Diam Substrates Research Articles

Field Evaluation of Repellents and Insecticidal Aerosol Compositions for Repelling and Control of Siphunculina funicola (Diptera: Chloropidae) on Aggregation Sites in Thailand

The oriental eye fly Siphunculina funicola, a small member (1.5-1.6 mm) of the family Chloropidae, is extremely annoying to humans and domestic animals, feeding on mucous membranes, secretions, and other moist surfaces of their hosts. In central Thailand heavy populations were detected during 2006-2007 in some rural, agricultural, and periurban areas of the region. They were noted to exhibit strong synanthropy and aggregation behavior, congregating on thin (1-5 mm diam) substrates hanging in or near human habitations and animal shelters and other structures open on one or more sides. We initiated studies on the repelling and control of this eye fly at their aggregation sites, the most vulnerable targets near or in human habitations. Four formulations of repellents consisting of Everside, 3 fatty acids (with 8, 9, and 10 carbons), permethrin, and the acids C8910 plus permethrin in Everside were diluted 1:3 in tap water and sprayed on to the aggregation sites. Prior to treatment all sites including controls were disturbed to dislodge eye flies, and then the blank sites were sprayed with the aqueous suspension of the repellents. Additionally, we evaluated 3 commercially available household insecticidal aerosol formulations by treating eye flies and their resting sites (without dislodging the flies) with puffs of the aerosols. Two treatments with permethrin alone and permethrin plus acids in Nakhorn Ratchasima Province caused a complete absence of flies from the sites up to 23 h. After treatment with the repellents, the repelled flies and others were found to congregate on untreated favorable sites close to the treated ones. The repellents tested against eye flies in Chonburi Province at 2 locations caused almost complete absence of this insect on aggregation sites up to 120 h. Three household insecticide aerosols applied to aggregation sites with resting and hovering eye flies produced high to complete mortality and reduction of eye flies for 48 h or possibly longer in the treated sites. This is the first time that procedures for the evaluation of repellents and insecticides against eye flies have been tested and developed. The use of commonly available insecticide aerosol products could provide a good source of materials for the elimination of eye flies from their domestic and peridomestic aggregation sites.

Plasma and Thermal ALD of Al2O3 in a Commercial 200 mm ALD Reactor

The deposition of by remote plasma atomic layer deposition (ALD) in the Oxford Instruments FlexAL reactor was studied and compared with results from thermal ALD in the same reactor. Trimethylaluminum was used as the metal precursor and plasma and were used as oxidizing agents for the plasma and thermal processes, respectively. For remote plasma ALD with a total cycle time of , the growth per cycle decreased monotonically with substrate temperature, from at 25°C to at 300°C. This growth per cycle was consistently higher than that obtained for thermal ALD. For the latter a maximum growth per cycle of was found at 200°C. The film properties investigated were nearly independent of oxidant source for temperatures between 100 and 300°C, with a slightly higher mass density for the remote plasma ALD films. Films deposited at 200 and 300°C were stoichiometric with a mass density of and low C and H contents. At lower substrate temperatures, oxygen-rich films were obtained with a lower mass density and higher H-content. Remote plasma ALD produced uniform films with nonuniformities of less than over diam substrates. Excellent conformality was obtained for films deposited in macropores with an aspect ratio of . Preliminary results on electrical properties of remote plasma deposited films showed high dielectric constants of 7.8 and 8.9 for as-deposited and forming gas annealed , respectively.

溶液気化CVD法による(Ba, Sr) TiO<sub>3</sub>高誘電率薄膜形成

High dielectric constant (Ba, Sr) TiO3 [BST] films have been deposited by liquid source chemical vapor deposition (CVD) method. The system consisted of a single-wafer, low-pressure thermal CVD reactor, a vaporizer for liquid source materials, and a shower-type gas nozzle head, giving stable BST film deposition on a 6-in. -diam substrate with uniform thickness and uniform chemical composition ratio. The source materials employed were Ba(DPM)2, Sr(DPM)2, and TiO(DPM)2 dissolved in tetrahydrofuran (THF), resulting in a conformal step coverage of BST films at lowered substrate temperatures, where DPM denotes dipivaloylmethanato. Moreover, the two-step deposition technique was developed to restrain protrusions formed on BST film surfaces at low temperatures, where BST films consisted of a buffer layer and a main layer; the buffer layer was an about 60-Å-thick layer of CVD-BST films annealed in N2 ambience. Thus, the two-step CVD deposition of BST films on Pt and Ru electrodes achieved an equivalent SiO2 thickness of teq_??_0.5nm, a leakage current of JL_??_1.0×10-8A/cm2 (at+1.1V) and a dielectric loss of tan δ_??_0.01 at a total film thickness of 250Å, along with a comformal coverage of 80% for a trench of an aspect ratio of 0.65. Then, for BST films deposited on patterned electrodes 0.24μm wide, 0.60μm deep, and 0.15μm high (each spaced by 0.14μm), the capacitance was demonstrated to be increased without a significant deterioration of the leakage current: the capacitance was measured to be increased in comparison with that for films on flat electrodes, by a factor corresponding to an increase in surface area due to sidewalls of storage-node-like pattern features. This capacitance increase reflects the most characteristic advantage of CVD, or an excellent step coverage on microscopic pattern features. These electrical properties obtained satisfy specifications of a capacitor for Gb-scale dynamic random access memories (DRAMS), giving a storage capacitance of more than 25fF/cell for a stacked capacitor having a storage node 0.2_??_0.3μm high.

A tungsten filament high temperature heater for thin film deposition

A reliable high temperature substrate heater for thin film deposition was constructed. The heater has a modular design and is built from parts that are easy to fabricate. The heater consists of a square arrangement of four tungsten filaments in a disk-shaped molybdenum susceptor. The electrical connections are placed near the edge where they are easily accessed. A finite element analysis shows that this design produces a more uniform temperature distribution than typical radial arrangements of filaments. The excellent performance of the new heater is demonstrated by thickness variations of less than 2% in thin films of lithium tantalate films grown on a 3.75 cm diam substrate by a high vacuum metal-organic chemical vapor deposition process.

Siamese cell for group V flux measurements, uniform arsenide phosphide alloys, and quaternary lasers

We have used an effusion cell with independently valved solid arsenic and red phosphorus sources and a common cracking zone to prepare extremely uniform composition GaAs(1−x)Px epitaxial films on 3 in. diam substrates. Mass spectrometry and ion gauge measurements of dimer species allowed determination of ionization sensitivities for phosphorus and arsenic species in good agreement with the relationship of Flaim and Ownby [J. Vac. Sci. Technol. 8, 661 (1971)]. From the mass spectrometer data, it was possible to determine the thermodynamic equilibrium constant 1.9+/−0.4, and hence free energy −0.55 eV molecule−1 for the process As2+P2■2 AsP. Finally double heterojunction GaInAsP/InP lasers grown with this cell and operating at room temperature have transparency threshold currents below 800 A cm−2.

Low oxygen and carbon incorporation in AIGaAs using tritertiarybutylaluminum in organometallic vapor phase epitaxy

High-quality AIGaAs epilayers have been grown by low pressure organometallic vapor phase epitaxy with a new aluminum precursor tritertiarybutylaluminum (TTBAl). Layers grown at 650°C have a featureless mirror surface morphology and strong room temperature photoluminescence. Carbon was not detectable in chemical analysis by secondary ion mass spectroscopy, nor in low temperature (4K) photoluminescence spectra. Oxygen concentration in Al0.25Ga0.75As is as low as ∼2−3 × 1017 cm−3. Nominally undoped AIGaAs layers exhibit n-type conductiv-ity with electron concentrations at ∼ 1−1.5 × 1016 cm−3. A high degree of compo-sitional uniformity over 5 cm diam substrates (0.268 ±0.001) was obtained. These results indicate the potential for TTBA1 as an aluminum precursor for low temperature growth of Al-containing III-V alloys.

Manifold arsenic and phosphorus effusion source for GaAsP alloys

We describe an independently valved solid arsenic and phosphorus effusion source for molecular beam epitaxy. A common posteffusion hot zone and orifice ensure constant flux ratios of arsenic, phosphorus, and mixed species in the beam. With this source, we have demonstrated molecular beam epitaxial growth of GaAs1−xPx layers with better than ±0.4% compositional variation over a 3-in.-diam substrate.

Large area depositon of Cd1-xZnxTe on GaAs and Si substrates by metalorganic chemical vapor deposition

Results of large-area (up to 1000 cm2/run) Cd1-xZnxTe heteroepitaxy on both GaAs and GaAs/Si substrates by metalorganic chemical vapor deposition (MOCVD) are presented. Cd1-xZnxTe (x = 0-0.1) films exhibited specular surface morphology, 1% thickness uniformity (standard deviation), and compositional uniformity (Δx) of ±0.002 over 100 mm diam substrates. For selected substrate orientations and deposition conditions, the only planar defects exhibited by (lll)B Cd1-xZnxTe/GaAs/Si films were lamella twins parallel to the CdTe/GaAs interface; these do not propagate through either the Cd1-xZnxTe layer or subsequently deposited liquid phase epitaxy (LPE) HgCdTe layer(s). Background Ga and As-impurity levels for Cd1-xZnxTe on GaAs/Si substrates were below the secondary ion mass spectroscopy detection limit. Preliminary results of HgCdTe liquid phase epitaxy using a Te-rich melt on Si-based substrates resulted in x-ray rocking curve linewidths as narrow as 72 arc-sec and etch-pit densities in the range 1 to 3 x 106 cm2.

Silicon Carbide Wafer Bonding

layers produced on Si substrates by rapid thermal chemical vapor deposition have been transferred onto oxidized Si substrates by bonding and etchback. For films with a mean surface roughness of about 20 Å room temperature bonding to smooth oxidized Si wafers is possible under the influence of an external force. For 4 in. diam substrates, bonding of ∼85% of the area was obtained. Sections of the layer of the bonded pair peeled off when the Si substrate of the layer is thinned down to ∼150 μm and below. This is probably caused by the low interface fracture energy due to trapped air at the bonding interface and by outgassing from the thermal oxide of in addition to the film stress. Multistep annealing at 1100°C between etches of the Si substrate can enhance the interface fracture energy of the bonded pairs. A densification step of the thermal oxide after dry oxidation helps to reduce the trapped gas in the oxide. Auger and transmission electron microscopy results have verified that the transferred layer retains its original properties.

High quality YBCO films grown over large areas by pulsed laser deposition

High quality films of YBCO have been grown in situ by pulsed laser deposition (PLD) on small samples as well as both 5 cm (2 in.) and 7.6 cm (3 in.) diam (100) LaAlO3 and 5 cm (100) NdGaO3 substrates. Films grown on small LaAlO3 and NdGaO3 substrates display critical temperatures Tc in excess of 89 K while critical current densities Jc of 5 MA/cm2 at 77 K have been obtained. Films grown on 5 cm diam substrates display Tc’s in excess of 89 K, and Jc’s in excess of 2 MA/cm2 at 77 K. Also, a patterned three-piece strip line resonator (1.56 GHz fundamental frequency) fabricated using samples cut from a 5 cm diam LaAlO3 substrate yielded a microwave surface resistance Rs of 700 μΩ at 77 K when scaled to a frequency of 10 GHz. Substrates were radiatively heated without the use of absorbing layers such as nickel or thermally conductive layers such as silver paint or indium, thus making backside film deposition a clean and simple process. YBCO films grown on the backside of small LaAlO3 substrates (previously coated with 5000 Å of YBCO) display Tc’s ≳88 K with no significant degradation in the front side film properties. Furthermore, recent results of backside PLD of YBCO onto three-inch diameter LaAlO3 substrates have yielded films on both surfaces with Tc’s ≳86 K, and Jc’s ≳2 MA/cm2. The novel features of the large area PLD system will be described, and the uniformity for a number of important electrical and physical film properties will be reported.

Effects of substrate heating on the spatial uniformity of threshold current and emission wavelength in GaAs and InGaAs graded-index separate-confinement heterostructure quantum-well lasers grown by molecular-beam epitaxy

We show that if the active region of a quantum-well (QW) laser is grown at a high temperature such that the sticking coefficients of group III species are less than unity, the emission wavelength λ and threshold current density Jth are sensitive to the spatial variations in substrate growth temperature Ts despite the time average flux variations of less than 1% across the surface of a rotating 7.5 cm diam substrate in our molecular-beam epitaxy system. InGaAs strained QW lasers, in which the active region is grown at Ts < 580 °C at which In and Ga have unity sticking coefficients, have uniform Jth (212±4 A cm−2) and λ(989±1 nm) on a 5 cm diam substrate. These lasers were grown with In mounting. In contrast, GaAs QW lasers, which are grown at ∼700 °C with In mounting, have less uniform Jth (395±20 A cm−2) and λ(850±9 nm). This is the result of nonuniform substrate heating which is partly due to voids in the In back coating. This causes variations in GaAs growth rate because of the high temperature dependence of the Ga sticking coefficient at ∼700 °C. Uniformity of GaAs QW lasers deteriorates further if direct radiation heating of the substrate with In free mounting is used. With In free mounting, the Jth is minimum (245 A cm−2) in the center and increases monotonically to maximum (365 A cm−2) towards the edge of the wafer, suggesting the degradation of material quality towards the edge. Variation of λ in GaAs QW lasers is random or systematic depending upon whether they are grown with In mounting or In free mounting, respectively.

Improved thickness uniformity in molecular beam epitaxial growth of GaAs using a tilted conical insert crucible

Significant improvements in the uniformity of epitaxial layers of GaAs, deposited using a V80-H molecular beam epitaxy system, can be obtained by modifying the crucible so that the flux is directed towards the center of rotation of the substrate. This has been obtained with a dual crucible system, consisting of a tilted conical insert inside a large capacity straight sided crucible. With this combination the layer uniformity can be improved to better than ±1.5% over the useable area of a 76 mm diam substrate and to ±0.7% for 50 mm diam substrates. These results are in excellent agreement with the predictions of recent flux modeling calculations.

Large-area sputtering of i n s i t u superconducting YBa2Cu3O7 films

High-temperature superconducting thin films of YBa2Cu3O7 are deposited on 2 in. MgO and LaAlO3 substrates by radio frequency magnetron sputtering from an 8 in. diam powder target. By locating the substrate above the center of the magnetron erosion ring and by placing a ‘‘negative ion shield’’ between the target and the substrate, negative ion resputtering is avoided and high quality films are grown in situ, and are superconducting on removal from the vacuum chamber without a high-temperature post anneal. Stoichiometric films on LaAlO3 and MgO have critical temperatures up to 88 K and critical currents above 5×105 A/cm2 at 77 K. Uniformity in thickness of ±5%, and in room temperature resistivity of ±7% were measured on 2 in. diam substrates. Microwave surface resistance measurements at 1.2 GHz and 4.2 K showed Rs≊0.1 mΩ for YBCO ground planes and ≊0.3 mΩ for patterned YBCO strip lines on MgO.

Ion current density and its uniformity at the electron cyclotron resonance position in electron cyclotron resonance plasma

Extremely high and uniform ion current density is achieved at the electron cyclotron resonance (ECR) position in a microwave cavity resonator with a 260 mm diam. Microwave power is most efficiently absorbed at the ECR position in the ECR plasma. The uniformity of the ion current density at the ECR position is 15±0.75 mA/cm2 in a 200 mm diam area. This high and uniform ion current density is accomplished with a large quartz window size with a 170 mm diam for microwave introduction and a flat profile of the 875 G equimagnetic field position. The ECR plasma etching system equipped with this microwave cavity resonator that is 260 mm in diameter has a high potential for uniform and high rate pattern fabrication in a ULSI circuit on a more than 6 in. diam substrate.

Development of ionized cluster beam source for practical use

Low-energy ion bombardment during film growth can significantly modify film properties. The practical advantages of using an ionized cluster beam (ICB) include reduced damages and high deposition rates at low temperature. The design and the characteristics of the ICB source are described. The ionized cluster trajectories and the potential profiles were numerically calculated in order to optimize the design. The ionization chamber has restrictive electrodes to enhance the ionization probability in the low cluster density region near the anode. With these electrodes, the source provides uniform ion current densities up to 30 μA/cm2 at voltages ranging from 200 to 8000 V over a 127 mm diam substrate at a distance of 300 mm from the source. The ICB source can operate over a wide temperature range up to 2000 °C. Deposition rates up to 120 nm/min are obtained for Ti, Si, and Cu. The source has successfully operated for more than 100 h in several industrial applications.

Dual ion beam deposition of oxide, nitride, and carbide films

Compound films such as oxides, nitrides, and carbides have been prepared in a dual ion beam (DIB) deposition system, which contains an ionized cluster beam (ICB) source and an ionized gas beam (IGB) source. The characteristic of the DIB system and the properties of compound films such as SiOx, TiNx, and C were investigated. The ion current density distribution was measured at acceleration voltages from 0 to 10 kV by an array of Faraday cups at the substrate position. Uniform ion current distributions over 5-in. diam substrates have been obtained for ICB of Au, Cu, and Si and IGB of CH4, N2, and O2. The composition of SiOx films prepared by DIB approaches stoichiometric SiO2 with increasing oxygen ion current density. The crystalline structure of TiNx films changes gradually from TiN to Ti2N as the atomic flux ratio of (N/Ti) decreases. The Knoop hardness values of TiN and C films prepared at 200 °C are over 1700 and 3000 kg/mm2, respectively. Therefore the advantages of using the DIB deposition system for low-temperature compound film growth include control over film composition and crystalline structure with excellent physical properties. Ion irradiation during film growth by both metal and gas beams enhances chemical reaction kinetics on the substrate.

Phosphorous coimplantation effect on threshold voltage uniformity of GaAs transistors

Phosphorous coimplantation effect on electrical uniformity of Si-implanted GaAs active layer is investigated for undoped as-grown, undoped ingot-annealed, and In-doped substrates. Pairs of field-effect transistors, fabricated with and without P coimplantation, are placed on whole 3-in.-diam substrates at a 200-μm interval. Threshold voltage measurements reveal that a concentration of 1018 /cm3 coimplanted P reduces the standard deviation in threshold voltage for undoped as-grown substrates to 1/2.5. Undoped ingot-annealed substrates achieve the same uniformity of threshold voltage as In-doped substrates, which showed the best data. Moreover, this method reduces the variation in the mean threshold voltage among substrates by one-half. These results indicate that P coimplantation successfully suppresses the change of As to Ga vacancy concentration ratio.

Behavior and characteristics of radiationally heated GaAs substrates

Molybdenum substrate holders, which secure GaAs substrates without indium bonding, have been fabricated and tested. The holder design permits quick substrate loading and is compatible for reflection high‐energy electron diffraction measurements. The substrate surface temperature is determined pyrometrically and the methodology is discussed in detail. The substrate temperature is stably controlled by regulating the substrate heater voltage as opposed to conventional thermocouple control. Using voltage regulation the temperature of the radiationally heated substrates can be rapidly changed with excellent control. The temperature uniformity for 2 in. diam substrates is ±5 °C at typical molecular‐beam epitaxial growth temperatures. Quantitative differences caused by free‐carrier absorption are observed in the heating behavior of undoped and N‐type substrates. After epitaxial growth has been initiated, negligible substrate temperature droop is observed. The substrates exhibit insignificant backside erosion and...

Vacuum evaporation system for depositing thick polycrystalline silicon

Thick polysilicon (>1 mm) deposition on heated SiO2-coated silicon substrates at high deposition rate (≥4 μm/min) at temperatures to 1100 °C was achieved by vacuum evaporation of silicon using two high power e guns. The deposition system was able to accommodate ten 75 mm diam substrates or eight 100 mm diam substrates. The system was designed as an alternative to the CVD process for depositing polysilicon material for dielectrically isolated integrated circuit substrates. This paper describes the system design and its capabilities.

Fabrication of Multilayer Dielectric Films

For the fabrication of multilayer dielectric films for mirrors or filters, an evaporation system was built for attaining (1) thickness variations below ±0.5% on substrates up to 6 in. in diameter and (2) simultaneous deposition on five such substrates. During deposition, the substrates perform a planetary rotation around the source thereby greatly reducing thickness variations and angle-of-incidence effects, together with inhomogeneities in the evaporation characteristic of the source. Details of the system and the optical monitoring arrangement are given. The experimental thickness variation amounted to ±0.15% on the 6-in.-diam substrates. Reflectances of up to 99.8% could be attained with the losses due to scattering. The application of the mirrors to optical information-storage experiments is briefly described.