Study on the Application and Reliability of High-k HfO₂/ZrO₂ Superlattice Dielectrics in Ge Stacked Nanosheet GAAFET at 4K Ultra-Low Temperature

This study explores the potential application of HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/ZrO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> superlattice (SL-HZO) in cryogenic CMOS technology. We fabricated HfO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/ZO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> with a thickness of 0.3nm per layer, and compared to conventional solid-solution 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.</inf><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>(HZO) thin films, SL-HZO with mixed ferroelectric-antiferroelectric phases exhibited a high dielectric constant, stable capacitance, and excellent reliability. Furthermore, after integrating this 0.3nm SL-HZO material into germanium nanosheet gate-all-around field-effect transistors (Ge NS-GAAFET), cryogenic tests at 4K achieved a subthreshold swing of 28.7 mV/dec, an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{I}_{\mathbf{on}}/\mathbf{I}_{\mathbf{off}}$</tex> ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.22 \times 10^{8}$</tex>, and a drain-induced barrier lowering (DIBL) of 8mV/V, demonstrating outstanding electrical performance. The results indicate that 0.3 nm SL-HZO holds significant potential for future high-performance computing applications (HPC).