On the Voltage and Frequency Distribution of Dielectric Properties and ac Electrical Conductivity in Al/SiO ₂ /p-Si (MOS) Capacitors

Abstract

An Al/SiO2/p-Si (MOS) capacitor with a thick (826 Å) interfacial oxide layer (SiO2) which is formed by using the thermal oxidation method is fabricated to investigate both frequency and applied bias voltage dependences of real and imaginary parts of dielectric constant (𝜀 ′ and 𝜀 ′′ ) and electric modulus (𝑀 ′ and 𝑀 ′′ ), loss tangent (tan 𝛿) and ac electrical conductivity (𝜎ac) in a wide frequency range from 1 kHz to 1 MHz at room temperature. The dielectric properties of the MOS capacitor are obtained using the forward and reverse bias capacitance-voltage (𝐶-𝑉 ) and conductance-voltage (𝐺/𝜔-𝑉 ) measurements in the applied bias voltage range 1.4-5.6 V. The values of 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac are found to be strong functions of frequency and applied bias voltage in the depletion region due to excess capacitance 𝐶ex and conductance 𝐺ex/𝜔 especially at low frequencies. The experimental results show that the interfacial polarization can occur at low frequencies more easily, consequently contributing to the dispersion in 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac values of the MOS capacitor. The other reason for dispersion in the dielectric properties may be attributed to a particular density distribution of interface states (𝑁ss) localized at the Si/SiO2 interface, as well as space charge carriers and inhomogeneity of interfacial oxide layer. The increase in conductivity with increasing frequency can be attributed to the hopping type conduction mechanism. It can be concluded that the 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac values of the Al/SiO2/p-Si (MOS) capacitor are strongly dependent on both the frequency and applied bias voltage especially in the depletion region.

Temperature-dependent dielectric properties of Au/Si 3 N 4 /n-Si (metal—insulator—semiconductor) structures

“…The increase in capacitance with temperature may be due to the interfacial spacecharge formation. [21][22][23][24] In addition, the value of capacitance increases with the frequency decreasing. The high values of the capacitance at low frequencies result from the presences of the interface states at metal/semiconductor interface.…”

Comparison of the MOS capacitor hydrogen sensors with different SiO2 film thicknesses and a Ni-gate film in a 4% hydrogen–nitrogen mixture

“…As indicated in Ref. [27] for MOS structures the value of the real part decreases with a rise in frequency for each bias voltage which corresponds to the depletion region. It remains constant in the inversion and accumulation regions.…”

Electrical and dielectric properties of Al/p-Si and Al/perylene/p-Si type diodes in a wide frequency range

“…Because at this sufficiently high frequency, the charges at interface cannot follow an external ac signal, the contribution of N ss to the total capacitance can be neglected. [10,17,[20][21][22][23][24] The C −2 -V plots for the MS-type and MPS-type SBDs are given in Fig. 6.…”