Ferroelectricity Enhancement in Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> Capacitors by Incorporating Ta<sub>2</sub>O<sub>5</sub> Dielectric Seed Layers (2020)

Recently, dielectric/ferroelectric (DE/FE) bilayer systems have been extensively investigated for achieving high remanent polarization in Hf <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Zr <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (HZO) based MFM capacitors. Herein, we report significant enhancement in the ferroelectric property of HZO capacitors by incorporating Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> as the dielectric seed layer. Thickness of the Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> layer was incorporated at both top and bottom of the HZO films and the thickness of the seed layer was varied from 10 to 50 Å. When the Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> dielectric films were inserted at the top, the highest remanent polarization ~ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{16.83}\ \mu\mathbf{C}/\mathbf{cm}^{\mathbf{2}}$</tex> was observed in case of 20 Å films as compared to that of ~ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{13.21}\ \mu\mathbf{C}/\mathbf{cm}^{\mathbf{2}}$</tex> of the reference HZO device. Similarly, for bottom Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> dielectric films, the highest remanent polarization ~ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{15.24}\ \mu\mathbf{C}/\mathbf{cm}^{\mathbf{2}}$</tex> was observed in case of 20 Å films. When we compared both the stacks, the best result was observed in case of top Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> . The coercive field <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{E}_{\mathbf{c}})$</tex> was also found to be nearly same with the HZO based device despite the incorporation of the dielectric layer. The enhanced ferroelectricity of these devices can be used in memory devices, FeFETs, FTJ and sensors applications.