Electrical characterization of high-kappa gate dielectrics for high frequency application

The aggressive scaling of CMOS devices is driving SiO2-based gate dielectrics to its physical limits as stated in the International Technology Roadmap for Semiconductors (ITRS). The replacement of SiO2 with a high-kappa material allows for an increase in the physical thickness of the gate insulator, while maintaining a low equivalent oxide thickness and low direct tunneling current. Hf-based dielectric stands out in comparison to the other high-kappa dielectrics and becomes the leading candidate to replace SiO2. The identification of alternate gate dielectrics requires complete characterization. Especially, the electrical characterization of high-kappa gate dielectric is crucial.;In this investigation, the MOS capacitors with various high-kappa materials deposited by atomic layer chemical vapor deposition (ALCVD) are employed as test structures to study the electrical properties of high-kappa materials in the low frequency region. ALCVD is a well-controlled surface saturating process using gas-solid interactions to deposit thin film, which is becoming the primary method for the deposition of gate dielectric in state-of-the-art silicon devices. Through conventional capacitance-voltage (C-V) and current-voltage (I-V) measurements, some important parameters, such as, dielectric constant, threshold voltage, oxide charge/interface states and leakage current density can be obtained. Since most material characterization is routinely performed only in the megahertz frequency range, there is limited information in literature on the performance of high-kappa dielectrics in the high frequency regime, i.e., radio frequency (RF) range. This investigation includes RF characterization of high-kappa dielectrics to provide a comprehensive description. In RF characterization, the focus is placed on hafnium dioxide. The dielectric constant and dielectric loss up to 65 GHz has been successfully measured by the reflection coefficient (S11) measured with a vector network analyzer. By creating a reliable equivalent circuit model, an optimization technique is applied to extract the intrinsic capacitance. The optimizer matches the measured and simulated data over entire frequency range. The error function is less than 0.1% at frequency of 65GHz, which is at least one order magnitude less than reported in literature. For our samples, the high-frequency characteristics are consistent with low-frequency characteristics measured with a LCR meter. This result demonstrates Hf-based high-kappa dielectric can be the promising alternative for high speed device gate dielectric application.