Channel Mobility With Higher-k Doped-HfO₂ for CMOS Logic

The integration of higher dielectric constant (higher-k) gate oxides, such as doped-HfO2, in field-effect-transistors (FETs) has gained attention for further reducing the equivalent oxide thickness (EOT) in the advanced CMOS technology. However, the gate oxide in the MOSFET should be carefully selected considering the enhancement of the inversion carrier surface density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}_{\text {s}, \text {inv}}$ </tex-math></inline-formula>) and channel mobility (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {ch}}$ </tex-math></inline-formula>), which has been a less concern in doped-HfO2. We study <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {ch}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}_{\text {s}, \text {inv}}$ </tex-math></inline-formula> in higher-k n-/p-channel FET (n/pFET) through gated-Hall measurement. Importantly, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {ch}}$ </tex-math></inline-formula> is not degraded by higher-k doped-HfO2, unlike conventional integrations of high-k gate oxides. This finding shows that using higher-k doped-HfO2 for the gate oxide promises a potential for achieving higher drain current without mobility degradation and without reducing the gate oxide thickness, compared to paraelectric HfO2.