bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray Microprobe Studies of Materials Problems Related to Microelectromechanical Systems (MEMS) Structures
Authors: Mölders N. , Schilling P.J. , Göttert J. , Moser H.O. , Saile V.
Published: April 2011

The understanding of the physical, chemical and mechanical properties of materials used in micro-electromechanical systems (MEMS) is essential for the successful application. For the characterization of such materials, it is often necessary to utilize a probe which can gather information on the same scale as the devices themselves. Based on these needs, x-ray microprobe analysis has been employed to perform spatially resolved measurements on several problems related to the fabrication of MEMS devices. These include spatially resolved transmission measurements of the homogeneity of transmitted flux through a graphite mask, micro-fluorescence measurements to assess elemental distributions, and micro-XANES measurements to follow the breakdown of new sulfone-based x-ray resists. These studies demonstrate the value of such an instrument in the characterization of micro-systems.
Defining Conditions for the Etching of Silicon in an Inductive Coupled Plasma Reactor
Authors: Ashraf H. , Bhardwaj J. K. , Guibarra E. , Hall S. , Hopkins J. , Hynes A. M. , Johnston I. , Lea L. , Mcauley S. , Nicholls G. , O'Brien P.
Published: April 2011

In high-density fluorinated plasma processes, the mechanisms that fundamentally limit the etching of silicon are poorly understood. In an effort to improve our understanding of limits to the performance of such systems, the etching of silicon wafers in an inductive coupled plasma reactor, using SF6, has been studied. A systematic empirical investigation has allowed us to define many of the experimental parameters that control the etching rate.

There is little temperature dependence of etching which suggests a diffusion limited process. Systematic variation of parameters controlling the rate of etching: total pressure in the reactor, flow rate, partial pressure of reactive species and the rf power supplied to the discharge enable us to accurately define the performance of the system. Experiments, which segregate the physical and chemical components of the etching process, support the conclusion that etching is dominated by electrically neutral species. These various results are interpreted in terms of accepted models for the reactive chemistry in plasmas containing SF6.

The MEMS industry is placing ever greater demands on etching processes, and there is a need to achieve the high degrees of anisotropy, and critical dimension control, at high etch-rates. The approach outlined allows us to develop effective strategies for evolving improved systems for the high rate plasma etching of silicon.
MOCVD of High-K Dielectrics and Conductive Metal Nitride Thin Films
Authors: Senzaki Yoshihide , Hamilton Richard F. , Reid Kimberly G. , Hobbs Christopher C. , Hegdec Rama I. , Tinerc Mike J.
Published: April 2011

A known liquid mixture of [(CH3CH2)2N]3 Ta=NCH2CH3 and [(CH3CH2)2N]3Ta[ð2-CH3CH2N=CH(CH3)] was studied to deposit Ta2O5 and TaN thin films by CVD. Films were deposited at temperatures below 400°C using oxygen for oxide and ammonia for nitride, respectively. XRD analysis revealed that as-deposited amorphous tantalum oxide films were converted to hexagonal Ta2O5 after annealing under oxygen, while tantalum nitride thin films contained cubic TaN as deposited. The low viscosity, thermal stability, and sufficient volatility of the precursor allows direct liquid injection to deliver the precursor, which results in high deposition rate and uniformity of the deposited films.
Epitaxial Growth of Sr0.3Ba0.7Nb2O6 Thin Films Prepared by Sol-Gel Process
Authors: Nishio Keishi , Thongrueng Jirawat , Watanabe Yuichi , Tsuchiya Toshio
Published: April 2011

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We succeeded in the preparation of strontium-barium niobate (Sr0.3Ba0.7Nb2O6 : SBN30)that have a tetragonal tungsten bronze type structure thin films on SrTiO3 (100), STO, or La doped SrTiO3 (100), LSTO, single crystal substrates by a spin coating process. LSTO substrate can be used for electrode. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)5 as raw materials, and acetic acid and diethylene glycol monomethyl ether as solvents. The coating thin films were sintered at temperature from 700 to 1000°C for 10 min in air. It was confirmed that the thin films on STO substrate sintered above 700°C were in the epitaxial growth because the 16 diffraction spots were observed on the pole figure using (121) reflection. The <130> and <310> direction of the thin film on STO were oriented with the c-axis in parallel to the substrate surface. However, the diffraction spots of thin film on LSTO substrate sintered at 700°C were corresponds to the expected pattern for (110).
Near-Stoichiometric Barium Titanate Synthesis by Low Temperature Hydrothermal Reaction
Authors: Woo Kyoungja , Choi Guang J. , Cho Young S.
Published: April 2011

Barium-deficiency of barium titanate particles prepared by low temperature hydrothermal reaction has been notorious. It has been believed that barium-deficiency is caused by the high solubility of barium source compared with titanium. Here is reported the synthesis of nearstoichiometric barium titanate powders with ultrafine particle size and high crystallinity by low temperature hydrothermal reaction from barium acetate and titanium tetra(methoxyethoxide). Barium titanate particles were synthesized in the spherical, metastable cubic crystalline grains with size distribution between 60 ∼ 90 nm in diameter. Ultrafine particle size was resulted from the control of the hydration rate and the decrease of Ti-O-Ti cross-linking extent of titanium precursor. Increasing barium to titanium molar ratio in reactant could not overcome the notorious barium-deficiency but, improved stoichiometry and produced finer and less agglomerated particles. Interestingly, adding a slight pressure to autogeneous one to make total 4 ∼ 10 atm has yielded near-stoichiometric, highly crystalline, and less agglomerated barium titanate particles. It seems like that the total pressure around 4 ∼ 10 atm provides strong force enough to push barium ions into the interstitial points of perovskite structure and stabilize it. These particles, which were in metastable cubic form as synthesized, initiated phasetransition to tetragonal form by calcination at 400 °C.
Study on ZrO2 Deposited Directly on Si as an Alternative Gate Dielectric Material
Authors: Qi Wen-Jie , Nieh Renee , Lee Byoung Hun , Jeon Youngjoo , Kang Laegu , Onishi Katsunori , Lee Jack C.
Published: April 2011

Reactive-magnetron-sputtered ZrO2 thin film has been deposited on Si directly for gate dielectric application. Both structural and electrical properties of the ZrO2 film have been investigated. An amorphous structure for 30Å ZrO2 and a semi-amorphous structure for 200Å ZrO2 have been revealed. The sputtered film shows a good stoichiometry and a good structural stability of ZrO2 based on the X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy data. Thin equivalent oxide thickness of about 11.5Å was obtained without the consideration of quantum mechanical effects. A low leakage of less than 10−2 A/cm2 at ±1V relative to the flat band voltage was obtained for this 11.5Å equivalent oxide thickness Pt/ZrO2/Si structure. High effective dielectric breakdown and superior reliability properties have been demonstrated for ZrO2 gate dielectric.
A Study on Hysteresis Effect of Barium Strontium Titanate Thin Films for Alternative Gate Dielectric Application
Authors: Qi Wen-Jie , Zawadzki Keith , Nieh Renee , Jeon Yongjoo , Lee Byoung Hun , Lucas Aaron , Kang Laegu , Lee Jian-Hung , Lee Jack C.
Published: April 2011

Hysteresis effect of barium strontium titanate (BST) thin films for gate dielectric application has been studied. It is found that the “counterclockwise” hysteresis has strong sweep voltage and operating temperature dependence. It can be reduced or eliminated by proper thermal annealing or by using a barrier layer. A charge trapping and detrapping mechanism has been proposed.
Growth of MgO by Metal-Organic Molecular Beam Epitaxy
Authors: Niu Feng , Hoerman Brent.H. , Wessels Bruce.W.
Published: April 2011

MgO thin films were deposited on (100) Si substrates by metal-organic molecular beam epitaxy (MOMBE). Magnesium acetylacetonate was used as the precursor and an oxygen RF plasma was used as the oxidant. The films were characterized by a combination of transmission electron microscopy, Auger spectrometry and atomic force microscopy. Analyses indicate that the films directly deposited on Si substrates are stoichiometric, phase-pure, polycrystalline MgO with a [100] texture. Carbon contamination of the films resulting from precursor decomposition was not observed within detection limits. Furthermore, the growth rate of MgO has been systematically investigated as a function of growth temperature.
Thermal Annealing Recovery of Intersubband Transition in Proton-Irradiated GaAs/Al0.3Ga0.7As Multiple Quantum Wells
Authors: Gingrich H.S. , Morath C. , Manasreh M.O. , Ballet P. , Smathers J.B. , Salamo G. J. , Jagadish C.
Published: April 2011

Optical absorption spectra of intersubband transitions in heavily proton irradiated n-type GaAs/AlGaAs multiple quantum wells were studied as a function of isochronal and isothermal annealing. The absorption spectra of intersubband transitions were depleted in samples irradiated with 1MeV proton doses higher than 1.0 × 1014 cm−2. Thermal annealing of the irradiated samples show that the intersubband transitions are recovered. The relatively lower annealing temperatures at which the recovery is observed indicate that the irradiation-induced defects that trapped the two-dimensional electron gas in the quantum wells are vacancy and interstitial related defects. Once these traps are thermally annealed the electrons are released back to the quantum wells, resulting in the recovery of the intersubband transitions.
2.3–2.7µm InGaAsSb/AlGaAsSb Broad-Contact and Single-Mode Ridge-Waveguide SCH-QW Diode Lasers Operating in CW Regime at Room Temperature
Authors: Garbuzov D. , Lee H.
Published: April 2011

A new approach in the design of (Al)InGaAsSb/GaSb quantum well separate confinement heterostructure (QW-SCH) diode lasers has led to CW room-temperature lasing up to 2.7 gm. To avoid QW material degradation associated with the miscibility gap in the 2.3–2.7 tim wavelength range, we used highly strained, “quasi-ternary” InxGa1−xSbl−yAsy compounds with 0.25<x<0.38 and y<0.07 as the material for QWs. Very low threshold current density (∼300 A/cm2) and high CW output powers (>100 mW) were obtained from broad contact devices operating in the 2.3–2.6 μm wavelength range. From the spontaneous emission measurements we have identified that the Auger process determines the rate of recombination in quantum well active region over the entire temperature range studied (15– 110 'C) for 2.6 gim lasers and only at temperatures higher than 65 'C for 2.3 pim lasers. If Auger recombination dominates, strong temperature dependence of Auger coefficient leads to the rapid increase of threshold current density with temperature (To ∼40 °C). In the range of 15 – 65 °C for 2.3 gim devicesa monomolecular, non-radiative mechanism dominates and To is about 110 °C. In addition, single-mode CW room temperature ridge-waveguide lasers with wavelength of 2.3-2.55 gim have been fabricated for the first time. The lasers display threshold currents around 50 mA with CW output powers of several milliwatts. Since for a certain range of temperatures and currents one of the longitudinal modes dominates in the spectra of the ridge lasers they have been successfully applied forgas spectroscopy.
Refractive Index Measurements and New Sellmeir Coefficients of Zinc Germanium Phosphide From 2-9 Microns With Implications for Phase Matching in Optical Parametric Oscillators
Authors: Zelmon David E. , Hanning Elizabeth A. , Schunemann Peter
Published: April 2011

Recent experiments in mid IR frequency conversion have revealed that older Sellmeir models for zinc germanium phosphide are inadequate. Erroneous predictions in phase matching angles based on older refractive index data have resulted in compromised device performance. We have conducted a complete study of the refractive indices of zinc germanium phosphide from 2 to 9 microns and calculated new Sellmeir coefficients. We have used these to explain the results of recent experiments with mid IR optical parametric oscillators. The phase matching calculations based on our new refractive index data predict much more closely the results of several different mid IR frequency conversion experiments.
Quantum Well Intermixing Using Sputtered Silica for Photonic Integrated Circuits Operating Around 1550 nm
Authors: Marsh John H. , Catrina Bryce A. , Kowalski Olek P. , McDougall Stewart D. , Ke Maolong , Qiu Bocang , Qian Yahong
Published: April 2011

A novel technique for quantum-well intermixing has been developed using sputtered silica. The technique relies on the generation of point defects via plasma induced damage during the deposition of the sputtered silica. The presence of the defects before annealing allows the intermixing to take place at lower annealing temperatures (>200 C) than those needed for conventional impurity free vacancy disordering. The low annealing temperature has allowed the technique to be applied to InP based quantum well systems such as InGaAs/InGaAsP and InGaAs/InGaAlAs, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices operating around 1550 nm.

Wavelength tuned broad area oxide stripe lasers have been demonstrated in InGaAs-InAlGaAs and InGaAs-InGaAsP quantum wells. Oxide stripe lasers with integrated intermixed slab waveguides have enabled the production of a narrow (3 degrees), single lobed far field pattern in InGaAs-InAlGaAs devices. Extended cavity ridge waveguide lasers operating around 1550 nm have been demonstrated with low loss (alpha = 4.1/cm) waveguides, the loss beinglimited by free carrier absorption in the waveguide cladding layers. Ridge waveguide, deeply etched surface grating DBR lasers were fabricated both with and without intermixing the grating section. Measurements show that a significant improvement in performance is obtained from the DBR lasers when the grating section is intermixed.

The intermixing technique has been further developed in order to realise 3 bandgaps on a chip in a single annealing step for the integration of amplifiers, passive waveguides and bandgap tuned electro-absorption modulators. Modulation depths of 25 dB were measured from the modulators.

The results illustrate that the technique can routinely be used to fabricate low-loss optical interconnects and bandgap tuned devices, offering a very promising route toward photonic integration.
Advanced GaSb/InGaAsSb/AlGaAsSb 2-2.4µm Photovoltaic Detectors
Authors: Piotrowski T.T. , Piotrowska A. , Kaminska E. , Golaszewska K. , Papis E , Piskorski M , Jung W , Katcki J , Kudla A. , Adamczewska J. , Piotrowski J. , Nowak Z. , Orman Z. , Pawluczyk J.
Published: April 2011

This paper reports on the design and fabrication of GaSb/n-InxGal1−xAsySb1−y/p-AlxGal−xAsySb1−y heterojuction photodetectors operating in the 2 - 2.4 µm wavelength region. Device structures were grown by LPE and fabricated as mesa-type diodes by RIE etching in CC14/H2 plasma. For mesa passivation a surface treatment in (NH42S water solution was carried out. The photodiodes structures are characterized by differential resistance RoA=400 ωcm2. Measured detectivity is in the range 3.1010 - 2. 1011 cmHz1/2/W, in dependence on the active area and cutoff wavelength.
Model for Staebler-Wronski Degradation Deduced from Long-Term, Controlled Light-Soaking Experiments
Authors: Roedern Bolko von , del Cueto Joseph A.
Published: April 2011

Long-term light-soaking experiments of amorphous silicon photovoltaic modules have now established that stabilization of the degradation occurs at levels that depend significantly on the operating conditions, as well as on the operating history of the modules. We suggest that stabilization occurs because of the introduction of degradation mechanisms with different time constants and annealing activation energies, depending on the exposure conditions. Stabilization will occur once a sufficient accumulation of different degradation mechanisms occurs. We find that operating module temperature during light-soaking is the most important parameter for determining stabilized performance. Next in importance is the exposure history of the device. The precise value of the light intensity seems least important in determining the stabilized efficiency, as long as its level is a significant fraction of 1-sun.
Colour Characterisation of a-Si:H-Based Three-Terminal Three-Channel Detector
Authors: Krĉ Janez , Topiĉ Marko , Smole Franc , Knipp Dietmar , Stiebig Helmut
Published: April 2011

Colour characterisation of a three-terminal three-channel colour detector in the assembly glass/TCO1/PI1NI2P/TCO2/PI3N/Al is performed, using a method of polynomial regression. The metameric errors of the detector calculated and investigated for different orders of polynomial colour correction are presented and discussed. The benefits of the first order colour correction are shown and graphically illustrated. The final transformation matrix for the first order colour correction and conversion to the output R, G and B signals is given. At the end, a demonstrational application with the a-Si:H-based detector and corresponding read-out and colour correction electronics is presented.
Carrier Transport and Photogeneration in Amorphous Silicon / Crystalline Silicon Heterojunctions with i/n and p/n Interfaces
Authors: Vygranenko Yu. , Fernandes M. , Nunes Carvalho C. , Lavareda G. , Louro P. , Amaral A. , Schwarz R. , Vieira M.
Published: April 2011

Amorphous hydrogenated silicon films deposited by Plasma Enhanced Chemical Vapour Deposition (PE-CVD) using standard rf-glow discharge at 13.56 MHz were used to produce amorphous silicon heterostructures. Junction properties were studied from current-voltage (IV), capacitance-voltage (C-V) and spectral response measurements. The photosensitivity of these structures was investigated for different amorphous film thicknesses and different applied bias voltages. It was shown that the output device characteristics could be improved by plasma hydrogen treatment before the deposition of the amorphous layer. The results show that ITO/a-Si:H/c-Si structures present high internal gain in the visible infra-red region and high collection efficiency in the blue range. They can be used as visible/near-IR photodiodes or for current amplifications proposes.
Comparison of low temperature growth of Si thin films on amorphous substrates by MBE and PECVD methods
Authors: Selvan J. A. Anna , Grützmacher D. , Müller E. , Rebien M. , Kummer M. , Känel H. von , Gobrecht J.
Published: April 2011

Low temperature growth of thin crystalline Si films on amorphous glass substrates by Molecular Beam Epitaxy (MBE) as well as by two different plasma enhanced chemical vapour deposition (PECVD) systems both using a DC plasma was carried out and the mictrostructural properties were analysed. In particular, the control over the texture along [220] orientation and the resulting columnar nature of the films were studied. The TEM cross section of Si films grown by MBE shows grains with an average width of 750 nm and a length of 3 microns. Using the low energy PECVD (LEPECVD) technique microcrystalline Si films were obtained with a growth rate of up to 35Å/sec. For high quality Si films with larger grains one may grow Si films by MBE whereas for Si films with passivated grain boundaries and for increased deposition rate, it is preferred to grow Si films by the newly developed methods of DC-PECVD.
Spectroscopic Ellipsometry for the Characterization of the Morphology of Ultra-thin Thermal CVD Amorphous and Nanocrystalline Silicon Thin Films
Authors: Hazra Sukti , Yamanaka Mitsuyuki , Sakata Isao , Tsutsumi Toshiyuki , Maeda Tatsuro , Taguchi Hirohisa , Suzuki Eiichi
Published: April 2011

Ultra-thin hydrogenated amorphous silicon thin films have been deposited by thermal chemical vapor deposition (CVD) to prepare smooth top surface of the films avoiding the ion bombardment. Rapid thermal oxidation of thermal CVD a-Si:H results in nanocrystalline dots in the ultra-thin silicon films. Spectroscopic ellipsometry (SE) and high resolution transmission electron microscopy (TEM) have been used to investigate the optical and structural properties of both ultra-thin a-Si:H and nanocrystalline silicon films. To analyze the ellipsometric data of ultra-thin a-Si:H films, a new parameterization i.e., the combination of Sellmeier law and four Lorentz peaks, has been successfully introduced. Width of the Lorentz peaks are directly related with the change of optical functions with the thickness of a-Si:H films. It has been certified that the dense Si matrix with smaller degree of disorder is formed when the thickness exceeds 8nm and the films with the thickness of less than 3.8 nm becomes voided. To interpret the ellipsometric data for nanocrystalline silicon films, three layer model (SiO2, poly-Si+a-Si+void and SiO2) has been adapted. It is inferred from SE and TEM analyses that the size and the density of nanocrystalline dots can be controlled by the morphology of initial ultra-thin a-Si:H films and RTO conditions.
Improved High Resolution Post-Transit Spectroscopy for Determining the Density of States in Amorphous Semiconductors
Authors: Main Charlie , Reynolds Steve , Badran Rashad I. , Marshall Joe M.
Published: April 2011

We show that the analysis of post-transit photocurrent i(t) in a multi-trapping context to determine the density of trapping states g(E) is capable of resolving features less than kT in width. A commonly used method uses a Laplace inversion of i(t) data giving the well-known result g(E) ∼ t i(t) but employs a delta function approximation for trap release times, which results in loss of energy resolution. We show that it is possible to retain the exponential distribution function for trap release time and solve the multi-trapping rate equations directly, giving significantly improved resolution. The analysis is performed on computer generated post-transit data for distributed and discrete traps, and compared with the earlier method and other related Fourier transform methods for determining g(E). In addition, the versatility of the new method in handling cases with either distributed traps or with discrete traps means that it can be applied to disordered materials or to crystalline materials with well-defined defect levels.
Influence of Mechanical Stress on The Electrical Performance of Polycrystalline-Silicon Resistors
Authors: Nakabayashi M. , Ohyama H. , Simoen E. , Ikegami M. , Claeys C. , Kobayashi K. , Yoneoka M. , Takami Y. , Sunaga H. , Takizawa H.
Published: April 2011

Results are presented of a study on the mechanical stress dependence of the resistance of polycrystalline silicon (Poly-Si) films, doped with different atomic species. Two types of Poly-Si film implanted with boron and phosphorus ions were studied, namely, B-doped films of 400 nm and P-doped layers of 250 nm thickness, which were deposited by LPCVD at 620 °C on thermally oxidized silicon wafers. Film doping was done by ion implantation at 50 keV, with a dose of boron and phosphorus of 2 × 1014 and 5.3 × 1014 cm−2, respectively. The Poly-Si films were annealed in a H2 ambient at 1000 °C for 20 min to activate the implanted atoms. A controlled amount of external stress was applied to the silicon wafers in order to study the impact on the electrical performance of the implanted Poly-Si resistors. The resistance of the B-doped Poly-Si films is shown to increase by the mechanical stress, while the resistance of the P-implanted Poly-Si films remained unchanged. It is concluded that this difference is related to the structural differences between Poly-Si films implanted with boron and phosphorus, respectively.
Temperature Dependence of the Photoinduced Degradation and Annealing in a-Si:H
Authors: Schultz Niko , Taylor P. Craig
Published: April 2011

We investigated the temperature dependence of the production and annealing kinetics of the light induced defect states in a:Si:H by electron spin resonance (ESR). At low temperatures (T ∼ 25 K) the silicon dangling bond production is about half as efficient as it is at 300 K. Defects, which are created below about 100 K, almost entirely anneal at room temperature. A sample of a-Si:H, which is subjected to several photo-excitation and annealing cycles, shows a very slow increase of both the degraded and annealed defect densities. The difference in the spin densities between the annealed and degraded states decreases with an increasing number of degradation/annealing cycles.
Comparison Study of a-SiGe Solar Cells and Materials Deposited Using Different Hydrogen Dilution
Authors: Povolny H. , Agarwal P. , Han S. , Deng X.
Published: April 2011

A-SiGe n-i-p solar cells with i-layer deposited via plasma enhanced chemical vapor deposition (PECVD) with a germane to disilane ratio of 0.72 and hydrogen dilution R=(H2 flow)/(GeH4+Si2H6 flow) values of 1.7, 10, 30, 50, 120, 180 and 240 were deposited on stainless steel substrates. This germane to disilane ratio is what we typically use for the i-layer in the bottom cell of our standard triple-junction solar cells. Solar cell current-voltage curves (J-V) and quantum efficiency (QE) were measured for these devices. Light soaking tests were performed for these devices under 1 sun light intensity at 50° C. While device with R=30 showed the highest initial efficiency, the device with R=120 exhibit higher stabilized efficiency after 1000 hours of light soaking.

Single-layer a-SiGe films (∼500 nm thick) were deposited under the same conditions as the i-layer of these devices on a variety of substrates including 7059 glass, crystalline silicon, and stainless steel for visible-IR transmission spectroscopy, FTIR, and hydrogen effusion studies. It is interesting to note 1) the H content in the film decreased with increasing R based on both the IR and H effusion measurements, and 2) while the H content changes significantly with different R, the change in Eg is relatively small. This is most likely due to a change in Ge content in the film for different R.
Light Trapping by Periodically Structured TCO in the Submicrometer Range
Authors: Eisele Christopher , Nebel Christoph E. , Stutzmann Martin
Published: April 2011

Amorphous hydrogenated silicon (a-Si:H) solar cells need efficient light trapping structures to achieve high efficiency. To this end, aluminum doped zinc oxide (ZnO:Al) as a transparent front contact was periodically structured. Solar cells with grating periods between 390 and 980 nm were realized. The structures were characterized by Atomic Force Microscopy (AFM) and optical reflection. A simple formula for the wavelength where total internal reflection starts is deduced for each diffraction order. Solar cells with a periodic grating show a significant reduction in the overall reflectance which is comparable to cells with an optimized statistical texture.
Efficient 18 Å/s Solar Cells with All Silicon Layers Deposited by Hot-Wire Chemical Vapor Deposition
Authors: Wang Qi , Iwaniczko Eugene , Xu Yueqin , Gao Wei , Nelson Brent P. , Mahan A.H. , Crandall R.S. , Branz Howard M.
Published: April 2011

Efficient hydrogenated amorphous silicon (a-Si:H) n-i-p solar cells have been fabricated with all doped and undoped a-Si:H layers deposited by hot-wire chemical vapor deposition (HWCVD). The total deposition time of all layers, except the top ITO-contact, is less than 4 minutes. On an untextured stainless steel (SS) substrate, an initial efficiency of 7.12% is reached, with a stable efficiency of 5.4% after 1000 hours 1 sun light soaking. This initial efficiency is reached by incorporating into the p/i interface about 60 Å of intrinsic a-Si:H “edge” material grown under conditions near the transition to microcrystallinity. This edge layer increases the cell's fill factor from 0.60 to 0.68 and the best open-circuit voltage is about 0.88 V. Using textured Ag/ZnOcoated SS supplied by United Solar Corporation, preliminary results of an all-HWCVD solar cell give an initial efficiency of 8.7 %.
Drastic Revolution in Catalytic Cvd using “Catalytic Plate” Instead of “Hot Wire”
Authors: Masuda Atsushi , Ishibashi Yoriko , Matsumura Hideki
Published: April 2011

Thermal influence on film preparation in catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD, is investigated since heat radiation from catalyzer and thermal transport by introduced gases are one of the dominant factors to determine the film properties. It was found that catalyzer-surface area is a key parameter determining not only the deposition rate but also the thermal influence. “Catalytic platE” instead of the conventional wire was proposed in order to suppress the heat radiation with keeping the catalyzer-surface area. Cat-CVD method employing the catalytic plate is superior to conventional “hot-wirE” CVD method.
A Multilevel Metal Interconnect Technology with Intra-Metal Air-Gap for Quarter-Micron-and-Beyond High-Performance Processes
Authors: Lin Mark , Chang Chun-Yen , Huang Tiao-Yuan , Lin Mout-Lim , Lin Horng-Chin
Published: April 2011

A multilevel metal interconnect with air-gap has been developed to reduce RC delay time for quick turn-around-time foundry manufacturing. The air-gap method has been successfully applied to 0.25 νm foundry technology. Measurements on ring oscillators confirm that the smallest delay time is indeed achieved with the air-gap method, compared with that using either conventional high-density-plasma (HDP) oxide or low-dielectric-constant spin-on-glass (SOG). In addition, we have also developed fitting equations for the delay time, thus provide a handy method for predicting the RC delay time. The oscillator delay time is also found to be critically dependent on not only the size, but also the position of the air-gap. Best delay time reduction is obtained when the air-gap is positioned in extended both above and below the metal lines to effectively reduce the fringing capacitance.
Processing, Properties, and CMP Characteristics of a Spin-on Polymer: HSQ
Authors: Lin Wei-Jung , Yang Chang-Jong , Chen Wen-Chang
Published: April 2011

The structures and properties of the HSQ film during the cage/network transformation were studied by curing at 300°C for 1 hour. The experimental results show that the ratio of the network/cage structure of the cured HSQ film increases from 0.21 to 0.39 by curing. The porosity of the cured film increases from 10.0% to 12.3 %, while the refractive index decreases from 1.413 to 1.376 during curing. These results suggest that the dependence of the structure and properties of the HSQ film by curing. The CMP characteristics of HSQ were studied by using different kinds of slurries and surfactant. The CMP results of polishing HSQ suggest that the hardness and charge status of the abrasive, the interaction of the surfactant with the abrasive and film surface significantly affect the polishing results.
Low Dielectric Constant Porous Silsesquioxane Films: Effect of Thermal Treatment
Authors: Siew Y. K. , Sarkar G. , Hu X. , Xu Y. , See A.
Published: April 2011

Low dielectric constant, nanoporous hydrogen silsesquioxane (HSQ) films were prepared using hybrid templating method by addition of a sacrificial labile polymer, polybutadiene (PB). Thermal gravimetric analyzer (TGA) was employed to monitor the decomposition behavior of HSQ-PB films. Curing of HSQ and decomposition of PB were performed by a two-stage thermal treatment to obtain a defect-free film. The porosity level and pore morphology of the resultant porous films were found to be dependent upon thermal treatment conditions applied.
Ultra Low-K Inorganic Silsesquioxane Films with Tunable Electrical and Mechanical Properties
Authors: Deis Thomas A. , Saha Chandan , Moyer Eric , Chung Kyuha , Liu Youfan , Spaulding Mike , Albaugh John , Chen Wei , Bremmer Jeff
Published: April 2011

Low-k dielectric films have been developed using a new silsesquioxane based chemistry that allows both the electrical and mechanical properties to be tuned to specific values. By controlling the composition and film processing conditions of spin-on formulations, dielectric constants in the range 1.5 to 3.0 are obtained with modulus values that range from 1 to 30 GPa. The modulus and dielectric constant are tuned by controlling porosity, which varies from 0 to >60%, and final film composition which varies from HSiO3/2 to SiO4/2. The spin-on formulation includes hydrogen silsesquioxane resin and solvents. Adjusting the ratio of solvents to resin in the spin-on formulation controls porosity. As-spun films are treated with ammonia and moisture to oxidize the resin and form a mechanically self-supporting gel. Solvent removal and further conversion to a more “silica-like” composition occur during thermal curing at temperatures of 400 to 450°C. The final film composition was controlled through both room temperature oxidation and thermal processing. Final film properties are optimized for a balance of electrical, mechanical and thermal properties to meet the specific requirements of a wide range of applications. Processed films exhibit no stress corrosion cracking or delamination upon indentation, with indenter penetration exceeding the film thickness, and followed by exposure to water at room temperature. Films also exhibit high adhesive strength (> 60MPa) and low moisture absorption. Processing conditions, composition and properties of thin are discussed.
Deposition of Fluorinated Amorphous Carbon Thin Films with Low Dielectric Constant and Thermal Stability
Authors: Han Sang-Soo , Bae Byeong-Soo
Published: April 2011

Fluorinated amorphous carbon (a-C:F) thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD) with increasing CF4:CH4 gas flow rate ratio, and then annealed with increasing annealing temperature (100, 200, 300, and 400.). We have found the reduction mechanism of the dielectric constant and the thermally stable condition for the a-C:F films. On the basis of the results, the optimal condition to satisfy both the low dielectric constant and the thermal stability is followed as; the a-C:F films have to have the compatible F content to make a compromise between the two properties; the C-Fx bonding configuration has to exist as a form of C-F2 & C-F3 instead of C-F; The films should be somewhat cross-linked structure.
Grain Orientation and Strain Measurements in Sub-Micron wide Passivated Individual Aluminum Test Structures
Authors: Tamura N. , Valek B. C. , Spolenak R. , MacDowell A. A. , Celestre R. S. , Padmore H.A. , Brown W. L. , Marieb T. , Bravman J. C. , Batterman B. W. , Patel J. R.
Published: April 2011

An X-ray microdiffraction dedicated beamline, combining white and monochromatic beam capabilities, has been built at the Advanced Light Source. The purpose of this beamline is to address the myriad problems in Materials Science and Physics that require submicron x-ray beams for structural characterization. Many such problems are found in the general area of thin films and nano-materials. For instance, the ability to characterize the orientation and strain state in individual grains of thin films allows us to measure structural changes at a very local level. These microstructural changes are influenced heavily by such parameters as deposition conditions and subsequent treatment. The accurate measurement of strain gradients at the micron and sub-micron level finds many applications ranging from the strain state under nano-indenters to gradients at crack tips. Undoubtedly many other applications will unfold in the future as we gain experience with the capabilities and limitations of this instrument. We have applied this technique to measure grain orientation and residual stress in single grains of pure Al interconnect lines and preliminary results on post-electromigration test experiments are presented. It is shown that measurements with this instrument can be used to resolve the complete stress tensor (6 components) in a submicron volume inside a single grain of Al under a passivation layer with an overall precision of about 20 MPa. The microstructure of passivated lines appears to be complex, with grains divided into identifiable subgrains and noticeable local variations of both tensile/compressive and shear stresses within single grains.
Stress, Microstructure and Temperature Stability of Reactive Sputter Deposited WNx Thin Films
Authors: Leedy K. D. , O'Keefe M. J. , Wilson J. G. , Osterday R. , Grant J. T.
Published: April 2011

Tungsten nitride (WNx) thin films can be used as Schottky barriers in high power, high temperature semiconductor devices or as diffusion barriers between Cu, low-k dielectric and silicon because each application requires a thermally stable film. Therefore, it is important to understand the thin film properties of WNx as a function of deposition conditions and elevated temperature exposure. In this investigation, the influence of nitrogen content and post deposition annealing on the stress and microstructure of reactive dc magnetron sputter deposited WNx films was analyzed. With an increasing N2 to Ar flow ratio, the as-deposited crystal structure of the films changed from α-W to β-W to amorphous WNx and finally to W2N. Rapid thermal anneals up to 650°C resulted in large tensile stress increases and phase transformations to W2N in the nitrogen-containing films. Grain growth during annealing decreased as the concentration of nitrogen in the film increased. The nitrogen content in the films was determined using x-ray photoelectron spectroscopy (XPS).
Planarization of Copper Damascene Interconnects by Spin-Etch Process: A Chemical Approach
Authors: Mukherjee Shyama P. , Levert Joseph A. , Debear Donald S.
Published: April 2011

The present work describes the process principles of “Spin-Etch Planarization” (SEP), an emerging method of planarization of dual damascene copper interconnects. The process involves a uniform removal of copper and the planarization of surface topography of copper interconnects by dispensing abrasive free etchants to a rotating wafer. The primary process parameters comprise of (a) Physics and chemistry of etchants, and (b) Nature of fluid flow on a spinning wafer. It is evident, that unlike conventional chemical-mechanical planarization, which has a large number of variables due to the presence of pads, normal load, and abrasives, SEP has a smaller number of process parameters and most of them are primary in nature. Based on our preliminary works, we have presented the basic technical parameters that contribute to the process and satisfy the basic requirements of planarization such as (a) Uniformity of removal (b) Removal rate (c) Degree of Planarization (d) Selectivity. The anticipated advantages and some inherent limitations are discussed in the context of process principles. We believe that when fully developed, SEP will be a simple, predictable and controllable process.
The Influence of Clusters on Vapor-Deposited thin Films: Atomistic Simulations
Authors: Torreg J. Dalla , Gilmer G. H. , Baumann F. H. , O'Sullivan P. , Rouhani M. Djafari
Published: April 2011

We investigate the morphology of films produced by cluster deposition using Monte Carlo atomistic simulations. Thin films of aluminum are considered as an example. The deposition of small Al clusters containing up to 5 atoms is simulated. Compared with monomer beams, Al cluster deposition increases the density of 3D islands nucleated on the substrate and tends to equalize the growth rate of the different crystal facets. We discuss the smoothening of the surface when the 3D islands merge. We find that there is an optimal size of the deposited clusters that produces the smoothest film.
Atomic Layer Deposition of TiN on Si (100) and (111) Substrates
Authors: Jeon Hyeongtag , Koo Jae-Hyoung , Lee June-Woo , Kim Young-Seok , Kang K. M. , Kim Yang Do , Kim Young Do
Published: April 2011

Titanium nitride (TiN) films were successfully deposited on ρ-type Si (100) and (111) substrates by atomic layer deposition (ALD) method at 450°C. In this ALD system, the TiCl4 and NH3 gases were supplied, separately and Ar purge gas was added between the source and reactant gases to suppress the direct reaction. The main purpose of this study is to investigate the properties of TiN film grown by ALD method. To investigate the growth mechanism, the growth model of TiN was suggested for the calculation of growth rate per cycle with Cerius program. The results of calculation by the model were compared with experimental values of the TiN film deposited by ALD method. TiN films deposited on Si (100) and (111) substrates were examined by TEM and showed the randomly oriented columnar structure. The thickness of TIN film deposited on Si(111) substrate was slightly thicker than that of TiN film deposited on Si(100) substrate. Chlorine content in both TiN films was below the detection limit of AES (<lat%). And the densities of TIN films deposited on Si (100) and (111) substrates were 4.85g/cm3 and 4.98g/cm3. which are higher than that of the films deposited by other conventional CVD methods.
Microstructure and Nanomechanical Properties of Amorphous Carbon Thin Films Prepared by Pulsed Laser Deposition in Various Atmospheres
Authors: Wei Q. , Yamolenko S. , Sankar J. , Sharma A.K. , Yamagata Y. , Narayan J.
Published: April 2011

We have investigated the effect of chamber pressure and atmosphere on the microstructure and nanomechanical properties of amorphous diamondlike carbon (DLC) thin films prepared by pulsed laser deposition. The amorphous carbon films were deposited in various atmospheres such as nitrogen and argon at different pressures. We used Raman spectroscopy and optical microscopy to study the bonding characteristics and microstructures of the DLC films. Nanoindentation measurements were carried out on various samples prepared under different conditions to study the effect of chamber pressure and atmosphere on the elastic modulus and nano-hardness of the films. It was found that reduced vacuum leads to softer amorphous carbon films. Amorphous carbon films prepared in higher pressures exhibit increased density of particulates, and significantly rough surface. The results were understood in terms of thermalization of the laser plasma due to increased possibility of collision.
On the Challenges and Opportunities of Sensing Materials Growth Within Production Deposition Tools
Authors: Bean John C. , Kanakaraju S. , Lau Mark
Published: April 2011

Scanning probe microscopy has yielded extraordinary advances in our ability to characterize surfaces at the atomic scale. These advances are paralleled by improvements in computational methods and platforms that now yield realistically complex multi-scale models of deposition processes. Combining these developments, it might now be possible to sense the dynamic state of an atomic surface, consulting with models to analyze the path of a deposition process. This real-time information might allow us to tweak the growing materials towards particularly unique and desirable final configurations. What we are largely missing are sensors that can monitor atomic scale evolution without, themselves, compromising the commercial deposition process. In a manufacturing environment, sensors cannot shadow the deposition process or contaminate the material. They cannot add significantly to the complexity of the deposition tool nor require that tool's extensive redesign. Importantly (at least over the long term) the sensors cannot even require us, that is, highly trained (and paid) individuals to operate and interpret their data!
Low Pressure Photo-Assisted Mocvd for the Production of Homogeneous, Low-Strain, Amorphous Titanium Oxide Films
Authors: Haycock P.W. , Lopez M.G. , Auld J. , Bull J.W. , Williams E.W.
Published: April 2011

Thin films of titania have been grown by photo-assisted MOCVD which are amorphous and relatively strain free, with high refractive index, low optical loss and structural features all less than 100 nm in size. The stoichiometry is very close to TiO2 and the impurity content is negligible except for a small amount of calcium, thought to have been leached from the glass substrate. The optimum deposition conditions were found to involve a deposition temperature of around 200 °C, a cell pressure of 5.6 torr and the introduction of nitrous oxide, decomposed by UV irradiation to give oxygen free radicals which acted as an oxidant.
Recent Progress On The Modeling Of Laser Surface Cleaning
Authors: Lu Y.F. , Song W. D. , Lukyanchuk B.S. , Hong M.H. , Zheng W.Y.
Published: April 2011

Laser cleaning has emerged to effectively remove contaminants from solid surfaces. In this paper, recent progress on laser cleaning has been studied. First, a cleaning model is established for removal of particles from substrate surfaces. The model not only explains the influence of fluence on cleaning efficiency, but also predicts the cleaning thresholds. Following that, the optical resonance and near field effect are discussed for transparent particles with a size of α ∼ λ (radiation wavelength) which strongly influences the intensity distribution in the contacted area (substrate surface). The characterization of ejected particles during laser cleaning is finally investigated. It is found that the particle distribution curves closely fit to Gaussian curve.
Surface Morphology Of PZT Thin Films Prepared By Pulsed Laser Deposition
Authors: Yamazato Masaaki , Nagano Masamitsu , Ikegami Tomoaki , Ebihara Kenji
Published: April 2011

Ferroelectric PbZr0.52Ti0.48O3(PZT)/YBa2 Cu3O7−x(YBCO) heterostructures on MgO substrate were fabricated by KrF pulsed laser deposition. The grid electrode was set between a substrate and target for improvement of surface morphology. The typical PZT layer had excellent ferroelectric properties; remnant polarization of 39 µC/cm2, coercive electric field of 41 kV/cm, loss tan δ=0.04, and dielectric constant of 950. X-ray diffraction results show that the films had highly c-axis and (a, b) plane orientation. The full widths at half-maximum (FWHM) of rocking curves was decreased with increasing the applied voltage of grid electrode. Atomic force microscopy (AFM) images of PZT layer showed that the film morphology was improved by using a grid electrode.
Properties of the magnetoresistive La0.8Sr0.2MnO3 film and integration with PbZr0.52 Ti0.48O3 ferroelectrics
Authors: Mitsugi Fumiaki , Ikegami Tomoaki , Ebihara Kenji , Narayan J. , Grishin A. M.
Published: April 2011

The colossal magnetoresistive La0.8Sr0.2MnO3 (LSMO) thin film was prepared on the MgO (100) single crystal substrate using KrF excimer pulsed laser deposition technique. The LSMO film deposited at the substrate temperature of 850 °C, oxygen pressure of 500 mTorr and laser energy density of 2 J/cm2(5 Hz) showed the resistivity peak temperature (Tp) of 330 K and the magnetoresi stance change of 15 %(H=0.7 T) at the room temperature. The large lattice mismatch with the substrate increased Tp and decreased the resistivity of the LSMO film.

The X-ray diffraction measurement for the PbZr0.52Ti0.48O3 (PZT) / LSMO heterostructures indicated both c-axis and in- plane orientation, with the good PZT surface morphology.
Ablation-Induced Stresses in Fused Silica by 157-nm F2-Laser irradiation
Authors: Konovalov Igor A. , Herman Peter R.
Published: April 2011

The F2laser is a promising source for direct etching of microstructures and the precise shaping of optical-grade surfaces on wide bandgap materials such as fused silica. We report here on residual tensile stresses induced in fused silica (Coming 7940, UV grade) by 157-nm laser ablation. Plastic strain of 160-mm thick rectangular strips, monitored with an optical interferometric microscope, revealed the presence of residual tensile stresses in the near-ablated surface. HF chemical thinning of the sample showed the thickness of ablation-affected layer provoking strain was ∼275 nm, a value independent of laser fluence (1.9-4.7 J/cm2) and scanning speed (94 - 220 µm/s). A near-surface mean residual tensile stress of ∼80 MPa was inferred from a thin film-substrate approximation.