摘要:

This document is the consensus view of the Calibrated Leak Subcommittee of the Recommended Practices Committee of the American Vacuum Society. It is divided into four main sections: Description, Calibration, Proper Usage, and Recommended Documentation of Leaks. Included in Sec. II are discussions of types of leaks, temperature effects, depletion rates, and units of leakage rate measurement. Section III addresses primary and secondary techniques for leak calibration, including uncertainties. Section IV addresses the proper handling and usage of leaks to achieve optimum results, recommendations of standardization of connections, and safety. The documentation to accompany and to be attached to each calibrated leak, recommended in Sec. V, is intended to provide the user with sufficient information about the leak for accurate and safe use. The appendices contain a glossary and a discussion of the use of throughput and flow rate units and conversions.

ISSN:0734-2101    

DOI:10.1116/1.578137

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Aluminum nitride thin films have been grown via low pressure chemical vapor deposition at substrate temperatures ranging from 584 to 732 K by the catalytic action of a heated tungsten filament. A tungsten filament heated to 2020 K was used to decompose ammonia, which reacted with trimethylaluminum introduced downstream of the filament to form aluminum nitride films at deposition rates between 50 and 200 nm/min. The resultant films were characterized by Fourier‐transform infrared spectroscopy, x‐ray photoelectron spectroscopy (XPS), scanning electron microscopy, and Raman spectroscopy. Infrared spectroscopy revealed hydrogen bonded to nitrogen in concentrations ranging from 2% to 8% on an atomic basis. Multiple internal reflection infrared spectra showed the presence of aluminum–oxygen bonds at the surface of the films. Surface‐enhanced Raman spectra indicated that the films were a mixture of amorphous and polycrystalline phases. XPS sputter depth profiles revealed that the concentration of oxygen in the films decreased, and the concentration of carbon in the films increased with increased trimethylaluminum flow rates. The oxygen concentration in the aluminum nitride films could be reduced to levels below the limits of detection for XPS, while the carbon concentration could be reduced to 0.8% under the best growth conditions explored.

ISSN:0734-2101    

DOI:10.1116/1.578135

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Coaxial impact collision ion scattering spectroscopy (CAICISS) has been applied to an analysis of As‐stabilized GaAs surfaces. CAICISS spectral changes were observed, depending on the incident beam angle to the crystal surface. The shadow cone radius of Ga atoms in the GaAs crystal was obtained from the angular dependence of the signal intensities. The atom positions of As atoms on the top surface are also discussed on the basis of the result that the distance between the dimer atoms is shortened by less than 10% from the normal lattice constant.

ISSN:0734-2101    

DOI:10.1116/1.578146

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We have measured transient and steady‐state reflected As4and desorbing As2fluxes during molecular beam homoepitaxy on the (001) surfaces of GaAs, AlAs, and InAs. In the absence of growth, the reflected As4flux decreases, and the desorbing As2flux increases, with increasing temperature. In the presence of growth, both fluxes decrease linearly, and then saturate, with increasing group III flux. The saturated reflected As4flux depends on temperature, and ranges from approximately 1/2 at temperatures commonly associated with high‐quality epitaxy, to zero at lower temperatures; the saturated desorbing As2flux is zero, independent of temperature. The reflected As4(but not the desorbing As2) flux also depends on surface reconstruction, resulting in unexpected transients as surfaces sequence through various reconstructions upon initiation of growth.

ISSN:0734-2101    

DOI:10.1116/1.578147

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The design of a tantalum nozzle for group V hydride cells in gas source molecular beam epitaxy is presented. The nozzle, which determines the flux distribution from the group V cell is optimized for uniformity and maximum flux utilization. Arsine cracking efficiency and relative concentrations of various gas species are measured by a quadrupole mass analyzer. The operating temperature for the source cell is determined as the region where maximum dimeric arsenic is available for growth.

ISSN:0734-2101    

DOI:10.1116/1.578148

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The ‘‘rate‐of‐rise’’ technique has been applied for the measurement of the flow rate of tetraethylgermanium carried in a stream of argon. A very precise time counter designed and constructed for this purpose is described. A simple model is presented where the flow rate of the vapor is proportional to its partial pressure and to the flow rate of the carrier gas and inversely proportional to the partial pressure of the carrier gas. The assumed applicability of the equation of state of the ideal gas to the discussed system is successfully tested by means of the flow rate dependence on temperature in the range from −19 to 20 °C and its comparison with data computed from the Clausius–Clapeyron equation. Finally thermodynamic properties of tetraethylgermanium namely vaporization enthalpy and saturated vapour pressure at standard temperature are calculated from the results of flow rate measurements.

ISSN:0734-2101    

DOI:10.1116/1.578149

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Hydrogen plasmas generated by electron cyclotron resonance currently provide the most efficient plasma exposure technique available for passivating the grain boundaries of polycrystalline silicon. In this report, we show that careful optimization may be required when using this passivation approach on polycrystalline silicon gated, polycrystalline silicon thin film transistors fabricated using low temperature oxides. Optimization is found to be necessary for thin film transistors (TFTs) with polycrystalline Si gates in order to prevent the onset of high leakage currents which can develop when exposures are too long. The effects of exposure time, substrate temperature, microwave power level, pressure, and plasma dilution with an inert gas are examined to determine the conditions for optimal improvement in electrical performance. A model is also presented to explain this need for optimization of the electron cyclotron resonance hydrogen plasma passivation of poly‐Si TFTs.

ISSN:0734-2101    

DOI:10.1116/1.578150

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The thermal decomposition of ammonia (NH3) and hydrazine (N2H4) on the Si(100) surface has been characterized using Auger electron spectroscopy (AES), temperature programmed desorption, and low energy electron diffraction (LEED). Successive cyclic dosing of the Si(100)‐(2×1) [E. A. Wood, J. Appl. Phys.35, 1306 (1964); H. H. Farrell, F. Stucki, J. Anderson, D. J. Frankel, G. J. Lapeyre, and M. Levinson, Phys. Rev. B30, 721 (1984)] surface with the nitride precursor resulted in the formation of an amorphous nitride layer as indicated by LEED. Hydrazine nitrided the Si(100)‐(2×1) surface much more rapidly than ammonia, as shown by a comparison of the AES nitridation curves for NH3and N2H4. These nitridation curves have very different slopes and clearly have different functional forms. The marked difference in nitride formation rates during cyclic dosing and heating, along with the absence of NH3desorption during N2H4decomposition, suggest that NH3and N2H4may result in the formation of different types of nitride overlayer and/or have different thermal decomposition mechanisms.

ISSN:0734-2101    

DOI:10.1116/1.578151

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Ferroelectric thin films of lanthanum modified lead zirconate titanate (PLZT) were deposited on platinum and fused quartz substrates by rf magnetron sputtering. Cold pressed powder was used as the target with excess PbO in the target composition. The PLZT films were deposited at different substrate temperatures and the thickness of the sputtered films were in the 1–2 μm range. The effect of post‐deposition anneal on the structure and ferroelectric properties are discussed. The structure and composition of the films were determined by x‐ray diffraction and energy dispersive x‐ray analysis and found to be strongly dependent on the excess PbO content in the target, and on the deposition parameters. Films deposited on platinum have (111) or (110) orientation depending on the deposition temperature and the oxygen content in the sputter gas. Film Pb/(Zr+Ti) ratios were determined from energy dispersive x‐ray spectra as a function of the sputtering geometry. Electrical properties were evaluated in terms of the dielectric constant,K, from capacitance measurements. Ferroelectric hysteresis characteristics were measured using a modified Sawyer–Tower circuit. The values of the remanent polarization,Pr, was in the range 5–15μC/cm2and the coercive field,Ec, between 17 and 35 kV/cm depending on the process parameters.

ISSN:0734-2101    

DOI:10.1116/1.578152

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

An ultrahigh vacuum, magnetron sputtering system designed for the deposition andinsituanalysis of nitride superlattices is described. Superlattices are deposited from two sputter sources aimed at a fixed substrate position. The chamber features a sample insertion load lock, a computer‐controlled shutter to modulate the sputtered fluxes, a retarding field analyzer forinsitulow energy electron diffraction and Auger electron spectroscopy (AES), and substrate heating to>800 °C. Deposition of epitaxial TiN, VN, NbN, and nitride superlattices is described. Deposition rates decreased, and the film nitrogen content increased until stoichiometry was reached, as the N2partial pressure was increased. The film thickness and composition were uniform to within 10% over the 1.2 cm wide substrates. AES studies of the initial stages of TiN deposition onto VN(100) indicated a layer‐by‐layer growth mechanism. Single‐crystal TiN/NbN(100) and TiN/V0.6Nb0.4N(100) superlattices were grown and found to have flat, sharp interfaces, and exhibited hardness enhancements in excess of 200% over homogeneous alloys of the same composition.

ISSN:0734-2101    

DOI:10.1116/1.578069

出版商:American Vacuum Society    

年代:1992

数据来源: AIP