摘要:

The scanning tunnel microscope (STM) technique was used to investigate the effect of preparative variables on the degree of aggregation of platinum clusters on a highly oriented pyrolytic graphite (HOPG). Two methods of depositing Pt were investigated: impregnation and vapor deposition. The diameters of the Pt clusters formed on an oxidized HOPG sample prepared by impregnation range from 50 to 500 Å. The clusters were apparently concentrated along the steps and rough patches on the surface. The sizes of the Pt clusters formed by vapor deposition range from 20 to 50 Å. However, the heights of the Pt clusters formed by these two methods are similar and range from about 10 to 40 Å. Distribution of Pt cluster size was formed to be depended on impregnated platinum loading on an oxidized HOPG surface prepared by impregnation. The platinum clusters observed were not mobile on an oxidized HOPG surface during scanning, and STM images were very reproducible.

ISSN:1071-1023    

DOI:10.1116/1.586413

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The authors have characterized in air, carbon films of thickness around 1 nm on Si (100) grown in ultrahigh vacuum conditions by pulsed laser vaporization of a graphite target. The substrate preparation procedure was chosen on the basis of minimizing surface roughness as viewed from scanning tunneling microscope topographic images. Atomic resolution images taken in the constant height mode revealed different atomic ordered configurations. A hexagonal structure was preferentially observed with a lattice parameter of 2.4 ű0.2 Å and extending up to 140×140 Å2. Also, a square lattice, 2.0 ű0.2 Å side, was imaged coexisting with the hexagonal one. Other structures were found which could be related with the substrate.I‐Vspectroscopy was performed in these films showing ap‐type rectifying behavior and an electronic band gap.

ISSN:1071-1023    

DOI:10.1116/1.586414

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A new method based on focused ion beam micromachining of optoelectronic semiconductor microdevices for cross‐sectional transmission electron microscope analyses has been developed. Electron transparent areas in excess of 200 μm2have been fabricated. These enabled an investigation of the origins of structural defects in a prespecified submicron‐sized region of GaInP/AlGaInP‐based semiconductor laser diodes.

ISSN:1071-1023    

DOI:10.1116/1.586415

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

PtSi–n‐Si(100) Schottky contacts have been studied by ballistic electron emission microscopy (BEEM) for PtSi layers from 30 to 195 Å thickness. Locally measured barrier heights were typically close to or above those determined from the diodeI–Vcharacteristics, with a tendency to higher barriers for the thinner silicide films. The ballistic transmission probability also showed local variations with a clear tendency to decrease for increasing PtSi layer thicknesses, which can be understood in terms of the mean free path of hot electrons in PtSi. From simultaneous measurements at several voltages over the same area, maps of the apparent barrier height and transmission rate have been obtained showing sometimes strong local variations of these quantities. Very low and very high apparent barriers that were occasionally observed seemed to show that the simple BEEM picture is not always applicable, possibly due to interface roughness.

ISSN:1071-1023    

DOI:10.1116/1.586416

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This paper presents the analysis of the mean crystallite size and microstress in thin titanium silicide films based on the broadening of x‐ray diffraction profiles. The titanium silicide specimens were obtained by rapid thermal annealing of thin titanium films deposited on single‐crystal silicon substrate. The experimental results have shown either the face centered orthorhombicC54 type TiSi2structure with mean crystallite size of 50 nm or the base centered orthorhombicC49 type TiSi2structure with 20 nm mean crystallite size, depending on annealing conditions. A decrease in the microstress has been observed with increasing annealing times at 800 °C, without significant variations of the mean crystallite size.

ISSN:1071-1023    

DOI:10.1116/1.586417

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Schottky barrier diodes (SBDs) were fabricated on epitaxially grownn‐GaAs by electron beam (e‐beam) deposition of Pt at various rates. The quality of the SBDs was evaluated by standard current–voltage (I–V) measurements and the defects introduced duringe‐beam deposition were characterized by deep level transient spectroscopy (DLTS). The results showed that if the GaAs was shielded from stray electrons originating at thee‐beam filament during deposition, then high quality SBDs were formed. However, if the GaAs was not shielded during deposition, then the quality of the devices was poor and the degree to which their characteristics deviated from ideal increased as the deposition rate decreased, i.e., as the total electron dose reaching the substrate during metallization increased. DLTS revealed that several surface and subsurface defects were introduced during metallization without the electron shield and, for the first time, it is shown that thesee‐beam induced defects result in poor SBD device characteristics.

ISSN:1071-1023    

DOI:10.1116/1.586418

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

In very large scale integrated circuit technology, Al–Si–Cu alloys have been used for interconnections to improve electromigration resistance and suppress stress‐induced voids. Copper addition, however, makes plasma etching difficult because of the formation of residues. We found that micromasks of Al2Cu remain on the etched surface that could cause conical residues of the aluminum alloy. In this article, the formation mechanism of the residues is presented based on structural analyses of the conical residues by transmission electron microscope/energy dispersive x‐ray analysis and x‐ray photoelectron spectroscopy. A multistep, sequential etching process is proposed that effectively eliminates the residues.

ISSN:1071-1023    

DOI:10.1116/1.586419

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The effects of substrate bias on microwave plasma etching have been theoretically analyzed, and the potentials at the surface of the semiconducting and the insulating materials being etched under a substrate bias have been derived. The computed results indicate that the etch rate increases with increasing impinging ion energy which depends strongly on the magnitude and the frequency of the substrate bias voltage. The theory correlates well with the experimental results on the electron cyclotron resonance microwave plasma etching of semiconducting Si and insulating Si3N4films under radio frequency (107Hz) substrate bias voltages.

ISSN:1071-1023    

DOI:10.1116/1.586420

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The electron cyclotron resonance plasma oxidation of silicon was investigated usinginsitustatic spectroscopic ellipsometry during process and dynamic real time ellipsometry at oxidation temperatures between 80 and 400 °C and at various applied bias’. Successful optical modeling of the ellipsometric data was accomplished using a two layer model, in which the top layer is a pure silicon dioxide film over an interface layer. The kinetics results are compatible with the Cabrera–Mott theory for the oxidation by charged species in the limit of low electric field. The effect of applied bias suggests that the oxidizing species is O−. The energy activation is 0.18 eV, substantially lower than the thermal oxidation value.

ISSN:1071-1023    

DOI:10.1116/1.586421

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

A ballistic deposition model (SIMBAD) has been extended to provide qualitative cross‐sectional depictions of the microstructure present in chemical vapor deposited (CVD) films. The model qualitatively depicts the pronounced columnar structure typical of refractory metal, nitride, and silicide films−especially when deposited over integrated circuit topography. The important factors affecting thin film microstructure are seen to be flux shadowing, precursor surface diffusion, and a nonunity sticking coefficient. While the conformal step coverage typical of refractory CVD films is primarily due to a low sticking coefficient, the detailed columnar structure is the result of all three of these mechanisms. The angular distribution of the incident precursor flux is important to the shadowing mechanism, and a sticking coefficient‐dependent angular distribution relevant to CVD is presented. Variations of the model to represent selective deposition (including selectivity loss) are also shown.

ISSN:1071-1023    

DOI:10.1116/1.586422

出版商:American Vacuum Society    

年代:1992

数据来源: AIP