Takashi Onaya

Improvement in ferroelectricity of Hf x Zr1− x O2 thin films using ZrO2 seed layer

The effect of crystallized ZrO2 (ZrO2-seed), amorphous Hf0.43Zr0.57O2 (HZO; HZO-seed), and amorphous Al2O3 (Al2O3-seed) seed layers on the ferroelectricity of HZO films was investigated. The remanent polarization () of a TiN-electroded capacitor with a ZrO2-seed layer was much larger than that of capacitors with a HZO-seed, Al2O3-seed, or no seed layer. Furthermore, the maximum 2P r was exhibited when the thickness of the ZrO2-seed layer was 2 nm. Large grain growth was observed, which satisfied the same lattice pattern between ZrO2 and HZO films, and indicates that the ZrO2 seed layer plays an important role in the nucleation of the HZO film.

Improvement of smooth surface of RuO2 bottom electrode on Al2O3 buffer layer and characteristics of RuO2/TiO2/Al2O3/TiO2/RuO2 capacitors

Ruthenium oxide (RuO2) thin films, which are deposited by plasma-enhanced atomic layer deposition (PE-ALD) with a Ru(EtCp)2 precursor and oxygen plasma, exhibit a smoother surface [root mean square (RMS) roughness <1 nm] on ionic Al2O3 and TiO2 buffer layers than on a covalent SiO2 buffer layer (RMS roughness of RuO2: 2.5 nm). The Al2O3 and TiO2 buffer layers which have some charges enable us to prolong the duration time of the Ru(EtCp)2 precursor on the buffer layer and cause the nucleation of RuO2 to occur uniformly. The RuO2 film deposited on the Al2O3 buffer layer by PE-ALD (hereafter “PE-ALD-RuO2”) was used as the bottom electrode for a metal-insulator-metal with a TiO2/Al2O3/TiO2 (TAT) insulator. RuO2/TAT/RuO2 capacitors on the Al2O3 and TiO2 buffer layers had a low enough leakage current density (J) (on the order of ∼10−8 A/cm2), unlike RuO2/TAT/RuO2 capacitors on the SiO2 buffer layer and TiN/TAT/TiN capacitors. These results suggest that the different J properties must be related to the surface r...