Effect of RuO 2 electrode on laser-MBE prepared HfO 2 gate dielectrics

Abstract

In this paper, we report our recent study of the effect of RuO 2 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 RuO 2, prepared by RF sputtering, was investigated as the gate electrode on the Laser MBE (LMBE) fabricated HfO 2 for pMOS devices. Structural, dielectric and electric properties were investigated. RuO 2/HfO 2/n-Si capacitors showed negligible flatband voltage shift (<10 mV), very strong breakdown strength (>10 MV cm −1). Compared to the SiO 2 dielectric with the same EOT value, RuO 2/HfO 2/n-Si capacitors exhibited at least 4 orders of leakage current density reduction. The work function value of the RuO 2 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 × 10 12 cm −2. All the results above indicate that RuO 2 is a promising alternative gate electrode for LMBE grown HfO 2 gate dielectrics.