The Critical Role of Passivation Layer and Semiconductor Interface on the Hydrogen Stability of ALD IGZO Transistors

In this work, we investigate the physical origin of hydrogen (H) stability at high temperature of atomic-layer-deposited (ALD) indium-gallium-zinc oxide (IGZO) transistors with different passivation stacks. The hydrogen stability of ALD IGZO transistors is found to be determined by the interfacial oxygen vacancy (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>O</roman></sub>) generation due to the broken of In-O bonds during passivation layer growth and the formation of substitutional H in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>O</roman></sub> (H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>O</roman></sub>) during high-temperature annealing in H-rich environment. Device fabrication process is optimized including silicon dioxide (SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>) passivation growth with O-rich process and post-annealing engineering. As a result, we demonstrate ALD IGZO transistors with passivation achieving a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>TH</roman></sub> change of 9 mV after forming gas annealing (FGA, 4% H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>/96% N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>) at 400 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C. Meanwhile, we also demonstrate ALD IGZO transistors without passivation achieving a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>TH</roman></sub> change of 0.13 V after FGA at 450 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C. Our work suggests suppressing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>O</roman></sub> generation is critical to enhance the H stability of ALD IGZO transistors.