HfO2–SiO2 interface in PVD coatings

Abstract

Structure of the interfacial region between polycarbonate and plasma-deposited SiN 1.3 and SiO 2 optical coatings studied by ellipsometry Hafnium oxide presents a strong interest either for optical coatings or for microelectronic applications. An important parameter to control is its chemical interaction with silicon oxide, since those two materials are usually in direct contact in both applications: For optical coatings, silica is the low refractive index used to make interference filters ͓see M. R. Kozlowski, Thin Films for Optical Systems ͑Marcel Dekker, New York͔͒, in microelectronics HfO 2 could be used as a gate insulator in metal-oxide semiconductor technology ͓B. H. Lee, Tech. Dig. Int. Electron Devices Meet. 99, 133͔. One interesting characterization method of the created interface is infrared spectroscopy in the so-called multiple internal reflection ͑MIR͒ technique. Mono-and bilayers of HfO 2 and SiO 2 have been deposited on germanium substrates by e-beam evaporation and ion beam sputtering. MIR measurements made on those samples show that when HfO 2 is deposited on SiO 2 , parts of the Si-O-Si bonds are broken and Hf-O-Si bonds, representative of hafnium silicate (HfSiO 4 ), are formed at the interface. Hafnium and silicon oxide have also been coevaporated in a reactive atmosphere to deposit the silicate and confirm the position of the Hf-O-Si bond. The results obtained by MIR are confirmed with x-ray photoelectron spectroscopy and transmission electron microscopy analysis.

Soft x-ray photoemission studies of Hf oxidation

“…This, in turn, may lead to incorrect assignments and conclusions. For example, the binding energy of the Hf 4 f 7/2 levels of a thick film HfO 2 can be estimated as 17.3 and 17.4 eV from the recently published data of Wilk et al and Cosnier et al,respectively,[6][7][8] again differing by about 1 eV from the previously reported values. Additional confusion may arise from incorrect assignment of the surface and the bulk states.…”

“…[5][6][7][8][9] As a result, extensive use of XPS and other surface techniques have recently been reported on hafnium oxide and related systems. [6][7][8][10][11][12] Although HfO 2 has a moderately high dielectric constant and band gap ͑both useful for ultrathin dielectric applications in micro-or nano-electronics͒, charging during photon or electron irradiation can make it difficult to determine the binding energies and/or the chemical states accurately. This, in turn, may lead to incorrect assignments and conclusions.…”

Atomic Layer Etching of HfO2Using Sequential, Self-Limiting Thermal Reactions with Sn(acac)2and HF

“…The negative absorption feature at ∼1250 cm −1 is assigned to the loss of absorbance from Si-O stretching vibrations in the SiO 2 substrate. 44 The positive absorption feature at ∼1000 cm −1 is attributed to the gain of absorbance from Si-O-Hf stretching vibrations in hafnium silicate. 41,44,45 The hafnium silicate forms almost entirely during the first two HfO 2 ALD cycles on the SiO 2 nanoparticles at 200…”

Hafnium Oxide Doped Mesostructured Silica Films

“…The atomic composition, after a Shirley-type background subtraction was evaluated by using sensitivity factors supplied by Perkin-Elmer. [23,25] Depth profiles were carried out by Ar + sputtering at 3 keV with an argon partial pressure of 5 ϫ 10 -6 Pa. A specimen area of 2 ϫ 2 mm 2 was sputtered. Samples were introduced directly by a fast entry lock system into the XPS analytical chamber.…”