Study on high-k dielectrics as alternative gate insulators for 0.1 micron and beyond ULSI applications

Over the last several decades, there has been a continuous miniaturization of microelectronics devices. As the scaling down process continues to sub 100nm regime, some fundamental problems arise. Gate oxide thickness limit is one of the major obstacles. Conventional thermal oxide or oxynitride will have to be replaced due to the excess direct tunneling current and reliability concerns. However, finding alternatives for the well-characterized thermal oxide is a tremendous task. Gate oxide is in the heart of the MOSFET. The alternatives would have to meet requirements such as thin equivalent oxide thickness, low leakage, acceptable channel mobility, good reliability, and good CMOS technology compatibility as well. High-k materials have been considered as alternatives. The objective of this work is to explore the feasibility of using ZrO2 and Zr-silicate as alternative gate dielectrics. These materials are chosen because of their high dielectric constant, thermodynamic stability in contact with Si, and high barrier heights for electrons and holes.;A DC-magnetron-reactive sputtering process has been developed for ZrO 2 deposition. Through process optimization, thin equivalent oxide thickness of less than 10A with low leakage can be obtained. ZrO2 also exhibits negligible frequency dispersion, low hysteresis, and low interface state density. ZrO2 shows excellent reliability characteristics such as good TDDB, less temperature acceleration, and high 10-year operating voltage. A DC-magnetron-reactive cosputtering process was developed for Zr-silicate deposition as well. A variety of Zr concentrations in Zr-silicate have been obtained. Zr-silicates also exhibit thin equivalent oxide thickness, low leakage, negligible hysteresis, and good reliability. Zr-silicate shows a single layer structure with a sharp interface with Si.;MOSFET characteristics have been studied for both ZrO2 and Zr-silicate. Both exhibit wellbehaved transistor characteristics such as low S, reasonable gm, and mobility. Zr-silicate shows high effective mobility compared to ZrO2, demonstrating some trade-offs between these two dielectrics.;Overall, encouraging results have been obtained for both ZrO2 and Zr-silicate gate dielectrics. They seem to be promising candidates for alternative gate dielectric applications.