摘要:

Photoelectron spectra have been taken from ZnTe/ZnSe and ZnSe/ZnTe heterostructures growninsituby atomic layer epitaxy. Synchrotron radiation within the photon energy range of 70–80 eV was used for excitation. The extent of the interface region was determined by an analysis of the Te 4dand Se 3dcore‐level shifts. The valence‐band offset was determined as a function of layer thickness. After a critical thickness is reached the lattice relaxes and the valence‐band offset becomes +0.50±0.05 eV for ZnTe/ZnSe and −0.55±0.05 eV for ZnSe/ZnTe. Obviously the commutativity rule is well fulfilled within the limits of the experiment.

ISSN:0734-2101    

DOI:10.1116/1.579423

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Partially ionized beam deposition, in which the starting material Ag is evaporated form a crucible with a restricted nozzle, partially ionized by electron bombardment, and the ions accelerated to the deposition substrate, has been used to deposit Ag films on both Si(111) and Si(100) substrates. Characterization of the deposited films has been carried out by x‐ray diffraction, scanning electron microscopy, α‐step roughness, Auger electron spectroscopy, and ellipsometry. As a comparison, Ag films deposited without ion acceleration and by evaporated conventionally from an open crucible were also investigated. Highly textured Ag films with strong (111) orientation on Si(111) have been obtained at high accelerating voltageVa=4 kV. The surface flatness improves and the resistance of the films to impurity diffusion from the surface increases as the accelerating voltage increases.

ISSN:0734-2101    

DOI:10.1116/1.579435

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The ability of the nuclear microprobe with a 2 μm focused beam of MeV He+ions to analyze the active region of individual Hg1−xCdxTe metal–semiconductor–metal (MSM) detectors has been demonstrated. Details of the channeling of Hg1−xCdxTe by Rutherford backscattering spectrometry and the incidence of defects imaged by channeling contrast microscopy were correlated with the performance of devices in a number of arrays. A series of linear growth defects was identified in the active region of some devices using channeling contrast microscopy. The channeling spectra that were extracted from these defective regions have shown a higher value of χmin=24% (the ratio of backscattered particle yield with the crystal 〈100〉 axis aligned with the beam to the yield for a random alignment) than the surrounding crystal χmin=9%–15%. The presence of these linear defects was linked to a degradation in the performance of the corresponding devices in an array. MSM detectors fabricated on Hg1−xCdxTe/GaAs/Si were lower in breakdown voltage than equivalent devices on Hg1−xCdxTe/GaAs. This trend corresponded to a higher value of χminfor the Hg1−xCdxTe on GaAs/Si than with the epitaxial layer grown on GaAs.

ISSN:0734-2101    

DOI:10.1116/1.579437

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Electron stimulated desorption of negative and positive fluorine ions from BaF2surfaces has been studied as a function of impact electron energy. Thresholds observed for F+and F−are correlated with core‐level binding energies of Ba atoms. We propose that core level ionization of Ba ions, followed by an interatomic Auger decay involving halogen ions, can initiate F+desorption, while the formation and subsequent breakup of superexcited molecular complexes containing a core hole can lead directly to the ejection of negative ions.

ISSN:0734-2101    

DOI:10.1116/1.579438

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Infrared spectroscopic experiments were performed to ascertain the mechanisms of molecular contaminant film removal with a carbon dioxide (CO2) gas/solid jet spray. In the jet spray nozzle, liquid CO2expands through an orifice and forms a spray of submillimeter‐sized solid particles entrained in a gas stream. This spray has been shown to be effective in removing particles and some molecular contaminant films. It has been hypothesized that the spray removes films by one of three methods: abrasion by the solid particles, thermal shock of the film, or formation of a transient liquid film into which the film dissolves, and which then resolidifies and scatters from the surface. We have compared the jet spray removal efficiency of contaminant films of varying solubility in CO2and measured in real time the cleaning rates of the jet spray for these films. The infrared spectroscopic data show strong correlations between film removal efficiency, the time required to remove a film, and the solubility of the film in liquid CO2. These data, combined with visual observations, indicate that the CO2jet spray cleaning occurs in two regimes. First, bulk film removal may occur via either thermal shock or abrasion. Second, the residual contaminant film is removed via solvation into the transient liquid CO2film formed by the impacting CO2particles. Not all contaminant films can be removed by this technique. Thick films that formed droplets could not be removed by the spray; the drops were simply moved around on the surface. Thin films that were not sufficiently soluble in CO2were not removed either. These results allow prediction of the jet spray removal efficiency based on identification of the contaminants.

ISSN:0734-2101    

DOI:10.1116/1.579439

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The adsorption and decomposition of dichlorosilane (SiH2Cl2) on silicon surfaces were studied using Fourier transform infrared (FTIR) transmission spectroscopy. These FTIR studies were conductedinsituin an ultrahigh vacuum chamber using high surface area, porous silicon samples. The FTIR spectra of porous silicon following saturation SiH2Cl2exposures at 200 K revealed the presence of primarily dihydride (SiH2) and monochloride (SiCl) surface species. These surfaces species are consistent with an adsorption mechanism involving Si–Cl bond breakage, i.e., SiH2Cl2(g)+2Si*→Si*–SiH2Cl+Si*–Cl. The stability of these surface species was then examined as a function of annealing temperature. The infrared absorbance for the SiH2scissors mode decreased as the temperature was raised from 300 to 660 K. Concurrently, the absorbance increased for the SiH monohydride stretch. These spectral changes indicated that the dihydride (SiH2) species were converted to monohydride (SiH) species. Above 660 K, the SiH species disappeared concurrently with H2desorption from the silicon surface. The uptake of dichlorosilane on porous silicon was also monitored as a function of substrate temperature. These experiments confirmed that SiH2is the major surface hydride species following SiH2Cl2adsorption at low temperatures. These studies of dichlorosilane adsorption and decomposition on silicon surfaces should help to clarify the mechanism of silicon chemical vapor deposition and atomic layer epitaxy with dichloro‐ silane.

ISSN:0734-2101    

DOI:10.1116/1.579440

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Thermal desorption spectroscopy (TDS) has been applied to detect contamination, produced in deep‐submicron contact holes during plasma etching. AlF and other Al‐containing fragments were observed as constituents of the contamination. The contamination is found to be accumulated in the holes, depending on an overetch time, acting as an inhibitor against achieving sufficiently low contact resistance. The effects of cleaning by Ar+ion sputtering after contact‐hole fabrication are also investigated. The sputtering improves the contact resistance significantly. The sharp TDS peaks of AlF and AlC clearly decreased in good relation to the improvement in the contact resistance. The TDS method has proven to be an effective tool in evaluating contamination in the submicron contact holes.

ISSN:0734-2101    

DOI:10.1116/1.579441

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The tunneling current through tin (∼50 Å) silicon dioxide films is observed to have a small oscillatory component at high electric fields. Three main results involving the oscillatory component of the tunneling current are reported. First, a new and improved analysis for obtaining the oscillatory component from the current measurements is described. Then, using this analysis, the dependence of the oscillatory component on oxide thickness and SiO2/Si interface roughness is studied. The thickness study shows that the oscillation amplitude decreases exponentially as the distance traveled by the electron in the conduction band of SiO2increases. This decrease is attributed to the scattering effects and the mean free path of the electron in SiO2is estimated to be 6 Å, in agreement with previous reports. The roughness study is performed on thermally oxidized purposely roughened Si surfaces, and the roughness is characterized by the atomic force microscopy. The oscillations in the tunneling currents show no dependence on the interface roughness, indicating that the roughness at the Si surface has little effect on the thickness uniformity of thermally grown thin oxide films and that oxide films grow uniformly over the roughened Si surfaces for at least the first 50 Å or so.

ISSN:0734-2101    

DOI:10.1116/1.579442

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Radio frequency (rf) plasma oxidation at the floating potential of tantalum silicides, TaSix(0.3≤x≤4.5), has been investigated. The oxidations were carried out in the 400–800 °C temperature range. Measurements of the overall oxygen (16O and18O) and cation contents as well as their distribution in the films were carried out using Rutherford backscattering spectrometry and nuclear microanalysis techniques. The oxidation rate was found to be primarily controlled by the diffusion of the oxidizing species through the oxide. The influence of silicide composition, temperature, and substrate nature on the nature of the oxide has been analyzed. The rf plasma oxidation of TaSixsilicides can be understood as the competition between two diffusion processes: oxygen diffusion from the plasma through the growing oxide and silicon migration from the silicide layer or from the silicon substrate. Both silicon and oxygen diffusion processes coexist and determine the nature of the grown oxide. The mechanisms of oxygen movement were studied using18O as the tracer. The data show the maintenance of the order of oxygen atoms during oxide growth and a partial exchange of16O present in the oxide with the18O of the plasma. These results show that the microscopic mechanism of oxygen transport involves a short‐range oxygen migration.

ISSN:0734-2101    

DOI:10.1116/1.579443

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The dry etching process of palladium thin films has been investigated in Ar–CF4and Ar–CF4–O2glow discharges by performing etch rate measurements and x‐ray photoelectron spectroscopic analyses. The results indicate that the process is one of physical sputtering and that fluorine atoms react with palladium forming a fluorinated layer (probably PdF) which is characterized by a lower sputtering rate than that of metallic palladium.

ISSN:0734-2101    

DOI:10.1116/1.579444

出版商:American Vacuum Society    

年代:1995

数据来源: AIP