Abstract
In this thesis, various Zr-based high-κ dielectrics are widely discussed for the application of nonvolatile memory, MOS device, and MIM capacitors. This study can be roughly divided into two parts. At first part, the tetragonal ZrO2 (t-ZrO2) or cubic ZrO2 (c-ZrO2) is formed by different fabrication process and used as charge-trapping layer for flash memory and gate dielectric for MOS device, respectively. For Nonvolatile memopry, a tetragonal ZrO2 film was introduced as the charge-trapping layer for nonvolatile memory and the impact of NH3 nitridation of the tetragonal ZrO2 film on memory performance was also explored. This is the pioneering research on the use of crystalline high-κ material as the charge-trapping layer and the drawbacks of the crystalline high-κ material have been avoided by the appropriate nitridation, which results in a high operation speed in terms of 2.6-V flatband voltage shift by programming at +10 V for 10 ms and a good retention characteristic. On the other hand, an amorphous ZrON film and ZrON crystallized to a cubic ZrO2 film by thermal annealing were used as the charge-trapping layer to explore the impact of crystallinity of high-κ dielectric on memory performance. The memory with a nitrogen-stabilized cubic ZrO2 film shows promising performance in terms of 3.81-V hysteresis memory window by ±7-V program/erase voltage. As compared to that with an amorphous ZrON film, the improved performance is due to the greatly enhanced κ-value of 32.8 and the increased trapping sites provided by grain boundaries. For the MOS device application, the tetragonal ZrO2 was deposited by the atomic layer deposition (ALD) as the gate dielectrics. In this work, the electrical characteristics of the t-ZrO2/Al2O3 or Al2O3/ t-ZrO2 gate stack sequence have been studied, and an approach to effectively suppress leakage current has been proposed. As compared to the Al2O3/t-ZrO2/Si stack, the thermally stable t-ZrO2/Al2O3/Si stack for the gate dielectric demonstrates larger capacitance, smaller hysteresis, better frequency dispersion, lower leakage current, and more robust reliability. A further reduced leakage current can be achieved by additional NH3 nitridation of t-ZrO2 to well passivate the grain boundaries without sacrificing its κ-value. In addition to the ALD system, a Ge-stabilized t-ZrO2 film formed by depositing a ZrO2/Ge/ZrO2 laminate by an electron beam evaporation tool and a subsequent annealing was proposed, which provides a more reliable approach to control the dopant concentration. By combining thin SiON as an interfacial layer, the SiON/t-ZrO2 gate stack shows tiny amount of hysteresis and negligible frequency dispersion in capacitance voltage (C–V) characteristics. In this work, by passivating leaky channels derived from grain boundaries with NH3 plasma, good leakage current is achieved and desirable reliability is also obtained. For the second part of this thesis, we focus on the amorphous Zr-based high-κ oxides applications, including (ZrO2)x(La2O3)1−x alloy and ZrLaOx/ZrTiOx/ZrLaOx Laminate. First, an amorphous (ZrO2)x(La2O3)1-x alloy formed by ZrO2/La2O3/ZrO2 laminate followed by a thermal annealing was integrated with a thermally grown SiON interfacial layer as a gate stack, and its chemical as well as electrical characteristics were investigated. By integrating the (ZrO2)x(La2O3)1-x alloy with an SiON interfacial layer as the gate stack, it displays good frequency dispersion in capacitance–voltage (C–V ) characteristics and low interfacial trap density of 1.52 × 1011 cm−2 eV−1 . In addition, the current conduction mechanism of the gate stack is observed to be Fowler–Nordheim tunneling and the leakage current of 3.6 × 10−6 A/cm2 at the gate voltage of −1 V for equivalent oxide thickness (EOT) of 1.1 nm can be achieved Moreover, satisfactory reliability is verified by bias temperature instability measurement. For the MIM capacitors application, ZrTiOx with an even higher κ value was found to have a negative VCC-α and its application for MIM capacitors was studied. further investigation on the possible effects of O2 annealing on VCC-α and interfacial layer formation for ZrTiOx was also performed in this work By integrating the ZrTiOx with ZrLaOx which corresponds to a positive VCC-α, MIM capacitors with ZrLaOx/ZrTiOx/ZrLaOx laminate demonstrate great potential for next-generation RF/analog ICs applications because of a high capacitance density of 14.6 fF/μm2, a low VCC-α of 33 ppm/V2, nearly frequency-dependence capacitance and satisfactory leakage performance. In this study, to overcome the continuous scaling challenge of CMOS device, the crystalline and amorphous Zr-based high-κ dielectrics have been successfully developed for nonvolatile memory、MOS device, and MIM capacitor applications. In addition, by integrating with high quality interfacial layer or the follow-up plasma nitridation treatment, it holds the great potential for next-generation CMOS technology.