Mobility and charge trapping comparison for crystalline and amorphous HfON and HfSiON gate dielectrics

Mobility and charge trapping results for $n$-channel transistors gated with HfON and HfSiON are reported as a function of physical thickness $(Tphys)$⁠. HfSiON peak mobility improves with $Tphys$ over the range of $1.8–2.7nm$⁠, achieving $260cm2∕Vs$ at $2.7nm$⁠. However, HfSiON mobility degrades at a critical thickness, $Tphys⩾3.5nm$⁠. HfON mobility response is different. It is a maximum $(230cm2∕Vs)$ at $Tphys=1.2nm$ but degrades with increasing thickness, particularly for the critical thickness $⩾2.5nm$⁠. Mobility loss and trapping occur concurrently for both dielectrics when these critical thicknesses are exceeded. These critical thicknesses are the minimum required to achieve dielectric crystallization. Interfacial defects along crystalline grain boundaries may negatively impact electrical performance of both dielectrics.