Jump to Content
View Cart
Top 20 Most Read Articles
May 2009
The 20 articles with the most full-text downloads during the month, in descending order.
 |
Resistor network simulation method for a vacuum system in a molecular flow region J. Vac. Sci. Technol. A 1, 84 (1983); http://dx.doi.org/10.1116/1.572317 (6 pages)
Full Text:
|
Download PDF
|
|||
|
Show Abstract
A simulation method to obtain the pressure distribution in a complex vacuum system has been proposed. The method introduces a new concept with regard to the function of each component of the vacuum system. The vacuum pump is regarded as a ‘‘vacuum resistor’’ connected at one side to the perfect vacuum. The gas source is regarded as a pressure generator connected to the vacuum. The conducting pipe is regarded as a vacuum resistor between the above elements. The vacuum sides of the pump element and the gas source element are assumed to be connected together by an imaginary route, and thus the vacuum system can be regarded as a closed vacuum circuit network. Such a vacuum circuit network may be replaced by an electric circuit network of a simulator for the vacuum system. The simulator was employed for the high vacuum system of an electron microscope in order to obtain the pressure distribution. The results obtained were in good agreement with the actually measured pressure distribution. |
||||
|
Show PACS
|
||||
|
|
J. Vac. Sci. Technol. A 27, 443 (2009); http://dx.doi.org/10.1116/1.3097849 (6 pages) Online Publication Date: 24 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
The uncontrolled formation of an interfacial layer between high-κ oxides and semiconductors is a major concern in advanced microelectronics not only for Si-based devices but also for those exploiting the higher mobility of Ge and GaAs. Using transmission electron microscopy, the authors investigate the interfacial layer formed between as-grown thin Al2O3 films, deposited using atomic layer deposition, and oxide free Si(100), Ge(100), and GaAs(100). In particular, they compare the effects of two different oxygen sources (H2O and O3) on interfacial layer formation during the growth process. They show that no interfacial layer can be distinguished unambiguously between the Al2O3 films, grown using TMA and H2O or O3, and all the semiconductor substrates.
|
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
J. Vac. Sci. Technol. A 27, 417 (2009); http://dx.doi.org/10.1116/1.3089242 (6 pages) Online Publication Date: 24 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Novel technical and technological solutions enabling effective stress control in highly textured polycrystalline aluminum nitride (AlN) thin films deposited with ac (40 kHz) reactive sputtering processes are discussed. Residual stress in the AlN films deposited by a dual cathode S-Gun magnetron is well controlled by varying Ar gas pressure, however, since deposition rate and film thickness uniformity depend on gas pressure too, an independent stress control technique has been developed. The technique is based on regulation of the flux of the charged particles from ac plasma discharge to the substrate. In the ac powered S-Gun, a special stress adjustment unit (SAU) is employed for reducing compressive stress in the film by means of redistribution of discharge current between electrodes of the S-Gun leading to controllable suppression of bombardment of the growing film. This technique is complementary to AlN deposition with rf substrate bias which increases ion bombardment and shifts stress in the compressive direction, if required. Using SAU and rf bias functions ensures tailoring intrinsic stress in piezoelectric AlN films for a particular application from high compressive −700 MPa to high tensile +300 MPa and allows the gas pressure to be adjusted independently to fine control the film uniformity. The AlN films deposited on Si substrates and Mo electrodes have strong (002) texture with full width at half maximum ranging from 2° for 200 nm to 1° for 2000 nm thick films.
|
|||
|
Show PACS
|
|||
|
|
Dry etching of polydimethylsiloxane for microfluidic systems J. Vac. Sci. Technol. A 20, 975 (2002); http://dx.doi.org/10.1116/1.1460896 (8 pages) Online Publication Date: 7 May 2002
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A fluorine-based reactive ion etch (RIE) process has been developed to anisotropically dry etch the silicone elastomer polydimethylsiloxane (PDMS). This technique complements the standard molding procedure that makes use of forms made of thick SU-8 photoresist to produce features in the PDMS. Total gas pressure and the ratio of O2 to CF4 were varied to optimize etch rate. The RIE recipe developed in this study uses a 1:3 mixture of O2 to CF4 gas resulting in a highly directional and stable etch rate of approximately 20 μm per hour. Selective dry etching can be performed through a photolithographically patterned metal etch mask providing greater precision and alignment with preexisting molded features. The dry etch process is presented in this article along with a brief comparison to recently reported wet etch approaches. © 2002 American Vacuum Society. |
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 27, 423 (2009); http://dx.doi.org/10.1116/1.3089243 (7 pages) Online Publication Date: 24 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Multiprocesses in a single plasma process chamber with high throughput require precise, sequential, high-speed alteration of partial pressures of multiple gas species. A conventional gas-distribution system cannot realize this because the system seriously overshoots gas pressure immediately following valve operation. Furthermore, chamber volume and conductance of gas piping between the system and chamber should both be considered because they delay the stabilizing time of gas pressure. Therefore, the authors proposed a new gas-distribution system without overshoot by controlling gas flow rate based on pressure measurement, as well as a method of pulse-controlled gas injection immediately following valve operation. Time variation of measured partial pressure agrees well with a calculation based on an equivalent-circuit model that represents the chamber and gas piping between the system and chamber. Using pulse-controlled gas injection, the stabilizing time can be reduced drastically to 0.6 s for HBr added to pure Ar plasma, and 0.7 s for O2 added to Ar/HBr plasma; without the pulse control, the stabilizing times are 3 and 7 s, respectively. In the O2 addition case, rapid stabilization can be achieved during the period of line/space pattern etching of poly-Si on a thin SiO2 film. This occurs without anomalous etching of the underlying SiO2 film or the Si substrate near the sidewall, thus obtaining a wide process margin with high throughput.
|
|||
|
Show PACS
|
|||
|
|
Surface chemistry and surface electronic properties of ZnO single crystals and nanorods J. Vac. Sci. Technol. A 27, 328 (2009); http://dx.doi.org/10.1116/1.3085723 (8 pages) Online Publication Date: 25 February 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||
|
Show Abstract
The surface chemistry of ZnO single crystals of (0001) and (10
 0) orientations and ZnO nanorods was studied using x-ray and ultraviolet photoelectron spectroscopies. Air drying and UV-ozone preparations were studied in particular as chemical treatments that could be applied to poly(3-hexylthiophene) (P3HT)-ZnO solar cells to enhance performance. The UV-ozone treatment showed negligible effect by photoelectron spectroscopy on the ZnO single crystal surfaces, but brought about electronic shifts consistent with increased upward band bending by ∼ 0.25 eV on the ZnO nanorod surface. Modest interface dipoles of ∼ 0.15 and ∼ 0.25 eV were measured between P3HT and the (100) and (0001) single crystal orientations, respectively, with the dipole moment pointing from ZnO to the P3HT layer. The sol-gel films showed evidence of forming a small interface dipole in the opposite direction, which illustrates the difference in surface chemistry between the solution-grown ZnO and the ZnO single crystals. |
||||||||||||||
|
Show PACS
|
||||||||||||||
|
|
Nonsinusoidal buckling of thin gold films on elastomeric substrates J. Vac. Sci. Technol. A 27, L9 (2009); http://dx.doi.org/10.1116/1.3089244 (5 pages) Online Publication Date: 24 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Buckling of stiff thin films on compliant substrates represents a variety of applications, ranging from stretchable electronics to micro-nanometrology. Different but complementary to previously reported sinusoidal buckling waves, this letter presents a nonsinusoidal surface profile of buckled thin Au films on compliant substrates, specifically, a secondary dip on top of buckling wave or rather broadened wave top with very sharp trough. This nonsinusoidal profile is likely due to tension/compression asymmetry, i.e., different strengths in tension and compression resulted from the polycrystalline, grained microstructure of metal film. Finite element analysis with asymmetric tension/compression material model has reproduced the experiments well qualitatively.
|
|||
|
Show PACS
|
|||
|
|
Gas temperature measurement in CF4, SF6, O2, Cl2, and HBr inductively coupled plasmas J. Vac. Sci. Technol. A 27, 471 (2009); http://dx.doi.org/10.1116/1.3106626 (8 pages) Online Publication Date: 30 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Neutral gas temperature (Tg) is measured in an industrial high-density inductively coupled etch reactor operating in CF4, SF6, O2, Cl2, or HBr plasmas. Two laser diodes are used to deduce Tg from the Doppler widths of 772.38 and 811.5 nm lines absorbed by Ar*(
 ) metastable atoms, when a small amount of argon (5%) is added to the gas flow. With the 811.5 nm beam passing parallel to the wafer, Tg near the wafer surface is obtained by laser absorption technique. With the 772.38 nm beam entering the top of the reactor perpendicular to the wafer surface, the volume averaged temperature is deduced by laser induced fluorescence technique. The volume averaged Tg increases with radio frequency power and with pressure, although the temperature near the walls is only weakly dependent on gas pressure. The main effect of increasing the pressure is an enhancement of the temperature gradient between the discharge center and the wall boundary. Due to the thermal accommodation, the authors always observe a significant temperature jump between the surface and the gas in its vicinity. This gap is typically about 200 K. Gas temperatures for a wide range of pressure and rf powers are reported. These data will be useful to validate and improve numerical models of high-density reactive plasmas. |
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 27, 479 (2009); http://dx.doi.org/10.1116/1.3106623 (6 pages) Online Publication Date: 31 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A rarefied gas flow through a thin slit into vacuum is studied on the basis of the direct simulation Monte Carlo method. The mass flow rate and flow field are calculated over the whole range of the gas rarefaction from the free-molecular regime to the viscous one. A comparison to other results on the same problem available in literature is performed. An interpolating formula for the reduced flow rate is obtained.
|
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 27, 352 (2009); http://dx.doi.org/10.1116/1.3081966 (4 pages) Online Publication Date: 27 February 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Three types of low-damage radio-frequency (rf) magnetron sputtering processes—an interruptive process, a rotating cylindrical holder method, and an off-axis sputtering method—were designed and studied to reduce the film surface temperature during deposition. Low-damage sputtering processes were investigated to improve the resistivity and optical transmittance in the visible range of Al doped ZnO (AZO) thin films deposited on polymer substrates. In the case of the polyethersulfone substrate, AZO films with a resistivity of 1.0×10−3 Ω cm and an optical transmittance of 75% were obtained by the rotating repeat holder method during rf sputtering.
|
|||
|
Show PACS
|
|||
|
|
Addition of yttrium into HfO2 films: Microstructure and electrical properties J. Vac. Sci. Technol. A 27, 503 (2009); http://dx.doi.org/10.1116/1.3106627 (12 pages) Online Publication Date: 13 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||||
|
Show Abstract
The cubic phase of HfO2 was stabilized by addition of yttrium in thin films grown on Si/SiO2 by metal-organic chemical vapor deposition. The cubic phase was obtained for contents of 6.5 at. % Y or higher at a temperature as low as 470 °C. The complete compositional range (from 1.5 to 99.5 at. % Y) was investigated. The crystalline structure of HfO2 was determined from x-ray diffraction, electron diffraction, and attenuated total-reflection infrared spectroscopy. For cubic films, the continuous increase in the lattice parameter indicates the formation of a solid-solution HfO2–Y2O3. As shown by x-ray photoelectron spectroscopy, yttrium silicate is formed at the interface with silicon; the interfacial layer thickness increases with increasing yttrium content and increasing film thickness. The dependence of the intrinsic relative permittivity εr as a function of Y content was determined. It exhibits a maximum of ∼ 30 for ∼ 8.8 at. % Y. The cubic phase is stable upon postdeposition high-temperature annealing at 900 °C under NH3.
|
||||||||||||||||
|
Show PACS
|
||||||||||||||||
|
|
J. Vac. Sci. Technol. A 25, 1317 (2007); http://dx.doi.org/10.1116/1.2764082 (19 pages) Online Publication Date: 30 July 2007
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Physical vapor deposition under conditions of obliquely incident flux and limited adatom diffusion results in a film with a columnar microstructure. These columns will be oriented toward the vapor source and substrate rotation can be used to sculpt the columns into various morphologies. This is the basis for glancing angle deposition (GLAD), a technique for fabricating porous thin films with engineered structures. The origin of the columnar structure characteristic of GLAD films is discussed in terms of nucleation processes and structure zone models. As deposition continues, the columnar structures are influenced by atomic-scale ballistic shadowing and surface diffusion. Competitive growth is observed where the tallest columns grow at the expense of smaller features. The column shape evolves during growth, and power-law scaling behavior is observed as shown in both experimental results and theoretical simulations. Due to the porous nature of the films and the increased surface area, a variety of chemical applications and sensor device architectures are possible. Because the GLAD process provides precise nanoscale control over the film structure, characteristics such as the mechanical, magnetic, and optical properties of the deposited film may be engineered for various applications. Depositing onto prepatterned substrates forces the columns to adopt a planar ordering, an important requirement for photonic crystal applications.
|
|||
|
Show PACS
|
|||
|
|
Influence of reactive sputter deposition conditions on crystallization of zirconium oxide thin films J. Vac. Sci. Technol. A 27, 577 (2009); http://dx.doi.org/10.1116/1.3119669 (7 pages) Online Publication Date: 1 May 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
Zirconium oxide thin films were prepared through reactive magnetron sputtering with a zirconium target using pulsed-dc and radio frequency (rf) sources. The film crystallization was studied with respect to sputtering growth variables such as sputtering power, sputtering pressure, source frequency, oxygen pressure, substrate temperature, and substrate material. The crystallization was studied through x-ray diffraction (XRD) 2θ scans and was quantified with peak full width at half maximum and crystallite size. Crystallization of the films was found to occur over a broad range of sputter deposition parameters, while the amorphous phase was produced only at high sputtering pressure and low sputtering power. With a decrease in sputtering pressure or power, the crystallite size decreased. Energy dispersive x-ray spectroscopy, electron microscopy, and XRD analysis revealed that at very low pressures, these films are polyphase assemblages of cubic phases of oxygen deficient zirconium oxides such as ZrO and Zr2O. When the sputtering oxygen content of these films is increased above 25%, monoclinic-ZrO2 phase is stabilized in the films and the deposition rate decreases. However, in the case of rf sputtering, an additional peak corresponding to tetragonal phase of ZrO2 is observed. The sputtering parameters were related to physical parameters such as sputtering mode, ion energy, and substrate temperature, which influence crystallinity.
|
|||
|
Show PACS
|
|||
|
|
Growth of high-quality SrTiO3 films using a hybrid molecular beam epitaxy approach J. Vac. Sci. Technol. A 27, 461 (2009); http://dx.doi.org/10.1116/1.3106610 (4 pages) Online Publication Date: 30 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
A hybrid molecular beam epitaxy approach for atomic-layer controlled growth of high-quality SrTiO3 films with scalable growth rates was developed. The approach uses an effusion cell for Sr, a plasma source for oxygen, and a metal-organic source (titanium tetra isopropoxide) for Ti. SrTiO3 films were investigated as a function of cation flux ratio on (001) SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates. Growth conditions for stoichiometric insulating films were identified. Persistent (>180 oscillations) reflection high-energy electron diffraction oscillation characteristic of layer-by-layer growth were observed. The full widths at half maximum of x-ray diffraction rocking curves were similar to those of the substrates, i.e., 34 arc sec on LSAT. The film surfaces were nearly ideal with root mean square surface roughness values of less than 0.1 nm. The relationship between surface reconstructions, growth modes, and stoichiometry is discussed.
|
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 27, 521 (2009); http://dx.doi.org/10.1116/1.3112623 (10 pages) Online Publication Date: 17 April 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The performance of a UHV vessel can be improved with a new CERN technology nonevaporable getter (NEG) coating, which is already widely used for accelerator vacuum chambers. Better understanding of the processes involved in NEG film deposition, activation, and poisoning should allow optimization and engineering of the film properties, which are necessary for a particular application. Ti–Zr–V NEG films were created by magnetron sputtering from a single Ti–Zr–V target, and the NEG performance and morphology dependence on deposition pressure, sputtering conditions, and substrate surface roughness have been investigated. It was found that the average grain size of the Ti–Zr–V film was 5–6 nm and was broadly independent of the substrate material and deposition conditions. However, film topography and density were shown to depend very much on the substrate surface roughness and deposition conditions. Rough substrates, high working pressures, and the absence of ion bombardment produced open columnar structures, whereas smooth substrates, ion assistance, and low pressures produced much denser layers. X-ray photoelectron spectroscopy studies have shown that full regeneration occurred at 300 °C but film activation started at temperatures of as low as 160 °C. The CO sticking probability reaches its maximum after activation at 250 °C and is found to be up to 0.3 with a pumping capacity in the range of 0.8–1.2 ML. The samples activated at 160 °C have a reduced pumping speed and capacity by an order of magnitude.
|
|||
|
Show PACS
|
|||
|
|
Revised structure zone model for thin film physical structure J. Vac. Sci. Technol. A 2, 500 (1984); http://dx.doi.org/10.1116/1.572604 (4 pages)
Full Text:
|
Download PDF
|
|||
|
Show Abstract
Thin films prepared under conditions of low adatom mobility are characterized by a highly anisotropic physical structure with a wide range of systematically varying column and void sizes. The structure zone models, previously developed to classify the larger sized physical structures, are revised to account for the evolutionary growth stages of structure development as well as the separate effects of thermal‐ and bombardment‐induced mobility. The zone T introduced by Thornton is shown to be a subzone within zone 1. |
||||
|
Show PACS
|
||||
|
|
J. Vac. Sci. Technol. A 27, 436 (2009); http://dx.doi.org/10.1116/1.3097848 (7 pages) Online Publication Date: 24 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
|||||||||||||||||||
|
Show Abstract
Undoped hydrogenated microcrystalline silicon (μc-Si:H) thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) at low temperature with different hydrogen dilutions and rf powers. Large complexity of microstructure in hydrogenated microcrystalline silicon and the existence of different sizes of crystallites are demonstrated by different characterizations. The authors correlate the transport properties with the structural properties of the rf PECVD grown μc-Si:H in the amorphous-to-crystalline transition region. For chamber pressure of 2.0 Torr and rf power density of 310 mW/cm2, the onset of crystallinity is observed for the film deposited at a hydrogen dilution of 94%. At a hydrogen dilution of 95%, amorphous-to-microcrystalline transition have been observed. This film exhibits a dark conductivity of 2.7×10−7 S cm−1 and a crystalline volume fraction of 21%. The mobility-lifetime product for these films are 3.8×10−6 cm2/V and hole diffusion length is 70 nm. Fourier transform infrared study shows mainly monohydride bonding in this film. This film becomes stable after 30 h of light soaking.
|
||||||||||||||||||||
|
Show PACS
|
||||||||||||||||||||
|
|
Plasma deposition of optical films and coatings: A review J. Vac. Sci. Technol. A 18, 2619 (2000); http://dx.doi.org/10.1116/1.1314395 (27 pages)
Full Text:
|
Download PDF
|
||
|
Show Abstract
Plasma enhanced chemical vapor deposition (PECVD) is being increasingly used for the fabrication of transparent dielectric optical films and coatings. This involves single-layer, multilayer, graded index, and nanocomposite optical thin film systems for applications such as optical filters, antireflective coatings, optical waveguides, and others. Beside their basic optical properties (refractive index, extinction coefficient, optical loss), these systems very frequently offer other desirable “functional” characteristics. These include hardness, scratch, abrasion, and erosion resistance, improved adhesion to various technologically important substrate materials such as polymers, hydrophobicity or hydrophilicity, long-term chemical, thermal, and environmental stability, gas and vapor impermeability, and others. In the present article, we critically review the advances in the development of plasma processes and plasma systems for the synthesis of thin film high and low index optical materials, and in the control of plasma–surface interactions leading to desired film microstructures. We particularly underline those specificities of PECVD, which distinguish it from other conventional techniques for producing optical films (mainly physical vapor deposition), such as fabrication of graded index (inhomogeneous) layers, control of interfaces, high deposition rate at low temperature, enhanced mechanical and other functional characteristics, and industrial scaleup. Advances in this field are illustrated by selected examples of PECVD of antireflective coatings, rugate filters, integrated optical devices, and others. © 2000 American Vacuum Society. |
|||
|
Show PACS
|
|||
|
|
Work function determination of zinc oxide films J. Vac. Sci. Technol. A 15, 428 (1997); http://dx.doi.org/10.1116/1.580502 (3 pages)
Full Text:
|
Download PDF
|
||
|
Show Abstract
Zinc oxide-silicon heterojunctions were fabricated using both n- and p-type silicon. The zinc oxide films were deposited by the magnetron sputtering process at various substrate temperatures to form these devices. The electrical properties of these devices were measured and the work function of the zinc oxide was evaluated from these properties. © 1997 American Vacuum Society. |
|||
|
Show PACS
|
|||
|
|
J. Vac. Sci. Technol. A 27, 456 (2009); http://dx.doi.org/10.1116/1.3100215 (5 pages) Online Publication Date: 30 March 2009
Full Text:
Read Online (HTML)
|
Download PDF
|
||
|
Show Abstract
The author investigated the etching characteristics of semi-insulating (SI) and n-doped (n-) 4H-SiC substrates at a high etch rate of about 2 μm/min using high-density SF6/O2 inductively coupled plasma. The etch rate of SI-SiC was found to be lower than that of n-SiC, and the etching profile of SI-SiC showed retrograde features with a larger sidewall angle and a rounder etched bottom compared to n-SiC. These characteristics are attributed to the difference in wafer heating and negative charging of the sidewall during plasma etching between both substrates. The temperature of n-SiC increases by radiative heating from the high-density plasma during etching because of the higher free-carrier absorption compared to SI-SiC. Furthermore, the negative charge buildup at the sidewall of SI-SiC becomes stronger because of the lower electrical conductivity compared to n-SiC.
|
|||
|
Show PACS
|
|||
This Publication
Scitation
SPIN
Scitopia
Google Scholar
PubMed