Impacts of Annealing Conditions on the Flat Band Voltage of Alternate La(2)O(3)/Al(2)O(3) Multilayer Stack Structures

The mechanism of flat band voltage (V(FB)) shift for alternate La(2)O(3)/Al(2)O(3) multilayer stack structures in different annealing condition is investigated. The samples were prepared for alternate multilayer structures, which were annealed in different conditions. The capacitance-voltage (C-V) measuring results indicate that the V(FB) of samples shift negatively for thinner bottom Al(2)O(3) layer, increasing annealing temperature or longer annealing duration. Simultaneously, the diffusion of high-k material to interfaces in different multilayer structures and annealing conditions is observed by X-ray photoelectron spectroscopy (XPS). Based on the dipole theory, a correlation between the diffusion effect of La towards bottom Al(2)O(3)/Si interface and V(FB) shift is found. Without changing the dielectric constant k of films, V(FB) shift can be manipulated by controlling the single-layer cycles and annealing conditions of alternate high-k multilayer stack.