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Nov 2011

Volume 29, Issue 6, Articles (06xxxx)

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J. Vac. Sci. Technol. A 29, 061502 (2011); http://dx.doi.org/10.1116/1.3632999 (7 pages)

Yoon-Young Choi, Han-Ki Kim, Hyun-Woo Koo, Tae-Woong Kim, and Sung-Nam Lee
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Formation and transfer of GaAsN nanostructure layers

R. R. Collino, A. W. Wood, N. M. Estrada, B. B. Dick, H. W. Ro, C. L. Soles, Y. Q. Wang, M. D. Thouless, and R. S. Goldman

J. Vac. Sci. Technol. A 29, 060601 (2011); http://dx.doi.org/10.1116/1.3630120 (6 pages)

Online Publication Date: 27 September 2011

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The authors report the simultaneous formation and transfer of GaAsN nanostructure layers to alternative substrates, a process termed “ion-cut synthesis.” Ion-cut synthesis is induced by nitrogen ion implantation into GaAs (GaAs:N), followed by spin-on-glass (SOG) mediated wafer bonding and high temperature rapid thermal annealing (RTA). Due to the low ion-matrix diffusivity of GaAs:N, RTA induces the formation of both nanostructures and gas bubbles. The gas bubble pressure induces the formation and propagation of cracks, resulting in transfer of the nanostructured layer. The authors discuss the critical role of the physical properties and the thicknesses of the substrates and the SOG layer to the achievement of ion-cut synthesis.
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81.05.Ea III-V semiconductors
81.07.Bc Nanocrystalline materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.72.uj III-V and II-VI semiconductors
62.20.mt Cracks
61.72.Cc Kinetics of defect formation and annealing
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Making a hybrid microfluidic platform compatible for in situ imaging by vacuum-based techniques

Li Yang, Xiao-Ying Yu, Zihua Zhu, Theva Thevuthasan, and James P. Cowin

J. Vac. Sci. Technol. A 29, 061101 (2011); http://dx.doi.org/10.1116/1.3654147 (10 pages) | Cited 2 times

Online Publication Date: 26 October 2011

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A self-contained microfluidic-based device was designed and fabricated for in situ imaging of aqueous surfaces using vacuum techniques. The device is a hybrid between a microfluidic poly(dimethyl siloxane) block and external accessories, all portable on a small platform (10 × 8 cm2). The key feature is that a small aperture with a diameter of 2-3 μm is opened to the vacuum, which serves as a detection window for in situ imaging of aqueous surfaces. Vacuum compatibility and temperature drop due to water vaporization are the two most important challenges in this invention. Theoretical calculations and fabrication strategies are presented from multiple design aspects. In addition, results from the time-of-flight secondary ion mass spectrometry and scanning electron microscopy of aqueous surfaces are presented.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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High-efficiency and highly stable a-Si:H solar cells deposited at high rate (8 Å/s) with disilane grading process

Guofu Hou, Qihua Fan, Xianbo Liao, Changyong Chen, Xianbi Xiang, and Xunming Deng

J. Vac. Sci. Technol. A 29, 061201 (2011); http://dx.doi.org/10.1116/1.3630052 (4 pages) | Cited 1 time

Online Publication Date: 23 September 2011

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This paper presents our recent results on the high-rate deposition of high-efficiency and highly stable hydrogenated amorphous silicon (a-Si:H) solar cells with all layers deposited by 13.56 MHz radio frequency glow discharge. Using a linear disilane (Si2H6) grading process, high initial active-area efficiency of 11.42% has been obtained for the a-Si:H top cells with an effective i-layer deposition rate of 8 Å/s. It is also found that the light-soaking stability of the a-Si:H top cells is much improved by the Si2H6 grading process with the best a-Si:H top cell exhibiting only 11.2% light-induced degradation after 1000 h of light-soaking. Integrating the high-rate deposited a-Si:H top cell in an amorphous silicon/amorphous silicon germanium (a-Si:H/a-SiGe:H) tandem cell, an initial active-area efficiency of 12.57% is achieved. After light soaking for 1008 h, the stable efficiency is still as high as 11.02%, corresponding to only a 12.31% degradation. To the best of our knowledge, this is the best performance for a-Si:H based solar cells at such a high deposition rate by 13.56 MHz RF-PECVD. Possible mechanisms responsible for the superior stability of the a-Si:H solar cells deposited by the Si2H6 grading process are discussed.
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88.40.jj Silicon solar cells
88.40.hj Efficiency and performance of solar cells
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Effects of the magnetic field strength on the modulated pulsed power magnetron sputtering of metallic films

Jianliang Lin, John J. Moore, William D. Sproul, and S. L. Lee

J. Vac. Sci. Technol. A 29, 061301 (2011); http://dx.doi.org/10.1116/1.3645612 (9 pages) | Cited 7 times

Online Publication Date: 26 October 2011

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The influence of the magnetic field strength (B) on the deposition rate and plasma properties for Ta, Cr, Ti, Al, Cu materials using the modulated pulsed power (MPP) magnetron sputtering technique in a closed field unbalanced magnetron sputtering system was investigated. The MPP deposition rates were compared to those obtained from the films deposited by direct current magnetron sputtering (DCMS) under similar experimental conditions. The time averaged ion energy and mass distributions of positive ions in the MPP plasmas at different magnetic field strengths were compared, using a Hiden electrostatic quadrupole plasma mass spectrometer. The effects of the repetition frequency and pulse length on the MPP deposition rate were investigated. For a given target power, the MPP deposition rate increased when the repetition frequency was increased. It also increased as the pulse length was increased at a constant repetition frequency and target power. The MPP deposition rate is strongly material dependent. The MPP deposition rate increased as B decreased for a given target power. For a B of 550 G, the RMPP/RDCMS ratio for Cu was in a range of 0.81–1.02, for Al it was 0.84–1.01, for Cr it was 0.64–1.01, for Ti it was 0.52–0.89, and for Ta it was 0.47–0.84. For a B of 350 G, the RMPP/RDCMS ratio for Cu was increased to 1.03–1.07, for Al it was 0.94–1.04, for Cr it was 0.8–1.03, for Ti it was 0.79–0.94, and for Ta it was 0.72–0.88. However, a decrease in the ionization of metal and gas species was observed as B was decreased, which affected the microstructure and mechanical properties of the deposited Cr films.
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68.55.A- Nucleation and growth
81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering
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Comparison of the self-cleaning effects and electrical characteristics of BeO and Al2O3 deposited as an interface passivation layer on GaAs MOS devices

J. H. Yum, T. Akyol, D. A. Ferrer, J. C. Lee, S. K. Banerjee, M. Lei, M. Downer, Todd. W. Hudnall, C. W. Bielawski, and G. Bersuker

J. Vac. Sci. Technol. A 29, 061501 (2011); http://dx.doi.org/10.1116/1.3628546 (6 pages) | Cited 6 times

Online Publication Date: 1 September 2011

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Beryllium oxide (BeO) is a promising dielectric because of its high energy bandgap (10.6 eV) and short Be and O atom bonds and its excellent electrical insulating characteristics and high thermal stability. In a previous study, the authors showed that BeO grown by atomic layer deposition (ALD) as a gate dielectric on Si and GaAs substrates has excellent electrical and physical characteristics. In this work, we used monochromatic x-ray photoelectron spectroscopy (XPS) and electrical analysis to compare the ability of ALD BeO and Al2O3 to reduce the surface oxide on GaAs substrates. High resolution XPS shows that the BeO reduced surface oxide more efficiently than Al2O3 and that the capacitance-voltage characteristics correspond with the XPS results. In addition, ALD BeO exhibits less interfacial oxide growth after post-deposition annealing and a more efficient suppression of the leakage current
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Rv Passivation
81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures
73.61.Ng Insulators

Flexible ZnSnO3/Ag/ZnSnO3 multilayer electrodes grown by roll-to-roll sputtering on flexible polyethersulfone substrates

Yoon-Young Choi, Han-Ki Kim, Hyun-Woo Koo, Tae-Woong Kim, and Sung-Nam Lee

J. Vac. Sci. Technol. A 29, 061502 (2011); http://dx.doi.org/10.1116/1.3632999 (7 pages) | Cited 1 time

Online Publication Date: 12 September 2011

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The authors report on the characteristics of flexible ZnSnO3 (ZTO)/Ag/ZTO multilayer electrodes sputtered on a flexible polyethersulfone substrate using roll-to-roll sputtering at room temperature. The sheet resistance and optical transmittance of the flexible ZTO/Ag/ZTO multilayer were mainly affected by the thickness and morphology of the Ag layer inserted between the ZTO layers. Dependence of photoluminescence peak intensity on the Ag thickness indicates that the high transmittance of the flexible ZTO/Ag/ZTO electrode can be explained by surface plasmon resonance as well as antireflection effects. At the optimized Ag thickness (10 nm), the flexible ZTO/Ag/ZTO exhibited a resistivity of 4.15 × 10−5 Ω-cm, an optical transmittance of 86.03%, and a figure of merit value of 42.83 × 10−3 Ω−1 comparable to those of conventional crystalline ITO electrodes. In addition, the optimized ZTO/Ag/ZTO sample showed constant resistance change (ΔR/R) during repeated bending cycles, indicating the robustness of the ZTO/Ag/ZTO electrode as a flexible electrode for cost efficient-flexible displays and photovoltaics.
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73.40.-c Electronic transport in interface structures
78.55.Hx Other solid inorganic materials
81.15.Cd Deposition by sputtering
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Manipulation of polycrystalline TiO2 carrier concentration via electrically active native defects

Meredith C. K. Sellers and Edmund G. Seebauer

J. Vac. Sci. Technol. A 29, 061503 (2011); http://dx.doi.org/10.1116/1.3635373 (8 pages)

Online Publication Date: 14 September 2011

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There is good reason to believe that the properties of semiconducting metal oxides for catalytic applications can be improved when designed according to the principles of microelectronic devices. Nevertheless, defect engineering of polycrystalline TiO2 is complicated by native charged point defects and grain boundaries that alter bulk carrier concentration in a manner that depends on synthesis and post-treatment protocols. These influences are difficult to decouple with standard electrical characterization methods, which typically induce rectifying Schottky barriers to wide-bandgap semiconductors like TiO2. Here, TiO2 donor carrier concentration (Nd) is investigated as a function of film thickness and annealing time using a rigorous Schottky diode-based electrical characterization approach. Nd scales inversely with film thickness due to a reduction in the concentration of electrically active grain boundaries in the bulk. Annealing of polycrystalline TiO2 at 550 °C induces film densification that reduces the void volume surface area available for charge trapping. Strategies for defect engineering polycrystalline metal oxides must focus on tuning electrical activity of grain boundaries and intergranular voids for successful control and manipulation of Nd.
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73.61.Le Other inorganic semiconductors
61.72.jj Interstitials
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
73.30.+y Surface double layers, Schottky barriers, and work functions
61.72.Mm Grain and twin boundaries
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Process-structure-property correlations in pulsed dc reactive magnetron sputtered vanadium oxide thin films

Chandrasekaran Venkatasubramanian, Orlando M. Cabarcos, William R. Drawl, David L. Allara, S. Ashok, Mark W. Horn, and S. S. N. Bharadwaja

J. Vac. Sci. Technol. A 29, 061504 (2011); http://dx.doi.org/10.1116/1.3636372 (7 pages) | Cited 2 times

Online Publication Date: 16 September 2011

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Cathode hysteresis in the reactive pulsed dc sputtering of a vanadium metal target was investigated to correlate the structural and electrical properties of the resultant vanadium oxide thin films within the framework of Berg’s model [Berg et al., J. Vac. Sci. Technol. A 5, 202 (1987)]. The process hysteresis during reactive pulsed dc sputtering of a vanadium metal target was monitored by measuring the cathode (target) current under different total gas flow rates and oxygen-to-argon ratios for a power density of ∼6.6.W/cm2. Approximately 20%–25% hysteretic change in the cathode current was noticed between the metallic and oxidized states of the V-metal target. The extent of the hysteresis varied with changes in the mass flow of oxygen as predicted by Berg’s model. The corresponding microstructure of the films changed from columnar to equiaxed grain structure with increased oxygen flow rates. Micro-Raman spectroscopy indicates subtle changes in the film structure as a function of processing conditions. The resistivity, temperature coefficient of resistance, and charge transport mechanism, obeying the Meyer–Neldel relation [Meyer and Neldel, Z. Tech. Phys. (Leipzig) 12, 588 (1937)], were correlated with the cathode current hysteric behavior.
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81.15.Cd Deposition by sputtering
61.72.-y Defects and impurities in crystals; microstructure
68.55.-a Thin film structure and morphology
73.61.Ng Insulators
78.30.Hv Other nonmetallic inorganics
78.66.Db Elemental semiconductors and insulators

Structural characterization of lead zirconate titanate thin films prepared on different electrodes and on silicon substrates

Marco Natali, Denis Garoli, Valentino Rigato, and Filippo Romanato

J. Vac. Sci. Technol. A 29, 061505 (2011); http://dx.doi.org/10.1116/1.3635366 (6 pages)

Online Publication Date: 23 September 2011

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Lead zirconate titanate (PZT) thin films were deposited by rf magnetron sputtering on Pt/Ti/SiO2//Si, Au/Ti/SiO2//Si, ITO//glass electrodes and on Si (100) substrates. As deposited films show large excesses of Pb and O and contain different Pb oxides. Annealing treatments in air at 650 and 750 °C carried out in a preheated muffle furnace lead to a decrease of Pb and O content and to formation of the perovskite phase via an intermediate nanocrystalline pyrochlore phase. Phase pure perovskite films are obtained on Pt and ITO electrodes by annealing at 750 °C for ~10min, while for the same treatment significant amounts of pyrochlore remained on Au electrodes and on Si substrates.
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68.55.J- Morphology of films
81.40.Gh Other heat and thermomechanical treatments
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Cd Deposition by sputtering
77.84.Cg PZT ceramics and other titanates

Optical emission characteristics of medium- to high-pressure N2 dielectric barrier discharge plasmas during surface modification of polymers

Dongping Liu, Jinhai Niu, and Naisen Yu

J. Vac. Sci. Technol. A 29, 061506 (2011); http://dx.doi.org/10.1116/1.3635372 (10 pages) | Cited 3 times

Online Publication Date: 30 September 2011

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The authors measured the band spectra (first and second positive systems) of the nitrogen molecule by optical emission spectroscopy with an aim to understand the mechanism of surface processing by medium- to high-pressure dielectric barrier discharge (DBD) plasmas. The experimentally measured and calculated spectra were compared to determine the vibrational and rotational temperatures of the N2 (C3Πu) state in the generated plasmas. The authors generated the N2 DBD plasmas at a driving frequency of 1–7 kHz and a discharge pressure of 20–105 Pa for the surface modification of a polyethylene terephthalate (PET) sample. It was found that the vibrational temperature was greatly affected by the N2 pressure while the rotational temperature remained constant in the N2 pressure range of 20–105 Pa. The emission intensity of N2 first positive system (B3Π → A3Σ) rapidly decreased at an increasing N2 pressure due to the collisional relaxation process of the B3Π state with N2 molecules. The N2+ (B2Σu+→X2Σg+) radiative transition was observed in the low-pressure DBD plasmas, which was attributed to the direct electron impact ionization of N2 molecules. The surface characterizations of treated PET samples by contact angle measurement and atomic force microscopy indicate that the low-pressure N2 DBD plasma is an effective method for the surface modification of polymers. Analysis indicates the plasma characteristics such as electron temperature and ion energy are mainly dependent on the N2 pressure, which turn to determine the surface properties of treated PET samples.
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52.77.Fv High-pressure, high-current plasmas (plasma spray, arc welding, etc.)
68.37.Ps Atomic force microscopy (AFM)
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
61.41.+e Polymers, elastomers, and plastics

Zirconium nitride films deposited in (Ar + N2 + H2) sputtering atmosphere: Optical, structural, and electrical properties

M. A. Signore, D. Valerini, L. Tapfer, G. Caretto, and A. Rizzo

J. Vac. Sci. Technol. A 29, 061507 (2011); http://dx.doi.org/10.1116/1.3646147 (9 pages)

Online Publication Date: 7 October 2011

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Zr–N films were grown on glass substrates via radio-frequency magnetron sputtering using an Ar + N2 + H2 mixture. Hydrogen was employed in order to reduce oxygen contamination coming from background pressure, as confirmed by secondary ion mass spectroscopy analysis. The tuned process parameter was the nitrogen flux percentage (RN2) in the mixture. The crystallographic structure of the films was studied using x-ray diffraction. The measurements show that the films deposited at low RN2 (lower than or equal to 50%) crystallize in the rocksalt ZrN structure. As RN2 exceeds 50%, the film exhibits the co-presence of ZrN and Zr3N4 (denoted as o-Zr3N4) phases. When the deposition is performed in only nitrogen atmosphere (RN2 = 100%), a broad peak located at 2θ ≈ 32.2° is mainly attributed to the contribution coming from (320) planes of the o-Zr3N4. An envelope method, based on the optical reflection and transmission spectra taken at normal incidence, has been applied for the optical characterization of the nitride films. Such a method allows the determination of the samples’ average thickness and optical constants (refractive index n and extinction coefficient k) in the ultraviolet-visible-near infrared regions. The evaluated thickness was about 2500 nm, which is in good agreement with the value obtained from profilometry. The absorption coefficient α was calculated from reflectance and transmittance spectra. The energy bandgap ranges from 2.3 eV to 2.4 eV. Electrical characterization was performed using capacitance-voltage measurements, which showed that the films evolve from insulating to semiconductor behavior when the nitrogen content in the sputtering atmosphere is decreased, confirming structural and optical results.
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68.55.aj Insulators
73.61.Ng Insulators
78.66.Nk Insulators
81.15.Cd Deposition by sputtering
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Dielectric performance of hybrid alumina-silicone nanolaminates synthesized by plasma enhanced chemical vapor deposition

Rakhi P. Patel, David Chiavetta, and Colin A. Wolden

J. Vac. Sci. Technol. A 29, 061508 (2011); http://dx.doi.org/10.1116/1.3652918 (6 pages) | Cited 3 times

Online Publication Date: 21 October 2011

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Plasma enhanced chemical vapor deposition (PECVD) was used to deposit hybrid nanolaminates comprising silicone and alumina at low temperature. Hexamethyldisiloxane was used as the sole precursor for silicone, and alumina synthesis was accomplished via pulsed PECVD using trimethyl aluminum and oxygen. Digital control over the nanolaminate structure and composition was demonstrated through spectroscopic ellipsometry and cross-sectional microscopy. The dielectric performance of alumina–silicone nanolaminates was examined as a function of the dyad composition and thickness. The effective dielectric constant could be tuned between those of the parent compounds, achieving high specific capacitance values ranging from 20 to 80 nF/cm2. Current-voltage measurements showed that the leakage current was a strong function of the thickness of the individual alumina layers, and nanolaminates with Al2O3 layers >10 nm displayed excellent performance. The leakage current density at a field strength of 1 MV/cm was ∼10−9 A/cm2, whereas breakdown required applied electrical fields in excess of 5 MV/cm.
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77.22.Ch Permittivity (dielectric function)
81.07.Pr Organic-inorganic hybrid nanostructures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
77.22.Jp Dielectric breakdown and space-charge effects
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Method to compensate radiation-induced errors in a hot-cathode-ionization gauge with correcting electrode

Hiroshi Saeki and Tamotsu Magome

J. Vac. Sci. Technol. A 29, 061601 (2011); http://dx.doi.org/10.1116/1.3645599 (4 pages)

Online Publication Date: 4 October 2011

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A previous method to compensate radiation-induced errors caused by the synchrotron radiation environment used a hot-cathode-ionization gauge with correcting electrode and shield tube. This compensating method was based on an approximate formula, and the compensated pressure measurement displayed large errors for pressures below ∼10−7 Pa. To overcome this problem, a new method, based on an exact formula, and use of precision electrometers, has now been developed and tested in a simulation experiment with excess electrons. This method reduced the pressure-measurement error to approximately 1% and is not restricted to use in a specific pressure range, even without use of a shield tube, unlike the previous method. The experimental result suggests that the new compensating method can be used in severe synchrotron radiation environments with photoelectrons.
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07.30.Dz Vacuum gauges
82.45.Fk Electrodes

Design of steady-state isothermal gas distribution systems consisting of long tubes in the whole range of the Knudsen number

Serafeim Misdanitis and Dimitris Valougeorgis

J. Vac. Sci. Technol. A 29, 061602 (2011); http://dx.doi.org/10.1116/1.3645582 (7 pages) | Cited 1 time

Online Publication Date: 5 October 2011

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A novel algorithm is developed to solve steady-state isothermal vacuum gas dynamics flows through pipe networks consisting of long tubes based on linear kinetic theory. For a pipe network of known geometry the algorithm is capable of computing the mass flow rates (or the conductance) through the pipes as well as the pressure heads at the nodes of the network. The pressure distribution along each pipe element may also be found. Since a linear kinetic approach is implemented the analysis is valid and the results are accurate in the whole range of the Knudsen number, provided that the local pressure gradient along each tube of the network is small. This latter condition is satisfied when the channel is sufficiently long. The involved computational effort is very small. This is achieved by successfully integrating the linear kinetic results for the single tubes into the general solver for designing the gas pipe network. To demonstrate the feasibility of the approach two typical piping systems one in the range of small and a second one in the range of moderate Knudsen numbers are simulated. The proposed algorithm simulates, in an exact manner, low-speed gas distribution systems under any vacuum conditions based on linear kinetic modeling and constitutes a significant advancement tool in vacuum technology.
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93.85.Tf Oil prospecting, pipelines, and conduits
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Improvements to bit line contact processing in trench DRAM

Chyuan-Haur Kao, Hsiang Chen, Yi-Chen Chen, Yao-Min Chiu, Shiao-Ge Tsai, Hong-Kai Lo, and Yun-Ru Chen

J. Vac. Sci. Technol. A 29, 06B101 (2011); http://dx.doi.org/10.1116/1.3653967 (5 pages)

Online Publication Date: 25 October 2011

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Ionized physical vapor deposition of titanium and titanium nitride contact metal was investigated to assess whether adding extra nitrogen into the chamber reduced contact current leakage and whether lowering the RF bias power would reduce ion bombardment. The results of multiple analyses confirm that plasma deposition with extra nitrogen can suppress the accumulation of Ti atoms and, therefore, the formation of TiSix, and that lowering the RF power can reduce the ratio of resputtering and decrease the thickness of the Ti layer. The two techniques can be effectively implemented in bit line contact processing to reduce current leakage while improving product performance and reliability.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
84.30.Sk Pulse and digital circuits

Electrical and material characterizations of HfTiO4 flash memory devices with post-annealing

Chyuan-Haur Kao, Hsiang Chen, Hun Wei Chang, and Chih Sheng Chuang

J. Vac. Sci. Technol. A 29, 06B102 (2011); http://dx.doi.org/10.1116/1.3653970 (3 pages)

Online Publication Date: 25 October 2011

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A metal-oxide-high-k HfTiO4-oxide-silicon-type novel nanocrystal memory was fabricated in order to examine temperature-induced effects at different annealing temperatures and find the optimal annealing condition. The material properties and electrical characteristics were investigated via multiple material analysis techniques such as x-ray diffraction, atomic force microscopy, and electrical analysis. Through a thorough study of the crystalline structure, material composition, memory window, and program/erase (P/E) cycle, the optimal annealing temperature at which to deposit a charge trapping layer with excellent material and electrical properties was determined. An HfTiO4 charge trapping layer annealed at 950 °C had a higher window of 5.8 V in the current-voltage hysteresis loop and a higher P/E speed than samples prepared under various annealing conditions. The results indicate that annealing can enhance the crystallization of HfTiO4 and produce a more effective electric field across a tunneling oxide of high quality.
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84.30.Sk Pulse and digital circuits
81.40.Gh Other heat and thermomechanical treatments

Etching characteristics and mechanisms of SiC thin films in inductively-coupled HBr-Ar, N2, O2 plasmas

Alexander Efremov, Sungchil Kang, Kwang-Ho Kwon, and Won Seok Choi

J. Vac. Sci. Technol. A 29, 06B103 (2011); http://dx.doi.org/10.1116/1.3655561 (6 pages)

Online Publication Date: 26 October 2011

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Etch characteristics and mechanisms of SiC thin films in HBr-Ar, HBr-N2, and HBr-O2 inductively-coupled plasmas were studied using a combination of experimental and modeling methods. The etch rates of SiC thin films were measured as functions of the additive gas fraction in the range of 0–100% for Ar, N2, and O2 at a fixed gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). The plasma chemistry was analyzed using Langmuir probe diagnostics and a global (zero-dimensional) plasma model. The good agreement between the behaviors of the SiC etch rate and the H atom flux could suggest that a chemical etch pathway is rather controlled by the gasification of carbon through the CHx or CHxBry compounds.
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81.65.Cf Surface cleaning, etching, patterning
68.55.ag Semiconductors
52.70.Ds Electric and magnetic measurements

Properties of double-layered Ga-doped Al-zinc-oxide/titanium-doped indium–tin-oxide thin films prepared by dc magnetron sputtering applied for Si-based thin film solar cells

Chao-Chun Wang, Dong-Sing Wuu, Yang-Shih Lin, Shui-Yang Lien, Yung-Chuan Huang, Chueh-Yang Liu, Chia-Fu Chen, Asheesh Nautiyal, and Shuo-Jen Lee

J. Vac. Sci. Technol. A 29, 06B104 (2011); http://dx.doi.org/10.1116/1.3651099 (5 pages)

Online Publication Date: 3 November 2011

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In this article, Ga-doped Al-zinc-oxide (GAZO)/titanium-doped indium–tin-oxide (ITIO) bi-layer films were deposited onto glass substrates by direct current (dc) magnetron sputtering. The bottom ITIO film, with a thickness of 200 nm, was sputtered onto the glass substrate. The ITIO film was post-annealed at 350 °C for 10-120 min as a seed layer. The effect of post-annealing conditions on the morphologies, electrical, and optical properties of ITIO films was investigated. A GAZO layer with a thickness of 1200 nm was continuously sputtered onto the ITIO bottom layer. The results show that the properties of the GAZO/ITIO films were strongly dependent on the post-annealed conditions. The spectral haze (Tdiffuse/Ttotal) of the GAZO/ITIO bi-layer films increases upon increasing the post-annealing time. The haze and resistivity of the GAZO/ITIO bi-layer films were improved with the post-annealed process. After optimizing the deposition and annealing parameters, the GAZO/ITIO bi-layer film has an average transmittance of 83.20% at the 400–800 nm wavelengths, a maximum haze of 16%, and the lowest resistivity of 1.04 × 10−3 Ω cm. Finally, the GAZO/ITIO bi-layer films, as a front electrode for silicon-based thin film solar cells, obtained a maximum efficiency of 7.10%. These encouraging experimental results have potential applications in GAZO/ITIO bi-layer film deposition by in-line sputtering without the wet-etching process and enable the production of highly efficient, low-cost thin film solar cells.
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88.40.jm Thin film III-V and II-VI based solar cells
61.72.Cc Kinetics of defect formation and annealing
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
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