Search

Epitaxial SrTiO 3 thin films were grown by molecular beam epitaxy (MBE) using an oxygen plasma source. SrO and TiO2 layers were alternately deposited on 0.5 wt% (001) Nb doped SrTiO3 substrates who...

In this work, we have studied the atomic layer deposition (ALD) of ZrO2 under various O3 dosing conditions and systematically investigated the interfacial properties of ZrO2/TiN during ALD fabrication using the CpZr(N(CH3)2)3 and O3 reactant combination. In a typical ZrO2 ALD process, the oxidation condition fundamentally determines the interface oxidation and bulk film properties. High oxidation power is required to enhance the crystallinity of the ZrO2 film with low defect densities but inevitably causes the growth of the interfacial oxide, which reduces the dielectric constant of the resulting film. In the current study, we propose a modulated ALD process with controlled O3 dosing to realize the high performance of a metal-insulator-metal (MIM) capacitor device. The initial ALD cycles proceeded with low O3 dosing to suppress the oxidation of the TiN substrate, and the subsequent bulk film was grown with high O3 dosing to improve the crystallinity of the ZrO2. As a result, we achieved a high dielectric constant ZrO2 material with a reduced defect density and a minimum interface capacitance equivalent thickness (CET) of the TiN/ZrO2/TiN MIM capacitor under modulated oxidation conditions. This work provides a useful method to control the interface and bulk properties of dielectric layers at the atomic level.

As the automotive and AI industries are expanding rapidly, global-shutter (GS) image sensors are playing a more significant role in the perception system. More specifically, GS image sensors are required in various fields involving IR, including the face-ID in mobile devices, the driver monitoring system in automotive applications, and factory automation. GS image sensors are necessary for these applications because they can capture freeze-frame images without motion distortion due to their advantage in the pixel operation method. The simultaneous pixel exposure and in-pixel storing capability allow GS image sensors to achieve high-quality imaging, while the sequential pixel exposure and readout of rolling-shutter (RS) image sensors results in image distortion known as the jello effect. For mobile and automotive applications, a small form factor while maintaining a low parasitic light sensitivity (PLS) and low noise is crucial. In conventional backside illuminated (BSI) charge-domain GS image sensors, a light-shielding structure over the storage area must be formed in order to suppress the influence of parasitic light during the readout operation. Therefore, the introduction of such a light-shielding structure reduces the effective photodiode area, which results in a loss of full-well capacity (FWC), light sensitivity of the sensor, and pixel scalability.

As the smart mobile device market continues to grow and the number of cameras per device rapidly increases, demand for CMOS image sensors (CIS) also increases. Two major trends in mobile device cameras are: (1) adopting smaller pixels that enable greater pixel count at similar optical format, and (2) bigger pixels for higher image quality. To be more specific, front-facing cameras have a trend towards smaller pixels, while rear main cameras have a trend towards both smaller and bigger pixels. The optical format of front-facing cameras is especially limited due to existing bezel-less or border-less display designs, yet higher resolution still-shot and video (such as 4K UHD) recording is desired. To implement greater pixel count in a limited camera module size, scaling of pixel size is required. The main challenges are to maintain acceptable photodiode full-well capacity (FWC) and sensitivity, while suppressing optical crosstalk [1]. To completely eliminate both electrical and optical crosstalk, deep-trench isolation (DTI) has evolved from early BDTI (Back-side DTI) to current FDTI (Front-side DTI) technology, which is also called full-depth DTI. In this paper, a 44Mpixel CIS with 0.7µm pixels using full-depth DTI is demonstrated.

Dipole layers can be formed at epitaxial interfaces of perovskite oxides by intentionally inserting charged atomic layers. Perovskite oxides such as SrTiO3 (STO) can provide dielectrics with very high dielectric constants, but their bandgaps are so small that the suppression of leakage current is one of the critical issues when they are applied for DRAM capacitors. However, their conduction band offset will be manipulated if we can control the dipole layer formation. In this study, we investigated the opportunities of band alignment manipulation using the interface dipole effect especially focusing on the number of charge-introducing atomic layers. STO/LaAlO3 (LAO)/SrRuO3(SRO) stacks were fabricated by pulsed laser deposition method, to demonstrate the modulation of the band alignment at STO/SRO interface as large as ± 0.5 eV, when we change the number of inserted atomic layers of LAO.

We report the Schottky barrier height (SBH) at metal–insulator interfaces in Pt/ZrO 2 –Al 2 O 3 –ZrO 2 (ZAZ)/TiN dynamic random access memory capacitors by analyzing the photoconductivity yield and internal photoemission (IPE) yield using IPE spectroscopy. The SBH values at the Pt/ZAZ and ZAZ/TiN interfaces in the Pt/ZAZ/TiN stack were found to be 2.77 and 2.18 eV, respectively. The SBH difference between the top electrode/oxide and bottom electrode/oxide interfaces is related to the work function difference between Pt and TiN, and the subgap defect state features (density and energy) of the given dielectric. By combining experimental analysis using IPE at the device level and ultraviolet photoelectron spectroscopy and spectroscopic ellipsometry at the film level, a band structure model is proposed.

In this study, we report the effect of process conditions on the crystallinity and energy band structure of atomic layer deposition (ALD) ZrO2 films deposited, using tris(dimethylamino) cyclopentadienyl zirconium as a precursor and ozone as a reactant. ZrO2 films exhibited systematic changes in phase and energy band gap as a function of the ozone concentration. The crystal phase was transformed from the monoclinic phase to a tetragonal phase in the presence of higher ozone concentrations. In addition, spectroscopic ellipsometry measurements showed that the optical band gap and oxygen vacancy defects decreased with increasing ozone concentration. The valence band maximum also shifted closer to the Fermi energy level with increasing ozone concentration. The change in electronic structure driven by a high concentration of ozone led to reduced leakage current density and a high dielectric constant in the ZrO2-based metal-insulator-metal capacitors. These improvements were not observed for depositions performed using conventional ZrO2 ALD with oxygen and water reactants.

Native oxide removal prior to poly-Si contact and epitaxial growth of Si is the most critical technology to ensure process and device performances of poly-Si plugs and selective epitaxial growth (SEG) layers for DRAM, flash memory, and logic device. Recently, dry cleaning process for interfacial oxide removal has attracted a world-wide attention due to its superior passivation properties to conventional wet cleaning processes. In this study, we investigated the surface states of Si substrate during and after dry cleaning process, and the role of atomic elements including fluorine and hydrogen on the properties of subsequent deposited silicon layer using SIMS, XPS, and TEM analysis. The controlling of residual fluorine on the Si surface after dry cleaning is a key factor for clean interface. The mechanism of native oxide re-growth caused by residual fluorine after dry cleaning is proposed based on analytical results.

DRAM capacitors are reaching the scaling limit and new approaches are necessary to enable further reduction of the physical thickness of the capacitor dielectric. The conduction band offset (CBO) of a platinum noble metal electrode on atomic layer deposited ZrO 2 /Al 2 O 3 /ZrO 2 is evaluated and compared to a titanium nitride electrode. Internal Photo Emission Spectroscopy and Photoconductivity measurement are used to estimate the barrier height and band gap, respectively. The barrier height difference between the two electrodes is evaluated in comparison with a previously reported model. Finally, the impact of an increased barrier height on dielectric scaling will be discussed based on a leakage current simulation of a ZrO 2 capacitor.

The SrRuO3 (SRO) thin films were epitaxially grown on (0 0 1) SrTiO3 (STO) substrates using plasma assisted molecular beam epitaxy (MBE). In order to identify how the cation flux affects the surface characteristics, films were grown at different Sr/Ru flux ratios. As Ru flux increased, SRO thin film exhibited a flatter but more bunched stepped terrace implying the prevalence of 2-D growth mode during the film formation, whereas excessive Sr flux led to 3-D film growth and resulted in a rough surface. In addition, XRD and STEM analysis provided that samples grown at Sr/Ru flux ratio higher than 2.7 showed volume expansion and crystal disorder by Ru vacancy which caused higher resistivity. But the samples grown at the ratio lower than 2.9 maintained the resistivity close to that of stoichiometric SRO.

Atomic layer deposition with O3 reactant is widely used to deposit thin and conformal films in a ZrO2 based metal-insulator-metal (MIM) capacitor. Post-deposition annealing (PDA) improves the MIM capacitor's performances by crystallizing tetragonal ZrO2 with high dielectric constant but it inevitably causes formation of excessive TiN/ZrO2 interface. Oxygen diffusion from ZrO2 to TiN bottom electrode oxidizes TiN to TiOx and TiOxNy during PDA, which increases the capacitance equivalent thickness of interlayer (CETint) and leakage current of the MIM capacitor. In this study, we inserted a Al2O3 thin film as the oxygen diffusion blocking layer (ODBL) between ZrO2 dielectric and bottom TiN electrode to improve the interfacial properties in TiN/ZrO2/TiN MIM capacitor. The angle-resolved X-ray photoelectron spectroscopy is employed to study the effects of Al2O3 OBDL on the chemical states of the interfacial layer in MIM capacitor, which confirmed that the Al2O3 ODBL inhibits the growth of TiN/ZrO2 interface. In addition, the electrical analysis of MIM capacitor showed that the CET of TiN/ZrO2 interface decreased from 0.493 to 0.209 nm and the leakage current highly decreased from 10−7 to 10−9 A/cm2 at 1 V although the dielectric constant slightly reduced from 35.1 to 30.7 with the insertion of Al2O3. This study offers a systematic investigation of interfacial layers in Al2O3 OBDL inserted ZrO2 MIM capacitor in the points of chemical and electrical characterization.

High-k dielectrics like Ta2O5, TiO2 etc. should overcome high leakage current due to the low energy band-gap property for applying to the future DRAM device below 50nm design rule beyond. Various techniques including metal doping and bi-layer scheme were studied to improve the leakage current of I-V characteristics. The leakage current of Dy or Zr doped TiO2 could be improved depending on the doping concentration. Nb doping in Ta2O5 could increase the dielectric constant within the appropriate level of leakage current at the operation voltage. Bi-layer scheme of high-k dielectrics like HfO2-TiO2 or ZrO2-TiO2 also applied to reduce the leakage current with the high work function Ru electrode. Combination of high work function Ru as a top electrode with the bottom TiN electrode could reduce the leakage current by increasing band offset at the interface between the high-k and the electrode.

We report the integration of SrRuO3, one of the most widely used oxide electrode materials in functional oxide heterostructures, with silicon using molecular-beam epitaxy and an SrTiO3 buffer layer. The resulting SrRuO3 film has a rocking curve full width at half maximum of 0.01°, a resistivity at room temperature of 250 μΩ cm, a residual resistivity ratio (ρ300 Kρ4 K) of 11, and a paramagnetic-to-ferromagnetic transition temperature of ∼160 K. These structural, electrical, and magnetic properties compare favorably to the best reported values for SrRuO3 films on silicon and rival those of epitaxial SrRuO3 films produced directly on SrTiO3 single crystals by thin film growth techniques other than molecular-beam epitaxy. These high quality SrRuO3 films with metallic conductivity on silicon are relevant to integrating multi-functional oxides with the workhorse of semiconductor technology, silicon.

Aiming for improvement of the ZrO2-based insulator properties as compared to the state-of-the-art ZrO2/Al2O3/ZrO2 stacks beyond 20 nm dynamic random access memory (DRAM) technology applications, ultra-thin (5 nm) ZrO2/SrO/ZrO2 stacks with TiN electrodes deposited by physical vapor deposition are addressed. By replacing the Al2O3 interlayer with SrO, the effective dielectric permittivity of the stack can be increased as indicated by electrical analysis. At the same time, no degradation of the insulating properties of the SrO-containing stacks and minor changes in the reliability, compared to an Al2O3 interlayer, are found. These results are indicating the possibility of further reducing the effective oxide thickness of the ZrO2-based stacks to come close to 0.5 nm for future DRAM capacitors. ispartof: Journal of Applied Physics vol:117 issue:22 pages:1-8 status: published

DRAM capacitors are reaching the scaling limit and new approaches are necessary to enable further reduction of the physical thickness of the capacitor dielectric. The Schottky Barrier Height (SBH) of a noble metal electrode (Pt) on atomic layer deposited ZrO 2 /Al 2 O 3 /ZrO 2 (ZAZ, 6 nm) was evaluated and compared to a TiN electrode. Internal Photo Emission Spectroscopy (IPE) and Photoconductivity measurement (PC) were used to estimate the SBH and band gap, respectively. The SBH difference between the two electrodes was evaluated in comparison with a previously reported model. Finally, the impact of an increased SBH on dielectric scaling will be discussed based on a leakage current simulation of a ZrO 2 capacitor.

Ta"2O"5/Nb"2O"5 bi-layers were prepared on Ru/SiO"2/Si substrate by Atomic Layer Deposition, and post annealed up to 575^oC. The crystallization temperature of the bi-layers was 550^oC, which was 100^oC lower than that of Ta"2O"5 single layer. The thickness of the dielectric layers was also important parameter for the crystallization temperature. Transmittance Electron Microscopy image and depth profile analysis showed that Ta"2O"5 and Nb"2O"5 mixed each other during the crystallization. It was suggested that inter diffusion of two layers decreased the crystallization temperature of the bi-layers. Equivalent oxide thickness of crystalline Ru/Ta"2O"5/Nb"2O"5/Ru capacitor was 7.6A with less than 100nA/cm^2 leakage currents, which satisfied the requirements for 60nm generation DRAM capacitor and beyond.

In this letter, a cost-effective vertical diode scheme for next-generation memory devices, including phase-change memories (PCMs), is realized. After the contact formation for diodes with only one mask layer, an amorphous silicon (a-Si) film was deposited within the contacts using SiH4 ramp-up ambient in a conventional batch-type furnace in order to minimize the growth of native oxide. A deposition/etch-back/deposition scheme enabled us to achieve robust vertical diodes without any seams or interfacial oxide layer within the vertical diode pillars. Subsequent annealing at 600 °C provided solid-phase epitaxial alignment of the a-Si layer. An ideality factor revealed that the new scheme provided noticeable crystallinity of the silicon diodes. Moreover, the electrical characteristics of the diodes verified that the scheme was suitable for full operation of PCM devices.

The low-temperature-atomic layer deposition (ALD) of SiO2 has a lot of applications in semiconductor devices. Moreover, it is hard to control the conformality and reproducibility in high aspect ratio structures. In this study, the authors investigated the ALD behaviors of SiO2 using various precursors in both 2D and 3D structures. It was shown that a high level of thickness control and perfect surface coverage techniques can be achieved even on a 200:1 aspect ratio structure at a low growth temperature of 250 °C by using bis(ethyl-methylamino)silane.

Epitaxial thin films of Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) and Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) were deposited on (0 0 1) SrTiO 3 and SrRuO 3 /SrTiO 3 single crystal substrates at 700°C by the solid-source MOCVD method, using tetramethylheptanedionate (THD) sources of Pb, Mg, Nb, and Ti. Sputtered SrRuO 3 was employed as an epitaxial bottom electrode layer so that electrical property measurements could be made. Pure PMN films were prepared using pre-mixed source material (5.5 moles of Pb(THD) 4 ,1 mole of Mg(THD) 2 and 2 moles of Nb(THD) 4 ). XRD results indicated that these films were single phase and had the pervoskite structure. Rutherford Backscattering showed that Pb/Mg/Nb/O=18%/7%/13%/62%. Films of PMN–10% PT and PMN–20% PT films were also epitaxially deposited on the same substrates. The dielectric constants for these films were in the range 1200–1500 and 600–700, respectively. A 150 nm thick PMN–20% PT film was strongly dispersive. The dielectric constant for a 150 nm thick film decreased from 700 at 1 kHz to 550 at 100 kHz. The dielectric loss factor increased from 0.15 to 0.4 with increasing frequency.

Yttrium iron garnet (YIG) single-crystal fibers of nominal composition Y 3 Fe 5 O 12 were grown by the laser-heated pedestal growth technique, a miniaturized float-zone process. YIG fibers in diameters ranging from 100 to 740 μm were grown at various rates and conditions, and analyzed by X-ray diffraction, electron microprobe, IR-VIS spectroscopy, and light scattering tomography. Infrared transparent YIG fibers were grown at rates below 10 mm/h in air. The transparency of the fibers was more dependent on the growth rate than on the stability of the molten zone. Some striations and surface ridges containing a Fe-rich composition were observed at all growth rates. Light scattering tomography studies revealed the presence of inclusions in some YIG fibers. Their size, density, composition and distribution depended on the growth conditions and molten zone stability. At growth rates below 10 mm/h, these defects and also the iron-oxide inclusions, which act as IR scattering centers, were significantly reduced.

The influence of two-step deposition on the electrical properties of sputtered (Ba,Sr)TiO3 thin films was investigated. BST thin films with thickness 40 nm were deposited by a simple two-step radio frequency-magnetron sputtering technique, where the BST thin film consisted of a seed layer and a main layer. The dielectric constant was strongly dependent on the thickness of seed layer, but there was no dependence on deposition temperature of the seed layer. For a 2 nm seed layer, the dielectric constants were higher by about 29% than those of single-step BST thin films due to higher crystallinity and the leakage current was nearly the same as that of a single-step sample in bias voltage from −2 to 2.5 V. However, an improvement of the dielectric constant was not observed for samples having above 4 nm thick seed layers. A 40 nm thick BST film with 2 nm thick seed layer deposited by a two-step method exhibited a SiO2 equivalent thickness of 0.385 nm and a leakage current density of 2.74 × 10−8A/cm2at+1.5V after post-annealing under an atmosphere of flowing N2 for 30 min at 750°C.

The oxidation behavior of mechanically alloyed(MA) Al-Ti alloys containing 5 and 10 at.% Ti wereinvestigated at 500-600°C under 1 atm of oxygen. Ateach temperature, alloys oxidized linearly during the initial stage and later followed the parabolicrate law. During the initial stage, the oxidation ratesof nanocrystalline (≤50 nm) Al-Ti alloys were fasterthan those of conventional (≤200 nm) alloys. It is suggested that more grain boundaries innanocrystalline alloys provide more nucleation sites foroxides, so that the oxide scales grew faster as denseprotective layers. During the parabolic stage, the nanocrystalline alloys had greater oxidationresistance than conventional alloys because of the denseprotective layer. Oxide scales on both alloys consistedof a mixture of γ-Al2O3 andTiO2 in the outer layer andγ-Al2O3 near the alloy as aprotective layer.

Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high-Tc lead-doped Bi2Sr2Ca2Cu3Ox (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters ( S, W, and S W ) showed significant change through Tc. This may result from having the highest positron density in the open BiO2 double layers and no significant positron density in the superconducting CuO2 layers where positrons, if mainly present, are known to be sensitive to the transition in other high-Tc superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample (τ1) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample (τ2) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps.

Enzyme-catalyzed hydrolyzations of various polysaccharides were investigated in two-phase, water and water-immiscible, organic solvent systems. Enzyme activity in water-immiscible organic solvents, such as dodecane, was strongly influenced by the amount of water present in the reaction mixture. Typical bell-shaped hydrolysis curves were obtained for the enzymatic catalysis of agar, chitin and soluble starch, using agarase, lysozyme and α-amylase, respectively. Maximal hydrolysis rates for all reactions were observed at a water content of 5–10% ( v v , total volume). The hydrolytic conversion by α-amylase of various starches to maltopentaose (G5), was greatly accelerated in the 10% ( v v , total volume) water content water-dodecane, biphasic system. The effects of pH, ionic strength and water content on the time courses and rates of the reaction in these biphasic systems were analyzed by high-performance liquid chromatography (HPLC) of the products. The hydrolysis of chitin by lysozyme was highly accelerated by a pre-treatment heating of the chitin to 90 °C in 10% ( v v ) water/dodecane, prior to the addition of the enzyme.

During dynamic random access memory (DRAM) capacitor scaling, a lot of effort was put searching for new material stacks to overcome the scaling limitations of the current material stack, such as leakage and sufficient capacitance. In this study, very promising results for a SrTiO3 based capacitor with a record low capacitance equivalent thickness value of 0.2 nm at target leakage current are presented. Due to the material properties of SrTiO3 films (high vacancy concentration and low band gap), which are leading to an increased leakage current, a physical thickness of at least 8 nm is required at target leakage specifications. However, this physical thickness would not fit into an 18 nm DRAM structure. Therefore, two different new approaches to develop a new ZrO2 based DRAM capacitor stack by changing the inter-layer material from Al2O3 to SrO and the exchange of the top electrode material from TiN to Pt are presented. A combination of these two approaches leads to a capacitance equivalent thickness value...

In this paper, current-voltage-temperature (I-V-T) characteristics of vertical diodes realized by different selective epitaxial growth techniques have been investigated. Diodes by the batch-type cyclic SEG process at low temperature have shown eligible performances for vertical switches, including ideality factor of 1.08, off-current of 1.0×10−12 A and on/off-ratio of 2.4×108. The optimization of crystallographic defects and series resistance is expected to be the most critical for the performances of vertical diodes for next generation memories.

We investigated the pressure dependence of the inductive coupled plasma (ICP) oxidation on the electrical characteristics of the thin oxide films. Activation energies and electron temperatures with different pressures were estimated. To demonstrate the pressure effect on the plasma oxide quality, simple N type metal-oxide-semiconductor (NMOS) transistors were fabricated and investigated in a few electrical properties. At higher pressure than 200mTorr, plasma oxide has a slightly higher on-current and a lower interfacial trap density. The on-current gain seems to be related to the field mobility increase and the lower defective interface to the electron temperature during oxidation.

As a new alternative for the DRAM capacitor of 50 nm generation, Ru/Insulator/TiN (RIT) capacitor with the lowest Toxeq of 0.85 nm has been successfully developed for the first time. TiO/sub 2//HfO/sub 2/ and Ta/sub 2/O/sub 5//HfO/sub 2/ double-layers were used as dielectric materials. After full integration into 512 Mbits DRAM device, the RIT capacitor showed good electrical properties and thermal stability up to 550/spl deg/C and its time-dependent-dielectric-breakdown behavior sufficiently satisfied 10-year lifetime within a DRAM operation voltage.

We first developed a novel self-aligned electroplating process to fabricate Pt electrodes for integrated high-dielectric capacitors. Electroplated Pt filled 120 nm-wide buried contact (BC) holes (aspect ratio 2:1). Pt pillars of 210 nm diameter and 650 nm height were successfully fabricated. The leakage current density of sputtered BST capacitors using electroplated bottom Pt was less than 200 nA/cm/sup 2/ at /spl plusmn/1.5 V. The oxide-equivalent thickness T/sub oxeq/ and dissipation factor of 40 nm-thick BST films were 0.70 nm and 0.0080 at 0 V, respectively.

A new two-step post-annealing process to prevent degradation of integrated BST capacitors was developed. By this process, the increment of capacitance and the reduction of leakage current were obtained without barrier oxidation. A concave-type capacitor structure with buried barrier using Pt electrodes and MOCVD BST films was demonstrated in order to solve the integration problems such as Pt etching and the contact between the BST and the barrier. The electrical properties of MOCVD BST capacitor in 3-dimensional structure were investigated.

In this paper, we investigated the interface band alignment of TiN/ZrO2 and TiN/ZrO2-Al2O3-ZrO2 (TiN/ZAZ) structures by analyzing the conduction band offset (CBO) and valence band offset at the electrode/dielectric interface using depth-resolved spectroscopy techniques. At the center of the interface, which is defined by the chemical composition depth profile, CBO values of 2.03 eV and 2.57 eV for ZrO2 and ZAZ were found, respectively. Subcutaneous TiON, which is induced by the process, was identified at this interface, and it played an important role in creating sub-band states. Based on combined analyses on both intrinsic and sub-band structures, a band alignment model is proposed. It was confirmed that the Al2O3 layer in ZAZ leads to a lowering of the Fermi energy or a p-doping effect, thereby increasing both the CBO and the tunneling barrier height in metal-insulator-metal capacitors.

Yttrium iron garnet (YIG) single crystal fibers of nominal composition Y3Fe5O12were grown by the laser heated pedestal growth (LHPG) technique, a miniaturized floated-zone process. YIG which melts incongruently, was grown at a temperature below the peritectic decomposition temperature under self-adjusting conditions even though it has very narrow solidification region according to the Y2O3-Fe2O3phase diagram. YIG fibers in diameter ranges from 100 to 750 μm were grown at various growth rates and conditions, and analyzed by x-ray diffraction, electron microprobe, and IR-VIS spectroscopy. Infrared transparent YIG fibers were grown at rates below 12 mm/h in air. At these growth rates, yttrium orthoferrite and iron-oxide inclusions within the YIG fiber, which act as IR scattering centers, were significantly reduced. The transparency of the fibers was more dependent on the growth rate than the stability of the molten zone. Surface ridges containing an Fe-rich composition were observed at all growth rates. These were associated with molten zone instability.

The positive bias temperature instability (PBTI) characteristics of the n-channel metal-oxide-semiconductor field emission transistors which had different kinds of high-k dielectric gate oxides were studied with the different stress-relaxation times. The degradation in the threshold voltage followed a power-law on the stress times. In particular, we found that their PBTI behaviors were closely related to the structural phase of the high-k dielectric gate oxide. In an amorphous gate oxide, the negative charges were trapped into the stress-induced defects of which energy level was so deep that the trapped charges were de-trapped slowly. Meanwhile, in a crystalline gate oxide, the negative charges were trapped mostly in the pre-existing defects in the crystallized films during early stage of the stress time and de-trapped quickly due to the shallow energy level of the defects.

Practical selectivity window of selective epitaxial growth (SEG) using a H2/SiH4/Cl2 cyclic chemical vapor deposition (CVD) system has been investigated with the batch-type vertical furnace equipment, replacing a conventional single-wafer H2/dichlorosilane/HCl CVD system. The process temperature was less than 700 °C, which is suitable for a low thermal budget process applicable to next-generation memories including vertical pn-diode switches. Selectivity loss is quantified by an in-line inspection tool to determine the practical number of selectivity losses. The H2/SiH4/Cl2 cyclic CVD system provides an excellent capacity of 40 wafers per batch. Selectivity loss, which is one of the most crucial features in the SEG process for the diode application, is controlled with both the amount of SiH4 and Cl2 and the period of gas supply, and the practical number of selectivity loss is confirmed to be less than 100 in 200 mm wafers. Without high temperature annealing in hydrogen ambient, low temperature cyclic SEG in the batch reactor ensures the clean interface and improved crystalline quality of SEG-Si, as well as high throughput.

not Available.

not Available.

The contact resistance (R C) between a Ru electrode and a TiN plug in a crystalline Ta2O5 capacitor using Ru electrodes was evaluated. The TiN plug was oxidized in TiO x to increase the R C to failure. Two origins of oxygen are determined by Auger electron spectroscopy (AES) analysis, namely, the seed step of Ru deposition and the initial step of Ta2O5 deposition. During Ta2O5 crystallization annealing at 700°C, the oxygen molecules from Ru diffused into the TiN plug, forming TiO x . Ru films with Ti exhibited a decreased R C below 1 kΩ/contact and an increased leakage current of a Ru/Ta2O5/Ru capacitor according to the applied voltage, compared with Ru films without Ti. The atomic layer deposition (ALD) Ru process including a H2 plasma treatment decreased the R C to 2.5 kΩ/contact on average. The fabrication scheme for the crystalline Ta2O5 capacitor using the Ru electrode for reducing RC between the Ru storage node and the TiN plug was proposed.

Ru thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using cyclopentadienyl-propylcyclopentadienlylruthenium(II) [RuCp(i-PrCp)] and the nucleation behaviors of Ru films on Ta2O5, TiN, Si3N4, SiO2, TiO2 substrates were investigated. It appeared that the difference in nucleation behaviors on various substrates is due to the bonding type between atoms in substrate materials. The nucleation property of Ru films on TiN was successfully improved by plasma treatment of the TiN substrate using Ar before film deposition. It was found that the Ar plasma treatment selectively removes N ions from the surface, makes the TiN surface more metallic or ionic (due to the residual Ti-O bonding), and reduces the nucleation barrier. In addition, the oxidation resistance of Ru/TiN layers was improved by H2 annealing, which made the Ru films more dense.

We have determined potentials of carboxymethyl cellulose (CMC) and carboxyethyl cellulose (CEC) membranes with various degrees of substitution in solutions of LiCl, NaCl, KCl and CsCl at 25°C. The ionic mobility ratio, D+/D-, in these membranes showed the same dependence on the Stokes radius of the cation as that in the bulk aqueous solution. D+/D- and the apparent transport number of the cation decreased with increasing effective charge density. The effectiveness of the fixed charge density, Cx, was approximately 0.19 for CMC and 0.13 for CEC membranes, respectively. Cx was found to depend on the ionic species.

Ultrathin nylon capsule membranes coated with synthetic bilayers, the hydrophilic head groups of which had cationic, anionic, zwitterionic and nonionic charges, were prepared. Permeation of NaCl trapped in the inner aqueous phase was reduced by a factor of 10-1000 relative to that of the uncoated, semipermeable capsules, and drastically changed at the phase transition temperature, T c , of the coating bilayers, depending on the charge of their hydrophilic head group. In the case of capsules coated with positively or negatively charged bilayers, NaCl permeation was enhanced at temperatures above the T c of the coating bilayers, as expected. On the other hand, NaCl release of capsules coated with neutral charged (nonionic and zwitterionic) bilayers was largely reduced at temperatures above the T c . From activation energy data of Arrhenius plots, the permeation mechanism of NaCl, depending on the membrane surface charge, below and above the T c was discussed.

Nylon ultrathin capsules coated with sodium didodecyl phosphate bilayer membrane were prepared. Permeation of NaCl from the inner aqueous phase of the coated capsule was reversibly increased by treating with Ca2+, and decreased to the original rate by washing with EDTA from outside.