摘要:

A three‐dimensional hybrid model for calculating sputter deposition profiles has been developed. Both Monte Carlo methods and methods of statistical physics have been used. Due to the negligible mutual interaction of the sputtered particles, the Monte Carlo simulation is only carried out by a point sputtering source. The point source deposition profile and the point source thermalization profile resulting from the Monte Carlo simulation are integrated over all relevant point sources. The spatial distribution of the thermalized particles enters in the well known diffusion equation as a source term. The stationary distribution of concentration of the thermalized particles results in the time invariant solution of the diffusion equation. Therefore, the flux of thermalized particles to the substrate is available. The evaluated model takes into consideration the pressure of the working gas, the initial energy and angular distribution of the sputtered particles, the masses of the working gas atoms and the sputtered particles, the emissivity of the target and the geometry of the sputtering system, and is applicable to all common sputter processes. To verify the model silicon layers have been deposited from a planar magnetron target at an argon pressure of 1.1 and 4.0 Pa. The simulations are in good agreement with experimental data. It is shown that the unexpected decrease in uniformity with increasing pressure is an effect of the pressure dependent source term.

ISSN:0734-2101    

DOI:10.1116/1.578958

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A model of the sputtering process for multiconstituent materials which accounts for variations in the deposition rate profiles of thin films sputtered with planar sputtering systems in the common face to face geometry has been developed. Excellent agreement between calculated and measured profiles resulting from various process parameters was obtained. The model accounts for resputtering of the growing film by high energy particles or reevaporation occurring during deposition. The experimental results demonstrated that the deposition rate and the resputtering rate profiles of sputtered films can be tightly predicted. Various films (Ti, Pyrex, MgO, YBaCuO, ZnO) were deposited in different sputtering apparatuses and at different process parameters. When resputtering effects occur, a direct correlation between the predicted local strength of resputtering and the observed variations of physical properties across the deposited material (stoichiometry and index of refraction) was found.

ISSN:0734-2101    

DOI:10.1116/1.578959

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

High resolution mass spectrometry is used to monitorinsitugaseous wear products that are generated during sliding of lubricated carbon–carbon interfaces in a vacuum. During the initial stages of sliding, significant amounts of polyperfluoroether lubricant fragments are detected, which resemble the mass patterns of scissioned lubricant in the thermal desorption experiment. The intermediate stage of sliding characterized by lower rate of lubricant fragmentation is followed by higher rate before wear of hydrogenated carbon overcoat occurs, which is accompanied by hydrogen emission and friction increase. Lubricant loss, removal, and alteration are precursors of the wear of solids and are determined by scanning microellipsometry. The amount of altered lubricant that is left on the disk and slider surfaces is quantified by x‐ray photoelectron spectroscopy and the chemical structure of altered lubricant is evaluated by time‐of‐flight mass spectrometry. It is found that the dominant process, before the wear of solids occurs, is tribochemical scission of fluorocarbon polymers. Some fragments desorb from the interface, while others containing carboxylic end groups attach by strong physisorption to solid surfaces.

ISSN:0734-2101    

DOI:10.1116/1.578960

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Vacuum arc discharges with evaporating anodes employing directly as well as indirectly heated thermionic cathodes are investigated. The observed volt‐ampere characteristics of these discharges depend strongly on the temperature of the thermionic cathode, the evaporated anode material, and the relative position of the electrodes. A simple model describing the observed discharge characteristics is proposed. With respect to a possible coating application, the plasma of this arc discharge is investigated at a distance of 250 mm from the evaporating anode. For arc currents between 2 and 4 A and Cu as evaporating anode material, the deposition rate is between 3.5 and 5.1 nm/s, the degree of ionization ranges from 0.6% to 6.2%, and electron temperatures are between 5.8 and 15 eV. The observed directed energy of the ions exceeds 100 eV. An examination of the deposited Cu films reveals as main results: Purity≳99.5%, compact structure, and smoothening of the film surfaces with increasing degree of ionization.

ISSN:0734-2101    

DOI:10.1116/1.578961

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Occasional vacuum leaks have occurred in bellows assemblies of helium pressure vessels at the Continuous Electron Beam Accelerator Facility. The flanged stainless steel bellows assemblies are used to connect the niobium rf cavity pairs to the surrounding liquid helium pressure vessels. An investigation of the source of these leaks has revealed a through‐thickness network of microcracks in the cuff weld zones. The cuff material contained a mixture of soft and very hard elongated intermetallic inclusions that were oriented parallel with the weld fusion line; these inclusions served as crack initiation sites. Surface‐exposed inclusions, in contact with a chlorine residue from a postweld machining process, induced crevice corrosion during a year of storage. Residual stresses in the weld led to a combination of lamellar tearing and stress corrosion cracking. Propagation of the cracks from one inclusion to another resulted in continuous vacuum leakage paths from the primary (2 K) helium circuit to the vacuum insulation space. Additional vacuum leaks were prevented by reconfiguring the weld geometry and avoiding any processing with chlorinated substances.

ISSN:0734-2101    

DOI:10.1116/1.578962

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A practical example of the use of single‐structure diffusion pumping groups in an experiment requiring hydrocarbon‐free, ultrahigh vacuum is presented. With the use of proper vacuum procedures and careful foreline design and operation, but with no exotic hardware or liquid nitrogen, we have demonstrated that such a pump could provide vacuum that was ‘‘clean,’’ i.e., which had no residual pump‐oil contamination to a partial pressure below 10−8mbar. Their use is thus compatible, at least in peripheral vacuum chambers, with standard ‘‘UHV‐surface science’’ processes. We discuss our vacuum system in detail, and present a review of the literature on the production of clean vacua with diffusion pumps.

ISSN:0734-2101    

DOI:10.1116/1.578963

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Nonlinearities of ∼10%–15% in the sensitivity of glass envelope Bayard–Alpert gages (BA gages) have been observed in the pressure range 10−7–10−2Pa. These nonlinearities were studied in modified BA gage tubes with platinum coatings on their inner glass surfaces by measuring the equilibrium potential of the platinum coating as a function of pressure. The sensitivities of the gage systems (gage tube plus controller) were found to depend on the inner surface potential, and this potential was found to depend on pressure and on the details of the filament potential waveform provided by the gage controller. It was found that the nonlinearities could be minimized by holding the inner surface to a fixed direct‐current (dc) potential, by modifying the alternating‐current filament potential wave form, or by using a controller that provides a noise‐free dc filament‐heating current.

ISSN:0734-2101    

DOI:10.1116/1.578964

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The results of 4.2‐K photodesorption experiments in two quasiclosed geometries are reported, (1) a simple tube and (2) a tube with a coaxial perforated liner. These experiments were designed to measure separately the desorption coefficients of tightly bound and physisorbed molecules. The results are important for the beam tube vacuum of the next generation of superconducting proton colliders that have been contemplated—the 20‐TeV Superconducting Super Collider in the United States and the 7.3‐TeV Large Hadron Collider at CERN.

ISSN:0734-2101    

DOI:10.1116/1.578965

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

ISSN:0734-2101    

DOI:10.1116/1.578966

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A completely ionized and clustered beam of Mo or Cu is deposited with variable kinetic energy on a substrate, and the filling of micron‐sized contact holes on semiconductor devices is studied. An excellent hole filling is obtained for the impact of charged copper clusters, if they contain 1000–3000 Cu atoms and impinge with a kinetic energy of about 10 eV per atom on a substrate having a temperature of 500 K. The morphology of small hole fillings by slow and energetic cluster impact is discussed.  

ISSN:0734-2101    

DOI:10.1116/1.578967

出版商:American Vacuum Society    

年代:1994

数据来源: AIP