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Due to its high intrinsic mobility, germanium (Ge) is a promising candidate as a channel material (offering a mobility gain of approximately ×2 for electrons and ×4 for holes when compared to conventional Si channels). However, many issues still need to be addressed before Ge can be implemented in high-performance field-effect-transistor (FET) devices. One of the key issues is to provide a high-quality interfacial layer, which does not lead to substantial drive current degradation in both low equivalent oxide thickness and short channel regime. In recent years, a wide range of materials and processes have been investigated to obtain proper interfacial properties, including different methods for Ge surface passivation, various high-k dielectrics and metal gate materials and deposition methods, and different post-deposition annealing treatments. It is observed that each process step can significantly affect the overall metal-oxide-semiconductor (MOS)-FET device performance. In this review, we describe and compare combinations of the most commonly used Ge surface passivation methods (e.g. epi-Si passivation, surface oxidation and/or nitridation, and S-passivation) with various high-k dielectrics. In particular, plasma-based processes for surface passivation in combination with plasma-enhanced atomic layer deposition for high-k depositions are shown to result in high-quality MOS structures. To further improve properties, the gate stack can be annealed after deposition. The effects of annealing temperature and ambient on the electrical properties of the MOS structure are also discussed. [ABSTRACT FROM AUTHOR]

Thermal stability, phase and interface uniformity of Ni-silicide are some key issues for NiSi Salicide technology. The improved stability of NiSi was achieved by Ni/Pt/Si and Ni/Pd/Si reaction. The increase of thermal stability can be explained by classical nucleation theory. The phase and interface uniformity of Ni-silicides formed by Ni–Si solid-state reaction were characterized by X-ray diffraction (XRD) and temperature-dependent current–voltage (I–V–T) techniques. Results show that the Schottky barrier height (SBH) inhomogeneity characteristic has strong dependence on annealing temperature for Ni-silicide formation. Deep level transient spectroscopy (DLTS) measurement shows that annealing at relatively low temperature may cause electrically active deep level defects in the film. These results show that choosing a proper annealing temperature for Ni/Si silicidation will be very important for device performance. [Copyright &y& Elsevier]

In situ NH3 plasma surface-nitridation treatments at 250 °C on both p- and n-type Ge(100) wafers were investigated. An ultrathin high quality GeOxNy interlayer was formed and exhibited dielectric breakdown for electric fields greater than 15 MV/cm. Well behaved capacitance-voltage characteristics were obtained for the complementary metal-oxide-semiconductor capacitors (CMOSCAPs) with HfO2(3 nm)/GeOxNy(1 nm) gate stacks. Gate leakage current density was below 5×10-7 A/cm2 at VFB±1 V for both MOSCAPs with an equivalent oxide thickness of 1.1 nm. Promising electrical properties of the CMOSCAPs indicate effective passivation of the Ge interface with GeOxNy interlayer formed by in situ NH3 plasma treatment. [ABSTRACT FROM AUTHOR]

Comments on the article 'Schottky Barrier Rectifier With High Current Density Using Vanadium As Barrier Metal,' by J.S. Kim, H.H. Choi, S.H. Son and S.Y. Choi, published in vol. 79 of the journal 'Applied Physics Letters' in 2001. Errors in the analysis of Schottky barrier rectifier (SBR) with high current density using vanadium as barrier metal; Forward density-voltage characteristics of vanadium-SBR.

In this paper, we propose a new form of nanostructures with Al film deposited on a patterned dielectric material for generating structural color, which is induced by local surface plasmonic resonant (LSPR) absorption in sub-wavelength-indented hole/ring arrays. Unlike other reported results obtained by using focus ion beam (FIB) to create metallic nanostructures, the nano-sized hole/ring arrays in Al film in this work are replicated by high resolution electron beam lithography (EBL) combined with self-aligned metallization. Clear structural color is observed and systematically studied by numerical simulations as well as optical characterizations. The central color is strongly related to the geometric size, which provides us with good opportunities to dye the colorless Al surface by controlling the hole/ring dimensions (both diameter and radius), and to open up broad applications in display, jewelry decoration, green production of packing papers, security code, and counterfeits prevention. [ABSTRACT FROM AUTHOR]

The inhibitory effect of glycine on corrosion and chemical mechanical polishing (CMP) of Mo in hydrogen peroxide (H 2 O 2 ) based abrasive-free alkaline slurry has been investigated. Results show that, in H 2 O 2 based slurry, both static etching rate (SER) and removal rate (RR) of Mo during chemical mechanical polishing were reduced by adding glycine and the inhibition efficiency was around 50%. From ex-situ and in-situ open circuit potential (OCP), current density transient and potentiodynamic polarization measurements, it is found that formation of oxides was delayed due to blocked contact between oxidizer and the sample surface by electrostatic adsorption of glycine zwitterion on the surface. Glycine can form complex with MoO 3 and promote dissolution of surface oxide, MoO 3 , resulting in a reduced passivation layer. The slowed oxidation reaction dominates the whole process, resulting inhibited Mo corrosion and leading to a smoother Mo surface. [ABSTRACT FROM AUTHOR]

In this work, an ultra-thin cobalt film is used as a passivation layer to achieve a Cu–Cu quasi-direct bonding process, and successful bonding was achieved at the bonding temperature of 230 °C with the bonding pressure of 0.5 MPa in non-vacuum conditions. A tensile bonding strength of over 12.8 MPa can be achieved. With the cobalt layer, the total film roughness is greatly reduced to around 1 nm, and the cross-sectional transmission electron microscope images reveal the presence of a void-free bonding interface. Time-of-flight secondary ion mass spectrometry depth analysis is carried out using a PVD deposited multilayer sample, which simulates the bonding process without pressure. It is found that a Cu–Co intermixing layer formed between the Cu and Co interfaces during annealing, and Cu has diffused into the Co layer. Due to the nanocrystalline structure of the Co film and the low roughness of the system, a low bonding temperature can be achieved. These results demonstrate that Co, which can be selectively grown on the Cu surface, can be used as a passivation layer to achieve low-cost and high-quality interconnect for the three-dimensional integrated circuits. [ABSTRACT FROM AUTHOR]

Abstract: Platinum thin films are deposited on anodic aluminium oxide (AAO) templates by atomic layer deposition (ALD). The highly ordered island-like platinum nanostructures formed on the AAO template produce a high Raman scattering signal because of the periodical hexagonal arrangement. As an illustration, dramatic enhancement is achieved using Rhodamine 6G (R6G) as a molecular probe.Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) show that the gap between the island-like structures is below 10 nm. Owing to activation by the incident laser beam, the localized electromagnetic field on the platinum island surface can be dramatically enhanced by the sub-10 nm regime subsequently amplifying the Raman signal. Finite-difference time-domain (FDTD) calculation matches the experimental phenomena suggesting that the excellent surface-enhanced Raman scattering (SERS) characteristics of the platinum structure arise from the high density and abundance of hot spots. Because the platinum film is inert in air, the SERS enhancing substrate can be used reliably in many trace chemical and biological detection applications. [Copyright &y& Elsevier]

Abstract: The influence of boron (B)/arsenic (As) on X-ray photoelectron spectroscopy (XPS) study of NiSi formation on shallow junctions is investigated in this paper. The Ni-silicide film was formed after 30s soak anneal at 450°C on ultra shallow p+/n or n+/p junctions. The atomic ratio of Ni/Si profile in depth was probed by XPS and the results show that a uniform NiSi layer forms on B-doped p+/n junction while a non-uniform, Ni-rich silicide layer forms on As-doped n+/p junction. It does not agree with the results of other independent phase identification methods such as X-ray diffraction, Rutherford backscattering spectroscopy, and Raman scattering spectroscopy, which all demonstrate the formation of NiSi on both n+/p and p+/n junctions. Comparing the raw binding energy spectra of Ni and Si for each silicide film, the similar spectra for Ni signals are revealed. But the Si signals with an obviously smaller intensity is found to be responsible for the apparent Ni rich silicide formation on As-doped n+/p junction. It indicates that As atoms in the silicide film can affect the sputtering yield of Ni and Si, while no noticeable effect is observed for B atoms. More As atoms than B atoms segregation into the silicide layer is indeed verified by secondary ion mass spectroscopy. And micro-Raman scattering spectroscopy further confirms that the degree of crystallinity for NiSi on n+/p junction is inferior to that on p+/n junction. [Copyright &y& Elsevier]

Amorphous Si0.87Ge0.13 is deposited on n-Si(100) substrate by ion beam sputtering (IBS) and doped through thermal diffusion of phosphorus to fabricate n-poly-Si0.87Ge0.13 thin film. The formation of Schottky junction is made by deposition Ni on n-poly-Si0.87Ge0.13 by IBS. Solid-phase reaction mainly occurred above 400 °C by rapid thermal annealing at the interface of Ni/n-poly-Si0.87Ge0.13. Phase identification and depth profile were investigated by X-ray diffraction (XRD) and Auger electron spectroscopy (AES), respectively. The electrical properties of both unannealed and annealed Ni/n-poly-Si0.87Ge0.13 were studied by current–voltage (I−V) measurement. The results demonstrate that the Schottky barrier height (SBH) changes little with the annealing temperature between 300 and 600 °C. The constancy of SBH is attributed to the properties of the interface itself which determine the SBH and substantially independent of whether the interfacial material is nickel or nickel germanosilicide. [Copyright &y& Elsevier]

• Positive charges from H 2 O molecule induced the parasitic current path, resulting in anomalous hump in subthreshold region at elevated temperature, which disappeared after N 2 annealing. • Hump still existed under PBS, while weakened hump were observed under NBS due to positive charges trapping. In this work, we investigated an anomalous hump in the bottom-gate amorphous-InGaZnO thin-film transistors. The hump in the subthreshold region appeared at elevated temperature and disappeared after N 2 atmosphere annealing. The anomalous hump phenomenon is attributed to the existence of both main current path composed by electron and parasitic current path induced by positive charges formed by adsorbed H 2 O molecules. With the increase of the testing temperature, the hump effect becomes significant since the formation of positive charges is strengthened by heat. This hump can be weakened by negative bias temperature instability stress at high temperature due to the charge-trapping mechanism. [ABSTRACT FROM AUTHOR]

Molecular and atomic permeability, thermal stability and interfacial reactions of ultrathin Ta, TaN and Ta/TaN stack as barrier to Cu/low - k interconnects have been studied. It is shown the barrier layers containing TaN and Ta/TaN have good thermal stability and barrier properties when their thickness is >3.5 nm while Ta cannot withstand 450 °C annealing. The thinner barriers are permeable for neutral molecules like heptane and demonstrate degradation of resistivity during the thermal anneal at 450 °C. Penetration of Ta precursors into low-k and formation of TaO/TaC type of bonds increase the dielectric function of low-k dielectric. Our results show that, on the low-k material with 23% porosity and 0.9 nm pore radius, the PVD deposited Ta(N) films <3.5 nm thick have poor barrier function and are sufficient for neutral molecules penetration, especially water molecules. • Permeability for neutral molecules is a limiting factor of TaN/Ta barrier thickness scaling. • Thermal stability of TaN/Ta barriers degrades when thickness is smaller than 3.5 nm. • Adsorption based ellipsometry is an efficient tool for the barrier quality evaluation [ABSTRACT FROM AUTHOR]

This work reports a first-principles study of copper adhesion on Ta(110) and Ru(0001) surface with the density functional theory. Adsorption energy, electron density difference, and geometrical structures of Cu on pure, oxygen, and nitrogen doped Ta(110), Ru(0001) surfaces, and Ru doped Ta(110) surface were investigated. By analyzing the calculated results and the existing experimental results, it is found that although Ta has stronger chemical interaction with Cu, its larger lattice mismatch with Cu, and easy oxidation and nitridation make Ta a poorer Cu adhesion layer in comparison with Ru. The adhesion ability of Cu on Ta can be improved by doping Ru in Ta. The agglomeration of Cu on Ta or Ru is also studied. The calculation results show that Cu adsorbed on Ta(110) surface is more likely to be desorbed and agglomerated on the top of the second Cu atom layer. The substitutional oxygen OTa in Ta will stimulate the agglomeration of Cu on the Ta surface. [ABSTRACT FROM AUTHOR]

This work investigates the effects of postannealing on the electrical properties of the n-ZnO nanorods/p-Si heterojunction. Well-aligned ZnO nanorods are grown on the p-Si substrate with a ZnO seed layer through a hydrothermal method. The as-grown ZnO nanorods are grown along the preferential [0001] direction with high single crystalline quality. The rectifying characteristics of the heterojunction are effectively improved and the rectification ratio is increased tens of times after annealing in air. The leakage current is decreased by two orders of magnitude and the forward-bias injection efficiency is largely enhanced after annealing. The photoluminescence and x-ray photoelectron spectroscopy results show that annealing in the air ambient can effectively reduce the loosely adsorbed oxygen on the surface of the ZnO nanorods so that the bound free electrons can be released, which can result in larger carrier concentration and improve the injection efficiency of the n-ZnO nanorods/p-Si structure in the forward voltage. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) of TiO2 thin films using Ti isopropoxide and tetrakis-dimethyl-amido titanium (TDMAT) as two kinds of Ti precursors and water as another reactant was investigated. TiO2 films with high purity can be grown in a self-limited ALD growth mode by using either Ti isopropoxide or TDMAT as Ti precursors. Different growth behaviors as a function of deposition temperature were observed. A typical growth rate curve-increased growth rate per cycle (GPC) with increasing temperatures was observed for the TiO2 film deposited by Ti isopropoxide and H2O, while surprisingly high GPC was observed at low temperatures for the TiO2 film deposited by TDMAT and H2O. An energetic model was proposed to explain the different growth behaviors with different precursors. Density functional theory (DFT) calculation was made. The GPC in the low temperature region is determined by the reaction energy barrier. From the experimental results and DFT calculation, we found that the intermediate product stability after the ligand exchange is determined by the desorption behavior, which has a huge effect on the width of the ALD process window. [ABSTRACT FROM AUTHOR]

A thin amorphous Si (α-Si) interlayer is produced between the sputtering deposited ytterbium layer and Si(001) substrate, and the growth of the ytterbium silicide (YbSi2-x) film is investigated in this paper. Formation of YbSi2-x was verified by x-ray diffraction (XRD). The silicide film morphology was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM results reveal that without the α-Si interlayer, pinholes form during YbSi2-x formation on Si(001). Furthermore, the XRD results demonstrate that there is a strong epitaxial relationship between the formed YbSi2-x and Si(001) substrate, and it is believed to be the reason for the formation of pinholes. To suppress the formation of pinholes, a thin α-Si interlayer with different thicknesses is introduced on the Si(001) substrate prior to Yb film deposition. The α-Si interlayer is produced by either sputter deposition employing a Si target or by Si ion implantation induced amorphization. In the presence of this thin α-Si interlayer, epitaxial growth of YbSi2-x is greatly suppressed even when the α-Si interlayer is so thin that full silicidation of the deposited Yb film still requires consumption of Si atoms from the Si(001) substrate. Fabrication of a pinhole-free YbSi2-x film is also demonstrated by SEM and AFM. The growth mechanism of the pinhole-free YbSi2-x film in the presence of a thin α-Si interlayer is discussed. [ABSTRACT FROM AUTHOR]

Different from the conventional current-voltage and capacitance-voltage methods, Schottky contact barrier height extraction by admittance measurement is proposed and discussed in this paper. In this method, the barrier height can be simply extracted from the difference between the measured admittance at zero bias and a reasonably high forward bias. Both simulation results and experimental data demonstrate that the proposed method is effective not only for extraction of Schottky contacts with higher barrier heights (>0.4 eV) but also for extraction of those with moderately lower barrier heights (0.2–0.4 eV). [ABSTRACT FROM AUTHOR]

The temperature-dependent current-voltage (I-V-T) technique has been used to study the Ni/Si solid phase reaction by measuring the Schottky barrier height (SBH) inhomogeneity of Ni-silicide/ Si Schottky diodes. The experimental results show the strong dependence of SBH inhomogeneity on the Ni/Si solid phase reaction. The SBH distribution of the diodes annealed at 500 and 600 °C can be described by a single-Gaussian function and the diode annealed at 500 °C is found to have the best homogeneity and the smallest leakage current. The SBH distribution of the diodes annealed at 400, 700, and 800 °C can be described by a double-Gaussian function in which the mean value of the second Gaussian function is substantially smaller than that of the dominant Gaussian function. The variation of SBH inhomogeneity, an interface property, is related to the phase evolution process in the Ni/Si solid phase reaction, and verified by reverse I-V measurements. Our results indicate that the I-V-T technique may be developed as a wafer-level testing tool to monitor the silicidation process in the complementary metal-oxide-semiconductor device fabrication. [ABSTRACT FROM AUTHOR]

• A sharp interface can be obtained through Ni/Ti/Si reaction. • NiSi 2 is formed after 500 °C annealing through Ni/Ti reaction with 130 nm Si nanowires. • Fully silicided Ni-rich phases form in 15 and 25 nm nanowires. The morphology and phase transformation of nickel silicide nanowires with and without a titanium (Ti) interlayer have been studied. The Ni (10 nm) layers with or without 1 nm Ti film were sputtered onto the Si nanowires onto the silicon-on-insulator substrate and blanket Si wafers. Nickel silicide was formed by rapid thermal annealing at 500 °C in N 2 ambient. Ni 3 Si 2 forms in the 100–130 nm wide nickel silicide nanowire without a Ti interlayer, while the presence of a Ti layer results in epitaxial NiSi 2 formation. The Ti interlayer acts as a diffusion rate limiting barrier for Ni atoms, not only resulting in NiSi 2 formation, but also causing a smooth interface between the nickel silicide nanowire and the substrate. Fully silicided nanowire can be formed on narrow wires, where Ni is excess, leading to the formation of the Ni-rich phase, i.e., Ni 3 Si in the 15 nm nanowire for the Ni/Si reaction; and Ni 3 Si 2 in the 25 nm nanowire for the Ni/Ti/Si reaction. [ABSTRACT FROM AUTHOR]

Abstract Non-destructive and fast evaluation of thin diffusion barriers deposited on top of porous low-k dielectrics by spectroscopic ellipsometry is demonstrated. Studying Physical Vapor Deposited (PVD) CoTa and CoW alloys has shown that 3 nm and 5 nm thick barriers still have holes sufficient for penetration of neutral molecules. This study also detected damage to OSG low-k films which occurs during barrier deposition. VUV light emitted by Ar plasma which is used for metal target sputtering is likely to have caused this damage. For this reason, low-k films were placed under the barriers in order to adsorb moisture during air storage. W atoms also penetrated pores of low-k film during the deposition phase. Graphical abstract Unlabelled Image Highlights • The paper reports a scalable application of ellipsometry for evaluation of critical properties of double thin diffusion films. • Present evaluation (TEM, TOF SIMS etc) is complicated, expensive and destructive. • Ellipsometry can provide basic important information about the barrier properties by non-destructive way very fast. • It makes this approach very efficient during the screening of new barrier materials and deposition conditions. [ABSTRACT FROM AUTHOR]

Mg-doped InZnO (MIZO) films were prepared by sol-gel method, and bottom-gate structured thin film transistors (TFTs) were prepared by using the MIZO films. Oxygen and argon (Ar) plasma treatments were carried out on the film and TFTs. The X-ray photoelectron spectroscopy (XPS) results show that both Ar and oxygen etching can increase the oxygen deficiencies, which effectively increase the content of carrier concentration in MIZO films. After both kinds of plasma treatment, the field effect mobility of the MIZO TFTs is greatly improved and the on/off current ratio increases two orders of magnitude. [ABSTRACT FROM AUTHOR]

Direct electrodeposition (ECD) process of copper film on ultra-thin molybdenum film is investigated in both copper sulfate - sulfuric acid (CuSO 4 - H 2 SO 4 ) acidic bath and copper sulfate - ethylenediamine (CuSO 4 - En) neutral bath (pH = 7.5). The neutral electrolyte containing 0.03 M CuSO 4 and 0.06 M En was chosen to avoid excessive corrosion of Mo and introduction of other ions. The complexing effect of En affects the electrodeposition process of Cu on Mo. Potentiodynamic polarization curves and scanning electron microscopic characterization show that Cu can be electroplated in CuSO 4 - En bath with lower corrosion rate, greater nucleation density and shorter fully-covering time than that in CuSO 4 - H 2 SO 4 bath. The fitting results of current-time transients using Scharifker and Hill's model support the instantaneous nucleation and growth of Cu on Mo in both CuSO 4 - H 2 SO 4 bath and CuSO 4 - En bath (with background electrolyte) at the initial stage of electrodeposition. By using an optimized two-step plating process (at the current density of 8 mA/cm 2 in the first step for a short time and 4 mA/cm 2 in the second step), the resistivity of direct ECD Cu on Mo was almost the same to that of ECD Cu on Cu/Mo in the same plating bath. [ABSTRACT FROM AUTHOR]

Abstract: The barrier height modulation of Ni-silicided Schottky contacts fabricated on n-Si(100), n-Si(110), p-Si(100) and p-Si(110) substrates using an antimony (Sb) interlayer was investigated. The Sb layer was directly sputter-deposited on Si substrate followed by the regular Ni deposition and rapid thermal annealing. It is revealed that NiSi can still form even with the Sb interlayer and the effective Schottky barrier height can be modulated on all kinds of Si substrates. The difference between Si(100) and Si(110) samples is attributed to the rougher NiSi/Si(110) interface, which results in a larger leakage current. [Copyright &y& Elsevier]

Abstract: This paper investigates the influence of CH4, NH3, H2 and He plasma on properties of porous low-k film and its effects on resisting moisture absorption during CMP and ions penetration from sputtering. It is found that the H2, He, NH3 plasma can cause aggressive carbon depletion in the porous low-k films and change the low-k surface from hydrophobic to hydrophilic, which will induce moisture uptake into the low-k material during the CMP process, and result in increase of the k value and leakage current density. The CH4 plasma can make low-k material more resist against moisture uptake and keep the k value stable and a good electrical property of the low-k films. [Copyright &y& Elsevier]

Light-emitting diodes (LEDs) were formed by hydrothermally growing n-ZnO nanostructures on p-GaN with or without seed layers. The performance of the fabricated LEDs was studied. The seed layers not only have a great influence on the morphology and density of the ZnO nanostructures but also determine the lighting bias and emitting mechanism. The LEDs without seed layers and with sputtered seed layers exhibit light emission only under reverse bias, which is believed due to the GaN buffer layer/p-GaN p-n junction. The LEDs with sol-gel seed layers exhibit light emission under both forward and reverse biases. With the increase of the forward bias, the LEDs first demonstrate a red electroluminescence emission coming from the sol-gel seed layers and then demonstrate an orange emission coming from the ZnO nanorods. The sol-gel seed layer and the interface play a very important role in the electroluminescence. [ABSTRACT FROM AUTHOR]

Abstract: Arrays of ferroelectric PZT nanostructures with lateral size down to 500nm were fabricated using nanoembossing technique. The static distribution of domain configurations was investigated by Piezoresponse Force Microscopy (PFM). The observed presence of patterned domains following the patterned morphology suggests that nanoembossing could be used as a potential method for nanoscale control of domain arrangements in ferroelectrics nanostructures. [Copyright &y& Elsevier]

Abstract: In this work, we demonstrate the fabrication of silicon nanowires, with their widths ranging from 22nm to 110nm, using the combination of bilayer nanoimprint and angle deposition. The approach makes the widths of the nanowires adjustable, offering an alternative solution for high-resolution, low-cost, and high-throughput fabrication of nanowire sensors. Using this approach, silicon nanowires with different widths are formed on the boron-doped top Si layers of the SOI substrates, and are used as sensing parts of the gas sensors. The Si nanowire sensors with wire widths of 60nm and 90nm demonstrate relative sensitivities of 155% and 44% to the testing gas of NO2. [Copyright &y& Elsevier]

Abstract: Nanoscale PZT gratings are successfully transferred to a Pt substrate using reversal nanoimprint technique without any chemical etch processes. The transfer process is preliminarily studied by measuring the surface topography of PZT coated on templates before transferring as well as the transferred patterns on substrates. Piezoelectric force microscopy (PFM) and Raman spectroscopy are used to investigate the transferred PZT nanostructures after annealing. Good ferroelectric and structural properties have been demonstrated by the transferred PZT nanostructures, indicating that this reversal imprint technique is applicable for forming nanoscale PZT domains, which may lead to the manufactures of high density data storage devices at economic cost. [Copyright &y& Elsevier]