Effect of Post Metallization Annealing for La 2 O 3 Thin Film

2.2 Characterization MethodsIn this section, the methods for characterization of MIS capacitors will bedescribed in pages that follow.2.2.1 Capacitance-Voltage (C-V) CharacteristicsC-V characteristics were obtained by using Precision LCR Meter (HP4284A, Agilent) to measure the MIS capacitor’s impedance as RC seriescircuit. The high-frequency from 10 kHz to 1MHz voltage, whose amplitudewas 20 mV, was applied on the d.c. voltage for bias.Figure 2-8 shows the ideal high-frequency C-V characteristics ofn-type Si MIS capacitor. The ideal equivalent circuit is composed of a seriescapacitance of insulator component, Cinsulator and silicon surface component,Cs. When positive bias is applied to the metal side, it is called accumulationregion. There is no current flow in the structure in the case of an ideal MIScapacitor. Therefore, voltage causes band bending at silicon surface andaccumulation of majority carriers (electrons). This is the reason that thiscase is called accumulation. Total capacitance in unit area of C isindependent on applied voltage and given byC C insulatorε εt0 r= = , (2.1)where ε0and ε rare vacuum and relative dielectric constant, respectivelyand t is the thickness of the insulator. The value of vacuum dielectricconstant is about 8.85× 10 −14 [F/cm]. C decreases near zero bias becausebroadening of accumulation charge causes series capacitance.When zero bias is applied and surface potential is zero, MIS capacitoris in flat band condition. Silicon surface capacitance of Cs is not zero andgiven byεε0 rNdCsfb= q , (2.2)kT−1923where q= 1.6× 10 C is the electronic charge, k = 1.38× 10 − J / K isBoltzmann’s constant, T is the absolute temperature and Nd is the density ofionized donors. From these equations, flat band capacitance of Cfb isobtained as following equation,- 22 -