David Eon

Zr/oxidized diamond interface for high power Schottky diodes

High forward current density of 103 A/cm2 (at 6 V) and a breakdown field larger than 7.7 MV/cm for diamond diodes with a pseudo-vertical architecture, are demonstrated. The power figure of merit is above 244 MW/cm2 and the relative standard deviation of the reverse current density over 83 diodes is 10% with a mean value of 10−9 A/cm2. These results are obtained with zirconium as Schottky contacts on the oxygenated (100) oriented surface of a stack comprising an optimized lightly boron doped diamond layer on a heavily boron doped one, epitaxially grown on a Ib substrate. The origin of such performances are discussed.

Etching behavior of Si-containing polymers as resist materials for bilayer lithography: The case of poly-dimethyl siloxane

This work is focused on the plasma development of siloxanes investigated as model Si-containing photoresist components that show a promise for bilayer lithography at 157 nm and other Next Generation Lithography technologies. In such lithography, the image is developed in the top photosensitive polymer and transferred to the (usually thick) organic underlayer by means of O2-based plasma etching. In this work particularly, the issue of line edge roughness (LER) induced by transfer etching and its reduction by means of plasma processing optimization is addressed. The experimental results reveal that low values of line-edge roughness are obtained in a high-density plasma reactor, if an F- but not O-containing etching first step is used in appropriate plasma conditions. The effect of different etching chemistries and processing conditions on imaging layer roughness formation is demonstrated with the aid of scanning electron microscopy images and image analysis for quantifying LER, and atomic force microscopy (...

Formation of oriented nanostructures in diamond using metallic nanoparticles

A simple, fast and cost-effective etching technique to create oriented nanostructures such as pyramidal and cylindrical shaped nanopores in diamond membranes by self-assembled metallic nanoparticles is proposed. In this process, a diamond film is annealed with thin metallic layers in a hydrogen atmosphere. Carbon from the diamond surface is dissolved into nanoparticles generated from the metal film, then evacuated in the form of hydrocarbons and, consequently, the nanoparticles enter the crystal volume. In order to understand and optimize the etching process, the role of different parameters such as type of catalyst (Ni, Co, Pt, and Au), hydrogen gas, temperature and time of annealing, and microstructure of diamond (polycrystalline and nanocrystalline) were investigated. With this technique, nanopores with lateral sizes in the range of 10-100 nm, and as deep as about 600 nm, in diamond membranes were produced without any need for a lithography process, which opens the opportunities for fabricating porous diamond membranes for chemical sensing applications.

Surface modification of Si-containing polymers during etching for bilayer lithography

Abstract Surface modification of polydimethylsiloxane (PDMS) under O 2 plasma exposure is studied by XPS and real time ellipsometry. Results show the conversion of the PDMS surface into a SiO x -like material. Total layer thickness and extension of the SiO x layer are controlled by the sample bias. We suggest that surface and line edge roughness defects occurring when using PDMS as top layer in bilayer lithography are intimately related to the rapid kinetics of conversion and to the formation of SiO x hard micromasks on the surface.

Plasma oxidation of polyhedral oligomeric silsesquioxane polymers

Copolymers containing polyhedral oligomeric silsesquioxane (POSS™) units have been developed to be used as photoresist components in a bilayer resist scheme for 193 nm lithography. This article reports on the behavior of these new POSS based materials under oxygen plasmas. The authors demonstrate using in situ ellipsometry and in situ x-ray photoelectron spectroscopy that during the first seconds in the plasma a silicon oxide layer is formed on the top surface of the POSS materials. This superficial layer prevents etching and material consumption. An ion-enhanced oxidation model is proposed to describe and explain the experimental data and further investigate POSS etching mechanisms in oxygen plasma. The model shows that the oxide formation rate is reduced exponentially with the oxide thickness. It also predicts that thickness loss has its main roots in the layer densification that occurs when the oxide is formed and shows that the oxide formation is ion enhanced and thus favored at − 100 V compared to 0 V bias.

Langmuir probe measurements in an inductively coupled plasma: Electron energy distribution functions in polymerizing fluorocarbon gases used for selective etching of SiO2

We are interested in the silicon oxide deep etching by inductively coupled fluorocarbon plasmas for integrated optical applications. The understanding and the improvement of this process requires to know at least the electrical characteristics of the plasma (electron and ion densities, electronic temperature,…). Up to now, very few measurements in these plasmas have been published because of problems encountered when using Langmuir probes in depositing environments. In the present article, we report problems we met and solutions we brought, and then present electron energy distribution function (EEDF) measurements in very polymerizing gases such as CHF3 and CHF3/CH4 mixtures. Experiments have been performed over a wide range of experimental conditions, from 3 to 50 mTorr and from 200 to 2000 W inductive power. The shape of the EEDF and the evolution of the plasma electrical characteristics with experimental conditions are discussed. Finally, we point out the presence of a large negative ion fraction when ...

Energy-band diagram configuration of Al2O3/oxygen-terminated p-diamond metal-oxide-semiconductor

Diamond metal-oxide-semiconductor capacitors were prepared using atomic layer deposition at 250 °C of Al2O3 on oxygen-terminated boron doped (001) diamond. Their electrical properties were investigated in terms of capacitance and current versus voltage measurements. Performing X-ray photoelectron spectroscopy based on the measured core level energies and valence band maxima, the interfacial energy band diagram configuration of the Al2O3/O-diamond is established. The band diagram alignment is concluded to be of type I with valence band offset ΔEv of 1.34 ± 0.2 eV and conduction band offset ΔEc of 0.56 ± 0.2 eV considering an Al2O3 energy band gap of 7.4 eV. The agreement with electrical measurement and the ability to perform a MOS transistor are discussed.

Electronic and physico-chemical properties of nanometric boron delta-doped diamond structures

Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6 K < T < 450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.6 ± 0.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm.

High density fluorocarbon plasma etching of methylsilsesquioxane SiOC(H) low-k material and SiC(H) etch stop layer: surface analyses and investigation of etch mechanisms

This paper focuses on plasma etching and XPS surface analyses of new dielectric materials used in integrated circuits. We investigate by XPS surface modifications of methylsilsesquioxane low-k polymer (SiOC(H)) and amorphous hydrogenated silicon carbide (SiC(H)) when exposed to Ar, SF6 and C2F6-based high density plasmas. Ar and SF6 plasmas remove the carbonaceous groups from the surface leading to the formation of fluorinated top layers (SiOF and SiF-like layers) in SF6 plasma. In the case of C2F6-based mixtures, the surface structure fits well with a two-layer model, consisting of a fluorocarbon top layer above a fluorinated interaction layer (SiOF or SiF) on the bulk materials (SiOC(H) or SiC(H)). Determination of top layer thicknesses from XPS data is discussed. We show that material etch rate is not correlated with the total modified thickness, in contrast to the top fluorocarbon layer thickness which is in good correlation with etch rates. Etch yields (etch rates divided by the ion flux) are calculated and are studied in order to draw material etch mechanisms in C2F6 based mixtures. We conclude that for both materials, etching mechanisms in C2F6/H2 mixtures, and to a lesser extent in C2F6/Ar mixtures, are close to those of silicon in fluorocarbon plasmas and different from those of the conventional interlevel dielectric material SiO2. On the contrary etching mechanisms in C2F6/O2 mixtures are similar to those of silicon dioxide in fluorocarbon plasmas.

Surface segregation of photoresist copolymers containing polyhedral oligomeric silsesquioxanes studied by x-ray photoelectron spectroscopya)

Copolymers containing polyhedral oligomeric silsesquioxane (POSS) pendant groups and various acrylate type monomers are studied by x-ray photoelectron spectroscopy. These copolymers have potential application as bilayer resist material for next generation lithography. Two methods are used in order to characterize resist surfaces, angular resolved XPS and inelastic background signal quantification (Tougaard method). The existence of a surface layer rich in POSS is proven. About 1.5nm thick, this layer stands above a material with uniform POSS concentration. Evaluation of POSS concentration depth profiles shows that surface segregation depends on the polymer comonomers and on the silicon content.