V. Misra et al., Use of metal-oxide-semiconductor capacitors to detect interactions of Hf and Zr gate electrodes with SiO2 and ZrO2, APPL PHYS L, 78(26), 2001, pp. 4166-4168
Metal-oxide-semiconductor capacitors were used to study the interaction of
Hf and Zr gate electrodes on SiO2, ZrSixOy, and ZrO2. A large reduction in
the SiO2 equivalent oxide thickness accompanied by an increase in the leaka
ge current was observed with Hf and Zr electrodes when subjected to anneal
temperatures as low as 400 degreesC. The reduction in electrical thickness
as observed from the capacitance-voltage measurements was attributed to the
combination of (a) physical thinning of the SiO2 and (b) formation of a hi
gh-K layer. A severe instability of Zr and Hf electrodes was also observed
on ZrSixOy and ZrO2 dielectrics. This behavior of Zr and Hf gates was attri
buted to high negative enthalpy of oxide formation and high oxygen solubili
ty resulting in the reduction of the gate dielectric and subsequent oxygen
diffusion to the gate electrode. (C) 2001 American Institute of Physics.