HfO2 MIS capacitor with copper gate electrode

Metal-insulator-semiconductor capacitors were fabricated using atomic vapor deposition HfO₂ dielectric with sputtered copper (Cu) and aluminum (Al) gate electrodes. The counterparts with SiO₂ dielectric were also fabricated for comparison. Bias-temperature stress and charge-to-breakdown (Q_BD) test were conducted to examine the stability and reliability of these capacitors. In contrast with the high Cu drift rate in an SiO₂ dielectric, Cu in contact with HfO₂ seems to be very stable. The HfO₂ capacitors with a Cu-gate also depict higher capacitance without showing any reliability degradation, compared to the Al-gate counterparts. These results indicate that HfO₂ with its considerably high density of 9.68 g/cm³ is acting as a good barrier to Cu diffusion, and it thus appears feasible to integrate Cu metal with the post-gate-dielectric ultralarge-scale integration manufacturing processes.