Memory functions of nanocrystalline indium tin oxide embedded zirconium-doped hafnium oxide MOS capacitors
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A floating gate metal-oxide-semiconductor capacitor memory device utilizing nanocrystalline indium tin oxide (ITO) layer embedded in a zirconium-doped hafnium oxide (Zr-doped Hf O2) high- k gate dielectric has been fabricated and studied. The embedded ITO layer has crystalline structure with a grain size of about 5.4 nm. Capacitance-voltage and current-voltage measurements show positive charge trapping under the negative gate bias operation condition. Comparison to a control sample shows a fourfold increase (5.3 10-12 cm-2 to 1.4 10-12 cm-2) in oxide trapped charge density and opposite trapped charge polarity, indicating that the observed effects are due to the inclusion of the ITO floating gate layer. The device maintains a large postwrite window (>100 mV) over a ten-year period. Furthermore, the prominent charge transfer mechanism is direct tunneling. The negative differential resistance in the current-voltage curve shows the existence of the coulomb blockade effect that may limit negative charge storing and retention. The asymmetrical barrier of the Zr-doped Hf O2 allows for the enhanced hole retention while eliminating the possibility of electron retention. 2007 The Electrochemical Society.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
author list (cited authors)
Birge, A., Lin, C., & Kuo, Y.
complete list of authors
Birge, Adam||Lin, Chen-Han||Kuo, Yue