Investigation of TiN/LaO <i> _x </i> Interface Dipole Effect on Negative Flat-Band Voltage ( <i>V</i> _FB ) Shift in TiN/LaO <i> _x </i> /HfO ₂ /SiO ₂ Gate Stacks Using Dipole-Last Technology

In this study, the effect of the TiN/LaO<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> _x </i> interface dipole on the negative flat-band voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {FB}}$</tex-math> </inline-formula>) shift in TiN/LaO<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> _x </i>/HfO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>/SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate stacks using La dipole-last technology was investigated. The experimental results demonstrated that the La dipole-last drive-in and removal (D&R) process enabled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {FB}}$</tex-math> </inline-formula> modulation of −171 mV, with the D&R process itself accounting for −123-mV shift. Due to the high thermal budget, although the LaO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> dipole layer suppressed the increase in trap/detrap electron density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}_{\text {ot}}$</tex-math> </inline-formula>), it also led to an increase in equivalent oxide thickness (EOT), interface trap density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}_{\text {it}}$</tex-math> </inline-formula>), and gate leakage current. Furthermore, high-resolution transmission electron microscopy (HRTEM) and X-ray photoemission spectroscopy (XPS) analyses revealed that La did not diffuse to the high-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\kappa}$</tex-math> </inline-formula>/SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interfacial layer (IL) to form La–O–Si bonds. Instead, the detected La–N bonds indicated that interface dipole formation at the TiN/LaO<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> _x </i> interface was responsible for the negative <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {FB}}$</tex-math> </inline-formula> modulation. Based on these experimental findings, a TiN/LaO<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> _x </i> interface dipole mechanism was proposed and subsequently validated through the fabrication and characterization of a La laminate stack using the La dipole-last laminate process. These findings provide insights into the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {FB}}$</tex-math> </inline-formula> tuning mechanism of the La dipole-last technology in HfO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\kappa}$</tex-math> </inline-formula> dielectric layers.