Hf1–xZrxO2/ZrO2 Nanolaminate Thin Films as a High-κ Dielectric

Abstract

Engineering of HfO2–ZrO2 ferroelectric thin films can substantially increase their dielectric constant. Here, we investigate dielectric and structural properties of ∼10 nm thin films consisting of stacked 1 nm thin ferroelectric (FE) Hf1–xZrxO2 (HZO(x)) and antiferroelectric (AFE) ZrO2 layers. At x < 0.5, the measurements of polarization vs electric field revealed pure FE hysteresis loops, whereas at x > 0.5, pinched hysteresis loops with some remnant polarization were observed, which indicate a coexistence of FE and AFE orderings. Finally, a pure ZrO2 thin film (x = 1) exhibits only an AFE double hysteresis loop. In this way, we demonstrate that the coexistence of FE and AFE orderings can be controlled by adjusting the composition of HZO(x) layers in the HZO(x)/ZrO2 nanolaminate films. At x = 0.5, the dielectric constant is ∼60 in nanolaminate films, which is much higher than that of the conventional HZO(x) solid solution thin films. Structural investigations confirm a coexistence of polar orthorhombic and nonpolar tetragonal structures, which is consistent with the observed polarization hysteresis loops. We also show that the strain generated in the nanolaminate structure significantly facilitates a field-induced transition from the AFE to the FE phase. The design does not considerably affect the leakage current in HZO(x)/ZrO2 nanolaminate films, which makes this system highly promising for complementary metal oxide semiconductor-compatible capacitors.