Estimation of detrimental impact of new metals candidate in advanced microelectronic

The increasing complexity and miniaturization of integrated circuits (IC) requires the introduction of a large number of new materials which represent possible risk of contamination. Indeed many integration steps use “exotic metals” to achieve the targeted device performance: - The transistor includes high-k dielectrics to replace SiO2, silicides to replace the polycrystalline Si gate, metals for electrodes, substrates with high mobility. - Interconnects need new barriers for Copper. - Non-volatile memories and Above IC components such as RF features or imagers introduce new materials to target specific electrical, magnetic or optical properties. This study follows work published in 2005 by Bigot et al. [1] and will focus on the behavior of each element toward Si and SiO2 properties. This work aims at completing previous work dealing with the seriousness of cross contamination and will report for the first time with “news” metals for which the behavior in Silicon and oxide is really unknown ( Sc, Er, Yb, La, Cd,...)

Analysis of hole-like traps in deep level transient spectroscopy spectra of AlGaN/GaN heterojunctions

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ToF SIMS depth profiling of linear and cross-linked methacrylate polymers thin films using monoatomic ion sputtering

International audienceOwing to their specific physical properties, polymeric materials are increasingly used in the field of nanotechnologies, for instance for nano-impression, lithography or organic light emitting diodes applications. These properties are largely controlled by polymer structural parameters such as molecular weight, polydispersity or crosslinking density…. It is then desirable to have characterisation technique able to provide structural information at the nanometer scale. Considering its intrinsic properties, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) appears particularly adapted to this purpose. It is then more and more used to investigate structures and chemical composition of polymers developed for nanotechnologies applications [1]. Specifically, low energy caesium sputtering appeared to be a successful path to depth profiling of polymer, providing a reliable chemical information weakly affected by damages generated by the energetic interactions between ions and the organic samples [2]. In this work, we will examine the ToF SIMS depth profiling, using monoatomic caesium ion beam for sputtering, of methacrylate thin film polymers with diverse structural properties. Two kind of nanometric layers coated on silicon wafers are studied: on one hand several molecular weight poly(methyl methacrylate) (PMMA); on another hand a hydroxy-ethyle (HEMA) / methyl methacrylate (MMA) copolymer cross-linked at different levels. Dual beam depth profiling has been performed on a ToF-SIMS 5 instrument (from IONTOF GmbH). The analysis is performed using a 15kV Bi$_3^+$ beam while the sputtering is performed with a Cs beam, energized between 2 keV and 250 eV. The results of these interactions are examined in terms of sputtering yield Y, which is the volume sputtered by each individual primary ion. The effects of structural parameters of polymers on Y will be then discussed considering polymers properties such as glass transition temperature Tg, especially for linear PMMA whose variations of Y has been measured at different temperature around T$_g$

Effect of the molecular weight on the depth profiling of PMMA thin films using low‐energy Cs + sputtering

International audienceIn this work, we investigate the influence of the molecular weight of poly (methyl methacrylate) (PMMA) thin films coated on silicon wafer on the ToF SIMS (Time of Flight Secondary Ion Mass Spectrometry) sputtering mechanisms and kinetics during depth profiling using low energy monoatomic caesium ions. The sputtering yield volumes are determined as function of molecular weight, film thickness and beam energy. The results show that the sputtering yield volume decreases with increasing molecular weight Mw down to a threshold value below which it becomes nearly constant, as previously observed with argon cluster ions. The relevance of physical parameters such as the glass transition temperature Tgdetermined here from ellipsometry measurements-and the entanglement of the polymer chains to account for this behaviour is discussed. The variation of the sputtering yield was also found to vary logarithmically with the primary beam energy. In addition, preliminary experiments carried out using a low molecular weight PMMA (4 kg/mol) evidenced a nano-confinement effect similar to that observed with argon cluster sputtering but of lower magnitude

Origine physico-chimique de l'amélioration des propriétés magnétiques et de transport de cellules STT-MRAM comprenant des couches de stockage de FeCoB avec couche de couverture en tungstène

International audienceWe investigated and compared the structural and magnetic properties of MgO/FeCoB based out-of-plane magnetized tunnel junctions at thin film level as well as the magneto-transport properties of corresponding patterned STT-MRAM cells comprising either Ta 1 nm or W2 /Ta1 nm cap layers for different annealing temperatures up to 455°C. W material in the cap was found to improve the structural stiffness of the perpendicular magnetic tunnel junctions and most importantly prohibits Fe diffusion from the FeCoB storage layer to the cap layer, remarkably improving the thermal robustness and magneto-transport properties of the stacks and of the corresponding patterned memory cells. As a result, the interfacial anisotropy constant of the MgO/FeCoB interfaces is improved by 17-29% compared to Ta cap. The STT-MRAM cells fabricated from the pMTJ stacks with W/Ta cap reveal a significant improvement of tunneling magnetoresistance and thermal stability factor, which are respectively 120% and 52 as compared to 70% and 35 for the stack with Ta cap. This improvements are ascribed to the enhancement of MgO crystallinity upon higher temperature annealing (425°C) as well as prohibition Fe out-diffusion

Filling of Nanometric Pores with Polymer by Initiated Chemical Vapor Deposition

International audienceThe integration of porous thin films using microelectronic compatible processes sometimes requires the protection of the interior of the pores during the critical integration steps. In this paper, the polymerization of neo-pentyl methacrylate (npMA) is performed via initiated chemical vapor deposition (iCVD) on a porous organosilicate (SiOCH) and on a dense SiOCH. The characterizations by FTIR, spectroscopic ellipsometry and time-of-flight secondary ion mass spectrometry (ToF-SIMS) of the different stacks show that iCVD is a powerful technique to polymerize npMA in the nanometric pores and thus totally fill them with a polymer. The study of the pore filling for very short iCVD durations shows that the polymerization in the pores is done in less than ten seconds and is uniform in depth. Then, the P(npMA) film growth continues on top of the filled SiOCH layer. These characteristics make iCVD a straightforward and very promising alternative to other infiltration techniques in order to fill the porosity of microporous thin films. The past decade has witnessed significant advances in the ability to fabricate new porous solids from a wide range of various materials. [1-3] This has resulted in materials with unusual properties and broadened their application range beyond their traditional use such as catalyst

Effect of Al 2 O 3 thickness and oxidant precursors on the interface composition and contamination in Al 2 O 3 /GaN structures

International audienceIn this paper, we investigate the Al 2 O 3 /GaN critical buried interface of the next generation of gallium nitride (GaN)‐based transistors using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and hard X‐ray photoelectron spectroscopy (HAXPES). Results highlight that gallium oxidation at this interface is enhanced when increasing the Al 2 O 3 thickness from 3 up to 20 nm. Gallium oxidation is reduced when using both O 3 and H 2 O as oxidant precursors, compared with only H 2 O during the growth of Al 2 O 3 . In addition, the O 3 /H 2 O‐based Al 2 O 3 favors a reduction of contaminants such as hydrogen and carbon but enhances the presence of halides (Cl − and F − ) at this Al 2 O 3 /GaN interface

Effects of Silane Monolayers on Lysophosphatidylcholine (LysoPC) Detection by Desorption Ionization on Silicon Mass Spectrometry (DIOS-MS) in Solution and Plasma

International audienceDesorption ionization on silicon mass spectrometry (DIOS-MS) enables the high throughput analysis of low molecular weight biomolecules. However, the detection of metabolites biomarkers from complex fluids, like plasma, is subordinated to sample pre-treatments which limit clinical applications. Herein, we show that porous silicon chemically modified using monolayers of n-propyldimethylmetoxysilane molecules, can be a good candidate for the fingerprinting of Lysophosphatidylcholine (LysoPC) in plasma, without any pre-treatment of the sample, for DIOS-MS-based diagnosis like sepsis diagnosis. Results are correlated to the location of LysoPC molecules inside/outside the pores, determined by time of flight-secondary ions mass spectrometry profiling, and to their physico-chemical properties

Swelling induced debonding of thin hydrogel films grafted on silicon substrates

International audienceWe report on the delamination of thin (≈ µm) hydrogel films grafted to silicon substrates under the action of swelling stresses. Poly(dimetylacrylamide) (PDMA) films are synthesized by simultaneously cross-linking and grafting preformed polymer chains onto the silicon substrate using a thiol-ene reaction. The grafting density at the film/substrate interface is tuned by varying the surface density of reactive thiol-silane groups on the silicon substrate. Delamination of the films from well controlled line defects with low adhesion is monitored under a humid water vapor flow ensuring full saturation of the polymer network. A propagating delamination of the film is observed under the action of differential swelling stresses at the debonding front. A threshold thickness for the onset of this delamination is evidenced which is increasing with grafting density while the debonding velocity is also observed to decrease with an increase in grafting density. These observations are discussed within the framework of a nonlinear fracture mechanics model which assumes that the driving force for crack propagation is the difference between the swelling state of the bonded and delaminated parts of the film. Using this model, the threshold energy for crack initiation was determined from the measured threshold thickness and discussed in relation to the surface density of reactive thiol groups on the substrate