Abstract
A comparative analysis of metal-oxide-semiconductor (MOS) capacitors by capacitance-voltage and current-voltage characteristics has been employed to characterize the thickness variations of the oxide on different length scales. Ultralarge area ultrathin ( oxide) MOS capacitors have been fabricated to investigate their functionality and the variations in oxide thickness, with the use as future electron emission devices as the goal. characteristics show very low leakage current and excellent agreement to the Fowler-Nordheim expression for the current density. Oxide thicknesses have been extracted by fitting a model based on Fermi-Dirac statistics to the characteristics. By plotting characteristics in a Fowler plot, a measure of the thickness of the oxide can be extracted from the tunnel current. These apparent thicknesses show a high degree of correlation to thicknesses extracted from characteristics on the same MOS capacitors, but are systematically lower in value. This offset between the thicknesses obtained by characteristics and characteristics is explained by an inherent variation of the oxide thickness. Comparison of MOS capacitors with different oxide areas ranging from , using the slope from Fowler-Nordheim plots of the characteristics as a measure of the oxide thickness, points toward two length scales of oxide thickness variations being and , respectively.
- Received 16 May 2007
DOI:https://doi.org/10.1103/PhysRevB.76.155315
©2007 American Physical Society