Liquid Precursor Delivery Research Articles

Very Low Temperature Tensile and Selective Si:P Epitaxy for Advanced CMOS Devices

Nowadays, “more Moore” and “more than Moore” device architectures are becoming more and more complex. In CEA-Leti, we work on the “CoolCubeTM” 3D sequential integration which is based on the stacking of FDSOI devices [1]. We present solutions, at T<500°C, for the integration of SiP Raised Sources & Drains (RSD) in the upper devices without degrading the electrical performances of the bottom ones. We also target a lowering of the RSD resistance and an increase of the electron mobility in the channel of NMOS devices thanks to tensile strain [2]. Such a know-how will be useful to minimize the contact resistance and fabricate other types of devices such as FINFETs or h-GAA (e.g. nano-sheet devices) with Si (110) surfaces.Experiments were carried out in an Applied Materials epitaxy reactor featuring (i) liquid precursor delivery, together with H2, N2 or He carrier gas capability, enabling the use of Cl2; (ii) “High Precision Temperature Control (HPTC)”, allowing excellent LT control and enabling flexible rotation speeds; (iii) “precision flow distribution PFD-III”, enhancing uniformity performances. Selective Epitaxial Growth (SEG) is usually obtained with “co-flow” processes at rather high temperatures (>600°C). Chlorinated precursors (SiH2Cl2 (+ GeH4) + HCl, typically) are then sent simultaneously into the growth chamber. At LT (<500C°C), HCl cannot decompose, however. To overcome those limitations, we used a Cyclic Deposition Etch (CDE) strategy, with non-selective depositions followed by selective chemical vapor etches, to obtain SiP SEG.This strategy allowed us to obtain high quality films, as shown in Fig.1. The Omega-2Theta scans around the (004) X-Ray Diffraction order for tensile SiP (t-SiP) layers grown at T < 500°C with different Phosphorus concentrations were indeed typical of monocrystalline layers, with well-defined and intense peaks together with numerous thickness fringes. The substitutional P contents in those ~ 60 nm thick t-SiP layers were in the 1.02% - 5.42% range. The good layer uniformity in terms of thickness and P content, over a 300mm wafer radius, is shown in figure Fig.2.These layers grown at T <500°C were smooth, as shown in Fig.3, with a 0.21 nm Root Mean Square (RMS) roughness for a 60nm thick Si:P layer, i.e. a value close to the typical RMS roughness for t-SiP layers grown at high temperature with a chlorinated chemistry.The electrical resistivity in various t-SiP layers is plotted in Fig.4 as function of the substitutional phosphorus concentration and for various growth temperatures in the 450°C – 525°C range. Reducing the temperature by 75°C halved the electrical resistivity. We were able to achieve a resistivity as low as 0.21 mOhm.cm for a t-SiP layer with 5.8% of P grown at 450°C.We then evaluated, at first on tests structures without gates, our process selectivity. A top view Scanning Electron Microscopy image of a t-SiP layer grown non-selectively, with numerous amorphous SiP nuclei on SiO2, is shown in Fig 5.a. After some careful optimization, we succeeded in having fully selective processes versus SiO2, as shown in Fig 5.b.We then tested such optimized processes on low density FD-SOI devices with 28 nm design rules. A top-view SEM image of transistors after such a growth is shown in Fig.6. The growth selectivity was excellent, with nitride spacers and hard masks as well as isolations free of a-SiP nuclei for 31 nm of t-SiP with 4.5% of P deposited in the Sources/Drains. The surface was smooth, with a RMS roughness as low as 0.30nm on active areas, as shown in Fig.7. Thanks to High Resolution Reciprocal Space Maps (HR-RSM), we measured a Phosphorus concentration of 4.5% for that SiP layer grown on SOI. The very high quality of that epitaxy layer, with well-defined thickness fringes, is obvious in Fig.8. Cross-sectional Transmission Electron Microscopy (TEM) images such as the one shown in Fig. 9 enabled us to confirm, at the nanoscale, the excellent quality of such layers in RSDs.To sum up, we were able to develop a tensile Si:P process which was shown to be selective, at a temperature lower than 500°C, against SiO2 and SiN. Such t-SiP layers were successfully integrated in the Sources/Drains regions of FD-SOI 28nm devices. The very low material resistivity and the high phosphorus content should yield, notably because of tensile strain, performant NMOS devices in the near future.[1] C. Fenouillet-Beranger et al., IEEE TED 68, 3142-3148 (2021)[2] V. Chan et al., IEEE 2005 Custom Integrated Circuits Conference 2005, pp. 667-674 Figure 1

Chemical vapor deposition of CoFe2O4 micropillar arrays with enhanced magnetic properties

Single-step thermal chemical vapor deposition was optimized at 400 °C for the growth of CoFe2O4 spinel thin films starting from the corresponding metal acetylacetonate precursors. Enhanced magnetization was observed for conditions leading to a columnar growth with a preferred (100) orientation. The implemented liquid precursor delivery secured a reliable films’ composition control and a straightforward dosage of acetylacetone, as a molecular growth inhibitor, to enhance the film conformality on structured surfaces. The optimized conditions enabled an efficient micro-pore filling, and the fabricated ordered micropillar arrays feature a coercivity of 1.8 kOe and a saturation magnetization of 350 emu/cm3. The implemented state-of-the-art up-scalable microfabrication technology, the reasonable thermal budget and the resulting high magnetic performance pave the way towards the development of innovative magnetoelectric devices.

Will Polyethylene furanoate (PEF) challenge Polyethylene terephthalate (PET)?

The preparation and characterization of SiN thin films using an aerosol-type liquid precursor delivery system (LDS) for application as a water-vapor permeation barrier layer in organic electronic devices is described. The proposed LDS consisted of three major parts: 1) an aerosol generator that transformed the liquid precursor to an aerosol molecule using a piezoelectric ultrasonic vibrator, 2) a vaporizer that transformed the injected aerosol molecules to a vapor state, and 3) a vapor storage canister. The instant evaporation fraction and maximum evaporation mass rate were measured to be 98.3% and 2.55 g/min, respectively. The temperature in the vaporizer was stable, showing a 1 °C variation from the set temperature. As the LDS temperature increased, the evaporation mass rate also increased from 0.035 to 2.55 g/min. A 30 nm thick SiN layer was prepared to evaluate the performance of the LDS, which was attached to a cyclic chemical vapor deposition system. The prepared SiN layer had a smooth surface with no defects or pinholes; the root mean square surface roughness of the prepared SiN film was measured to be 0.185 nm, which is adequate to be used as encapsulation layers in organic electronic devices. The water vapor transmission rate through the 30 nm thick SiN layer was calculated to be 1.31 × 10−6 g/m2/day by Ca-degradation test. The results indicated that the produced films meets the requirement for application as an encapsulation layer to protect the organic layer in organic electronic devices from water vapor penetration, especially in organic light-emitting diodes.

Characterization of bubbler performance for low-volatility liquid precursor delivery.

The performance of a bubbler to deliver the low-volatility, liquid cobalt precurso - -(tBu-acetylene) dicobalthexacarbonyl (CCTBA) for reduced-pressure chemical vapor deposition and atomic layer deposition processes was characterized. A relatively large process window was investigated by varying carrier gas flow rate, system pressure, and bubbler temperature. For this range of conditions, the CCTBA partial pressure was measured using a custom-designed non-dispersive infrared gas analyzer, and the CCTBA flow rates were derived from these partial pressure measurements. The dependence of CCTBA flow rate on these process parameters was modeled to obtain a deeper understanding of the factors influencing bubbler performance. Good agreement between measured and modeled CCTBA flow rates was obtained using a model in which a constant CCTBA partial pressure in the bubbler head space for a given bubbler temperature was assumed and in which the pressure drop between the bubbler head space and the pressure measurement location was included. The dependence of CCTBA head space partial pressure on temperature was parameterized in the form of the August equation, which is commonly used to describe the temperature-dependence of vapor pressure. While this report was focused specifically on CCTBA, the results are expected to apply to other low-volatility, liquid precursors of interest in vapor deposition processes.

Preparation and characterization of SiN water-vapor permeation barrier coated by aerosol-type liquid precursor delivery system equipped on a cyclic chemical vapor deposition system

Abstract The preparation and characterization of SiN thin films using an aerosol-type liquid precursor delivery system (LDS) for application as a water-vapor permeation barrier layer in organic electronic devices is described. The proposed LDS consisted of three major parts: 1) an aerosol generator that transformed the liquid precursor to an aerosol molecule using a piezoelectric ultrasonic vibrator, 2) a vaporizer that transformed the injected aerosol molecules to a vapor state, and 3) a vapor storage canister. The instant evaporation fraction and maximum evaporation mass rate were measured to be 98.3% and 2.55 g/min, respectively. The temperature in the vaporizer was stable, showing a 1 °C variation from the set temperature. As the LDS temperature increased, the evaporation mass rate also increased from 0.035 to 2.55 g/min. A 30 nm thick SiN layer was prepared to evaluate the performance of the LDS, which was attached to a cyclic chemical vapor deposition system. The prepared SiN layer had a smooth surface with no defects or pinholes; the root mean square surface roughness of the prepared SiN film was measured to be 0.185 nm, which is adequate to be used as encapsulation layers in organic electronic devices. The water vapor transmission rate through the 30 nm thick SiN layer was calculated to be 1.31 × 10−6 g/m2/day by Ca-degradation test. The results indicated that the produced films meets the requirement for application as an encapsulation layer to protect the organic layer in organic electronic devices from water vapor penetration, especially in organic light-emitting diodes.

Liquid‐Assisted Plasma‐Enhanced Chemical Vapor Deposition of Catechol and Quinone‐Functionalized Coatings: Insights into the Surface Chemistry and Morphology

Liquid‐assisted plasma‐enhanced chemical vapor deposition (LA‐PECVD) provides a convenient approach toward the preparation of functional surfaces. In this work, the LA‐PECVD approach is reported for the high deposition rate of tuneable catechol and quinone‐functionalized coatings from plasma polymerization of vinyltrimethoxysilane (VTMOS) and dopamine acrylamide (DOA). Most particularly, the influence of the liquid precursor delivery rate and of the plasma power density on the chemistry and morphology of the formed layers are investigated. Precursor delivery rate and plasma power conditions are found, through mass measurement, XPS, FTIR, and Raman spectroscopy, to enable the high deposition rate of cross‐linked coatings. Interestingly, the integration and conservation of the catechol functional group from the DOA monomer are highlighted through the reduction of a silver nitrate solution and silver nanoparticles formation observation via SEM/EDX. Due to the presence of oxidant species and to the bombardment of the layer with highly energetic species, quinone groups formation is likely to occur during the plasma treatment and is then highlighted via ToF‐SIMS analyses of a surface successfully derivatized with a β‐lactamase. The conservation of both functional groups on the surface makes this type of layer promising for numerous applications. Quinone groups provide a real platform for the immobilization of biomolecules with various properties, e.g., antibiotics degradation, antibacterial, while the catechol groups are interesting for trapping radicals or metal ions for water treatment applications.

Epitaxial growth and properties of cobalt-dopedZnOonα−Al2O3single-crystal substrates

$\mathrm{Co}$-doped $\mathrm{ZnO}({\mathrm{Co}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}\mathrm{O})$ is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial ${\mathrm{Co}}_{x}{\mathrm{Zn}}_{1\ensuremath{-}x}\mathrm{O}$ films on ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}(012)$ substrates by metalorganic chemical vapor deposition using a liquid precursor delivery system. High concentrations of $\mathrm{Co}(x\ensuremath{\leqslant}0.35)$ can be uniformly incorporated into the film without phase segregation. $\mathrm{Co}$ is found to be in the $+2$ oxidation state, independent of $x$, by both surface-sensitive core-level $x$-ray photoemission and bulk-sensitive optical absorption spectroscopies. This material can be grown $n$-type by the deliberate incorporation of oxygen vacancies, but not by inclusion of $\ensuremath{\sim}1$ at. % $\mathrm{Al}$. Semiconducting films remain ferromagnetic up to $350\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In contrast films without oxygen vacancies are insulating and nonmagnetic, suggesting that exchange interaction is mediated by itinerant carriers. The saturation and remanent magnetization on a per $\mathrm{Co}$ basis was very small $(l0.1\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}∕\mathrm{Co})$, even in the best films. The dependence of saturation magnetization, as measured by optical magnetic circular dichroism, on magnetic field and temperature, agrees with the theoretical Brillouin function, demonstrating that the majority of the $\mathrm{Co}(\mathrm{II})$ ions behave as magnetically isolated $S=3∕2$ ions.

Studies of two- and three-dimensional ZnO:Co structures through different synthetic routes

Multilayers of Co and ZnO, with nominal layer thicknesses on the atomic scale with up to 25 bilayers, were deposited by ion beam sputtering on silicon and glass substrates at ambient temperature. Thick epitaxial CoxZn1−xO films on Al2O3(012) substrates were grown by metalorganic chemical vapor deposition using a liquid precursor delivery system. All were co-doped with Al. Comparative analysis of magnetization, resistivity, and magnetoresistance measurements, performed in the temperature range 2.5–300 K, is presented. At small thickness of Co layers in the multilayer samples, these structures are diluted magnetic semiconductor (DMS) superlattices, with properties close to the epitaxial films. A crossover from DMS to discontinuous magnetic metal/semiconductor multilayers is observed with increasing metal content in the multilayers. This leads to changes in conduction mechanisms, with increasing contribution of quasithree-dimensional or quasitwo-dimensional intergranular hopping, and superparamagnetism.

HRTEM characterization of YBa 2Cu 3O 7− δ thick films on LaAlO 3 substrates

High-quality superconducting YBa 2Cu 3O 7− δ (YBCO) thick films with thickness over 2 μm were grown on LaAlO 3 (LAO) substrates by photo-assisted metalorganic chemical vapor deposition (PhA-MOCVD) with a single liquid precursor delivery system. The YBCO thick films fabricated are single-crystal like with no visible grain boundaries or voids. Surface and interface microstructures of YBCO thick films have been systematically investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. Large precipitates were observed on the surface of these films. These precipitates are mostly composed of crystalline BaCu 3O 4, along with some polycrystalline and amorphous YBCO phases, and were found to exist only on top of the YBCO films, with no penetration into the films. The high quality of the prepared YBCO thick films was confirmed further by the results of X-ray diffraction and T c/ J c measurements. Thus, these thick YBCO films prepared by PhA-MOCVD have promising application potential in fields such as coated conductors.

Microstructures of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-δ/ thick films grown by photoassisted metal-organic chemical vapor deposition

Epitaxial, high-quality YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thick films were grown by a photoassisted metal-organic chemical vapor deposition technique with a single liquid precursor delivery system, and characterized by X-ray diffraction (XRD), scanning electron microscopy, and low-high-resolution transmission electron microscopy techniques. Very dense and single-crystal-like film structure was observed in all of these YBCO thick films. Large precipitates on these thick films were identified as BaCu/sub 3/O/sub 4/, sprinkled only at surface of these YBCO thick films. YBCO thick films with high crystalline and superconductive quality were confirmed by data of XRD analyses and superconductivity measurements. At the same time, the reason why epitaxial YBCO thick films with high-quality single-crystal-like structure can be grown up to about 4.5 /spl mu/m thick is illustrated from the point of view of photoactivation. It is also found that these thick films were optimally oxygenated with their superconductive properties in concern.

(Ba,Sr)TiO 3 thin film growth in a batch processing MOCVD reactor

Thin films of different compositions within the (Ba x ,Sr 1− x )TiO 3 solid solution series were deposited in a planetary multi-wafer MOCVD reactor using different solutions of Sr(thd) 2, Ba(thd) 2 and Ti(O-i-Pr) 2(thd) 2 precursors. Structural and electrical properties of Pt/BST/Pt MIM structures are presented. On the base of film thickness series ranging from 10 to 150 nm the electrical permittivity is discussed within the dead layer model. The performance of two different liquid precursor delivery systems, characterized by flash evaporation and liquid injection, respectively, are compared for the example of different SrTiO 3 films. Finally, the growth of SrTiO 3 on Pt(111) is compared with the growth on Si(100) and the electrical characteristics of the Pt/STO/Si MIS structures are discussed.

Solution-Based Precursor Delivery for Copper CVD

AbstractWe have measured growth rates and film properties for copper CVD using Cu(hfac)2 dissolved in isopropanol as the precursor delivery method. This approach offers the convenience and control associated with liquid precursor delivery, while avoiding the need to handle the precursor at its high melting point. The method provides similar growth rates to those observed using conventional delivery by solid sublimation, with the additional benefit that these growth rates are achieved using a much lower partial pressure of precursor in the reactor. The growth rate is nearly independent of the partial pressure of Cu(hfac)2, isopropanol, and H2 over the range of operating conditions examined. The film morphology and resistivity are also largely unaffected by the deposition conditions. These results strongly suggest that the mechanism proceeds via an adsorbed intermediate formed by the reaction of Cu(hfac)2 and isopropanol, and that the surface is nearly fully saturated by this intermediate.

Single liquid precursor delivery photo-assisted metalorganic chemical vapor deposition of high quality YBa 2Cu 3O 7− x thin/thick films

High quality superconducting YBa 2Cu 3O 7− x (YBCO) films were deposited on LaAlO 3 ( 1 0 0 ) substrates at a high growth rates of 0.2–1 μm /min with high reproducibility by a novel photo-assisted metalorganic chemical vapor deposition process with single liquid precursor delivery technique. The photo irradiation technique can dramatically increase the growth rate and the single liquid precursor delivery technique can significantly improve the process reproducibility. X-ray diffraction analysis indicated that single phase, c-axis oriented and well ab-aligned YBCO films were high reproducibly prepared. The as-grown YBCO films showed critical temperatures ( T c) of 91 K with the transition width ( ΔT c) less than 1 K, and self-field critical current densities ( J c) of 4.6×10 6 A/cm 2 at 77 K.

Nanocrystalline Titania Films and Particles by Chemical Vapor Synthesis

Thick crystalline titania films with grain sizes below 30 nm, as well as nanocrystalline titania particles with sizes below 10 nm, are prepared by a modified CVD method called chemical vapor synthesis (CVS). Pyrolysis of titanium tetraisopropoxide (TTIP) is performed in a hot-wall reactor, in a mixed helium/oxygen atmosphere, using liquid precursor delivery. Film thicknesses of up to 150 μm on silicon (100) substrate materials are achieved. The influence of process parameters (particularly reactor position) on the microstructure and growth rate is examined. Process temperatures, starting at film-forming (CVD) conditions and going up to exclusive particle formation (CVS) are investigated. Grain size, particle size, and crystallographic phases are determined by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Metal-Organic Chemical Vapor Deposition and Characterization of Strontium Bismuth Tantalate (SBT) Thin Films

The metal-organic chemical vapor deposition (MOCVD) of ferroelectric thin films is being widely investigated for the manufacture of devices requiring a high density of volatile or non-volatile memory which goes beyond the limits of current mass production techniques. One of the more important challenges in the MOCVD of multi-component oxide thin films is the precise control of stoichiometry which relates directly to the films' electrical characteristics. A novel approach to liquid precursor delivery embodied in the AIXTRON TriJetTM liquid delivery system is reported. Physical and electrical properties of thin films as well as deposition characteristics as a function of various process parameters are described in detail. Most notably 2Pr=13 µC/cm2 at 5 V with leakage current density Jl=1E-8 A/cm2 @≤5 V were obtained. In addition, films with excellent thickness uniformity with 3σ=2.25% at 180 nm were deposited on 6′′ Pt/TiOx/Si wafers. Finally, near 100% step coverage with a maximum 2:1 aspect ratio (0.5 µm) was achieved.

Deposition of electroceramic thin films by MOCVD

MOCVD (metal–organic chemical vapor deposition) of new materials, such as perovskite-type ceramic thin films, will be a major key technology in the field of ULSI non-volatile and volatile memory applications. This article outlines the latest trends in the field of MOCVD equipment and process development, in particular in the field of high k-dielectric and ferroelectrics. Using liquid precursor delivery systems reproducible evaporation can be achieved. Furthermore, perfect temperature control, as well as a precise gas and vapor flow control through the gas inlet to the substrate, ensure high quality BST, PZT and SBT thin films, bearing superior electrical and microstructural properties and near 100% step coverage at low process temperatures. Copyright © 2000 John Wiley & Sons, Ltd.