Atomic Layer Deposited Amorphous Ge-Doped Indium Oxide with Enhanced Mobility-Stability-Crystallization Resistance Tradeoff

In this work, we demonstrate the potential of germanium-doped indium oxide (Ge:In<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">3</inf>) as a promising oxide semiconductor offering an improved tradeoff among mobility, electrical stability, and crystallization resistance. This makes it suitable for both <400°C back-end-of-line (BEOL) monolithic 3D integration and >500 °C 1T1C DRAM process. Through a comparative study with silicon-doped In<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">3</inf> (Si:In<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">3</inf>), we show that: (i) the more delocalized Ge 4s orbitals yield higher electron mobility compared to Si doping, supported by first-principles calculations and experimental results, with mobilities of 21 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V•s and 42 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V•s for 1:5 Si:In and Ge:In doping ratios, respectively; (ii) strong Ge-O and Si-O bonds raise the oxygen vacancy formation energy by ~0.4eV and ~1 eV, respectively, enhancing both bias stability and crystallization resistance—both films remain amorphous after a 500°C prolonged anneal, with Si:In<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">3</inf> stable even up to 800 °C; (iii) devices exhibit excellent performance, with subthreshold swing ~60 mV/dec, ON/OFF ratio ~10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup>, and ON currents of 150 μA/μm (Si:In<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">3</inf>) and 330 μA/μm (Ge:In<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">3</inf>) V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OV</inf> = 1V, V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf>=1V; (iv) both channels show high reliability with |ΔV<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf>| < 100 mV under ±2 V overdrive stress for 1000 s, even with ultra-thin (5-10 nm) gate dielectrics. These results position ALD-grown Ge:In<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">3</inf> as a versatile oxide semiconductor platform capable of unifying BEOL logic and FEOL DRAM requirements in advanced monolithic 3D integration schemes.