| The continuous scaling of CMOS devices has necessitated the replacement of SiO2 by an alternative dielectric with a high dielectric constant. Among the extensively studied high-kappa materials, HfO2 is considered to be one of the leading candidates.; The HfO2 film CVD deposition process was investigated first. The introduction of nitric oxide with hafnium t-butoxide leads to smaller effective oxide thickness (EOT) and greatly reduced gate leakage current. EOTs below 1.0 nm have been achieved with this combination of sources. Several different gate electrode materials and processes were then studied. By selecting the proper material and processes, a damage-free metal gate MOS capacitor and MOSFET process has been successfully developed.; Using nMOS capacitors made by the damage-free metal gate process, charge in HfO2 gate stacks, grown from various MOCVD sources, has been evaluated. The charge in the stack is mainly concentrated at the interfaces and is negative at the HfO2/interfacial layer (IL) interface and positive at the Si/IL interface. In general, the calculated charge densities at both interfaces are of order 1012 cm-2. A forming gas anneal can reduce interface charge, hysteresis, and interface state densities. The effect of post deposition anneal depends on the high-kappa film deposition chemistry, indicating that different mechanisms were involved for films grown from different sources.; Stacks consisting of ultrathin (0.2 to 1.2 nm) thermal nitride and HfO 2 were formed and the properties were studied. Measurements of the charge in these stacks appear to be consistent with a model suggesting that the majority of the charge resides at the interface between layers. The presence of a Si 3N4 IL at the (100)Si/HfO2 interface results in significant additional contribution to the trap density.; Finally, both N- and P-channel MOSFETs have been fabricated using a damage-free Cr metal gate non-self-aligned process. The study on the inversion layer mobility indicates that coulomb scattering due to interface trapped charge accounts mainly for the hole mobility degradation. Electron mobility experiences much more severe degradation than hole mobility, suggesting the existence of multiple scattering sources. |
