Hf Precursor Research Articles

Impact of Hf Metal Predeposition on the Properties of HfO2 Grown by Physical and Chemical Vapor Deposition

Electrical and microstructural properties of a hafnium oxide (HfO2) grown by physical vapor deposition (PVD) and chemical vapor deposition (CVD) onto a predeposited hafnium metal (Hf) are investigated. In PVD in an Ar/O2 plasma atmosphere, energetic oxygen species oxidize the Si substrate through HfO2, generating a thick interfacial layer between the HfO2 and Si substrates. The interfacial layer, however, is found to be controllable to have a minimum equivalent oxide thickness (EOT) and lower leakage current by the predeposition of Hf metal due to the blocking of oxygen diffusion into the Si substrate by the oxidation of Hf metal itself. In addition to the oxygen blocking, the CVD-grown HfO2 films on the predeposited Hf metal layer are improved due to the easy dissociation of the Hf precursor on the metallic Hf layer with a shorter incubation time. The leakage current with the predeposited Hf metal is two orders of magnitude lower than that on the Si substrate, whereas the EOT and the interfacial layer thickness are invariant.

Suppressed crystallization of Hf-based gate dielectrics by controlled addition of Al2O3 using atomic layer deposition

We demonstrate significantly improved thermal stability of the amorphous phase for hafnium-based gate dielectrics through the controlled addition of Al2O3. The (HfO2)x(Al2O3)1−x films, deposited using atomic layer deposition, exhibit excellent control over a wide range of composition by a suitable choice of the ratio between the Al and Hf precursor pulses. By this method, extremely predictable hafnium aluminate compositions are obtained, with Hf cation fractions ranging from 20% up to 100%, as measured by medium energy ion scattering. Using x-ray diffraction, we show that (HfO2)x(Al2O3)1−x films with Hf:Al∼3:1 (25% Al) remain amorphous up to 900 °C, while films with Hf:Al∼1:3 (75% Al) remain amorphous after a 1050 °C spike anneal.

HKrF in solid krypton

A new krypton-containing compound, HKrF, has been prepared in a low-temperature Kr matrix via VUV photolysis of the HF precursor and posterior thermal mobilization of H and F atoms. All three fundamental vibrations have been observed in the FTIR spectra at ∼1950 cm−1 (H–Kr stretch), ∼650 cm−1 (bending), and ∼415 cm−1 (Kr–F stretch). Two distinct sites of HKrF have been identified. The energy difference between the H–Kr stretching vibrations for the two sites is remarkably large (26 cm−1), indicating a strong influence of the environment. In annealing after the photolysis of the precursor, HKrF is formed in two different stages: at 13–16 K from closely trapped H+F pairs and at T>24 K due to more extensive mobility of H and F atoms in the matrix. HKrF in a less stable site decreases at temperatures above 32 K, the other site being stable up to the sublimation temperature of the matrix. The photodecomposition cross section for HKrF has been measured between 193 and 350 nm and compared with the cross sections of the previously reported HArF and HKrCl molecules. The condensed-phase VSCF (vibrational self-consistent field) calculations suggest that the more stable form is a single-substitutional site and the less stable form is a double-substitutional site of HKrF in solid Kr. The gas to matrix shifts for these sites are predicted to be +(9–26) cm−1 for the H–Kr stretching and the bending vibrations and −(7–10) cm−1 for the Kr–F stretching vibrations.

High mobility HfO 2 n- and p-channel transistors

High permittivity HfO 2 films have been deposited directly on silicon using the thermal decomposition of the hafnium nitrato precursor Hf(NO 3) 4. These films were then used to build n- and p-channel field effect transistors. N+ poly, P+ poly, and Pt have been used as gate electrodes. The mobility of the poly gate devices is comparable to that of SiO 2/Si, however, these devices show a thicker equivalent oxide thickness than the Pt devices. The effect of the composition of the films on their electrical performance is discussed.

Mass spectrometric study of some zirconocene and hafnocene diadamantanolates

AbstractThe electron ionization mass spectrometric behaviour of a new series of hafnocene and zirconocene diadamantanolates is discussed. They are also compared on the basis of mass‐analyzed ion kinetic energy spectrometry. Fragmentation patterns of the complexes in question give relevant information on their gas‐phase behaviour as MO2/MC (M = Zr, Hf) precursors for metal‐organic chemical vapour deposition.