Frequency Dependence of C-V Characteristics of MOS Capacitors Containing Nanosized High-κ Ta₂O₅ Dielectrics

Abstract

Capacitance of metal-insulator-Si structures containing high permittivity dielectric exhibits complicated behaviour when voltage and frequency dependencies are studied. From our study on metal (Al, Au, W)-Ta 2 O 5 /SiO 2 -Si structures, we identify serial C-R measurement mode to be more convenient for use than the parallel one usually used in characterization of similar structures. Strong frequency dependence that is not due to real variations in the dielectric permittivity of the layers is observed. Very high capacitance at low frequencies is due to the leakage in Ta 2 O 5 layer. We found that the above observation is mainly due to different leakage current mechanisms in the two different layers composing the stack. The effect is highly dependent on the applied voltage, since the leakage currents are strongly nonlinear functions of the electric field in the layers. Additionally, at low frequencies, transition currents influence the measured value of the capacitance. From the capacitance measurements several parameters are extracted, such as capacitance in accumulation, effective dielectric constant, and oxide charges. Extracting parameters of the studied structures by standard methods in the case of high-/interfacial layer stacks can lead to substantial errors. Some cases demonstrating these deficiencies of the methods are presented and solutions for obtaining better results are proposed.

Refined analysis of C–V and I–V characteristics of Al/dielectric/Si structures containing nanosized Ta2O5/SiOxNy dielectric stack

“…The position of the knee in this case is at about 1.5 V at negative gate polarity. Such a knee is not observed in the case of nonreactive gates (W and Au [23]), even if the dielectric layer is nanosized (10 nm thick Ta 2 O 5 /SiO 2 dielectric stack), while in the case of the reactive Al gate, a small knee at around 1.5 V at negative gate polarity is clearly visible. For substantially thicker films than 10 nm, even in the case of the reactive Al gate, no peak in the distribution of D it close to the valence band edge is observed ( [8] for 50 nm thick Ta 2 O 5 /SiO 2 dielectric stack and [24] for 30 thick Ta 2 O 5 /SiO x N y Based on this, it is to be concluded that in the case of nanosized Ta 2 O 5 dielectric layers, reaction of the Al with Ta 2 O 5 causes damage in the interfacial layer.…”

The effect of the thickness on structural, optical limiting, and dielectric properties of hybrid coatings rhodamine B dye films on an epoxy polymeric substrate for display applications

“…To investigate the frequency dependence of the effective series and parallels capacitance for the pure epoxy polymeric substrate and its coatings RhB dye thicknesses, we measured the capacitance in Cs (serial) mode in the frequency range from 3 kHz to 10MHz, with the use of a semiconductor characterization system 4200-SCS KEITHLEY. The model developed in [48] was used to explain the obtained results. More details on the model and its application can be found in the same work.…”

“…More details on the model and its application can be found in the same work. The measured serial capacitance C s can be expressed as follow [48]:…”