Hafnium oxide and hafnium aluminum oxide for CMOS applications

The continued scaling of the CMOS gate dielectric to its fundamental limit governed by the large gate leakage current requires the introduction of high-k material for sub-100-nm technology nodes. This dissertation research deals with the physical and electrical properties of a promising high-k candidate, hafnium oxide, as a gate dielectric for CMOS applications.; Hafnium oxide made by the Jet-Vapor-Deposition process shows very promising properties in terms of surface roughness, dielectric constant, and energy bandgap, but there are also severe challenges, such as low crystallization temperature, high charge trapping probability, and low channel mobility, which have been studied in detail in this thesis.; We have found that the crystallization of HfO₂ could result in a significant increase of the leakage current. This problem has been solved by adding Al in the HfO₂ film. The impacts of Al inclusion in HfO ₂ film on crystallization temperature, bandgap energy, and dielectric constant have been investigated. Considering the trade-off among the crystallization temperature, bandgap energy, and dielectric constant, we have concluded that the optimum concentration is about 30% Al for conventional self-aligned CMOS gate processing technology.; The charge trapping properties of ultra-thin HfO₂ in metal-oxide-silicon capacitors during constant voltage stress have also been investigated. The effects of stress voltage, substrate type, annealing temperature, and gate electrode have been studied in detail, and reported in this dissertation.; Accurate measurements and degradation mechanisms of the channel mobility for MOSFETs with HfO₂ as the gate dielectric have been systemetically studied. The error in mobility extraction caused by a high density of interface traps for a MOSFET with high-k gate dielectric has been analyzed, and a new method to correct this error has been proposed. Other sources of error in mobility extraction, including gate leakage current, channel resistance, and contact resistance for a MOSFET with ultra-thin high-k dielectric have also been investigated and reported in this thesis. Based on the accurately measured channel mobility, we have analyzed the degradation mechanisms of channel mobility for a MOSFET with HfO₂ as the gate dielectric. The mobility degradation due to Coulomb scatting arising from interface trapped charges, and that due to remote soft optical phonon scattering are discussed.