AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM2-TuM

Paper EM2-TuM4
Oxygen Diffusion and Reduction of Interfacial Layer in high-k Metal Oxide Gate Stacks

Tuesday, November 1, 2005, 9:20 am, Room 312

Session: High-k Dielectric Characterization
Presenter: L.V. Goncharova, Rutgers University
Authors: L.V. Goncharova, Rutgers University
M. Dalponte, Universidade Federal do Rio Grande do Sul, Brazil
T. Gustafsson, Rutgers University
E. Garfunkel, Rutgers University
Correspondent: Click to Email
Deposition of high-k metal oxide films onto Si substrates is accompanied almost unavoidably by the formation of a thin interfacial SiO@sub 2@ layer as a result of oxidation of the Si surface. This layer grows during metal oxide deposition in an oxygen-rich atmosphere or as a result of post-growth annealing treatments. Recently it has been found that deposition of an oxygen-gettering overlayer such as Ti on top of the high-k metal oxide can result in reduction and even possibly elimination of the SiO@sub 2@ interfacial layer. In our the work reported here we use Medium Energy Ion Scattering (MEIS) to focus on understanding (i) the diffusion and thermal stability of oxygen in multilayer high-k gate stacks and (ii) the reduction of interfacial SiO@sub 2@. HfO@sub 2@ films of different thickness were grown on Si(001) substrates with and without nitride incorporation on the interface. To study oxygen transport some of the films were re-oxidized in isotopically labeled @super 18@ O@sub 2@. The interfacial layer and the HfO@sub 2@ layer remain constant during deposition of the Ti overlayer at 300K, with the exception of a small amount of interdiffusion at the Ti/HfO@sub 2@ interface. There is no significant change in interfacial SiO@sub 2@. An ultra-high vacuum anneal (600K, P=10@super -9@ Torr) of the stack results in an immediate change in the oxygen region of the spectrum, accompanied by a lowering and broadening of Ti peak. This is clear evidence that some oxygen is moving towards the outer surface of the film and oxidizes Ti. The oxygen growth in the Ti layer occurs at least partially in parallel with a reduction of interfacial SiO@sub 2@ as it is suggested by a decrease of the interfacial Si peak. This process changes with increasing HfO@sub 2@ crystallinity, opening more permeable diffusive pathways via crystallite grain boundaries. Additional studies of the effects of nitrogen incorporation in the interfacial region and film thickness will be presented.