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The nucleation of TaCN films during plasma enhanced atomic layer deposition (PEALD) using pentakis-(dimethylamino)tantalum (PDMAT) in combination with H2/Ar plasma was investigated on several substrate surfaces by X-ray photoelectron spectroscopy (XPS) without vacuum break. A cluster tool combining a process reactor with a surface analysis unit under high vacuum conditions ensures a direct qualification and quantification of the chemical surface composition by XPS starting from the very first precursor pulse. Due to the high sensitivity of in vacuo XPS measurements, tantalum can be detected at the substrate surface already after the very first precursor pulse of the PEALD process. The amount of adsorbed tantalum precursor molecules on the silicon oxide surface is much higher compared to the H-terminated Si and low-k surfaces. The early cycles are characterized by the onset of Ta O bonds. A Ta O interface layer grows on the substrate surface until all the reactive OH-groups are consumed. This is followed by the emergence of Ta C and Ta N bonds when the homogenous growth mode begins. The PEALD nucleation of TaCN was also investigated on low-k substrates (SiCOH). The homogeneous film body on all substrates consist of Ta- carbide -nitride, and -oxide compounds. In summary, we obtained precise information about the initital tantalum precursor adsorption on several substrate materials and explored the capability to enhance the initial growth on low-k substrates. These examples demonstrate as well that in-vacuo XPS measurements are ideally suited for studying film growth nucleation.

The copper electrochemical deposition (Cu-ECD) filling capability of high aspect ratio through silicon vias (HAR-TSVs) and homogeneity over 300 mm wafers were investigated on a film stack of thermal ALD (thALD) TaxNy barrier with thermal ALD Ru seed in comparison to TixNy barrier with a standard Cu i-PVD seed layer using a commercial 300 mm plating tool. As a first step, Cu-ECD was conducted on wafers with TSV blind holes with aspect ratios (AR) of 10 to 12. To achieve this, a thermal ALD film stack of approximately 6 nm TaxNy and 9 nm Ru (with a sheet resistance of [25.6 ± 1.4] Ω/ϒ) were deposited at 250 °C. The reactants for the barrier layer were (tert-butylimido)tris(diethylamino)tantalum(V) (TBTDET) and ammonia (NH3) as co-reactant. For the Ru seed layer deposition (ethylcyclopentadienyl)(pyrrolyl)ruthenium(II) (ECPR) and molecular oxygen as co-reactant were used supplemented by a hydrogen purge step after every third ALD cycle. The corresponding ALD growth was observed during the entire process by in-situ real-time spectroscopic ellipsometry (irtSE). Blister-free deposition and satisfactory film stack adhesion with no delamination was verified ex situ by scanning electron microscopy (SEM). The deposited copper inside the TSVs was analyzed by focused ion beam (FIB) imaging and X-ray tomography. The Cu ECD filling capability in HAR-TSVs was shown on a film stack of thALD TaxNy thALD Ru seed using a commercial industry standard 300 mm plating tool. A novel blister-free ultra-thin Ru ALD film having good adhesion properties and unique advantages, e. g. high conformity in high-aspect-ratio through-silicon vias large-scale film uniformity over 300 mm wafers, as well as good reproducibility was developed.

This work describes the fabrication of anisotropically etched, faceted pyramidal structures in amorphous layers of silicon dioxide or glass. Anisotropic and crystal-oriented etching of silicon is well known. Anisotropic etching behavior in completely amorphous layers of silicon dioxide in combination with purely isotropic hydrofluoric acid as etchant is an unexpected phenomenon. The work presents practical exploitations of this new process for self-perfecting pyramidal structures. It can be used for textured silica or glass surfaces. The reason for the observed anisotropy, leading to enhanced lateral etch rates, is the presence of thin metal layers. The lateral etch rate under the metal significantly exceeds the vertical etch rate of the non-metallized area by a factor of about 6-43 for liquid and 59 for vapor-based processes. The ratio between lateral and vertical etch rate, thus the sidewall inclination, can be controlled by etchant concentration and selected metal. The described process allows for direct fabrication of shallow angle pyramids, which for example can enhance the coupling efficiency of light emitting diodes or solar cells, can be exploited for producing dedicated silicon dioxide atomic force microscopy tips with a radius in the 50 nm range, or can potentially be used for surface plasmonics.

In this work, the precursor tert -butylimido-tris-ethylmethylamido-tantalum (TBTEMT) was applied for the atomic layer deposition (ALD) of tantalum oxide (Ta 2 O 5 ) thin films for the first time. Water was used as the second reactant. A self-limiting, and hence, ALD-like film growth was confirmed in the temperature range from 100 to 300 °C. The temperature window of this process extends from 250 to 300 °C and features a growth rate of about 0.56 A/cycle. For lower temperatures, the growth rate increases gradually up to 0.92 A/cycle at 100 °C. At a deposition temperature of 200 °C, the process showed perfect layer-by-layer growth with 0.64 A/cycle and without any noticeable incubation period on both silicon with native oxide and hydrogen-terminated silicon. In addition, the conformal coating of structures with an aspect ratio of 40:1 is demonstrated as well. According to XPS analyses, the films are oxygen rich (Ta:O ratio around 0.34 ± 0.01 for films grown at 150–300 °C) and contain a significant amount of carbon (6 ± 2 at.%) and some nitrogen ( 3 , 2.25 and 31, respectively. Films grown at 200 °C are amorphous and smooth. They exhibit a film density of 7.8 ± 0.1 g/cm 3 , a refractive index of 2.17 (at 550 nm) and a dielectric constant of 26 ± 1. However, the films suffer from high leakage currents (> 10 − 4 A/cm 2 ). In addition, electrical measurements revealed the formation of an interfacial layer between the Ta 2 O 5 films and bare silicon. By using substrates with a thin thermally grown silicon oxide, the leakage could be reduced by three orders of magnitude. Post-deposition annealing at 800 °C in nitrogen resulted in the crystallization of the Ta 2 O 5 films, which is also accompanied by an increase in film density and refractive index. Moreover, the crystallized films exhibit an enhanced dielectric constant of 48 ± 2. Electrical measurements revealed the growth of an interfacial layer with an equivalent oxide thickness of around 2.4 nm due to the 800 °C annealing. While this interfacial layer degrades the effective permittivity of the dielectric ( e.g. 20.5 ± 0.5 for a 20 nm Ta 2 O 5 film), it also causes a reduction of the leakage currents by more than three orders of magnitude ( e.g. to 1·10 − 7 A/cm 2 for a 20 nm Ta 2 O 5 film).

In order to remove the local openings for contacting PERC Solar cells, one has to introduce passivating contacts. The Al 2 O 3 -TiO x double layer stack is an attractive candidate for this purpose. This study will guide a way to enhance the conductivity of those contacts by doping TiO x with a. Additionally, it is shown, that major parts of the stacks are deposited by sputtering. This demonstrates a higher feasibility for industrial applications than atomic layer deposition as reported earlier [1], [2].

Al2O3-TiO2 nanolaminates are very attractive candidates for future conductive passivation layers because they are purely based on dielectric materials, which allow a simple integration in the state-of-the-art manufacturing process. In this study, Al2O3-TiO2 double and multilayers are grown by atomic layer deposition and systematically investigated. The nanolaminates feature good silicon surface passivation and moderate electrical conductivity. The best performance is found for a double-layer stack consisting of a 5 nm Al2O3 interface layer and a 15 nm TiO2 capping layer after postdeposition annealing in N2 or forming gas. With this stack, a surface recombination velocity of 15 cm/s and a contact resistance of 20 Ω·cm2 are achieved. In Al2O3 -TiO2 nanolaminates, the electrical transport is strongly influenced by the interaction of TiO2 and Al2O3 during layer growth. Raman measurements reveal that high conductivity correlates with a phase transition of TiO2 from amorphous to anatase.

Microcrystalline silicon thin-film solar cells were fabricated at high absorber layer deposition rates from 1.0 up to 2.5 nm/s. High efficiencies of 9.6% (1.0 nm/s) and 8.6% (2.5 nm/s) were achieved using a very high frequency (VHF) of 140 MHz for the deposition of all silicon layers (p–i–n). Using such a high frequency in the VHF band is unique in the field of thin-film silicon solar cells. The efficiencies obtained especially at very high rates belong to the highest reported efficiencies so far for this technology. This shows that VHF deposition with frequencies larger than 100 MHz is very well suited for a highly productive solar cell fabrication. The VHF power homogeneity problem can be solved by using for example the linear plasma source concept developed at FAP GmbH/TU-Dresden. We show that the efficiency at very high rates of 2.5 nm/s is limited by an increased crack formation in the absorber layer.

Current trends in electronic industry, such as Internet of Things (IoT) and Cloud Computing call for high interconnect bandwidth, increased number of active devices and high IO count. Hence the integration of on silicon optical waveguides becomes an alternative approach to cope with the performance demands. The application and fabrication of horizontal (planar) and vertical (Through Silicon Vias - TSVs) optical waveguides are discussed here. Coupling elements are used to connect both waveguide structures. Two micro-structuring technologies for integration of coupling elements are investigated: μ-mirror fabrication by nanoimprint (i) and dicing technique (ii). Nanoimprint technology creates highly precise horizontal waveguides with polymer (refractive index nC = 1.56 at 650 nm) as core. The waveguide ends in reflecting facets aligned to the optical TSVs. To achieve Total Internal Reflection (TIR), SiO2 (nCl = 1.46) is used as cladding. TSVs (diameter 20-40μm in 200-380μm interposer) are realized by BOSCH process1, oxidation and SU-8 filling techniques. To carry out the imprint, first a silicon structure is etched using a special plasma etching process. A polymer stamp is then created from the silicon template. Using this polymer stamp, SU-8 is imprinted aligned to vertical TSVs over Si surface.Waveguide dicing is presented as a second technology to create coupling elements on polymer waveguides. The reflecting mirror is created by 45° V-shaped dicing blade. The goal of this work is to develop coupling elements to aid 3D optical interconnect network on silicon interposer, to facilitate the realization of the emerging technologies for the upcoming years.

In this work we discuss optical coupling technologies for the manufacturing of out-of-plane optics integrated in planar waveguide for interposer-and board-level. Each technology is evaluated on a silicon interposer with optical dielectric through silicon vias (TSV) with SU8 (core) and SiO2 (cladding). First, applying a nanoimprint technology a polymer waveguide has been created with round-shape curvatures to realize focusing of the light, which enhances the coupling efficiency. Furthermore due to the round shape the light is focused in the waveguide to reduce the transmission losses. Additionally as a second technology a moving mask method is shown to achieve a tilted mirror face by this special exposure procedure for better compability of mirror fabrication with lithography processes. As a third technology the mirror fabrication by dicing into a polymer waveguide has been applied, which results in a V-groove mirror. The feasibility of all fabrication technologies have been performed on rigid substrate. For enhanced yield of electro-optical system implementation of out-of plane optics on flexible substrate has been performed. In this case diced mirrors have been manufactured on polymeric waveguides with Ormocere® on a flexible PEN-foil. The influence of dicing blade on optical losses caused by the scattering on rough diced mirror surface has been analyzed. The min. power losses of the diced mirror of 0.22 dB have been measured.

Plasma-enhanced atomic layer deposition (PE-ALD) of cobalt (Co) using cyclopentadienylcobalt dicarbonyl [CpCo(CO)2] combined with hydrogen, nitrogen, ammonia, and argon based plasma gases was investigated. The utilized ALD tool was clustered to an ultrahigh vacuum analytic system for direct surface analyses including X-ray photoelectron spectroscopy (XPS). The combination with a nondestructive surface analysis system enabled a sample transfer without vacuum break and thereby a direct qualification and quantification of the chemical surface composition under quasi in situ conditions. The authors studied the influence of process parameters (e.g., pulse times, plasma power, and substrate temperature) on film compositions and film properties. The occurrence and prevention of sputtering effects due to ion bombardment at high plasma powers were discussed. Beyond those results, precise information about the impact of different plasma gas compositions on the resulting film properties was obtained. Cobalt films grown using a hydrogen/nitrogen (H2/N2) plasma as a coreactant showed a stable film composition (CoNx) with a high Co content of 75 at. %. Using scanning electron microscopy and four point probe measurements, a moderate electrical resistivity of about 56 μΩ cm was calculated for a 20 nm film. The high sensitivity of in vacuo XPS measurements allowed investigations of interface reactions for a single PE-ALD pulse as well as investigations of the initial film growth mechanisms. The nucleation of CoNx films during PE-ALD using H2/N2 plasma as a coreactant was investigated on several substrate materials by XPS. After the very first cycle of the PE-ALD process, no Co could be detected on all the investigated substrates. XPS revealed that the plasma pulse was needed to provide active binding sites for the adsorption reaction of precursor molecules due to the formation of Si-Nx or Si-NxOy surfaces. Therefore, the plasma pulse plays an important role in the PE-ALD process of Co on silicon surfaces. The early cycles were characterized by the onset of Co—O bonds. The homogeneous film body on all substrates consisted of Co-nitride compounds.

A porous ultra low-κ dielectric (pULK) and a dense SiCOH dielectric were investigated before and after a plasma treatment with argon in terms of the change in the bonding types, the relative permittivity and the water uptake. Fourier transform infrared (FTIR) spectroscopy revealed a change in the bonding types of the dielectrics in general and a significant increase in the hydroxyl band especially. The high hydroxyl amount leads to an increase in the relative permittivity of these dielectrics by up to 6.25% for SiCOH and up to 12.5% for the pULK material. Furthermore, if water diffuses into the dielectric films from the environment, the moisture uptake is up to 2.7 times higher in saturation at 80% relative humidity in comparison to the untreated samples. Due to the plasma damaged upper layer of the materials, the diffusion process of water into the bulk dielectrics is significant reduced. Overall, it has been found that the pULK material is more vulnerable to the used plasma treatment in comparison to the dense SiCOH film. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0041501jss] All rights reserved.

A novel transistor with a graphene base embedded between two n-type silicon emitter and collector layers (graphene-base heterojunction transistor) is fabricated and characterized electrically. The base voltage controlled current of the device flows vertically from the emitter via graphene to the collector. Due to the extremely short transit time for electrons passing the ultimately thin graphene base, the device has a large potential for high-frequency RF applications. The transistor exhibits saturated output currents and a clear modulation of the collector current by means of the graphene base voltage. The vertical transfer current from the emitter via the graphene base to the collector is much lower than expected from device simulations. A comparison of the graphene-base transistor and a reference silicon n-p-n bipolar transistor is performed with respect to the main DC transistor characteristics. A common-emitter gain of larger than one has been achieved for the reference device while the graphene-base transistor so far exhibits a much lower gain.

The initial growth behavior of ruthenium during the thermal-activated atomic layer deposition (ALD) using [(ethylcyclopentadienyl)(pyrrolyl)ruthenium(II)] (ECPR) and molecular oxygen was investigated in a cluster tool combining an ALD reactor with a surface analysis unit under high vacuum conditions. A direct qualification and quantification of the chemical surface composition by X-ray photoelectron spectroscopy (XPS) and a determination of the surface topography by atomic force microscopy (AFM) were conducted in the course of the ALD cycles without vacuum break. XPS revealed a substrate-inhibited Ru growth on a hydrogen-terminated silicon surface, which was preceded by an incubation period of 20ALD cycles. The Si surface oxidized during the first 50cycles. AFM measurements showed a roughness maximum around the 40th ALD cycle, which suggested an island growth mode and thus corresponded with the substrate inhibition. As verified from the AFM data with an analytical model by Nilsen et al. the Ru islands coalesced between the 40th and 50th ALD cycle. The ALD growth initiation of Ru was also investigated on aluminum oxide and tantalum nitride. XPS revealed a similarly inhibited growth behavior on all the investigated substrates. However, the ECPR adsorption during the very first Ru precursor pulse differed as the amount of chemisorbed Ru on the NH"y-terminated TaN"x(O, C) surface was much higher compared to the OH-terminated Al"2O"3 and the H-terminated Si surface. Summarizing, we demonstrated that in-vacuo XPS and AFM as well as the combination of both are ideally suited for studying the ALD growth initiation of Ru. Furthermore, we provided important chemical information about the initial Ru precursor adsorption on several foreign substrate materials, which will direct further investigations towards a non-inhibited Ru growth.

The paper presents atomic layer deposition (ALD) processes and process integration for the deposition of insulating liners, copper diffusion barriers, and seed layers for direct copper plating in high aspect ratio (>20:1) through silicon vias. A TaN-based copper diffusion barrier was deployed on an aluminum oxide insulating liner. The latter has the potential to act also as a dielectric barrier against copper diffusion according to BTS and TVS measurements. Furthermore, ruthenium ALD films applied as seed layers for direct copper plating were deposited with an intermediate annealing step to improve film adhesion and ensure the deposition of thick films without any delamination. The step coverage of the presented ALD processes was confirmed by SEM measurements on cross-sections of coated TSV structures. Finally a subsequent electrochemical deposition (ECD) of copper was conducted revealing the satisfying functionality of the Ru seed layer.

The dependence has been investigated of electrical, optical and structural properties of undoped ZnO films grown on single-crystal c -sapphire substrates by pulsed laser deposition on the substrate temperature in the range between 50 °С and 650 °С. It has been shown that an increase in energy density of laser radiation at the target surface leads to lowering of the temperature of epitaxial growth of zinc oxide films. The surface roughness of the films produced at the substrate temperature of 450 °C does not exceed several monolayers, and the width of X-ray diffraction peaks 2 Θ at half maximum near the lattice site (00.2) makes 0.035°.

Applied physics letters 110(10), 101103 (2017). doi:10.1063/1.4977882, In response to the conjecture that the numerical aperture of x-ray optics is fundamentally limited by the critical angle of total reflection [Bergemann et al., Phys. Rev. Lett. 91, 204801 (2003)], the concept of adiabatically focusing refractive lenses was proposed to overcome this limit [Schroer and Lengeler, Phys. Rev. Lett. 94, 054802 (2005)]. We present an experimental realization of these optics made of silicon and demonstrate that they indeed focus 20 keV x rays to a 18.4 nm focus with a numerical aperture of 1.73(9) × 10$^{−3}$ that clearly exceeds the critical angle of total reflection of 1.55 mrad., Published by American Inst. of Physics, Melville, NY

In order to deposit thin films on a substrate several techniques can be used, e.g. chemical vapour deposition, atomic layer deposition or sputter deposition, depending on their specific advantages and disadvantages due to the related application. A significant parameter is the energy incident upon the substrate by the specific technique, especially when the heat capacitance of the substrate is low. Within this paper we analyse the energy transported into a thin wire (few 10 μm in diameter) during a dynamic inline aluminium sputter process in a cylindrical magnetron source. The evoked heating is important for the tensile strength of the wire and uniformity of the sputtered layer. Therefore, mathematical models were created to estimate the energy input into the wire supported by monte-carlo-simulations of the sputtering process using the TRIM-simulation (Transport and Range of Ions in Matter). Measurements with a Langmuir probe and the corresponding deposition rate were used to quantify these models, showing that at an aluminium coating process of a gold wire, the significant energy input is only due to electrons and ions of the processing gas (argon). Using the heat equation based on the sputtering apparatus' parameters, it was also possible to determine the energy input into the wire with in situ electrical resistance measurements. Both methods did show similar results, whereby the resistance results were more stable. The determined energy input made it possible to calculate the temperature profile during the wire-coating process which can be useful for estimations about film diffusion and process optimisation.

Hydrogenated amorphous silicon (a-Si:H) is conventionally deposited using static plasma-enhanced chemical vapor deposition (PECVD) processes. In this work, a very high frequency (VHF) dynamic deposition technique is presented, on the basis of linear plasma sources. This configuration deploys a simple reactor design and enables continuous deposition processes, leading to a high throughput. Hence, this technique may facilitate the use of flexible substrates. As a result, the production costs of thin-film silicon solar cells could be reduced significantly. We found a suitable regime for the homogeneous deposition of a-Si:H layers for growth rates from 0.35–1.1 nm/s. The single layer properties as well as the performance of corresponding a-Si:H solar cells are investigated and compared with a state-of-the-art radio frequency (RF) PECVD regime. By analyzing the Fourier transform infrared spectroscopy spectra of single layers, we found an increasing hydrogen concentration with deposition rate for both techniques, which is in agreement with earlier findings. At a given growth rate, the hydrogen concentration was at the same level for intrinsic layers deposited by RF-PECVD and VHF-PECVD. The initial efficiency of the corresponding p–i–n solar cells ranged from 9.6% at a deposition rate of 0.2 nm/s (RF regime) to 8.9% at 1.1 nm/s (VHF regime). After degradation, the solar cell efficiency stabilized between 7.8% and 5.9%, respectively. The solar cells incorporating intrinsic layers grown dynamically using the linear plasma sources and very high frequencies showed a higher stabilized efficiency and lower degradation loss than solar cells with intrinsic layers grown statically by RF-PECVD at the same deposition rate. Copyright © 2012 John Wiley & Sons, Ltd.

Thin‑film silicon solar cells based on hydrogenated amorphous silicon (a‑Si:H) and hydrogenated microcrystalline silicon (μc‑Si:H) absorber layers are typically deposited using static plasma-enhanced chemical vapor deposition (PECVD) processes. It has been found that the use of very‑high frequencies (VHF) is beneficial for the material quality at high deposition rates when compared to radio-frequency (RF) processes. In the present work a dynamic VHF‑PECVD technique using linear plasma sources is developed. The linear plasma sources facilitate the use of very-high excitation frequencies on large electrode areas without compromising on the homogeneity of the deposition process. It is shown that state-of-the-art a‑Si:H and μc‑Si:H single-junction solar cells can be deposited incorporating intrinsic layers grown dynamically by VHF-PECVD at 0.35 nm/s and 0.95 nm/s, respectively.

The growth of ultra-thin Ta-N films using atomic layer deposition (ALD) is investigated by in-situ X-ray photoelectron spectroscopy (XPS) starting from the first precursor pulse, as precursor substances tert-butylimido-tris(diethylamido)tantalum (TBTDET) and tert-butylimido-bis(diethylamido)cyclopentadienyl)tantalum (TBDETCp) are applied mainly on SiOH and SiH surfaces. The chemical composition, the growth mode, and the film thickness are derived as functions of the cycle number and the substrate chemistry. The growth rates are significantly higher on SiOH than on SiH substrates, which is related to the oxygen surface concentration. The film composition changes with the cycle number but stabilizes at an approximate stoichiometry of Ta2N2O for both precursors.

By an ALD process with the solid precursors HfCl 4 and (CpCH 3 ) 3 Y and the oxidant water Yttrium doped HfO 2 was deposited on TiN layer on highly doped silicon. The films were analysed by ellipsometry, XRR, RBS and XRD. For the electrical characterisation, capacitance and I-V measurement on MIM structure were used. By doping the HfO 2 with 6.2 at.% Yttrium and annealing the film at 500 °C in N 2 the k-value increased by 60% for a 9.5 nm thick film, the leakage current also increased. The deposited amorphous film crystallises at 450 °C into the cubic phase.

The temperature dependence of the sticking coefficient (SC) of precursor molecules used in atomic layer deposition (ALD) was investigated. Tetrakis(ethylmethylamino) hafnium (TEMAHf) and Pentamethylcyclopentadienyltitan-trimethoxid (Cp*Ti(OMe)(3)) were used in combination with ozone to deposit hafnium dioxide and titanium dioxide films at different substrate temperatures. The SC of TEMAHf was determined at 180, 230, and 270 degrees C. The SC of TEMAHf depends exponentially on the substrate temperature. The activation energy and the pre-exponential factor were obtained for this ALD process. The SC of Cp*Ti(OMe)(3) was determined at 270 degrees C. A possible explanation for the small SC of Cp*Ti(OMe)(3) could be the reduced symmetry of the precursor molecule. Therefore, symmetric precursor molecules and high process temperatures appear beneficial for efficient ALD processes.

The mechanisms of technologically important atomic layer deposition (ALD) processes, trimethylaluminium (TMA)/ozone and tetrakis(ethylmethylamino)hafnium (TEMAH)/ozone, for the growth of Al(2)O(3) and HfO(2) thin films are studied in situ by a quadrupole mass spectrometer coupled with a 300 mm ALD reactor. In addition to released CH(4) and CO(2), water was detected as one of the reaction byproduct in the TMA/O(3) process. In the TEMAH/O(3) process, the surface after the ozone pulse consisted of chemisorpted active oxygen and -OH groups, leading to the release of H(2)O, CO(2), and HNEtMe during the metal precursor pulse.

Electromigration failure of copper interconnects in microelectronics evokes a need for materials with improved resistance against electromigration effects. Copper-silver alloy thin films are a promising material for the next generation of interconnects and were investigated with respect to their electromigration resistance. The investigations were done by atom drift experiments by means of Blech structures fabricated in single damascene technology with two different Ta-based liner systems. Electromigration induced atom drift could be demonstrated. The resistance against electromigration of Cu(Ag) films appears to be slightly higher than for pure Cu films. However, significant experimental errors are still present. Additionally, de-alloying effects were observed.

Amorphous and microcrystalline silicon single layers and p–i–n solar cells were produced dynamically using an inline deposition system called “line source”. A highly uniform deposition of thin-film silicon layers with layer-thickness variations of less than ±5% was achieved. Amorphous and microcrystalline silicon single junction solar cells were dynamically fabricated with initial efficiencies of 8.3% and 6.3%, respectively. The dynamic deposition rate of these solar cells is 6.75 nm m/min in case of a-Si:H and 3.3 nm m/min for μc-Si:H. In this work it will be shown that an enhancement of the deposition rate up to 15.6 nm m/min during the i-layer deposition of a-Si:H solar cells has only a weak negative influence on the initial efficiencies of the cells. Further on, the effect of substrate velocity on solar cell characteristics of a-Si:H solar cells is investigated. Finally, a productivity estimation of the line source concept is presented.

A method to determine the sticking coefficient of precursor molecules used in atomic layer deposition (ALD) will be introduced. The sticking coefficient is an interesting quantity for comparing different ALD processes and reactors but it cannot be observed easily. The method relies on free molecular flow in nanoscale cylindrical holes. The sticking coefficient is determined for tetrakis(dimethylamino)titanium in combination with ozone. The proposed method can be applied independent of the type of reactor, precursor delivery system and precursors.

To increase the electromigration resistance of copper interconnects copper alloy systems are of interest. In the present paper electrical properties of Cu(Ag) films will be discussed with respect to heat treatment and in comparison to copper and other alloy systems. The investigations show that the electrical resistivity of Cu(Ag) films is very low in comparison to other copper alloy systems. Up to an alloy content of about 2 at.% Ag the International Technology Roadmap for Semiconductors criterion of 2.2 μΩcm (scattering by geometrical constraints neglected) can be fulfilled after heat treatment. The various components of the electrical resistivity will be discussed in detail. The investigations show that grain growth and the redistribution of silver and impurities dominate the electrical resistivity evolution.

Ta-N based thin films were grown by thermal atomic layer deposition (ALD) with an alternating supply of the reactant source TBTDET (tert-butylimidotris(diethylamido)tantalum) and NH3 (ammonia). The films were deposited using a newly designed and constructed atomic layer deposition prototype tool combined with several in situ metrology. It was observed that thin films were successfully deposited on a 300mm Wafer with a saturated growth rate of approximately 0.55i?/cycle at 270?C. The as deposited films resulted in the formation of Ta(C)N consisting of 38at% Ta, 32at% N and 10at% C. With in situ spectroscopic ellipsometry (SE) the growing behaviour of the film was investigated and compared to atomic force microscopy (AFM) images.

To avoid plasma induced erosion of chamber hardware, the application of remote plasma sources to activate the etch gases was introduced. We present results on the etch behaviour of titanium nitride (TiN) using mixtures of NF"3, Cl"2 and argon. The gas mixture was excited in a remote plasma source and then routed through a reaction chamber to study the etch behaviour of TiN samples which simulate the situation at the chamber walls. The dependency of the TiN etch rate on temperature, gas flow, composition and pressure was examined. While the temperature (studied in the range 25-300^oC) turned out to be the most sensitive parameter, the general etch rate was mainly dependent on the availability of atomic fluorine. Etch products and NF"3/Cl"2 dissociation have been monitored by quadrupole mass spectrometry and infrared spectroscopy. While NF"3 showed a high decomposition up to 96%, chlorine decomposition was not observed. However the addition of chlorine increased the etch rates up to 260% in the low pressure/low temperature regime. Surface effects of chlorine addition are indicated by X-Ray Photoelectron Spectrometry and REM surface analysis.

The aim of this study is to reduce the amount of harmful substances in the effluent gas in the plasma cleaning process of vacuum chambers by substituting the greenhouse gas SF 6 . We present comparative studies for the optimised cleaning rates which are based on C 4 F 8 / O 2 and NF 3 diluted with He, Ar and N 2 in comparison to SF 6 /O 2 . Since the deposition of amorphous silicon (a-Si) requires a temperature of 200-250 °C in the vacuum chamber, the cleaning process has to match with these conditions, creating especially limitations on the maximum plasma power that can be used. The results for C4F 8 /O 2 turn out to be unsatisfactory. NF 3 however appears to be more promising. We find that the utilisation of NF 3 as etching gas in the vacuum chamber approaches up to 90% and the dilution can be up to 80%. This high dilution and utilisation demonstrates also that cleaning with NF 3 can be cheaper than cleaning with SF 6 even though NF 3 is much more expensive than SF 6 .

In thin tantalum films grown by pulsed laser deposition in a vacuum, the resistivity versus thickness dependence is found to oscillate. The oscillation periods equal 5.0 and 5.6 nm for α-and β-Ta films, respectively. This observation is interpreted as the quantum-size effect in thin tantalum films.

Aluminum oxide was deposited on arsenic doped silicon, using atomic layer deposition (ALD) with either a silicon oxide or a silicon nitride interface. The physical properties of these films were investigated by elastic-recoil-detection, X-ray-photoelectron-spectroscopy and transmission electron microscopy. Special focus was given to contamination of the film and the interface, crystallization and temperature effect on diffusion. The films remained stoichiometric and did not have Al–Al clusters, even post annealing steps. Evidence of diffusion of silicon and arsenic into the dielectric and of aluminum from the film was found. Carbon and hydrogen were seen in the film and at the interface as well, whereas hydrogen diffused out of the film to some extent due to anneal. Carbon content in the layer was reduced by using O3 as oxidant. Grain size of crystalline Al2O3 films was in the order of film thickness.

The integration of ultra low k materials in copper damascene architecture is one of the main issues in finding microelectronic-process-compatible dielectric materials. The aim of this paper is to show the integration conformity with common equipment and process steps using a PECVD (plasma enhanced chemical vapor deposition) CF polymer ultra low k material in a Cu single damascene architecture (Proceedings of the Advanced Metallization Conference, 2002). The intermetal dielectric low k material used in the described structures has 2.1≤k≤2.3 (k depends on deposition process parameters [Microelectron. Eng. 50 (2000) 7-14]) and the copper was deposited by a metal organic chemical vapor deposition process. After chemical mechanical polishing the structures were characterized by scanning electron microscopy and electrical measurements.

The objective of our investigations was to develop a new etching process, which accomplished well defined positive etch profiles in silicon. Using this so-called PPE-process (Positive Profiles Etching process) we realized patterns in silicon with tilt angles of the sidewalls between 60 and 88° and an etch depth up to 200 μm. Etch rates between 3 and 5 μm/min can be achieved and a large number of process parameters enables the variation of the etch profiles in a wide range. Based on these results we could create complex etch profiles by a combination of several silicon etching processes according to application-oriented demands.

The erosion plume resulting from ablation of copper and tantalum targets in vacuum with excimer laser irradiation (308 nm) was studied using Langmuir probe and optical emission spectroscopy. The ion and electron probe currents were obtained in the range of energy densities from 0.2 to 2.2 J/cm2 at the target with a probe-to-target distance from 10 to 133 mm. The ion velocity distribution calculated from the time-of-flight measurements has been revealed as a multimodal kind. Curves of the spatial and time dependence of electron probe current were obtained in real time. The electron temperature of different plume regions was determined from a series of I-U characteristics taken at different distances between the Langmuir probe and target. It was established that the plume electron temperature is nonuniform and it has a maximum in front of the plume. The optical emission spectra were used to study the plume composition qualitatively. In addition, the optical emission spectroscopy allowed us to measure both t...

Aluminum oxide was deposited using atomic layer deposition on either a silicon oxide or a silicon nitride interface. Water vapor or ozone were used as oxidation precursors. The structural properties of these films were investigated by time-of-flight secondary-ion-mass-spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and elastic recoil detection (ERD). Special attention was given to contamination issues of the film and the interface, bonding conditions and temperature influence on diffusion. The results suggest that the silicon most likely diffused along grain boundaries of polycrystalline Al2O3. Carbon and hydrogen were located at the interface and furthermore hydrogen diffused out of the film to some extent due to anneal. Carbon content in the layer was reduced when using O3 as an oxidant. The formation of metallic aluminum clusters was not observed for any of the investigated process conditions.

A new vertical field-effect transistor (FET) has been fabricated inside a through silicon VIA (TSV). Front side and backside of a 200- $\mu \text{m}$ -thin p-doped Si wafer were highly n-doped to shape the source/drain areas of the FET. The lateral surface of the TSV forms the channel with a length of $200~\mu \text{m}$ (wafer thickness) and a width of $63~\mu \text{m}$ (circumference of the 20- $\mu \text{m}$ hole). A stack of SiO2 and Al2O3 was used as gate dielectric material and Ru/TaN/Ru was deposited as gate metal using atomic layer deposition. The n-channel TSVFETs showed saturation currents of 150 $\mu \text{A}$ for a gate voltage of 4 V and an ON/OFF current ratio of about 104.

N-type doped amorphous hydrogenated silicon (a-Si:H) is deposited on top of graphene (Gr) by means of very high frequency (VHF) and radio frequency plasma-enhanced chemical vapor deposition (PECVD). In order to preserve the structural integrity of the monolayer graphene, a plasma excitation frequency of 140 MHz was successfully applied during the a-Si:H VHF-deposition. Raman spectroscopy results indicate the absence of a defect peak in the graphene spectrum after the VHF-PECVD of (n)-a-Si:H. The diode junction between (n)-a-Si:H and graphene was characterized using temperature dependent current-voltage (IV) and capacitance-voltage measurements, respectively. We demonstrate that the current at the (n)-a-Si:H-graphene interface is dominated by thermionic emission and recombination in the space charge region. The Schottky barrier height (qΦB), derived by temperature dependent IV-characteristics, is about 0.49 eV. The junction properties strongly depend on the applied deposition method of (n)-a-Si:H with a cl...

As a result of the continuous miniaturization of integrated circuits, width and depth of Cu interconnects are reduced for every new technology node, implying that also the Ta or TaN Cu diffusion barrier and Cu seed layer must be thinned in order to avoid top feature pinch-off during Cu electroplating [1]. On the other hand, a reduction of Ta or TaN film thickness may also be desirable from a cost perspective, e.g. in ICs with less aggressive scaling. Cabral et al. showed that a 1 nm TaN film prevented Cu diffusion upon annealing at temperatures below 650 °C [2]. However, no electric fields were applied in this study, and TaN was deposited on Si.

The erosion plume resulting from an ablation of a tantalum target in vacuum with an excimer laser radiation (308 nm) was studied using the Langmuir probe technique. The spatial and temporal dependencies of the electron probe currents were obtained in real time. The electron temperature of different plume regions was determined from a series of I–U characteristics taken at different distances between the probe and the target. We determined that the plume electron temperature is non-uniform and has a maximum value in front of the plume.

A Langmuir probe was used to study the erosion plume produced during the ablation of a tantalum target in vacuum by radiation from an excimer laser at 308 nm. The spatial and temporal dependences of the electron and ion currents of the probe were obtained in real time. The electron temperature of different regions of the plume at different distances from the target was measured for the first time from a series of dependences of the electron probe current on the probe voltage. The nonuniformity of the electron temperature and its lowering in different plume regions with increasing expansion time were determined. The ion density in the plume was determined at different distances from the target.

An advanced CMOS scheme for the integration of a graded epitaxial Silicon Germanium (SiGe) layer is presented. SiGe is deposited into the source drain regions right after gate formation to create compressive strain in the transistor channel of the pMOSFETs and thus improve charge carrier mobility. The SiGe layer is exposed to subsequent process steps such as cleaning, implantation and annealing which cause erosion and dopant loss. This effect becomes more severe with increasing Ge content, which is wanted to increase stress in the channel. The negative effect of SiGe erosion on DC transistor performance is shown in this paper and how it can be reduced by optimized SiGe deposition utilizing a two layer stack with different Ge content. First a film with higher Ge concentration is deposited followed by a lower percent Ge film which is aimed to protect the SiGe film underneath. Electrical data for PMOS devices with 55 nm embedded SiGe with 20–30% Ge are presented and compared to the corresponding graded SiGe stack (25–30%, 50 nm with 5 nm thick 15% cap). Comparing Embedded Silicon Germanium (eSiGe) devices with 30 at% Ge, we see a 5% I DSAT improvement for the graded layer over the monolithic one.

The inversion field-effect transistor is the basic device of modern microelectronics and is nowadays used more than a billion times on every state-of-the-art computer chip. In the future, this rigid technology will be complemented by flexible electronics produced at extremely low cost. Organic field-effect transistors have the potential to be the basic device for flexible electronics, but still need much improvement. In particular, despite more than 20 years of research, organic inversion mode transistors have not been reported so far. Here we discuss the first realization of organic inversion transistors and the optimization of organic depletion transistors by our organic doping technology. We show that the transistor parameters—in particular, the threshold voltage and the ON/OFF ratio—can be controlled by the doping concentration and the thickness of the transistor channel. Injection of minority carriers into the doped transistor channel is achieved by doped contacts, which allows forming an inversion layer., Inversion type transistors – which are widely used in silicon-based industries – are thought to not be obtainable in organic devices. Lüssem et al. realize the first inversion organic field-effect transistor by doping at the source and drain contacts without degrading its ON/OFF ratio.

Low temperature etching of Si with SF"6 has been studied, using a DECR system and a special Helicon type plasma source. In contrast to the current understanding of low temperature etching, we did not observe a ''freezing'' of the lateral etching reaction, but obtained isotropic etch profiles, even at temperatures below -120^o C. Anisotropic etch profiles are obtained by an addition of O"2. We therefore propose a sidewall passivation mechanism to explain the reduction of the lateral etching. Si etch rates of [email protected]/min at selectivities Si/SiO"2 well above 100/1, with anisotropic profile have been obtained.

ALD-Co(W) was found to have a potential to replace the conventional PVD-Ta/TaN bi-layer in further shrinking interconnects as a single-layered barrier/liner material. We could confirm good barrier property of CVD/ALD-Co(W) film by BTS-TVS method after 350 °C annealing. ALD-Co(W) showed lower resistivity of 60 µΩ-cm and good adhesion to Cu. Complete trench filling with Co(W) followed by Cu seed deposition was demonstrated. These properties were confirmed to be derived from W stuffing into grain boundaries of oxygen-free ALD-Co(W) films. We would like to suggest ALD-Co(W) as a next-generation barrier/liner layer for future development.

To fulfill the requirements of future technology nodes new resists with high resolution, high sensitivity and low LWR and LER respectively are needed. A new inorganic non-chemically amplified resist (XE15IB, an experimental resist provided by Inpria Corp.) was investigated. The resist is spin-cast from aqueous solution and is based on hafnium oxide. Metal oxide based resist as XE15IB supersede other resist materials due to its high etch resistance. 1, 2 This new material can be considered as a direct patternable spin on hard mask. XE15IB was processed in a 300mm complementary metal oxide semiconductor (CMOS) manufacturing environment and exposed on a 50 kV VISTEC SB3050DW variable shaped electron beam direct writer at Fraunhofer Center Nanoelectronic Technologies (CNT). The resist was evaluated in terms of contrast, sensitivity and resolution. The process characteristics required for CMOS manufacturing such as delay stability were also examined. Furthermore, by printing a large static random access Memory (SRAM) pattern (design CD of 22 nm), the exposure of a real application pattern was demonstrated.

We developed Fluor-based RIE processes to fabricate nanoimprint template in silicon and to transfer patterns from the imprint resist to the silicon substrate. The etched silicon patterns have slightly tapered and smooth sidewalls. The sidewall angle can be controlled between 85° and 90° by varying the ratio of the used gas. The dimension of the etched structures is identical with the patterns in the resist. We demonstrated line structures in silicon substrate down to 50 nm. The etching rate is over 100 nm per minute and the maximal achieved aspect ratio is more than 10.

In this study Ru-Mn alloys are discussed in terms of some of the major questions that are typically associated with the development of new types of barriers. First, the Cu diffusion barrier performance after annealing at high temperatures and under subsequent bias temperature stress is investigated, on SiO 2 and on low-k dielectrics. Second, the origin of the barrier performance - either a self forming barrier caused by segregation of an alloyed element, or the stuffing of grain boundaries - is investigated, since this is of importance with regard to an electromigration barrier at the bottom of a via. Third, Cu plating and Cu adhesion behavior are addressed, since they are also important with regard to electromigration, specifically along the side walls of trenches. Fourth, the blocking of oxygen diffusion is investigated. Furthermore, down-scaling of the Mn content to a lowest possible level is pursued in order to reduce line and via resistances.

Erratum: Investigation of Argon Plasma Damage on Ultra Low-κ Dielectrics [ECS J. Solid State Sci. Technol., 4, N3023 (2015)] C. Kubasch,a T. Olawumi,a H. Ruelke,b U. Mayer,b and J. W. Barthaa aTechnische Universitat Dresden, Fakultat Elektrotechnik und Informationstechnik, Institut fur Halbleiterund Mikrosystemtechnik, 01062 Dresden, Germany bGLOBALFOUNDRIES Dresden Module One, Limited Liability Company & Co. KG, 01109 Dresden, Germany