Effect of RuO2 electrode on laser-MBE prepared HfO2 gate dielectrics

In this paper, we report our recent study of the effect of RuO2 as an alternative top electrode for pMOS devices to overcome the serious problems of polysilicon (poly-Si) gate depletion, high gate resistance and dopant penetration in the trend of down to 50 nm devices and beyond. The conductive oxide RuO2, prepared by RF sputtering, was investigated as the gate electrode on the Laser MBE (LMBE) fabricated HfO2 for pMOS devices. Structural, dielectric and electric properties were investigated. RuO2/HfO2/n-Si capacitors showed negligible flatband voltage shift (<10 mV), very strong breakdown strength (>10 MV cm−1). Compared to the SiO2 dielectric with the same EOT value, RuO2/HfO2/n-Si capacitors exhibited at least 4 orders of leakage current density reduction. The work function value of the RuO2 top electrode was calculated to be about 5.0 eV by two methods, and the effective fixed oxide charge density was determined to be 3.3 × 1012 cm−2. All the results above indicate that RuO2 is a promising alternative gate electrode for LMBE grown HfO2 gate dielectrics.