grown layers. Additional measurements showed that the negative charge in SiO2 also persisted on p-type substrates. We suggest that plasma oxidation of the silicon surface results in SiO2 layers with a surplus of oxygen. This surplus of oxygen is able to accumulate a negative charge. This assumption is addressed in this paper by a review of earlier work on silicon oxidation, and by a first series of experiments wherein oxygen is implanted into thermal SiO2. It is shown that the implantation can result in a negative charge to the bulk oxide layer. The effect of the negative charge on the flatband voltage can be described by the implantation profile.
    Original languageUndefined
    Title of host publication219th ECS Meeting
    Place of PublicationUSA
    PublisherThe Electrochemical Society Inc.
    Number of pages14
    Publication statusPublished - 1 Jul 2011
    Event219th ECS Meeting - The Palais des Congres de Montreal, Montreal, QC, Canada
    Duration: 1 May 20116 May 2011
    Conference number: 219

    Publication series

    NameECS Meeting Abstracts
    PublisherThe Electrochemical Society
    ISSN (Print)1938-5862
    ISSN (Electronic)1938-6737


    Conference219th ECS Meeting
    CityMontreal, QC

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