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The determination of the chemical content is crucial for the quality control in high-precision device fabrication and advanced process development. For reliable chemical composition characterization, certain interaction volume of the target material is necessary for conventional techniques such as energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). This remains however a challenge for nanostructures. We hereby propose an alternative technique for measuring chemical composition of nanostructures with limited volume. By measuring the differences in the optical absorption of the nanostructure due to the differences in the chemical composition with the resonance frequency detuning of a nanomechanical resonator as well as the assistance of the analytical optical modelling, we demonstrate the possibility of characterizing the carbon content in the direct-write focused electron beam induced deposition (FEBID) gold nanostructures., 14 pages, 3 figures

Focused electron beam induced etching (FEBIE) with chlorine as etching agent has been used to geometrically shape and to electrically modify semiconductor nanodevices. Selected sections of monocrystalline nanowires were modified directly without the requirement for a photomask or a resist layer. FEBIE as a subtractive nanofabrication technology allows to locally etch active semiconductor devices made of Si or Ge. In this work, chlorine is used as the etchant gas to thin germanium channel structures fabricated by standard photolithography. For effective material removal a sufficiently high electron influence is essential to avoid the pitfalls of this method. Topography and conductivity of FEBIE-modified structures prior and after the etching process was studied by AFM and by electrical I–V characteristics. The presented work demonstrates the potential of Cl-based FEBIE for device prototyping and electrical trimming of future Ge-based nanodevices.

[Zr(NEtMe)2(guan-NEtMe2)2], a recently developed compound, was investigated as a novel precursor for the atomic layer deposition (ALD) of ZrO2. With water as the oxygen source, the growth rate remained constant over a wide temperature range, whereas with ozone the growth rate increased steadily with deposition temperature. Both ALD processes were successfully developed: the characteristic self-limiting ALD growth mode was confirmed at 300 °C. The growth rates were exceptionally high, 0.9 and 1.15 A/cycle with water and ozone, respectively. X-ray diffraction (XRD) indicated that the films were deposited in the high-permittivity cubic phase, even when grown at temperatures as low as 250 °C. Compositional analysis performed by means of X-ray photoelectron spectroscopy (XPS) demonstrated low carbon and nitrogen contamination (

High-k ZrO2 thin films are grown on p-type silicon by metal–organic chemical vapor deposition based on zirconiumtetrakistrifluoroacetylacetonate as single-source precursor system. Annealing of the as-grown films is performed to investigate the impact of oxidative and reductive atmospheres on thin film properties. The composition of the ultrathin films is examined by Auger spectroscopy, whereas metal–oxide–semiconductor (MOS) structures are employed to extract electrical characteristics. Equivalent oxide thicknesses down to 2 nm and interface trap densities of 5×1011 cm−2 eV−1 at midgap are obtained. MOS capacitors show extremely low leakage currents, promising to reduce gate leakage by more than a factor of 103 compared to SiO2. The correlation between compositional and electrical properties is discussed on the basis of postdeposition annealing procedures resulting in a consistent explanation of the observed effects.

This work reports on focused electron beam induced deposition (FEBID) using a custom built gas injection system (GIS) equipped with nitrogen as a gas carrier. We have deposited cobalt from Co2(CO)8, which is usually achieved by a heated GIS. In contrast to a heated GIS, our strategy allows avoiding problems caused by eventual temperature gradients along the GIS. Moreover, the use of the gas carrier enables a high control over process conditions and consequently the properties of the synthesized nanostructures. Chemical composition and growth rate are investigated by energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM), respectively. We demonstrate that the N2 flux is strongly affecting the deposit growth rate without the need of heating the precursor in order to increase its vapour pressure. Particularly, AFM volume estimation of the deposited structures showed that increasing the nitrogen resulted in an enhanced deposition rate. The wide range of achievable precursor fluxes allowed to clearly distinguish between precursor- and electron-limited regime. With the carrier-based GIS an optimized deposition procedure with regards to the desired deposition regime has been enabled

In this work, we explore the electrical properties of a metal–oxide–semiconductor system that incorporates a high-k zirconia dielectric with an equivalent oxide thickness of 3 nm deposited by metalorganic chemical vapor deposition. In general, the thin films examined exhibit excellent electrical properties. However, dynamic I–V measurements unveil the presence of trapping sites with response times up to 3 s. By applying a recently proposed model, this slow trap response can be consistently explained by traps located at the inner interface of a two-layer dielectric consisting of the high-k material itself and a transition layer in contact with the semiconductor. Trap energies are found to be distributed around two distinct levels.

Recently focused-electron-beam-induced etching of silicon using molecular chlorine (Cl(2)-FEBIE) has been developed as a reliable and reproducible process capable of damage-free, maskless and resistless removal of silicon. As any electron-beam-induced processing is considered non-destructive and implantation-free due to the absence of ion bombardment this approach is also a potential method for removing focused-ion-beam (FIB)-inflicted crystal damage and ion implantation. We show that Cl(2)-FEBIE is capable of removing FIB-induced amorphization and gallium ion implantation after processing of surfaces with a focused ion beam. TEM analysis proves that the method Cl(2)-FEBIE is non-destructive and therefore retains crystallinity. It is shown that Cl(2)-FEBIE of amorphous silicon when compared to crystalline silicon can be up to 25 times faster, depending on the degree of amorphization. Also, using this method it has become possible for the first time to directly investigate damage caused by FIB exposure in a top-down view utilizing a localized chemical reaction, i.e. without the need for TEM sample preparation. We show that gallium fluences above 4 × 10(15) cm(-2) result in altered material resulting from FIB-induced processes down to a depth of ∼ 250 nm. With increasing gallium fluences, due to a significant gallium concentration close beneath the surface, removal of the topmost layer by Cl(2)-FEBIE becomes difficult, indicating that gallium serves as an etch stop for Cl(2)-FEBIE.

A new beam-assisted process for removing silicon from a surface in the nanometer scale in a conventional scanning electron microscope is presented. This approach is based on focused electron beam induced etching with pure chlorine gas being used as the precursor. In contrast to the established etching process using a focused ion beam (with or without the addition of a precursor), no amorphization and gallium implanting of the substrate takes place. The observed low etch rates facilitate removal with sub-nanometer precision. No spontaneous etching of silicon as in the case of xenon difluoride was observed. Etch rates of up to 4 nm min( - 1) could be achieved as well as a minimum feature size of below 80 nm. The effect of etching parameters like electron beam energy, electron beam accelerating voltage or pixel spacing were systematically examined. Finally, the underlying etching mechanism in terms of secondary electron interactions and precursor replenishment is discussed.

There is an increasing interest in cell-based microelectronic biosensors for high-throughput screening of new products from the biotech pipeline. This requires fundamental knowledge of the biocompatibility of the materials used as the growing support for the cells. Using monolayer-forming Caco-2 cells of human origin, the biocompatibility of silicon wafers coated with various metals, dielectrics and semiconductors was assessed. Besides microscopic inspection, proliferation of cells indicating viability as well as brush border enzyme activity indicating differentiation of adherent growing cells were chosen as parameters to estimate biocompatibility. The type of wafer used for deposition of the coating initially influences the biocompatibility of the final product. Whereas p-doped silicon was fully biocompatible, n-doped silicon reduced the proliferation of cells. Among the different coatings, Al and Ti even increased the cell growth as compared to glass. Culturing the cells for 6 days on coated wafers demonstrated that the differentiation of adhering cells on Ti- and ZrO2-coated wafers was comparable to glass, whereas coatings with Si3N4, Au, Al, and ITO reduced differentiation to 15–35%. In the cases of Au and Si3N4 this effect equilibrated with prolonged culturing. These results demonstrate the importance of a careful selection of the materials used for the production of cell-based biosensors.

In this study we investigate the nucleation and growth mechanisms of tungsten films processed by focused ion beam (FIB) induced chemical vapor deposition. For our investigation we use a 50 keV Ga+ ion beam focused on the substrate target and tungsten hexacarbonyl (W(CO)6) as precursor gas. Mediated by the substrate the energy of the impinging ions leads to the decomposition of the tungsten hexacarbonyl molecules adsorbed on the substrate into volatile parts and nonvolatile residues forming a metal deposit. Time resolved FIB secondary electron microscope imaging in combination with atomic force microscopy reveal first the formation of isolated nuclei and further their coalescence finally resulting in the formation of a contiguous metal layer. Despite the local impacts of the ion beam within the irradiated area of the substrate the localization of the nucleation spots is neither correlated to the spot centers nor to the scan path of the ion beam. After formation, the nanoscale tungsten nuclei preserve their positions and typical shapes during further deposition. Only after merging the nuclei to a contiguous tungsten layer, a further regime of growth sets on which is characterized by deposition of tungsten on a tungsten surface. In this regime the deposition process is determined by the total ion dose and the average current density the samples are subjected to. In this regime, deposition yields up to 3.5 atoms per incident gallium ion are achieved. The contiguous layer quality is determined by Auger electron analysis. The measured growth data were interpreted by adopting the analytic Ruedenauer Steiger approach mainly incorporating ion current density, precursor gas transformation rate, and ion induced sputtering. As a result, the critical ion current density, where ion sputtering exceeds deposition, was identified by the model. Because the model shows excellent agreement with the measurement it should be suitable for further survey concerning focused ion beam process development.

We report on metal-organic chemical vapor deposition (MOCVD) of ultrathin zirconium dioxide on (100) silicon. Special emphasis is put on the evolution of surface topography and the impact of processing parameters on the chemical composition of the films. Electrical characterization by means of MOS structures has been performed to assess the interface quality and the dielectric properties of the layers. Interface trap density is observed to be around 5.1011 cm-2.eV-1 at midgap for (100)-oriented substrates. Leakage currents in the ultrathin regime are significantly reduced compared to equivalent SiO2-layers. Trap density and leakage current are strongly sensitive to annealing in different atmospheres. However, electrical characteristics are shown to be positively affected rather by annealing in slightly reducing than in oxidizing atmospheres. All temperatures throughout the gate insulator formation process do not need to exceed 650°C, and thus allow to keep the thermal budget low.

The quality of masks is the crucial key to reliable and cost-efficient lithography. For conventional optical masks focused ion beam (FIB) has become popular as an approved tool for repairing defects detected in mask inspection. However, the repair of phase shift masks by FIB technology remains critical due to the lack of local deposition processes for materials issuing both, a sufficient optical transparency and an etching rate comparable to quartz glass. A focused ion beam tool utilizing a gallium ion beam with a tunable acceleration voltage of 5-50 kV is used to investigate a siloxane based deposition process of silicon oxides on quartz glass substrates. Tetramethyltetracyclosiloxan together with oxygen is decomposed by the ion beam on a silicon substrate and on a quartz glass surface. A chemical investigation of deposited dielectric layers is performed by Auger spectroscopy (AES) and Secondary Ion Mass (SIMS) spectroscopy. Optical quality of FIB-deposited silicon oxide is investigated by measuring the transmission at 248 nm. The etching selectivity of “as deposited layers” versus pure silicondioxide are determined in in-situ sputter etch experiments. We found a significant influence of process parameters such as precursor gas composition ratios, exposure times, and scan rates on the chemical composition of the deposited layers. Moreover, for optical transmission as well as for etch-rate selectivity the parameters of the deposition process are found to be decisive factors. A model explaining the correlation between process parameter, related chemical composition of dielectrics and resulting etch selectivity and optical transmittance is proposed. In summary, proper control of FIB CVD process parameters in combination with appropriate precursor gas system design are prerequisites for a promising approach in phase mask repair. Keywords: focused ion beam; phase-shift mask; mask repair; silicondioxide, SiO2, CVD

A crystallinity-retaining, implantation-free focused electron beam induced etching (FEBIE) process has been exploited to modify germanium nanowires. This technique shows a high selectivity to the metal contacts applied to the nanowires as well as to the substrate which did not exhibit significant etching. Raman-spectroscopic as well as electrical measurements have been performed on the FEBIE-modified nanowires. Experimental data obtained in this study suggest than unintentional stress is often applied to the nanowires by the defined electrical contacts. Electrical measurements indicate that the electronic properties of the as-grown Ge nanowires can be significantly altered already by a slight surface modification, resulting in an increased conductivity of more than two orders of magnitude.

In this work, a well-controllable, direct-write, resistless, and crystallinity-retaining etching process for germanium using a focused electron beam with nanometer resolution has been developed. This process allows for precise, local, and efficient removal of germanium from a surface without showing any spontaneous etching effects. This focused electron beam induced etching process of germanium substrates employs pure chlorine gas as etchant. The presented process was carried out in a conventional scanning electron microscope equipped with a custom-tailored gas injection system. The etch rate of this etching process was observed to be up to 0.32 μm3 min−1 or 12 nm min−1 for an area of 1.5×1.5 μm2. The influence of various etching parameters such as electron beam current, acceleration voltage and chlorine gas flow on the etch rate as well as the shape of the etch pits have been studied systematically by atomic force microscopy analysis. It is demonstrated that etching of amorphous germanium films can be pe...

The quality of electron-beam deposited, few nanometers thick, SiO2 layers on silicon substrates was investigated by scanning capacitance microscopy and spectroscopy. Rapid thermal annealing had to be applied prior to the capacitance versus voltage [C(V)] measurements to obtain typical metal-oxide-semiconductor behavior, and it was found that the total oxide charge is negative on the deposited oxide layers. Higher annealing temperatures resulted in an overall reduction of the number of oxide charges. This opens up the possibility to use electron-beam deposited SiO2 as a dielectric material in metal-oxide-semiconductor prototyping applications.

Focused ion beam techniques are among the most important tools for the nanostructuring of surfaces. As the physical phenomena during milling are not fully understood yet, we have applied the phase imaging capabilities of tapping mode atomic force microscopy to the investigation of surface amorphization, sputtering, and redeposition caused by focused ion beam irradiation. We have performed single spot as well as large area (20×20 μm2) irradiation of silicon (100) wafers. We describe the localized formation of amorphous and electrostatically charged domains, which do not correlate to topographic features.