Structural and electrical characteristics of the interfacial layer of ultrathin $ZrO2$ films on partially strain compensated $Si0.69Ge0.3C0.01$ layers

The structural characteristics of $ZrO2$ films along with the interfacial layers deposited on partially strain compensated $Si0.69Ge0.3C0.01/Si$ heterostructure have been investigated using x-ray diffraction (XRD), high resolution transmission electron microscopy (TEM), time-of-flight secondary ion mass spectroscopy (SIMS), and x-ray photoelectron spectroscopy (XPS) measurements. XRD spectra show the films to be polycrystalline with both monoclinic and tetragonal phases. The $ZrO2$ film with physical thickness of ∼8.5 nm and an amorphous interfacial layer with a physical thickness of ∼3.6 nm have been observed by high resolution TEM, SIMS and XPS. SIMS and XPS analyses show the formation of an amorphous Zr–germano–silicate interfacial layer between the deposited oxide and SiGeC films. The electrical properties in terms of capacitance–voltage $(C–V),$ conductance–voltage, current density–voltage, and gate voltage shift $(ΔVg)$ under a constant current stressing have been studied using a metal–insulator–semiconductor (MIS) structure. A dielectric constant of 17.5 for $ZrO2$ and 7.0 for interfacial Zr–Ge–silicate layer have been calculated from the high frequency $C–V$ characteristics. These dielectrics show an equivalent oxide thickness (EOT) as low as 1.9 nm for $ZrO2$ and 2.0 nm for the interfacial silicate layer. The MIS capacitor shows an extremely low leakage current density of $∼9×10−8 A/cm2$ at a gate voltage of −1.0 V, breakdown field of 7 MV/cm based on EOT as the length scale, and moderate interface state density $(Dit)$ of $4.8×1011 cm−2 eV−1$ for $ZrO2$ with interfacial layer. The Zr–Ge–silicate interfacial layer separately shows a low leakage current density of $3×10−2 A/cm2$ at $Vg$ of −1 V and $Dit$ of $1×1012 cm−2 eV−1.$ Significant improvements in the charge trapping properties under Fowler–Nordheim constant current stressing in both $ZrO2$ with the interfacial layer and Zr–Ge–silicate layers have been observed.