Relationships among equivalent oxide thickness, nanochemistry, and nanostructure in atomic layer chemical-vapor-deposited Hf–O films on Si

Abstract

The relationships among the equivalent oxide thickness (EOT), nanochemistry, and nanostructure of atomic layer chemical-vapor-deposited (ALCVD) Hf–O-based films, with oxide and nitrided oxide interlayers on Si substrates, were studied using x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in annular dark-field imaging (ADF), and parallel electron energy-loss spectroscopy (PEELS), capacitance–voltage, and leakage-current–voltage measurements. The XPS (Hf 4f binding energy shift) studies indicated the formation of Hf–O–Si bonds in as-deposited amorphous films, the amount of which was influenced by the interlayer composition and annealing conditions. After post-deposition annealing in N2 and O2, the Hf–O layers were nanocrystalline. Although HRTEM images showed a structurally sharp interface between the Hf–O layer and the interlayer, angle-resolved XPS, ADF imaging, and PEELS in the STEM revealed a chemically diffused HfSiOx region in between. This interdiffusion was observed by the detection of Si (using Si L edge) and Hf (using Hf O2,3 edge) in the Hf–O layer and the interlayer. For an annealed Hf–O/interlayer stack, with an ALCVD target thickness of 4.0 nm for the Hf–O layer on 1.2 nm of nitrided chemical oxide, the experimentally measured EOT and leakage current (at −1 V) were 1.52 nm and ∼10−8 A/cm2. A three-layer (1.2 nm interlayer of nitrided chemical oxide/compositionally graded, 2 nm region of HfSiOx/2 nm HfO2 layer) capacitor model was used to determine the respective contributions to the measured EOT, and the dielectric permittivity of the interlayer was found to be 6.06. These studies clearly indicate that a total EOT of 1 nm and below is attainable in the Hf–N–O–Si/Si–N–O system.

Photoelectron spectroscopy study of the effect of substrate doping on an HfO2/SiO2/n-Si gate stack

“…A key figure of merit is the equivalent oxide thickness (EOT) which expresses the capacitance of the high j gate oxide in terms of an effective SiO 2 thickness. Dey's model [14], using a permittivity gradient in the interface silicate, returns an EOT of 0.5 nm particularly good for future CMOS applications. The gate stack is shown schematically in Fig.…”

Effects of Nitrogen Incorporation in Lanthanum-Based Dielectric Films

“…For a 3.5 nm LaAlO 3 film deposited on SiON/Si, the extrapolated EOT and the extracted dielectric constant are respectively equal to 1.2 nm and 25. To obtain these values, we assumed this film was homogeneous and deprived of a graduated interface (justified by the following SE and XRR analysis) [12]. Unfortunately, both fixed charges and interface-state densities are also affected by the Si substrate thermal nitridation, and increase much more.…”

Investigation of Crystallization Processes from Hafnium Silicate Powders Prepared from an Oxychloride Sol‐Gel

“…However, others find that the as‐deposited sample remains amorphous until annealing temperatures greater than 600°C . In the area of which crystalline phase, the layer forms many report the expected monoclinic hafnia ( m ‐HfO 2 ), but orthorhombic, tetragonal, and cubic phases have also been observed . As a result, there has been an interest in reexamining the properties of Hf compounds in the bulk phase to help interpret the conflicting data arising from the study of thin films used to make devices.…”