Wen-Qi Zhang

CHEMICAL VAPOR DEPOSITION OF ZrxHf1-xO2 THIN FILMS USING ANHYDROUS MIXED-METAL NITRATES PRECURSORS

ABSTRACT Hafnium-based dielectrics have been extensively investigated as a possible replacement for SiO2. A novel volatile anhydrous Zr/Hf mixed-metal nitrate precursor ZrxHf1-x(NO3)4(ZHN) was successfully synthesized. ZrxHf1-xO2 thin films were first prepared by the chemical vapor deposition (CVD) technique from the precursor of this mixed-metal nitrate. Differential scanning calorimetry (DSC) and infrared spectra (IR) measurements of ZHN indicated that ZHN may be mixture of single Hf(NO3)4 and a solid solution of Zr(NO3)4 and Hf(NO3)4. The ZrxHf1-xO2 thin films exhibit good dielectric properties with a moderate bandgap value of 5.6 eV and a value for k of 22. ZrxHf1-xO2 is, therefore, a promising candidate for gate-dielectric application, and the anhydrous mixed-metal nitrate can be a potential precursor for high-k materials derived from CVD.

Effect of annealing on interfacial and band alignment characteristics of HfO2/SiO2 gate stacks on Ge substrates

The authors have investigated the effect of 500 °C annealing for 60 s in N2 on interfacial and band alignment characteristics of HfO2/SiO2 gate stacks on n-type Ge substrates. X-ray photoelectron spectroscopy analyses reveal that the SiO2 interlayer can effectively suppress Ge outdiffusion during HfO2 growth and subsequent postdeposition annealing process. The electrical measurement shows that capacitance equivalent thickness of 1.75 nm and a leakage current density of 3.9 × 10−3 A/cm2 at gate bias of flatband voltage (Vfb) + 1 V was obtained for the annealed sample. The conduction band offsets at the HfO2/SiO2/Ge with and without annealing are found to be 2.22 and 2.07 eV, respectively.

Properties of Hf 0.7 Zr 0.3 O 2 thin films chemical vapor deposited using a single-source precursor of anhydrous Hf x Zr 1−x (NO 3 4 precursors

Hafnium-based dielectrics have been extensively investigated as a possible replacement for SiO<inf>2</inf>. Anhydrous Hf/Zr mixed-metal nitrate precursor Hf<inf>x</inf>Zr<inf>1−x</inf>(NO<inf>3</inf><inf>4</inf> (HZN) was successfully synthesized and hafnium zirconate (Hf<inf>x</inf>Zr<inf>1−</inf>O<inf>2</inf>) thin films were prepared by the chemical vapor deposition (CVD) technique from this precursor. The basal dielectric properties of Hf<inf>x</inf>Zr<inf>1−</inf>O<inf>2</inf> films were studied, and C-V curves with negligible hysteresis are achieved.

Chemical Vapor Deposition of Zr x Ti 1-x O and Hf x Ti 1-x O Thin Films Using the Composite Anhydrous Nitrate Precursors

Zr/Ti an Hf/Ti composite nitrate were developed as single-source precursors for deposition of multi-component metal oxide films. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) analyses confirmed that Zr x Ti 1-x O 2 and Hf x Ti 1-x O 2 films were successfully prepared by the CVD technique from these composite precursors. The Zr/Ti nitrate can be taken as a solid solution of the individual Zr and Ti nitrate, and the Zr/Ti molar ratio in as-deposited ZrxTi1-xO2 films is nicely consistent with that of the precursor. The Hf/Ti nitrate appears to be a mixture of the Zr and Ti nitrates and the composition of the as-deposited Hf x Ti 1-x O 2 films depends remarkably on the heating time of precursor. Both Zr x Ti 1-x O 2 and Hf x Ti 1-x O 2 films exhibit trading-off properties between band gap and dielectric constant, which suggesting that Zr x Ti 1-x O 2 and Hf x Ti 1-x O 2 can be the promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the next generation complementary metal-oxide-semiconductor transistor (CMOS) devices.