(Invited) Role of Oxidant Gas for Atomic Layer Deposition of HfxZr1−XO2 Thin Films on Ferroelectricity of Metal-Ferroelectric-Metal Capacitors

We fabricated 400°C-annealed TiN/HfxZr1−xO2 (HZO)/TiN metal–ferroelectric–metal (MFM) capacitors using H2O and O2 plasma as oxidant gases of thermal (TH) and plasma-enhanced atomic layer deposition (PE-ALD), respectively, for HZO films. The PE-ALD film formed a more ferroelectric orthorhombic phase compared with the TH-ALD case. Therefore, the MFM capacitor with the PE-ALD film showed higher remanent polarization and dielectric constant. For the PE-ALD case, moreover, an oxygen-rich interfacial layer (O-rich-IL) was formed between the HZO film and TiN-bottom electrode during the ALD process. Thus, the MFM capacitor with the PE-ALD film showed less degradation of switching polarization during field cycling compared with the TH-ALD case, because an O-rich-IL should prevent the interface reaction and formation of additional oxygen vacancies in the PE-ALD film during field cycling. Based on these results, it is important to consider the selection of an ALD oxidant gas for the fabrication of HZO-based MFM capacitors.