ALD Polycrystalline Ga-Doped In₂O₃ (Poly-IGO) Nanosheet Exceeding Intrinsic Mobility of 120 cm²/Vs for Process-Friendly BEOL-Compatible FET Application

We have evaluated ALD polycrystalline Ga-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> (poly-IGO) nanosheets and investigated their thickness scaling and electron transport properties through FET operation. Ga-doping to 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> enhances the FET performance as well as patterning properties. A 5-nm-thick poly-IGO showed a high mobility of 120 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/Vs with a low contact resistivity of 9.2 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−7</sup> Ωcm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The poly-IGO exhibited excellent thickness scaling down to ~3 nm keeping the intrinsic mobility of 100 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/Vs. The mobility of poly-IGO is predominantly degraded by tensile lattice strain. A strain-free lattice structure obtained with thin channel (< 10 nm) ALD poly-IGO nanosheets are advantageous for 3D-integrated devices.