bluuebunny/crossref_metadata_2025_split huggingface dataset:
RCA and IMEC/SC2 Clean: Metallic Immunity and Gate Oxide Integrity
Authors: Chen Weidong , Dhayagude Tushar , Chaparala Prasad , Demirlioglu Esin , Shenasa Mohsen , Bearda Twan , Arnauts Sophia , Meuris Marc 
Published: April 2011

ABSTRACTDilute HF/RCA and IEMC/SC2 cleans have been evaluated on two process lines with different metallic contamination levels. VPD-DSE-TXRF and SPV techniques were used to monitor the metallic contamination. Gate oxide integrity(GOI) tests were performed on several structures. Both HF/RCA and IMEC/SC2 cleans have shown good Qbd and Ebd results for the clean process line. Lower Qbd and Ebd values were obtained for both cleans in the relatively contaminated process line. These results suggest that poor GOI is related to the metallic contamination in the oxide or at the SiO2/Si interface.
Effects of Wafer Cleaning Reduction on Metals Removal and
Ultrathin Gate Oxide Quality
Authors: D'Emic Christopher P. , Cohen Stephan , Zaitz Mary Ann 
Published: April 2011

ABSTRACTThe drive to reduce chemical consumption for cost savings is high in the
semiconductor industry. Recently, studies have shown that the traditional
1:1:5 ratios of the SC1, SC2 cleans can be reduced and still
maintain good cleaning. The optimization of process parameters must be done
in accordance with the type of cleaning tool. Processes in wet decks may be
optimized differently from single chamber tools, especially if extended bath
lifetimes are expected. In this study, temperature reduction and dilution of
the SC1 and SC2 cleans in a wet deck are examined for their effects on
metals removal efficiency from silicon surfaces as measured by TRXRF. For an
HF, SC1, SC2 sequence, good metal removal can be maintained by dropping the
SC1 temperature down to 35°C and chemical ratio to 1:1:40. At too low an SC1
dilution and temperature, the Cu removal efficiency drops. In SC2, good
metals removal remains without peroxide and a lower limit for HC1 is
determined. It is also found that peroxide must be reduced if HCl is reduced
in SC2. otherwise metals plating out from SC1 cannot be removed effectively.
To understand the impact of these reduced cleans on gate oxide integrity,
the electrical properties of 30 A gate oxides grown using these experimental
pre-gate cleans is discussed.
Effects of the underlayer surface state on the interconnecting
aluminum film properties
Authors: Kim Sam-Dong , Shin Chan-Soo , Kwak Noh-Jung , Lee Kyeong-Bock , Shin Cheol-Ho , Kwon Oh-Jung , Kim Chung-Tae , Yang Hong-Seon 
Published: April 2011

ABSTRACTA gradual change in thermal oxide surface state from hydrophilic to
hydrophobic was observed with time -delay in a clean room environment.
Surface quality and reflectivity for the Al/Ti metal layers showed a strong
dependency on the oxide surface state. From the hydrophilic oxide substrate,
a lower (002) Ti preferred orientation was obtained than from hydrophobic
ones. This resulted in a degraded (111) Al preferred orientation and rough
metal surface. The RF-etch process increased the smoothness and hydrophobic
surface property for the inter -metal dielectric (IMD) oxides, and therefore
greatly improved Al/Ti surface quality. When conventional CMOS double layer
metal interconnection process is performed, metal inter-line bridge yield
was strongly affected by the surface state of substrate oxides.
AFM analysis of HF Vapor Cleaned SiO2
Surfaces
Authors: Carter R. J. , Bergman E. J. , Lee D. R. , Owyang J. , Nemanich R. J. 
Published: April 2011

ABSTRACTSi(100) surfaces were cleaned using HF/IPA vapor chemistries at ambient
pressure and temperature with nitrogen as the carrier gas. Three distinct
cases for oxide removal were studied: vapor etching of native oxides, RCA
chemical oxides, and thermal oxides. Atomic Force Microscopy (AFM) was used
to characterize the surface morphology after the HF vapor etching process.
The AFM indicated exaggerated peaks in random places on the surface, These
peaks were identified as residue remaining after the vapor etching process.
The average lateral width of the peaks were ∼ 50 nm. The average height of
the peaks for native and chemical oxide etched surfaces was relatively the
same, approximately 8 nm. The average height of the peaks after thermal
oxide removal was significantly smaller, approximately 1–2 nm. Peak density
for native oxide etched surfaces was significantly greater than chemical or
thermal oxide etched surfaces. We suggest that impurities in the oxide
contribute to residue formation on the surface.
Thermoelectric BehaVior of Conducting Polymers: On the Possibility of “Off-Diagonal” Thermoelectricity
Authors: Mateeva N. , Niculescu H. , Schlenoff J. , Testardi L. 
Published: April 2011

AbstractNon-cubic materials, when structurally aligned, possess sufficient anisotropy to exhibit thermoelectric effects where the electrical and thermal currents are orthogonal (“off-diagonal” thermoelectricity). We discuss the benefits of this form of thermoelectricity for devices and describe a search for suitable properties in the air-stable conducting polymers polyaniline and polypyrrole. We find the simple and general correlation that the logarithm of the electrical conductivity scales linearly with the Seebeck coefficient on doping but with proportionality in excess of the conventional prediction for thermoelectricity. The correlation is unexpected in its universality and unfavorable for thermoelectric applications. A simple model suggests that mobile charges of both signs exist in these polymers, and this leads to reduced thermoelectric efficiency. We also briefly discuss non air-stable polyacetylene, where “ambipolar” transport does not appear to occur, and where properties seem more favorable for thermoelectricity.
Modeling of Mid-Infrared Multi-Quantum Well Lasers
Authors: Andreev A. D. 
Published: April 2011

AbstractThreshold characteristics of mid-infrared MQW lasers have been studied theoretically. Auger recombination rates in strained quantum wells have been calculated in the framework of 8×8 Kane model taking account of spin-orbit interaction. It is demonstrated that the Auger coefficients of both CHCC and CHHS processes essentially depends on the QW parameters (strain, QW width, barrier bandgap), but have relatively weak (non-exponential) temperature dependence. It is shown that the laser characteristics can be improved for optimized laser structures, when the Auger rate is decreased.
MID-IR Photodetectors Based on InAs/InGaSb Type-II Quantum Wells
Authors: Brown G. J. , Ahoujja M. , Szmulowicz F. , Mitchel W. C. , Lin C. H. 
Published: April 2011

AbstractWe report on the growth and characterization of InAs/InxGal..Sb strained-layer superlattices (SLS) designed with a photoresponse cut-off wavelength of IOlim. The structural parameters, layer thicknesses and compositions, were chosen to optimize the infrared absorption for a superlattice with an energy band gap of 120 meV. The energy band structure and optimized absorption coefficient were determined with an 8×8 envelope function approximation model. The superlattices were grown by molecular beam epitaxy and were comprised of 100 periods of 43.6Å InAs and 17.2Å In.23Ga.77Sb lattice-matched to the GaSb substrates. In order to reduce the background carrier concentrations in this material, superlattices grown with different substrate temperatures were compared before and after annealing. This set of superlattice materials was characterized using x-ray diffraction, photoresponse and Hall measurements. The measured photoresponse cut-off energies of 116 ± 6 meV is in good agreement with the predicted energy band gap for the superlattice as designed. The intensity of the measured mid-infrared photoresponse was found to improve by an order of magnitude for the superlattice grown at the lower substrate temperature and then annealed at 520 °C for 10 minutes. However, the x-ray diffraction spectra were very similar before and after annealing. The temperature dependent Hall measurements at low temperatures (<25K) were dominated by holes with quasi two-dimensional behavior. An admirably low background carrier concentration of 1×1012 cm−2 was measured at low temperature.
Monolithically Integrated Dual-Band Quantum Well Infrared Photodetector
Authors: Sengupta D. K. , Gunapala S. D. , Bandara S. V. , Pool F. , Liu J. K. , McKelvey M. , Luong E. , Torezan J. , Mumulo J. , Hong W. , Gill J. , Stillman G. E. , Curtis A. P. , Kim S. , Chou L. J. , Mares P. J. , Feng M. , Hseih K. C. , Chuang S. L. , Bishop S. G. , Chang Y. C. , Liu H. C. , Wang W. I. 
Published: April 2011

AbstractA monolithic quantum well infrared photodetector (QWIP) structure has been presented that is suitable for dual bands in the two atmospheric transmission windows of 3 – 5.3 μm and 7.5 – 14μm, respectively. The proposed structure employs dual stacked, strain InGaAs/AlGaAs and latticematched GaAs/AlGaAs quantum well infrared photodetector for mid wavelength and long wavelength detection. The response peak of the strain InGaAs/AlGaAs quantum well is at 4.9 μm and the lattice-matched GaAs/AlGaAs is at 10.5μm; their peak sensitivities are in the spectral regions of 3 – 5.3mu;m and 7.5 – 14μm. The peak responsivity when the dual-band QWIP is biased at 5 Volts is ∼0.065A/W at 4.9μm and ∼0.006A/W at 10.5μm; at this voltage the dual-band QWIP is more sensitive at the shorter wavelengths due to its larger impedance thus exhibiting wavelength tunability characteristics with bias. Additionally, single colored 4.9 and 10.5μm QWIPs were fabricated from the dual-band QWIP structure to study the bias-dependent behavior and also to understand the effects of growing the strain layer InGaAs/AlGaAs QWIP on top of the lattice-matched GaAs/AlGaAs QWIP. In summary, two stack dual-band QWIPs using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells have been demonstrated with peak spectral sensitivities in the spectral region of 3 – 5.3μm and 7.5 – 14μm. Also, the voltage tunable dual-band detection have been realized for this kind of QWIP structure.
Mapping of Large Area Cadmium Zinc Telluride (CZT) Wafers: Apparatus and Methods
Authors: Brunett B. A. , Van Scyoc J. M. , Yoon H. , Gilbert T. S. , Schlesinger T. E. , Lund J. C. , James R. B. 
Published: April 2011

AbstractCadmium Zinc Telluride (CZT) shows great promise as a semiconductor radiation detector material. CZT possesses advantageous material properties over other radiation detector materials in use today, such as a high intrinsic resistivity and a high cross-section for x and γ-rays. However, presently available CZT is not without limitations. The hole transport properties severely limit the performance of these detectors, and the yield of material possessing adequate electron transport properties is currently much lower than desired. The result of these material deficiencies is a lack of inexpensive CZT crystals of large volume for several radiation detector applications. One approach to help alleviate this problem is to measure the spatial distribution (or map) the electrical properties of large area CZT wafers prior to device fabrication. This mapping can accomplish two goals: identify regions of the wafers suitable for detector fabrication and correlate the distribution of crystalline defects with the detector performance. The results of this characterization can then be used by the crystal manufacturers to optimize their growth processes. In this work, we discuss the design and performance of apparatus for measuring the electrical characteristics of entire CZT wafers (up to 10 cm × 10 cm). The data acquisition and manipulation will be discussed and some typical data will be presented.
Low Optical Loss Wafer Bonded GaAs Structures for Quasi-Phase-Matched Second Harmonic Generation
Authors: Wu YewChung Sermon , Feigelson Robert S. , Route Roger K. , Zheng Dong , Gordon Leslie A. , Fejer Martin M. , Byer Robert L. 
Published: April 2011

AbstractA periodic GaAs wafer-bonded structure has been proposed for quasi-phase-matched (QPM) second harmonic generation (SHG). However, current bonding processes often lead to unacceptable optical losses and poor device performance. In this study, three sources of optical losses in wafer-bonded structures were investigated, (1) interfacial defects between the wafers, (2) bulk defects within the wafers, and (3) decomposition at the exposed outer surfaces. Surface losses due to incongruent evaporation were easily eliminated by repolishing the outer surfaces. However, to minimize the losses from interfacial and bulk defects, it was necessary to investigate the relationship between these defects and the bonding parameters. It was found that an increase in bonding temperature and/or time led to a decrease in interfacial defects, but an increase in bulk and surface defects. Through a trade-off process, optimized processing conditions were developed which permitted the preparation of bonded stacks containing over 50 (100)-oriented GaAs wafers, and about 40 layers of (110))-oriented GaAs wafers. Optical losses as low as 0.1 - 0.3% /interface (at 5.3 μm and 10.6 μm) were achieved.
Characterization of CdGeAs2 Using Capacitance Methods
Authors: Smith S. R. , Evwaraye A. O. , Ohmer M. C. 
Published: April 2011

AbstractThermal Admittance Spectroscopy(TAS) has been used to detect energy levels in the bandgap of CdGeAs2 specimens. Capacitance-Voltage(CV) measurements were used to determine the net free carrier concentration of the specimens as well as the conductivity type. All specimens were found to be p-type. CV measurements determined that the free carrier densities ranged from 1.2 × 1017 cm−3 to 8 × 1018 cm−3. Usually one peak (but in some cases two) was observed in the thermal admittance spectra. One peak present in two samples indicates an acceptor with a thermal activation energy of Ev+(0.10–0.13) eV which corresponds closely to the value of 0.10–0.12 eV found from Hall effect measurements on these specimens. The additional peak observed could correspond to a second deeper acceptor at Ev+0.346 eV, however, the energy could not be accurately determined because the peak was not fully resolved. Evidence for the existence of two native acceptors from electron paramagnetic resonance has recently been reported which tends to support a two acceptor model.
Photo-Assisted Resonant Tunneling Through Localized States in AlAs/GaAs Double-Barrier Structure With Undoped Spacer Layers
Authors: Chu H. Y. , Lee K. -S. , Park H. -H. , Lee E. -H. 
Published: April 2011

AbstractWe report on the evidence of photo-assisted resonant tunneling through localized states in AlAs/GaAs double-barrier structures (DBSs) with undoped GaAs spacers. In the photocurrent measurement, additional peaks were observed at voltages lower than that of resonance and were enhanced with the laser power. This behavior was more pronounced as the thickness of spacer layers in the DBS increased. These results are attributed to the resonant tunneling of electrons through the localized states, they are induced in the neighboring barriers, by the photoexcited carriers in spacers. We discuss the localization effect of photoexcited carriers on the resonant tunneling.
Dislocations and Traps in MBE Grown Lattice Mismatched p- InGaAs/GaAs Layers on GaAs Substrates
Authors: Du A. Y. , Li M. F. , Chong T. C. , Zhang Z. 
Published: April 2011

AbstractDislocations and traps in MBE grown p-InGaAs/GaAs lattice-mismatched heterostructures are investigated by Cross-section Transmission Electron Microscopy (XTEM), Deep Level Transient Spectroscopy (DLTS) and Photo-luminescence (PL). The misfit dislocations and the threading dislocations observed by XTEM in different samples with different In mole fractions and different InGaAs layer thickness generally satisfy the Dodson-Tsao's plastic flow critical layer thickness curve. The threading dislocations in bulk layers introduce three hole trap levels HI, H2 and H5 with DLTS activation energies of 0.32 eV, 0.40 eV, 0.88 eV, respectively, and one electron trap El with DLTS activation energy of 0.54 eV. The misfit dislocations in relaxed InGaAs/GaAs interface induce a hole trap level H4 with DLTS activation energy between the range of 0.67–0.73 eV. All dislocation induced traps are nonradiative recombination centers which greatly degrade the optical property of the InGaAs/GaAs layers.
Chemical Etching and Post-Annealing for High Performance CdZnTe Strip Detectors
Authors: Shi Z. Q. , Stahle C. M. , Shu P. 
Published: April 2011

AbstractOne of the critical issues in CdZnTe detector fabrication is the surface treatment. This will not only affect the electrical properties, such as leakage current, but also influence the physical properties, such as smoothness and adhesion between the metal and the semiconductor. The latter will determine the wire bonding yield. Historically, there has been a problem in achieving both low leakage current and excellent wire bonding yield. In this paper, we report our new approach to fabricate high performance doubled sided CdZnTe strip detectors. The new surface treatments involve chemical etching and post-annealing. The leakage current, interstrip resistance and energy resolution were studied as a function of different etchants/time and post-annealing temperature. It was found that a chemical etch with bromine in ethylene glycol (Br/EG) is suitable for the double sided strip detector process. Keeping a relatively smooth surface is critical for achieving a high yield of good strips. To improve the adhesion of the metal to CdZnTe for wire bonding, the detectors were annealed from 100 to 175°C for 10 hours. It has been observed that after annealing, not only has the strip leakage current decreased, but the interstrip resistance is increased for a temperature less than 150°C.
Portable P-I-N CdZnte Gamma-Ray Spectroscopy System
Authors: Sudharsanan R. , Stenstrom C. , Vakerlis G. , Pantazis J. , Huber A. , Redus R. , Jordanov V. T. 
Published: April 2011

AbstractA portable Gamma-Ray Spectroscopy system has been designed and tested for identification of nuclear materials in the field. A P-I-N CdZnTe detector was developed to minimize the leakage current and to improve energy resolution. The detector has a sensitive volume of 200 mm3 and has been constructed with novel heterojunction contacts. Thermoelectric cooling is used to reduce leakage currents in the detector element and the input thermal noise to the FET. Risetime discrimination is used to offset the negative effects of incomplete charge collection. The detector probe is connected to a single unit comprised of detector electronics, an MCA and a portable computer, all operated from battery power. Results from testing with laboratory radioisotopic sources are presented.
Mapping Detector Response Over the Area of a CdZnTe-Multiple-Electrode Detector
Authors: Lingren C. L. , Apotovsky B. , Butler J. F. , Doty F. P. , Friesenhahn S. J. , Oganesyan A. , Pi B. , Zhao S. 
Published: April 2011

AbstractSemiconductor multiple-electrode detectors have been developed for the purpose of reducing effects of hole trapping in room-temperature radiation detectors. Some reported geometries maintain a nearly-uniform electric field inside the detector, but others generate an electric field that is very non-uniform and highly-concentrated at the anode. This paper reports the results of mapping such a detector (having a non-uniform electric field) with a finely collimated gamma-ray beam to determine the detector response as a function of position.
A CdTe Position Sensitive Detector for a Hard X-and Gamma-Ray Wide Field Camera
Authors: Caroli E. , Bertuccio G. , Cesare G. De , Donati A. , Dusi W. , Landini G. , Perotti F. , Sampietro M. , Stephen J. B. 
Published: April 2011

AbstractAn important region of the electromagnetic spectrum for astrophysics is the hard X- and gamma ray band between 10 keV and a few MeV, where several processes occur in a wide variety of objects and with different spatial distribution and time scales. In order to fulfill the observational requirements in this energy range and taking into account the opportunities given by small/medium size missions (e.g. on the ISS), we have proposed a compact, wide field camera based on a thick (1 cm) position sensitive CdTe detector (PSD). The detector is made of an array of 128×96 CdTe microspectrometers with a pixel size of 2×2 mm2. The basic element of the PSD is the linear module that is an independent detection unit with 32 CdTe crystals and monolithic front-electronics (ASIC) supported by a thin (300 μm) ceramic layer. The expected performance of the PSD over the operative energy range and some of the required ASIC functionality are presented and discussed.
Neutron Detectors Made From Chemically Vapour Deposited Semiconductors
Authors: Foulon F. , Bergonzo P. , Brambilla A. , Jany C. , Guizard B. , Marshall R. D 
Published: April 2011

AbstractIn this paper, we present the results of investigations on the use of semiconductors deposited by chemical vapour deposition (CVD) for the fabrication of neutron detectors. For this purpose, 20 μm thick hydrogenated amorphous silicon (a-Si:H) pin diodes and 100 μm thick polycrystalline diamond resistive detectors were fabricated. The detectors were coupled to a neutron-charged particle converter : a layer of either gadolinium or boron (isotope 10 enriched) deposited by evaporation. We have demonstrated the capability of such neutron detectors to operate at neutron fluxes ranging from 101 to 106 neutrons/cm2.s. The fabrication of large area detectors for neutron counting or cartography through the use of multichannel reading circuits is discussed. The advantages of these detectors include the ability to produce large area detectors at low cost, radiation hardness (∼ 4 Mrad for a-Si:H and ∼ 100 Mrad for diamond), and for diamond, operation at temperatures up to 500°C. These properties enable the use of these devices for neutron detection in harsh environments. Thermal neutron detection efficiency up to 22 % and 3 % are expected by coupling a-Si:H diodes and diamond detectors to 3 μm thick gadolinium (isotope 157) and 2 μm thick boron layers, respectively.
Internal Field Distribution in Organic Light Emitting Diodes with Double Layer Structure
Authors: Hochfilzer C. , Jost T. , Niko A. , Graupner W. , Leising G. , Tang C. W. , Forsythe E. , Gao Y. 
Published: April 2011

AbstractDouble layer organic light emitting devices (OLED) are constructed by evaporating tris(8 -hydroxy) quinoline aluminum (Alq3) on a spin cast thin film of a methyl substituted ladder type poly -para -phenylene (m -LPPP). A thick layer of Mg:Ag is used as the cathode material. These organic materials are very suitable for application in OLEDs both, as transporting materials as well as active layers. Alq3 predominantly transports electrons while m - LPPP is a conjugated polymer having higher hole mobilities. Due to these transport properties the formation and radiative recombination of the excitons in ITO/m -LPPP/Alq3/Mg:Ag devices occur close to the m -LPPP/Alq3 interface. We compare the device performance of OLEDs with varying Alq3 layer thickness (0, 50, 150, 300, 500Å) and constant m -LPPP layer thickness (900Å). A difference in the device parameters and performance as a function of the Alq3 layer thickness is observed. We analyze these results with respect to the internal electric field distribution of the double layer devices derived from electroabsorption measurements.