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(Color online) Schematic of the Quantox system setup. From left to right, the corona ion source, the surface voltage measuring Kelvin probe, and the SPV light source. A high DC voltage placed across the corona wire produces an atmospheric corona ion discharge that diffuses toward the dielectric surface at atmospheric pressures. Charge increments are measured by a backside Coulomb meter connected in series with the wafer chuck. The surface voltage is a contact potential difference (CPD) measurement carried out by a Kelvin probe, typically placed 0.1-1 mm from the dielectric surface. The SPV uses a flash of light, followed consecutively by a surface voltage measurement, to determine the voltage drop on the dielectric.
(a) Low-frequency CV curves of samples measured by COS on Quantox. SiO2 on P-Si (solid points) and an ideal, low-frequency CV curve are obtained by modeling (black dashed line). (b). Capacitance versus silicon band bending graph of samples measured by COS on Quantox. SiO2 on P-Si (solid points) and an ideal, low-frequency capacitance curve are obtained by modeling (black dashed line).
(a) SPV as a function of gate bias in the Si-SiO2 sample. At zero SPV, the MOS is at flat band condition so the applied gate bias is equal to the flat band voltage. (b). Gate bias versus the calculated silicon band bending potential from the experimental data (black dots), and the theoretical fit based on an interface trap free ideal MOS capacitor (dashed line). A diagram of the equivalent circuit of the MOS is inserted, where Cit is the interface traps capacitance, Cs is the capacitance of the Silicon SCR, and Cox is the capacitance of the oxide.
Interface states distribution Dit (E) of the Si-SiO2 interface is obtained by LFCV model fitting of the COS QSCV curve.
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