| Scaling of lateral dimensions of Si field effect transistors to <100 nm requires replacement of thermally grown SiO2 by deposited dielectrics with higher dielectric constant than that of SiO2. Physically thicker films with dielectric constants greater than that of SiO2 reduce tunneling and at the same time produce low defect densities at the interfaces. Process-structure relationships are studied for deposition and annealing of ultra-thin films of Ta2O5, alumina doped Ta 2O5, and HfO2 as replacement gate dielectrics for silicon dioxide in complementary metal oxide semiconductor and other devices.; Novel high dielectric constant nanometer scale hetero-structures of Ta 2O5 and alumina-doped Ta2O5 as well as their resulting interfaces are studied in detail and process-structure relationships are established.; Thin films of hafnium oxide are deposited on Si(100) substrates by means of the novel technique of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and HfCl4 as the hafnium precursors and water vapor as the oxygen source. The thermal stability of ALD HfO2 films is probed with subsequent annealing at various temperatures (600--1000°C) in Ar ambient. No growth of interfacial silicon oxide is observed during deposition. The post annealed films show increase in interfacial silicon oxide thickness coupled with formation of silicate-like structure as the annealing temperature is increased. This is evident from independent sets of data of infrared and x-ray photoelectron spectroscopies. At the highest annealing temperature used (i.e., 1000°C), formation of hafnium silicide is observed at the interface. From these studies, detailed fundamental information of interfacial changes due to thermal annealing is obtained, presented and discussed.; For the first time, technique with a spatial resolution of 0.2 nm has revealed interfacial changes in hetero-structures containing SiOx, HfO2 and HfSiOx, when such structures are ALD grown and annealed in inert ambient at temperatures up to 1000°C. Annealing within the electron microscope up to 800°C and subsequent probing has also been done for the first time in these systems. All results are discussed in the context of the SiOx interlayer, HfO2:SiO 2 inter-diffusion, the formation of silicate-like structures, and ultra thin film stoichiometric analyses. |
