Determination of Hafnium Zirconium Oxide Interfacial Band Alignments Using Internal Photoemission Spectroscopy and X-ray Photoelectron Spectroscopy

Doped ferroelectric HfO2 is highly promising for integration into complementary metal-oxide semiconductor (CMOS) technology for devices such as ferroelectric nonvolatile memory and low-power field-effect transistors (FETs). We report the direct measurement of the energy barriers between various metal electrodes (Pt, Au, Ta, TaN, Ti/Pt, Ni, Al) and hafnium zirconium oxide (Hf0.58Zr0.42O2, HZO) using internal photoemission (IPE) spectroscopy. Results are compared with valence band offsets determined using the three-sample X-ray photoelectron spectroscopy (XPS) as well as the two-sample hard X-ray photoelectron spectroscopy (HAXPES) techniques. Both XPS and IPE indicate roughly the same dependence of the HZO barrier on metal work function with a slope of 0.8 +/- 0.5. XPS and HAXPESderived barrier heights are on average about 1.1 eV smaller than barrier heights determined by IPE, suggesting the presence of negative charge in the HZO.

Automated summary

In this study, energy barriers between various metal electrodes and doped ferroelectric HfO2 were directly measured using internal photoemission (IPE) spectroscopy, and the results were compared with valence band offsets determined by X-ray photoelectron spectroscopy (XPS) and hard X-ray photoelectron spectroscopy (HAXPES). Both XPS and IPE methods showed similar dependence of the HfO2 barrier on metal work function. However, barrier heights determined by XPS and HAXPES were on average about 1.1 eV smaller than those determined by IPE, indicating the presence of negative charge in the HfO2.