Enhanced Reliability of Ferroelectric HfZrO_<i>x</i> on Semiconductor by Using Epitaxial SiGe as Substrate

Abstract

As compared with Si as the substrate, ferroelectric (FE) HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> with orthorhombic phase on Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.56</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.44</sub> substrate was found to demonstrate improved FE characteristics. Through the incorporation of Ge into the silicon substrate, remanent polarization (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) can be further enhanced by 58% magnitude to 15 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Moreover, devices on Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.56</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.44</sub> show significant reliability enhancement in terms of negligible Pr degradation up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> cycles under ±4 MV/cm with 10-kHz bipolar stress and desirable retention up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s arising from smaller imprint effect against time at 85 °C. The major role of Ge introduction into the substrate is to suppress the formation of the interfacial layer (IL) between HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /substrate and further reinforce the quality of the IL. The suboxide IL of the enhanced quality can be explained by the fact that it is too thin to trap charges while less vulnerable to defect generation due to stronger bonding with fewer oxygen vacancies. The results suggest that as the technology advances from Si into SiGe platform, HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> -based devices possess more reliable ferroelectricity for metal-FE-semiconductor (MFS) gate-stack for the nextgeneration FeFET.