Hirohisa Yamazaki

Scalability of TiN/HfAlO/TiN MIM DRAM capacitor to 0.7-nm-EOT and beyond

We have proposed guiding principle of material selection of electrode/dielectric combination for MIM DRAM capacitors by theoretically taking the tunneling barrier height into account. Accordingly, we found that phase-controlled HfO2 (HfAlO) with TiN electrode is promising. TiN/HfAlO/TiN MIM capacitors with an ultra-thin Al2O3 on the bottom TiN electrode were fabricated and an EOT of 0.7 nm with a leakage current of 80 nA/cm2 was successfully achieved.

Theoretical Screening of Candidate Materials for DRAM Capacitors and Experimental Demonstration of a Cubic-Hafnia MIM Capacitor

To screen candidate materials for dynamic random-access memory capacitors, the tunneling probability at a constant equivalent oxide thickness (EOT) of metal-insulator-metal (MIM) capacitors was theoretically maximized according to a tradeoff between permittivity and band offset. As a result, it was found that cubic HfO2 with a TiN electrode is a promising candidate. TiN/Al-doped HfO2/TiN MIM capacitors were fabricated by inserting Al2O3 layers for phase control of HfO2 and for suppression of TiN oxidation. The fabricated capacitors exhibit leakage current of 80 nA/cm2 at 1 V and EOT of 0.7 nm. Moreover, the main leakage current was estimated to originate from oxygen vacancies.