bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Si(100) Surface Roughness at the Initial Stage of Etching in F2 and XeF2 Gases - Ellipsometric Study
Authors: Aliev V.S. , Kruchinin V.N.
Published: April 2011

The development of the roughness of the Si (100) surface has been investigated at the initial stage of etching in the molecular flow of F2 and XeF2 gases. It was discovered that roughness grew during etching in XeF2 gas and decreased during etching in F2 gas, that is, F2 gas polishes Si surface unlike XeF2. This difference was explained with the help of ellipsometric study of the kinetics of adsorption layer formation.
Impact of Chemical and Epitaxial Treatment on Surface Defects on Silicon Wafers
Authors: Schmolke R. , Gräf D. , Suhren M. , Kirchner R. , Piontek H. , Wagner P.
Published: April 2011

Defects on polished as well as hot SC1 treated silicon wafers were investigated with an Atomic Force Microscope (AFM) and Surface Scanning Inspection Systems (SSIS). Measurement with two SSIS of different type allows to identify most of the surface defects as non particulate scatterers. AFM of these defects reveals tiny pits or groups of pits. An almost linear relation is found between the geometrical lateral defect dimension and their average size in units of LSE (Latex Sphere Equivalent; an effective measure for the scattering cross section) as reported by one of the SSIS for the defects on wafers treated with hot SC1. Growth rates of about 40 nmLSE/h are observed for the defects during subsequent treatments of wafers with hot SC1. The LSE-size distribution of as-grown defects with a peak at about 105 and 110 nmLSE is obtained for two types of wafer by modeling the defect evolution during hot SC1 treatment. The number of surface flaws ≥ 0.12 μmLSE on a substrate is reduced by two orders of magnitude for epitaxial layers as thin as 1.5 μm.
Comparison Of Gettering Ability between I/I Defects And Si Substrate
Authors: Horikawa Mitsuhiro , Kitano Tomohisa
Published: April 2011

A Si wafer is contaminated with 1.5 × 1013 Fe/cm3 and the Fe gettering ability of low dose I/I defects is compared with that of a Si substrate with/without a poly-silicon back seal. Polysilicon has higher gettering ability than I/I defects and prevents Fe from gettering at these defects. When there is no poly-silicon and temperature is as low as 700°C, however, I/I defects act as gettering sites for Fe, even if the dose is as low as 2 × 1013 cm−2. Fe gettering by I/I defects leads to a decrease in minority carrier diffusion length. DLTS measurement reveals that Fe getters at I/I defects in the interstitial atom state.
Interstitial Defect Reactions In Silicon
Authors: Zhao S. , Agarwal A. M. , Benton J. L. , Gilmer G. H. , Kimerling L. C.
Published: April 2011

The interaction between self-interstitials (Sii), impurities, and dopants in Si leads the formation of undesirable point defects which affect device operation. Electron beam irradiation has been used to generate Sii and initiate defect reactions, and the hierarchy and competition of interstitial defect reactions involving O, C, B, and P in Si have been explored by DLTS measurements. We describe the interstitial defect reactions as a three-step process: (i) displacement reaction for the generation of Sii, (ii) Watkins replacement reaction for the generation of C and B interstitials (Ci and Bi), and (iii) diffusion limited reaction for the formation of pairs. Within the framework of reaction kinetics, for the first time, we have successfully set up a nonlinear system model to simulate the reaction processes. The interstitial migration enthalpy and the pair formation capture radius are two parameters used in the model to describe long range migration and near neighbor interaction. The good agreement between the model and experiments not only supports the defect assignments by DLTS, but also provides an initial glimpse into the interaction of point defects in Si.
Effects of H+-Implantation On Electron Traps In N-Type Si Induced by P+ Pre-Implantation
Authors: Ito Akira , Iwata Hiroyuki , Tokuda Yutaka
Published: April 2011

The change of the concentration of electron traps in n-type Si induced by P+ implantation (300keV, l×109 cm−2) with subsequent H+-implantation has been studied by deep level transient spectroscopy. H+-implantation is performed at room temperature to a dose of 2×1010cm−2 in the range 30 to 120keV. First P+ implantation induces six electron traps (Ec-0.12, 0.15, 0.21, 0.26, 0.39, 0.49eV). H+-implantation additionally induces an electron trap (Ec-0.32eV) which is related to hydrogen. The subsequent H+-implantation partly decreases the concentration of the electron traps induced by P+ implantation, although it increases the concentrations near the H+ projected range. 30 keV H+-implantation is mdst effective to reduce the trap concentration. The reduction of the concentration of the traps is ascribed to the reaction of pre-existing defects with interstitial or vacancy defects formed by subsequent H+-implantation.
Evaluation Of Proton-Induced Deep Levels In n-Si
Authors: Kono K. , Kishimoto N. , Amekura H. , Saito T.
Published: April 2011

Deep level transient spectroscopy (DLTS) has been conducted to reveal electronic states of deep centers in n-Si, under 17 MeV-proton irradiation. The DLTS device was installed into the beam line of the cyclotron. The in-situ experiment was concentrated on, to study the dynamical defect evolution and the effect of irradiation temperature on the deep centers. DLTS signals of four deep levels E0-E3 were observed when n-Si was irradiated at 300 K. Three of the four peaks were identified as V-O, V-V2− and P-V centers, in comparison with the past data of electron irradiation. The other unknown level (EO) was located at 0.16 eV below the conduction band, and 0.02 eV lower than the V-O level. The E0 peak showed a characteristic behavior dependent on the irradiation temperature. The EQ did not emerge when irradiated at 200 K, but appeared after being annealed at 300 K following the 200 K irradiation. The evolution of these levels was consecutively investigated with accumulating the proton fluence and with annealing after the irradiation.
Effect Of Pressure On Boron Diffusion In Silicon
Authors: Zhao Yuechao , Aziz Michael J. , Mitha Salman , Schiferl David
Published: April 2011

We are studying the effect of pressure on boron diffusion in silicon in order to better understand the nature of the point defects responsible for diffusion. Si homoepitaxial layers deltadoped with boron were grown using molecular beam epitaxy. Diffusion anneals were performed in a high temperature diamond anvil cell using fluid argon as a pressure medium. Diffusivities were deduced from B concentration-depth profiles measured with using secondary ion mass spectrometry. Preliminary results indicate that pressure enhances B diffusion in Si at 850 °C, characterized by an average activation volume of -0.125±0.02 times the atomic volume, and thus appear consistent with an interstitial-based diffusion mechanism. Results are compared with previous hydrostatic-pressure studies, with results in biaxially strained films, and with atomistic calculations of activation volumes for self diffusion.
The Effect Of Ion-Implantation Induced Defects On Strain Relaxation In GexSi1−x/Si Heterostuctures
Authors: Glasko J. M. , Zou J. , Cockayne D. J. H. , Gerald J. Fitz , KringhøJ P. , Elliman R. G.
Published: April 2011

This study examined the effect of ion irradiation and subsequent thermal annealing on GeSi/Si strained-layer heterostructures. Comparison between samples irradiated at 253°C with low energy (23 keV) and high energy (1.0 MeV) Si ions showed that damage within the alloy layer increases the strain whereas irradiation through the layer/substrate interface decreases the strain. Loop-like defects formed at the GeSi/Si interface during high energy irradiation and interacting segments of these defects were shown to have edge character with Burgers vector a/2<110>. These defects are believed responsible for the observed strain relief. Irradiation was also shown to affect strain relaxation kinetics and defect morphologies during subsequent thermal annealing. For example, after annealing to 900°C, un-irradiated material contained thermally-induced misfit dislocations, while ion-irradiated samples showed no such dislocations.
Effect of Stresses on Defect Nucleation in Si1−.xGex/Si Heteroepitaxial Systems
Authors: Ozkan Cengiz S. , Nix William D. , Gao Huajian
Published: April 2011

Strained layer semiconductor structures provide possibilites for novel electronic devices. When a semiconductor layer is deposited epitaxially onto a single crystal substrate with the same structure but a slightly different lattice parameter, the semiconductor layer grows pseudomorphically with a misfit strain that can be accomodated elastically below a critical thickness. When the critical thickness is exceeded, the elastic strain energy builds up to a point where it becomes energetically favorable to form misfit dislocations. In the absence of a capping layer, surface roughening may also take place which causes strain relaxation in the form of 2D ridges or islands via surface diffusion. At sharp valley regions on the surface, amplified local stresses can cause further defect nucleation and propagation. These defects can be detrimental to the electrical performance of devices by acting as electron-hole recombination centers or current leakage channels. In this paper, we present observations and analyses of two novel defects nucleated in heteroepitaxial Si1−xGex thin films through surface roughening. Heteroepitaxial films 500 Å thick and containing 22% Ge are deposited by LPCVD. These initially flat films are subjected to various annealing conditions in a H2 atmosphere to induce morphological evolution and defect formation. High resolution transmission electron microscopy and atomic force microscopy have been used to study the morphology of defects at the film surface and at the film/substrate interface.
Characterization Of Hydrogen-Related Defects In Iron-Doped Indium Phosphide
Authors: Leigh W. B. , Bliss D. , Bryant G. , Iseler G. , Larkin J. , Wolk J.
Published: April 2011

We have investigated the effect of annealing on hydrogen-related donors in crystals of InP using Hall effect, infrared absorption, and photorefractive gain measurements. Hydrogen is believed to be incorporated during growth, forming a donor complex around an indium vacancy with hydrogen saturating all four dangling bonds. By observing the local vibrational mode of the hydrogen complex using infrared absorption at 2316 cm−1 was possible to observe a decrease in the concentration of the hydrogen defect after annealing. In the undoped crystal, the disappearance of this defect is accompanied by a decrease in the free carrier concentration as measured by Hall effect. These changes are correlated with a decrease in the absorption due to Fe2+ centers, which form when donors are compensated by the neutral acceptor Fe3+. The existence of the hydrogen-related donor complex is further substantiated by photorefractive experiments using 1064nm irradiation on the iron doped samples. All of the measurements point to the role of hydrogen as a contributor to the net shallow donor concentration in InP crystals.
Long-Living Shallow Donor Excited States And Fir-Ir Up-Conversion In Gap:Te
Authors: Ganichev S. D. , Yassievich I. N. , Raab W. , Zepezauer E. , Prettl W.
Published: April 2011

Tellurium donors in GaP have been ionized by phonon assisted tunneling in the electric field of pulsed far-infrared laser radiation. In response to the laser pulse a photoconductive signal has been detected with a fast component reproducing the laser pulse and a slow component which rises after the irradiation has ceased and finally exponentially decays with a strongly temperature dependent time constant in the range of microseconds to several milliseconds. This temporal structure of the signal is explained by a cascade capture mechanism and subsequent accumulation of carriers in a long-living shallow donor excited state, identified as valley-orbit split 1s(E) level of Te. The final step of recombination is achieved by radiative transitions, which is proved by the observation of far-infrared to mid-infrared up-conversion.
A Refined Model For Threading Dislocation Filtering In InxGa1−xAs/GaSAs Epitaxial Layers
Authors: Macpherson G. , Goodhew P. J.
Published: April 2011

A model is presented for the filtering of threading dislocations in InxGa1−xAs/GaAs epitaxial single layers by accurate control of the layer thickness. The model developed differs from previous models since the InxGa1−xAs growth is restricted to less than ten times the Matthews and Blakeslee critical thickness (hc) where the asymmetry in the [110] and [110] dislocation densities is the greatest. Beyond this thickness it is shown that the removal or annihilation of threading dislocations (TDs) in the epilayer is more than offset by the introduction of new TDs from spiral and Frank-Read type sources. Results from strain sensitive etching with CrO3 aqueous solutions show that the TD density can be reduced by up to a factor of ten below that found in the substrate. Atomic force microscopy shows that these thin layers maintain a high level of surface quality with an absence of striations. Evidence is also shown that this type of defect etching is suitable for revealing large scale dislocation blocking in samples that have been grown significantly beyond 10hc.
Electrical Characterization Of Defects Introduced During Plasma-Based Processing Of GaAs
Authors: Auret F. D. , Myburg G. , Meyer W. E. , Deenapanray P. N. K. , Nordhoff H. , Murtagh M. , Ye Shu-Ren , Masterson H. J. , Beechinor J. T. , Crean G. M.
Published: April 2011

DLTS revealed that each plasma type (He and SiCl4) introduced its own characteristic set of defects. Some of the defects created during He processing and one defect introduced by SiCl4 etching had identical electronic properties to those introduced during high energy (MeV) He ion bombardment. SiC14etching introduced only two prominent defects, one of which is metastable with electronic properties similar to a metastable defect previously reported in high and low energy He-ion bombardment of Si-doped GaAs. IV measurements demonstrated that the characteristics of SBDs fabricated on He-ion processed surfaces were very poor compared to those of control diodes (diodes fabricated on surfaces cleaned by conventional wet etching). In contrast, the properties of SBDs fabricated on SiCl4 etched surfaces were as good as, and in some cases superior to, those of control diodes. SBDs fabricated on annealed (at 450°C for 30 minutes) He-processed samples exhibited improved but still poor rectification. In contrast, SBDs fabricated on annealed SiCl4 etched surfaces had virtually the same characteristics as those fabricated on unannealed SiCl4 etched samples.
Photoluminescence And Electron Paramagnetic Resonance Of Nitrogen-Doped Zinc Selenide Epilayers
Authors: Moldovan M. , Setzler S.D. , Yu Z. , Myers T.H. , Halliburton L.E. , Giles N.C.
Published: April 2011

Photoluminescence (PL) and electron paramagnetic resonance (EPR) studies were performed on a series of ZnSe samples grown by molecular beam epitaxy. The PL has been studied as a function of excitation wavelength, power, temperature, and time. The PL data indicates that the broad emission from a heavily nitrogen-doped ZnSe film is composed of three distinct recombination processes. The EPR spectra taken at 8 K and 9.45 GHz show an isotropic signal at g = 2.0027(3) which we attribute to singly ionized selenium vacancies (Vse+). The PL and EPR data help to clarify the role of defects in the compensation of heavily nitrogen-doped ZnSe thin films.
Surface Of Li-Doped ZnSe Grown On Misoriented GaAs(001) Substrates
Authors: Yoneta Minoru , Ohishi Masakazu , Saito Hiroshi , Ohura Mitsuhiro , Fujii Katsumoto , Hioe Yoshihiko
Published: April 2011

The surface of Li-doped ZnSe grown on misoriented GaAs(001) substrates by molecular beam epitaxy is studied by means of reflection high energy electron diffraction. Sharp and curved streaky RHEED patterns are observed for all the layers grown on the misoriented substrate towards [110], irrespective of off-angles. No curved pattern, however, is observed on ZnSe layers grown on misoriented GaAs(001) towards [110] with off-angle larger than 5°. We confirmed that the Li-array is surely formed along [110], and that the length of the Li-array is longer than 32Å to be observable as curved streaks. It is also confirmed that the growth rate of Li-doped ZnSe is proportional to the step density, and that the growth rate on the misoriented substrate towards [110] is higher than that on the misoriented substrate towards [110]. The photoluminescence spectra of Li-doped ZnSe layers grown on misoriented GaAs are reported.
Damage Induced By A Low-Biased 92-MHz Anode-Coupled Reactive Ion Etcher Using Chlorine-Nitrogen Mixed Plasmas
Authors: Saitoh Tadashi , Gotoh Hideki , Sogawa Tetsuomi , Kanbe Hiroshi
Published: April 2011

Dry-etch damage, introduced by a low biased 92-MHz anode-coupled reactive ion etching (RIE), in MBE-grown undoped GaAs has been characterized by photoreflectance (PR) and photoluminescence (PL) measurements. PL spectra show emission peaks at 1.516 eV (excitons) and at 1.494 eV (D-A, B-A) before etching, whereas a new emission peak at around 1.488–1.490 eV appears after the RIE. The depth distribution of this new emission center, examined by PL measurements with a combination of step wet etching, has a Gaussian-shape with a l/e value of 56 nm. A very small number of nonradiative recombination centers are considered to be generated, because the integrated PL intensity including both emission peaks at 1.490 eV and at 1.516 eV is the same before and after the RIE. The surface recombination rate of the sidewall formed by the RIE is almost the same as that of the wet-etched surface. This low-damage etching has been applied to fabricate ultra-fine GaAs patterns to provide a nanometer-scale ridge structure with a cross-section 15-nm wide by 150-nm high. The low damage etching condition is also suitable for precise fabrication.
Electronic Properties Of Defects Formed In n-Si During Sputter-Etching In An Ar Plasma
Authors: Deenapanray P. N. K. , Auret F. D. , Schutte C. , Myburg G. , Meyer W. E. , Malherbe J. B. , Ridgway M. C.
Published: April 2011

We have employed current-voltage (IV), capacitance-voltage (CV) and deep level transient spectroscopy (DLTS) techniques to characterise the defects induced in n-Si during RF sputter-etching in an Ar plasma. The reverse leakage current, at a bias of 1 V, of the Schottky barrier diodes fabricated on the etched samples was found to decrease with etch time reaching a minimum at 6 minutes and thereafter increased. The barrier heights followed the opposite trend. The plasma processing introduced six prominent deep levels below the conduction band of the substrate. A comparison with the defects induced during high energy (MeV) alpha-particle, proton and electron irradiation of the same material revealed that plasma-etching created the VO- and VP-centres, and V2-10. Some of the remaining sputter-etching-induced (SEI) defects have tentatively been related to those formed during either 1 keV He- or Ar-ion bombardment.
Diamondlike Carbon Materials as Low-k Dielectrics for Multilevel Interconnects in Ulsi
Authors: Grill A. , Patel V. , Saenger K.L. , Jahnes C. , Cohen S.A. , Schrott A.G. , Edelstein D.C. , Paraszczak J.R.
Published: April 2011

A variety of diamondlike carbon (DLC) materials were investigated for their potential applications as low-k dielectrics for the back end of the line (BEOL) interconnect structures in ULSI circuits. Hydrogenated DLC and fluorine containing DLC (FDLC) were studied as a low-k interlevel and intralevel dielectrics (ILD), while silicon containing DLC (SiDLC) was studied as a potential low-k etch stop material between adjacent DLC based ILD layers, which can be patterned by oxygen-based plasma etching

It was found that the dielectric constant (k) of the DLC films can be varied between >3.3 and 2.7 by changing the deposition conditions. The thermal stability of these DLC films was found to be correlated to the values of the dielectric constant, decreasing with decreasing k. While DLC films having dielectric constants k>3.3 appeared to be stable to anneals of 4 hours at 400 °C in He, a film having a dielectric constant of 2.7 was not, losing more than half of its thickness upon exposure to the same anneal. The stresses in the DLC films were found to decrease with decreasing dielectric constant, from 700 MPa to about 250 MPa. FDLC films characterized by a dielectric constant of about 2.8 were found to have similar thermal stability as DLC films with k >3.3. The thermally stable FDLC films have internal stresses <300 MPa and are thus promising candidates as a low-k ILD.

For the range of Si contents examined (0-9% C replacement by Si), SiDLC films with a Si content of around 5% appear to provide an effective etch-stop for oxygen RIE of DLC or FDLC films, while retaining desirable electrical characteristics. These films showed a steady state DLC/SiDLC etch rate ratio of about 17, and a dielectric constant only about 30% higher than the 3.3 of DLC.
Optimization of AICu Wiring Delay in Advanced CMOS Technology
Authors: Stamper A. K. , McGahay V. , Shapiro M. , Miller L. A. , Tian X. , Bryant A. , Serianni L. A.
Published: April 2011

Fluorinated high-density plasma and plasma-enhanced CVD SiO2 inter-metal dielectrics have been evaluated for 0.50- through 0.25- μm generation CMOS. Several integration issues are discussed, including the impact of fluorine-doped SiO2 on the yield, reliability, and RC delay of 0.7 - 1.8 μm pitch back-end-of-the-line AlCu/tungsten-stud wiring.
Interconnect Process Technology Using Perfluorocyclobutane (PFCB)
Authors: Townsend P. H. , Shaffer E. O. , Mills M. E. , Blackson J. , Radler M. J.
Published: April 2011

A novel polymer dielectric derived from tris-perfluorocyclobutene(PFCB) monomer has been investigated as a thin film dielectric. The dielectric constant of this material has been measured at 2.35. PFCB is applied from a hydrocarbon solvated solution using conventional spin coating equipment onto the substrate and produces highly uniform films after curing at 300 °C.

This paper describes the processing and properties of films derived from PFCB, and examines the interactions between the polymer and metals at the interfaces. In particular, the interfaces formed by the deposition of Cr or Co onto PFCB are unchanged after 30 minutes at 390 °C. The interface formed by the application of the polymer onto Ta is similarly unaffected by high temperatures. The interfaces formed by the deposition of Ta or Ti onto the polymer surface did not remain intact, with substantial quantities of the metals permeating the polymer after high temperature exposures. This behavior is discussed relative to the thermo-physical properties of the metal fluorides.
Toughened, Inorganic-Organic Hybrid Materials for Microelectronic Application
Authors: Hedrick J. L. , Srinivasan S. , Cha H.-J. , Yoon D. , Flores V. , Harbison M. , Pietro R. Di , Hinsberg W. , Deline V. , Brown H. R. , Sherwood M. , Paulson E. , Miller R. D. , Cook R. , Liniger E. , Simonyi E. , Klaus D. , Cohen S. , Hummel J.
Published: April 2011

Transparent, nanophase-separated, inorganic-organic hybrid polymers with dielectric constants below 3.0 have been prepared from reactively functionalized poly(amic ester) derivatives and substituted, oligomeric silsesquioxanes. These hybrid materials are stable to 400 °C and above and form tough, crack-free films. Induced cracking and crack propagation studies performed with the application of external stress suggest a maximum critical film thickness of at least 2.0 μm under severe stress conditions. These hybrid materials appear to be significantly toughened by the chemical incorporation of the polyimides relative to organically modified silicates and spin-on-glasses without significantly effecting other important polymer properties of the silicates.
Mechanical and Dielectric Properties of Low Permittivity Dielectric Materials
Authors: Alptekin A. , Czeremuszkin G. , Martinu L. , Meunier M. , Sacher E. , DiRenzo M.
Published: April 2011

The dielectric and mechanical properties of low permittivity dielectric/metal system consisting of fluoropolymers and copper were studied. The types of polymers in this study include sputtered Teflon, plasma-deposited fluoropolymers and the soluble Teflon AF1600. All these fluoropolymers have dielectric constants below 2.0 and dissipation factors below 0.001. Copper was either evaporated or sputtered. Adhesion of copper to fluoropolymers was studied using scratch and peel tests. Different thermal treatment techniques were applied to enhance adhesion, including preannealing in vacuum or in atmosphere, as well as postannealing in vacuum. The results show generally poor adhesion for evaporated copper, with substantial improvement for sputtered copper; however thermal treatments enhance adhesion in some cases. FTIR, surface tension and XPS experiments were carried out in an effort to understand these effects. Our findings will be discussed in terms of the various effects contributing to copper/fluoropolymer adhesion.
Evaluation of PTFE Nanoemulsion as a Low Dielectric Constant Material ILD
Authors: Sun S. C. , Chiang Y. C. , Rosenmayer C. T. , Teguh J. , Wu H.
Published: April 2011

Polytetrafluoroethylene (PTFE) has been studied as a low dielectric constant material for ULSI. A novel nanoparticle dispersion of PTFE was developed that permits the spin-coat deposition of PTFE with a thickness range of 0.2 to 1.5 μm. These PTFE nanoemulsions are aqueous emulsions containing sub-50 nm size PTFE particles and surfactant that are thermodynamically stable, optically clear, and have low viscosity and surface tension. The films cast from this nanoemulsion are uniform in thickness with a standard deviation of < 2%. From FTIR spectra, significant amounts of C-F bonds (1153 cm−1 and 1211 cm−1) are detected in the films. The index of refraction from ellipsometry measurement is about 1.35 and the dielectric constant measured from high frequency C-V curves is about 1.85. The dielectric strength is about 170 V/ μm. TGA data indicates a weight loss rate of less than 0.25%/hr. at 425 °C. The moisture absorption is less than 0.01%. After sintering, the films are extremely resistant to chemical attack by sulfuric acid, buffered HF, and positive photoresist developer. The etch rate in an oxygen plasma at 30 W is around 200 nm/min. Stud pull tests indicate good adhesion to SiO2, Al, and Cu. Results of thermal, dielectric, chemical, and adhesion tests indicate that these PTFE films have potential for use as an integrated circuit dielectric material.
Optimization of Pecvd Sin Films Using A Statistically Designed Experiment
Authors: Brierley Steven K. , Kazior Thomas E. , Nguyen Lan
Published: April 2011

A statistically designed experiment was run to optimize the deposition of PECVD SiN on GaAs substrates. Five deposition parameters were varied: RF power, temperature, pressure, plasma frequency, and ammonia/silane ratio. Four film properties were used to evaluate the quality of the nitride: the fraction of hydrogen bound to nitrogen atoms, the index of refraction (and its uniformity), thickness uniformity, and stress. From the screening phase of the experiment, it was determined that only the plasma frequency and ammonia/silane ratio influenced the quality of the nitride film. High frequency deposition was preferable to low frequency deposition since it resulted in lower film stress. The results of the optimization phase showed that SiN films with near‐zero stress, low N‐H bond density and good index of refraction could be obtained by deposition at a very low ammonia/silane ratio.
Effect of Oxygen Dose Variation on the Simox Microstructure
Authors: Datta R. , Krishnamoorthy V. , Allen L.P. , Chandonnet R. , Farley M. , Jones K. S.
Published: April 2011

The effect of oxygen dose variation on the SIMOX SOI structure has been investigated extensively in this work. Keeping other implantation parameters constant, the dose has been varied from 0.2x1018cm–2 to 1.4xl018cm–2. Our studies show that a critical dose exists for a particular implant energy, below which a continuous buried oxide layer does not form. Further, the SiO2 precipitates enhance the pinning of defects in the as-implanted state which subsequently grow into threading dislocations. A dose window exists, where the dislocation density is a minimum.

The oxygen depth distribution in the as-implanted and annealed state has been studied using SIMS. HRXRD measurements have been performed to reveal the strain state as a function of dose variation. The defect microstructure has been investigated using PTEM, XTEM and Secco Etching. AFM studies show the quality of the Si surface and Si/BOX (Buried OXide) interface roughness. This work gives us a fundamental understanding of the evolution of the defect microstructure and strain from the as-implanted to the annealed state using independent implantation parameter control.
Growth of Transparent SiO2 Thin Film on Silicon at Room Temperatüre by Using I72nm Xe2* Excimer Lamp
Authors: Suzuki T. , Murahara M.
Published: April 2011

SiO2 insulator was fabricated by using Xe2* excimer lamp at room temperature. In this method, a mixrine of NF3 and O2 gases was employed as a reaction gas. When the NF3 and O2 gases were exposed to the Xe2* excimer lamp light NF3 and O2 gases inside the chamber where Si substrate was placed, SiFn and NO2 were produced by photo‐chemical reaction. The SiFn accumulates on the Si substrate, and SiO2 is formed by oxidation reaction between SiFn and NO2. Subsequently SiFn adheres onto the formed SiO2 and again oxidizes by NO2. These processes occur spontaneously, and on SiO2 film is grown. Experimental conditions were NF3:O2 = 10:1, the total gas pressure 330 torr, photo‐chemical reaction time 5 minutes, and chain reaction time 5 minutes. The results of the film characterization were a SiO2 film thickness of about 1500Å, a refractive index of 1.38, specific resistance of 1.67*1010 Ω cm and relative dielectric constant of 6.96.
Preparation and Physical Properties of BI2TI2O7 Single Crystal Thin Film on SI (100) Substrate by Mocvd
Authors: Wang Hong , Shang S. X. , Su X. J. , Wang Z. , Wang M.
Published: April 2011

Insulating thin films of Bi2Ti2O7 with (111) orientation have been prepared on silicon (100)–substrates at a temperature range of 480–550 °C by a MOCVD technique. The dielectric and C‐V properties were studied. The dielectric constant (ɛ) and loss tangent (tanδ) were found to be 180 and 0.01, respectively. The temperature and frequency dependence of dielectric constant were also measured. The Bi2Ti2O7 films are suitable to be used as a novel buffer layer and new insulating gate material in FET devices.
Sputtered Barium Titanate Films for Capacitor Applications
Authors: Hung Tsao Bang , Fries Carr Sandra , Weimer Joseph A.
Published: April 2011

BaTiO3 films prepared by RF sputtering was studied for capacitor applications. Some films produced have a capacitance storage of 0.85 μF/cm2, a high resistivity of 1014 ω‐cm, and a low dissipation factor of 0.005. The dielectric constant of these BaTi03 films were approximately 10 to 30, which is superior to that of the typical polymer film capacitor and had little dependence on frequency. However the breakdown strength of BaTi03 was approximately 5MV/meter. The theoretical breakdown strength of BaTi03 is reported to be as high as 200MV/m. The processing parameters of BaTi03 films must be optimized to obtain the potential benefit of the BaTi03.
Chemical Vapor Deposition and Properties of Amorphous Aluminum Oxide Films
Authors: Gordon Roy G. , Kramer Keith , Liu Xinye
Published: April 2011

Films of amorphous aluminum oxide were deposited from vaporized alkylaluminum alkoxide compounds and oxygen. For example, a gaseous mixture of triethyldialuminum tri-sec-butoxide vapor and dry air deposits amorphous aluminum oxide films on substrates heated to temperatures around 400 °C. Transparent, smooth, adherent films of aluminum oxide were formed on silicon, glass and metal substrates. The new precursors display a number of advantages over previously used sources for aluminum oxide. They are non-pyrophoric, low-viscosity, low-cost liquids. High deposition rates, over 0.2 μm/min, were observed. The coatings have high purity, high electrical resistivity and high transparency to light. They are excellent barriers to diffusion of water and of ions, such as sodium. These films are useful in optical coatings, as wear-resistant hard coatings, and as diffusion barriers that protect flat panel displays, computer microcircuits, solar cells and metals from corrosion and degradation by impurities.
Doped Yttrium Iron Garnet (Yig) Thin Films For Integrated Magneto-Optical Applications
Authors: Stadler Bethanie J.H. , Li Yi-Qun , Cherif Mondher , Vaccaro Kenneth , Lorenzo Joseph P.
Published: April 2011

A novel single-source MOCVD technique was used to deposit Ce:YIG ((Ce,Y)3Fe5O12) films which were investigated for integrated magneto-optical applications, such as waveguide isolators. These films were grown on gadolinium gallium garnet substrates in order to optimize the growth conditions before growth on semiconductor substrates was attempted. We were able to achieve very high ratios of Ce:Y (= 0.4) due to the nonequilibrium nature of MOCVD. Ce:YIG films on GGG substrates were epitaxial with excellent optical and magnetic properties, along with high Faraday rotations that were comparable to commercial Bi:YIG. Planar waveguiding was observed in Ce:YIG films on both GGG and MgO substrates. MgO also proved to be a successful buffer layer for protecting the semiconductor substrates during YIG deposition. The Ce:YIG films on MgO-buffered GaAs had very promising magnetic properties, but the MgO deposition on InP must be optimized before successful Ce:YIG films on InP can be achieved.
Raman and Ft‐Ir Study on Structure and Its Stability of Hydrogenated Amorphous Germanium‐Nitrogen Alloys
Authors: Xu Jun , Chen Kunji , Feng Duan , Miyazaki Seiichi , Hirose Masataka
Published: April 2011

A series of hydrogenated amorphous germanium‐nitrogen (a‐GeN:H) alloys have been synthesized by plasma enhanced chemical vapor deposition. The structure and its thermal stability have been investigated by means of Raman Scattering and Fourier Transform Infrared techniques. It was found that the structure is changed from Ge‐Ge‐like to Ge‐N‐like when the nitrogen content x in a‐Ge1‐xNx:H is larger than 0.3. Some a‐GeN:H alloys were annealed for 30min at different temperature and it is shown that the film structural stability is significantly improved compared with pure a‐Ge:H film.
Investigation of Dipolar Relaxation Processes in a Side-Chain Nonlinear Optical Polymer
Authors: Cheng Z. -Y. , Katiyar R. S. , Bauer S. , Bauer-Gogonea S.
Published: April 2011

Amorphous thin films of a typical side-chain nonlinear optical polymer were investigated by means of dielectric spectroscopy and thermally stimulated depolarization current (TSDC) within the temperature range -40°C to 230°C. Three distinct relaxation processes, labelled α, β and γ were observed. The α-relaxation, associated with the glass transition, is well described by the Vogel-Fulcher relation, while the sub glass transition β and γ-relaxation follow Arrhenius relations. The advantage of TSDC over dielectric spectroscopy is demonstrated for the investigation of the weak β-relaxation in the side-chain polymer. Furthermore, the β -relaxation is responsible for the initial, fast decay of the electro-optical response of the side-chain polymer at room temperature.
Minimization of Di Water Consumption In Wet Clean Rinse Tanks
Authors: Cook J.
Published: April 2011

The use of resistivity‐monitored dump‐rinse tanks in semiconductor wet processing allows the rinse process to be optimized, substantially reducing DI water consumption while minimizing the deleterious effects of water on bare silicon surfaces. Optimization experiments performed on the Metals wet clean hoods at ACT yielded optimum rinse cycles consisting of two or three dump cycles plus an overflow rinse to 10ΜΩ, with a calculated savings of about 40,000 gallons of DI water (about 40%) per year compared to previously accepted standards. Experiments indicate that the time required for rinsing is a competing function of the effectiveness of each dump cycle and the time required to physically perform the chosen number of dump cycles.
In‐Situ Monitoring of Hf Reprocessing in an Industrial Scale Recirculator Bath
Authors: Reddy A.J. , Norga G.J. , Park A.S. , Smith A.L. , Michel J. , Kimerling L.C. , Parekh B. , Shyu J.‐H. , Deane E.
Published: April 2011

High chemical purity is essential for achieving satisfactory device yield in submicron CMOS processing. Reprocessing of liquid chemicals to maintain high purity can drastically reduce both environmental impact and cost of ownership (CoO) of wafer cleaning operations. We propose the use of a novel membrane Filter technology for control of contamination spikes and reduction of liquid chemical usage in pre‐gate HF cleaning. To ensure filter effectiveness, we have developed an in‐process sensor that monitors solution cleanliness by measuring the deposition rate of reducible ions on silicon. Metals are detected through their effect on the surface recombination of photoexcited carriers. This detection method allows quantification of copper and noble metal ions down to 108 atoms/cm2 levels. We have investigated the effect of chemical purity during HF cleaning on the gate oxide integrity (GOI) of 70–200 Å gate oxides. A significant increase in the low‐field breakdown is observed for HF‐last cleaning using chemicals containing more than 10 ppt Cu. We present the results of Cu spiking experiments to evaluate our ability to quantify contamination down to the stringent levels required for an industrial scale wet‐bench. We observe a linear correlation between metal deposition rate and Cu concentration in the 1–5 ppb range.
Perhalogenated Organic By-Products from Plasma Etching Processes and Their Effects on Human Health and Environmental Impact
Authors: Bauer S. , Wolff I.
Published: April 2011

Complex analytical and toxicological studies of the waste products from aluminium plasma etching were performed over a four-year period. Many different organic compounds were identified and quantified in the waste gases, vacuum pump oils, and the solid debris collected from the air pipe systems. The identified compounds were exclusively perhalogenated hydrocarbons. Toxicological investigations showed clear genotoxic, embryotoxic, and teratogenic effects resulting from the waste products.

The study left no doubt, that workers in semiconductor production processes are potentially in danger of coming in contact with small amounts of plasma by-products, either through accidents, maintenance procedures, or insufficient protection.
Spontaneous and Stimulated Intersubband Emission Under Optical Pumping
Authors: Boucaud P. , Sauvage S. , Gauthier-Lafaye O. , Moussa Z. , Julien F.-H. , Prazeres R. , Glotin F. , Ortega J.-M. , Planel R. , Leburton J. P. , Berger V. , Nagle J.
Published: April 2011

We have investigated the mid-infrared spontaneous and stimulated emission between confined subbands in the conduction band of GaAs/AlGaAs quantum wells. The carriers which give rise to the intersubband emission are excited in the upper subbands using an intersubband optical pumping in coupled asymmetric quantum wells. The quantum wells are designed using phonon engineering in order to obtain population inversion between the second and first excited subband. This is obtained by adjusting the subband energy spacing between E2 and E1 close to the optical phonon energy which in turn allows an efficient relaxation. We have first observed intersubband spontaneous emission between E3 and E2 at 14 μm using an intersubband pumping with a CO2 laser in resonance with the E1-E3 transition. In a second set of experiments, the quantum wells are embedded in an infrared waveguide. We have measured the stimulated intersubband gain using a picosecond two-color free electron laser. The first color bleaches the E1-E3 transition and provides the population inversion. The intersubband stimulated gain is measured versus the waveguide length and photon energy. Stimulated gains ≈ 80 cm−1 are reported thus demonstrating that laser emission under optical pumping appears feasible in optimized structures. Finally, we show that intersubband emission can also be observed in quantum wells using an interband optical pumping.
Stark Shift and Field Induced Tunneling in Doped Quantum Wells with Arbitrary Potential Profiles
Authors: Panda S. , Panda B. K. , Fung S. , Beling C. D.
Published: April 2011

The energies and resonance widths of single doped quantum wells consisting of Al-GaAs/GaAs with rectangular and annealing induced diffusion modified shapes are calculated under an uniform electric field using the stabilization method. The electronic structure is calculated without an electric field in the finite temperature density functional theory with exchange-correlation potential treated in the local density approximation. Our scheme for solving the Schrödinger and Poisson equations is based on the Fourier series method. The electric field is added to the self-consistent potential and energies are obtained as a function of the combined width of the well and barriers. This yields us the stabilization graph from which the energies and resonance widths at different field strengths are extracted using the Fermi Golden rule.
Normal Incidence Photoresponse as a Function of Well Width in P-Type GaAs/AlGaAs Multi-Quantum Wells
Authors: Brown G. J. , Capano M. A. , Hegde S. M. , Eyink K. , Szmulowicz F.
Published: April 2011

We have performed an optimization study of the mid-infrared photoresponse of p-type GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIPs) designed for normal incidence detection. In these p-type quantum wells, normal incidence absorption is allowed (by the dipole selection rules for optical transitions) especially for transitions from the heavy-hole ground state to the second light-hole state. Previous theoretical modeling predicted that this transition will produce the strongest bound-to-continuum infrared absorption when the second light-hole state is located very near the top of the GaAs quantum well. For AlGaAs barrier layers with 30% aluminum, our modeling showed that a well width between 45Å and 50Å would optimize the normal incidence photoresponse of this p-type QWIP. In this work, photore^oonse spectra are reported for well widths ranging from 40Å to 65Å. A series of samples were tudied in which only the GaAs well width was varied in two monolayer increments, from 11 to 20 monolayers. Photoluminescence and X-ray diffraction measurements were used to verify the composition, well width, and structural quality of each sample. This study verified that the spectral range of the normal incidence photoresponse is narrower, as predicted by theory, for well widths in which the second light-hole state approaches the top of the valence band well.
High Performance HgCdTe-Detectors Grown by Molecular Beam Epitaxy
Authors: Rajavel R. D. , Jamba D. M. , Jensen J. E. , Wu O. K. , Cockrum C. A. , Wilson J. A. , Patten E. A. , Kosai K. , Rosbeck J. , Goetz P. , Venzor G.
Published: April 2011

Molecular beam epitaxy (MBE) offers benefits such as the capability for growth of compositionally-tailored heterostructures and in-situ doping of HgCdTe alloys. These capabilities were applied to the growth of long wave infrared unispectral focal plane arrays (FPA) with 480×4 elements. The detectivity (D*) map of the FPA demonstrated performance that was higher than the specification value, with no defective channels. Two-color detectors with the n-p-n architecture, for the simultaneous detection of two closely spaced bands in the midwave infrared spectrum were also grown by MBE. These devices exhibited sharp turn-off and turn-on in both bands. The quantum efficiency was greater than 70% and average R°A values exceeded 1×106 Ω-cm2 in both bands. These result demonstrate that high performance HgCdTe devices can be grown by MBE.
The Role of Atomic Hydrogen for Substrate Cleaning for Growth of CdTe Buffer Layers at Reduced Temperatures on Silicon, CdTe, and HgCdTe
Authors: Hirsch L. S. , Yu Zhonghai , Richards-Babb M. R. , Myers T. H.
Published: April 2011

Atomic hydrogen is shown to be efficacious for cleaning CdTe and HgCdTe substrates for subsequent CdTe growth by molecular beam epitaxy. While single crystal ZnTe and CdTe growth was obtained on Si substrates that underwent an ex-situ HF-based etch, only polycrystalline CdTe or ZnTe could be obtained on surfaces cleaned using an atomic hydrogen source. This result is possibly related to gas-phase transport of Te to the Si surface.
Off-Area Bonding of HgCdTe Photoconductive Infrared Detectors using Tri-Layer Photolithography and Wet/Dry Etching Techniques
Authors: Manthripragada Sridhar , Hu Kelley , Peters Frank , Burgess Andre , Babu Sachidananda , Shi Jack , Krebs Danny , Mott D. Brent , Shu Peter
Published: April 2011

On-area wire bonding of HgCdTe photoconductive (PC) infrared detectors usually causes material damage underneath the bonding pads. Such damage may propagate into the active area, potentially degrading performance and posing long-term reliability problems. Some off-area bonding fabrication techniques can also induce some degree of semiconductor material damage. In this paper, we report a relatively straightforward off-area bonding scheme that solves these problems. The process uses multiple photolithography and chemical etching steps to create a continuous slope or staircase in the HgCdTe leading down to the epoxy surface. The staircase ensures smooth step coverage for the subsequent metalization. Tri-layer photolithography (resist /metal/resist) and reactive ion etching (RIE) is then used to remove the epoxy in the bonding pad area. Since all areas other than the pad region are protected by the metal film, no RIE radiation damage is induced to the active area. The contact metalization is achieved by using standard liftoff techniques. Our so called staircase off-area bonding fabrication technique can be used to fabricate highly reliable, high density, small-size, detector arrays.
Quantum Well Intermixing in Gain As/Gainasp and Gaas/Algaas Structures Using Pulsed Laser Irradiation
Authors: Bryce A. C. , De La Rue R. M. , Marsh J. H. , Ooi B. S. , Qiu B. , Button C.C. , Roberts J.S.
Published: April 2011

An essentially impurity free, direct write and potentially high spatial resolution quantum well intermixing technique using pulsed laser irradiation is reported. This technique uses a Q-switched Nd:YAG laser emitting at 1.06 μm with a pulse length of ∼20 ns and repetition rate of 10 Hz. The typical energy densities used for both Gain As/Gain AsP and GaAs/AlGaAs structures were ∼ 5 mJ mm−2. Multiphoton interactions with carriers lead to phonon emission, the phonons interact with the lattice thus generating point defects which diffuse during a subsequent annealing stage in a rapid thermal annealer and cause intermixing. Photoluminescence measurements have demonstrated that the spatial resolution of the process is better than the resolution of the PL measurement (ie better than 25 μm) and the technique has been used to write directly a grating of period 1.25 μm into a GalnAs/GalnAsP quantum well structure. This was achieved using a grating of period 2.5 μm etched into the surface of the substrate; when illuminated by the Q-switched pulses this grating generated a volume hologram of point defects within the sample at half the etched period. A clear dip in the transmission spectrum of the waveguide which had been processed in this way was observed at 1.525 μm. Differential bandgap shifts of up to 40 meV have been observed in GaAs/AlGaAs double quantum well samples. 3 μm wide ridge waveguide lasers were fabricated from the intermixed and control samples. The threshold currents of the intermixed and the control lasers were comparable. The slope efficiency of the intermixed lasers showed insignificant changes when compared to the as-grown lasers.