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It has been shown that titanium disilicide is an appropriate material for producing contacts for electrical characterization of chemically altered silicon surfaces and nanostructures produced by ultrahigh vacuum or wet chemical techniques. The TiSi2/Si system can be flash cleaned at temperatures of up to 1200 deg C because of low diffusivity of the TiSi2.

Research was conducted to examine the increase in static friction force as the duration of stationary contact increases. A comprehensive kinetic meniscus model was developed to explain the phenomenon both for multiple asperity and single asperity contacts at a liquid mediated interface. Results reveal that the static friction increases up to a certain equilibrium time after which it remains constant.

Research was conducted to achieve a low specific contact resistance to p-type GaN by developing a contact. A bi-layer Ni/Au film deposited on p-type Ga followed by heat treatment in air to transform the metallic Ni into NiO along with an amorphous Ni-Ga-O phase and large Au grains comprised the contact. A model was used to explain the mechanism for obtaining low-resistance ohmic contacts for the oxidized Ni/Au films using energy band diagrams of the Au/pp-NiO/p-GaN structure.

A study was conducted to investigate the feasibility of preparing low dielectric constant materials using a conventional, parallel plate, plasma enhanced chemical vapor deposition (PECVD) process and processing the film at 400 degrees centigrade. The SiC-based films investigated in the experiment were deposited in a parallel-plate radio frequency PECVD reactor. Experimental methodology, results and conclusions are discussed.

The reliability of and prevention of nucleation and growth of voids in interconnects in microelectronic circuits has become a major concern for the microelectronics industry. Diffusion is believed to have an important part in the nucleation and growth of voids in interconnects. A parametric study was therefore conducted to investigate in detail of void migration and evolution in an idealized interconnect due to electromigration induced surface diffusion. Results are discussed.

The electrical properties of titanium silicide contacts to nitrogen implanted 6H-SiC were studied by applying linear transmission line technique structures at temperatures up to 673 K. Nitrogen was implanted into a p-type 6H-SiC epilayer at 500 deg C and activated at 1700 deg C, resulting in an activated donor concentration of N(sub D) = 5 X 10(super 9) cm(super -3) to a depth of 300 nm with a decreased electrically active surface concentration of about N(sub D) approximately = 5 X 10(super 18) cm(super -3).

A study was conducted to analyze the ageing of aluminum electrical contacts to porous silicon. Electrochemical etching was utilized to form the porous silicon layers under different conditions. The backsides of the wafers were coated with an aluminum layer and were annealed at 400 degrees C. Experimental results indicated that the chemical etching of the surface of the porous silicon correlated with the low diminution of the current.

The conductivity of thin wires depends heavily on the properties, particularly the geometry, of contacts. Three hypothetical cases of thin wires, which possess a radius less than the bulk screening length, are studied to show that the current-voltage characteristic of a wire differs in all cases and depends on the type of contacts, which can be the Ohmic or Schottky type. Wire conductivity increases with signal frequencies for any type of low-dimensional contacts.

Contact electrification measurements were performed on micrometer-sized spheres composed of polystyrene and flat substrates of either freshly cleaved, highly oriented pyrolytic graphite (HOPG) or a 0.2-micron-thick Au(111) film grown on mica. Atomic force microscopy was employed. The polystyrene/HOPG interaction showed substantial electrostatic charging relative to the polystyrene/Au system.

Ohmic contacts on p-type GaN films were developed using Ni/Au layers prepared by thermal alloying and electron beam evaporation. The presence of Ga-Ni and Ga-Au compounds at the metal-semiconductor interface was found to cause a decrease in Schottky barrier height. X-ray diffraction measurements also reveal that Ni3N and Ga4Ni3 compounds developed at the metal-semiconductor interface.

A study was conducted on the microstructural reactions of PdGe ohmic contact to n-type GaAs using x-ray diffraction, slow positron beam and Auger electron spectroscopy. The lowest contact resistance of 1.7 ohm mm and the formation of a PdGe compound were found at the annealing temperature of 240 degrees C. Moreover, Ga vacancies were formed below PdGe during the formation of PdGe ohmic contact to n-type GaAs.

Thermally stable, low-resistance ohmic contacts to GaAs were produced by utilizing PdIn metallization sputter-deposited from an alloy target. Average specific contact resistances (rho(sub c)) in the 10(super -6) ohm-sq.cm. range were attained upon annealing at 600 degrees C or higher. Contacts annealed under the optimum condition of 850 degrees C for 15 sec. showed an average rho(sub c) of 2.5 X 10(super -6) ohm-sq.cm. The 100 hours of thermal aging at 400 or 500 degrees C increased their average rho(sub c) to 3.0 X 10(super -6) and 1.0 X 10(super -5) ohm-sq.cm., respectively.

Phase formation in rapid thermally annealed Pd/Ge contacts on In0.53Ga0.47As was examined through cross-sectional transmission electron microscopy, convergent-beam electron diffraction and energy-dispersive x-ray analysis. Solid-phase regrowth occurred in the same way as in Pd/Ge contacts on GaAs or InP. The reaction began at low temperatures with the formation of an amorphous Pd-In-Ga-As layer, which crystallized at higher temperatures producing hexagonal Pd4In0.53Ga0.47As. Above 250 degrees C, this phase decomposed due to epitaxial solid-phase regrowth of In0.53Ga0.47As and formation of Pd-Ge phases. The stable composition was attained at temperatures beyond 350 degrees C.

Interfacial microstructures of Pd/Ge/Ti/Au ohmic contact to n-type GaAs were studied utilizing cross-sectional transmission electron microscopy and the results are employed for interpreting the electrical characteristics. Annealing at 300 degrees C produces a contact resistance of 0.62 ohm mm and the layer structure is modified to GaAs/PdGe/Au4ti/TiO. The ohmic contact is formed through a solid phase regrowth of GaAs heavily doped with Ge below the PdGe layer. The lowest contact resistance of 0.43 ohm mm was measured at 380 degrees C. The layer structure is modified to GaAs/(Ge-Ti)/PdGe/TiO.

The ohmic contacts are modelled by using the modified sheet resistance to define the region of alloying/reaction below the region of metallization. The sheet resistance is used as a function of the annealing temperature. The definition of the alloying/reaction regions reveals that the diffusion of the Zn results in the generation of low resistivity phases in this region.

A detailed study of liquid-encapsulation Czochralski- and metal-organic chemical vapor deposition-grown ohmic contacts such as Pd or Ni indicates that the nature of the p-InP substrates influences the contact resistivity and current-voltage characteristics of these single-element contacts. The absence of p-type dopants ensures better ohmic character of these contacts, which can be explained by a tunneling mechanism mediated by the contact defects. These single-element contacts possess contact resistivities almost similar to those of the Au-based contacts.

A study of the thermal degradation of ohmic contacts reveals that a single degradation process cannot rationalize the contact degradation at different temperatures. Ohmic contacts used in the study are produced by solid-phase regrowth process. Degradation is caused by reaction-controlled and diffusion-controlled mechanisms, the former being suppressible by the use of SiN(x) capping layers.

Experimental data reveal the dependence of ohmic contacts on rapid thermal annealing-treated GaAs on Si on annealing temperature. The electrical resistivity in the GaAs layer and hence, the contact resistance increases with an enhancement of annealing temperature. The amphoteric nature of Si dopants and high density of lattice defects in heteroepitaxial layers account for the deviating behavior of GaAs on Si.

Analysis of the electrical properties of Pd/Zn/Pd/Au ohmic contact to p-type InGaAs/InP with respect to annealing and interfacial ZnPd layer ratio shows that interactions between InGaAs and Pd and that a Zn atom-induced doping process at the surface region accounts for the effects of annealing and Zn and Pd interfacial layers on electrical properties. Annealing of contacts with more than 450 degrees Celsius temperature causes an intermixing of InGaAs and metal layers. Annealing also reduces specific contact resistance when the Pd and Zn interfacial layer thicknesses exceed 100 and 50 Angstrom units, respectively.

The addition of Au to NiGe ohmic contacts of n-type GaAs yields a contact resistance that is about 0.2 ohm mm less than that of the NiGe(In) contact. The NiGe(Au) contact surface is smooth and thermally stable during isothermal annealing at 400 degrees Celsius. The GaAs/metal interface is stable and uniform and the contact metal's diffusion depth is shallow.

Electrical and microstructural analyses of NiGe ohmic contacts reveal that In addition to the contacts greatly reduce contact resistance. The resistance reduces without degradation of contact thermal stability, surface smoothness and shallow diffusion depth. The reduction in contact resistance occurs due to regrown GaAs and InGaAs layer formation between NiGe and GaAs substrate.

A comparison of two differently doped n-InAs/InGaAs and n-InGaAs layers containing non-alloyed Ti/Pt/Au contacts as deposits reveals that the n-InAs/InGaAs is superior with respect to ohmic properties. Very rapid thermal processing prevents ion-damage-induced decrease in semiconductor properties and improves the contacts tunneling operation. The InAs/InGaAs layer yields low resistance contacts without thermal processing.

The characteristics of near-micron and submicron-sized InP transferred electron devices with alloyed metal cathode contacts were investigated using experimental and numerical analysis. The results showed that there was a significant deviation from long device behavior as the device length decreased into the submicron region.

An approach based on barrier strength parameters for investigating the electrical characteristics of normal: superconductor point contacts was presented. The technique determined the characteristics of point contacts by using barrier strength as the sole parameter and considered the differential conductance of a point contact at zero bias as a function of temperature. Several different strategies for determining barrier strength parameters were discussed.

Decomposition of the GaAs substrate during the formation of Au(Zn)/p-GaAs ohmic contacts by furnace annealing either in open or closed configurations with a dielectric cap was investigated. The results showed that GaAs decomposition was determined by the application of the capping layer and the amount of Ga diffused into the Au(Zn) metallization. Arsenic loss was reduced by using thin 10 nm Au/10 nm Zn/30 nm Au metallization annealed with a sputter-deposited insulating capping layer.

The electrical and metallurgical characteristics of a low resistance Ag-InP contact system were investigated. The results showed that low specific contact resistivity can be easily obtained on n-InP after a 400 degree celsius sintering process. However, this is accompanied by InP dissolution into the metallization which caused degradation of device quality. The system exhibited characteristics similar to those of Au-InP systems.

The influence of surface hydrogen on the characteristics of metal-diamond interfaces was investigated using photoelectron spectroscopy. The results showed that surface band bending on the reconstructed surfaces was not affected by metal thickness. The surface-state densities on the unreconstructed surfaces were significantly lower, indicating a Fermi level which was not strongly-pinned.

The electrical and metallurgical characteristics of low resistance Ni contacts to InP were investigated. The results showed that sintering for several minutes at 400 degrees celsius resulted in low specific contact resistivity for Ni-only contacts on n-type InP. After extended sintering, contact metallization decreased from the initial three layers to only two. The low resistivity was attributed to the presence of Ni3P.

The thermal stability of the Al/Al12W/W2N/Si contact system was investigated using Auger electron spectroscopy. The results showed that the Al12W layer acted as an effective barrier and was able to suppress any reaction between Al and W. The effect was achieved by the successive combination of the thin film assembly where the materials on the border of each side consisted of one common constituent metal.

The effects of an argon presputtering process and postdeposition annealing onthe formation of aluminum electrical contacts on polycrystalline diamond were investigated using x-ray photoelectron spectroscopy and Auger electron spectroscopy. The results showed that presputtering induced the Al overlayer toreact with the diamond surface to form Al-C bonds after annealing at 430 degrees celsius. Defects in the surface region played a role in the solid statediffusion of Al and C at the interface and in the promotion of the reaction.

The hightempearture properties of amorphous TiWSi nonalloyed ohmic contacts to GaAs were investigated. The results showed that the As-deposited contacts exhibited ohmic behavior even without any post-deposition heat treatment. Contact resistivity values as low as 9 x 10(super -7) were obtained from the contacts. There was no observed interdiffusion at the metal/semiconductor interface.

The fabrication of metal Schottky barrier contacts to n-type 6H-SiC was investigated using x-ray photoemission spectroscopy. The results showed that Schottky barrier height was dependent on the 6H-SiC crystal face. Mg and Al had a Schottky barrier height of 0.3 eV, which was applicable for nonalloyed ohmic contacts. The Schottky barrier heights for several metal contacts with near ideal interfaces to 6H-SiC had a wide 1.3 eV range.

The microstructure and electrical characteristics of nonalloyed epitaxial Au-Ge ohmic contacts were investigated using scanning electron microscopy, Auger electron spectroscopy, transmission electron microscopy and secondary ionmass spectroscopy. The results showed that localized reactions across the surface with significant levels of Ge, Ga and As interactions were present. Localized reactions and island growth and thermodynamics were found to be heavily influential in ohmic contact formation.

The ideal process parameters for the development of low resistance thermally stableNiSiW ohmic contacts were investigated. The results showed that the Si concentration levels in the NiSiW contacts and the annealing conditions determined the ohmic behavior. Ohmic contacts with 40 at.% Si prepared by annealing at 650 degrees celsius exhibited smooth surfaces and good thermal stability during subsequent annealing at 400 degree celsius. The NiAs compoundsformed during contact annealing was the main parameter that affected the electrical characteristics.

The thermal stability of nongold NiGe ohmic contacts prepared by the conventional AuGeNi contact fabrication process was evaluated. In addition, the microstructure of these contacts were investigated. The results showed that thermal stability wasaffected by the microstructure at the GaAs/metal interface. When the NiGe contacts formed high melting point NiGe compounds, excellent stability was obtained.

A study was done on the temperature dependence of the electrical properties of metal/n-InP diodes fabricated at low temperature and room temperature. It was shown that diodes produced at room temperature show a decrease in the reverse saturation current density with a decrease of measuring temperature. On the other hand the value of reverse saturation current density fabricated at low temperature was found to be six times smaller than diodes produced at room temperature.

The electric contact properties of NF3 plasma cleaned Si surfaces were studied using x-ray photoemission spectroscopy. A thin silicon residue composed of chemically bonded fluorine, nitrogen and oxygen atoms were found on the surface of Si after plasma cleaning. It was shown that the surface residue is characteristic of fluorine etched silicon whose chemical structure depends on other active materials it reacts with. Further study of the residue show that they do not produce significant effects on electrical contact properties.