Reactions between Pt and SiGe alloy have been studied by comparing several structures: Pt/Ge, Pt/SiGe, and Pt/Si-SiGe superlattices. The Ge, SiGe layers and Si-SiGe superlattices were grown on (100) Si substrates by the ultrahigh vacuum/chemical vapor deposition technique. Pt-Ge reactions start around 200 °C, forming PtzGe. This is followed by the formation of PtGe around 300 °C. The Pt-Ge reactions are thus similar to those of Pt-Si. The reactions between Pt and SiGe, however, involve a preferential Pt-Si reaction. At 200 °C, for example, while Pt2Ge is normally seen from the Pt/Ge system, only PtzSi is detected from both x-ray diffraction and Rutherford backscattering measurements. At higher temperatures, both the PtGe and PtSi phases form. This preferential Pt-Si reaction is observed in both Pt/SiGe and Pt/Si-SiGe superlattice structures.

Chemical/mechanical (C/M) planarization is a technique that has received attention lately due to the industry-wide trend toward multilevel device processing. In most multilevel schemes, the most commonly planarized layer is the interlevel dielectric, usually an oxide. In order to understand the response of this oxide layer to the planarization process, the authors have addressed the issues of chemical and structural effects of C/M planarization on silicon dioxide films. Transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) spectroscopy were used to examine the films and revealed that there are chemical and structural changes that occur within 200 nm of the film surface.

The step-coverage and gap-filling characteristics of SiO2 films deposited by TEOS based plasma CVD and Thermal CVD processes on AlX and Cu/X metallizations were studied. It was found that the conformality of the films, in the case of plasma CVD, is influenced by the relative flow rates of TEOS to oxygen. The suitability of the two types of SiO2 films for filling gaps of different aspect ratios on AlX and Cu/X metallizations with different aspect ratios was examined. The results are discussed and correlated with the other important characteristics of these SiO2 films.

Some metallization systems consisting of barrier metals and Au-Sn (multiple alternating layers) were studied as a bonding schemes of InP-based laser diodes to the first time used, CVD-diamond submounts. The first system to be studied, which was traditionally used in various other applications was Ti(100nm)/Pt(200nm)/Au(500nm)/Au-Sn(2.5 μm). This structure provided a molten Au-Sn layer of eutectic composition (80:20 wt%) on top of the Ti/Pt metals for about 6 sec, while heated at temperatures of 300 to 350°C, and allowed for efficient bonding of the device to the submount. Longer heating durations, however, led to reaction between Pt and Sn to consume significant amounts of Sn from the solder, thus elevating its melting temperature and resolidifying the solder. With optimum bonding conditions, a high quality bond of the InP-based laser diode to the CVD-diamond submount was observed, and a superior electrical performance of the diode was measured compared to diodes that were bonded with the standard In/BeO configurations. In order to maintain the superior performance of the InP laser diode bonded assembly but improve the thermodynamic stability of the metallurgical system and thus extending the bonding processing window, various metals such as W and Cr were studied as a replacement for the Ti/Pt barrier metals in between the CVD-diamond submount and the Au-Sn solder. While applying the W layer, a thin Ti(10nm) layer was introduced in between it and the Au-Sn to improve the solder wettability. The W layer was found to remain intact after heating at 350°C for durations as long as 5 min, and thus, due to the inert nature of the Au-Sn/W interface, the Au-Sn ratio was kept uniform at the eutectic liquid composition through a long heating duration (up to 5 min). Minimum reaction was observed, as well, at the Au-Sn/Cr interface, while executing a Ti(100nm)/Cr(200nm)/Au-Sn(1.5 μm) system, and thus allowed for an excellent bonding of the InP laser diodes to the CVD-diamond submounts.

A process has been developed for the deposition of patterned adherent metal on diamond substrates using low temperature processing conditions. CVD diamond films on Si wafers were oxidized with an RFO2 plasma and subsequently functionalized by attachment of self-assembled ultrathin films (UTFs) to the oxidized diamond surface. The UTFs were exposed to patterned deep UV radiation, and selectively metallized by electroless (EL) deposition. EL Ni and Co patterns, with feature sizes to 20 μm linewidth have been produced. Oxidized and UTF-modified surfaces were characterized by surface spectroscopie and wettability techniques. The EL metal deposits on the diamond substrate passed the Scotch tape adhesion peel test.

An investigation of the temperature stability and high temperature characteristics of GaAs FETs on CVD diamond heat sinks was carried out by modeling the high temperature electrical characteristics for GaAs MESFETs and by experimentally measuring the elevated temperature performance. The thermal characteristics were determined experimentally using infrared microscopy techniques. The thermal measurements by infrared microscopy were correlated with results of a finite element analysis calculation of the GaAs FET thermal distribution. Reliability testing at 230°C resulted in an MTF of approximately 2000 hours.

For the application in self-aligned processes, it was supposed that CoSi2 could be superior to TiSi2, since, unlike Ti, a reaction between Co and SiO2 was not observed up to now. We studied the reaction of Co and SiO2 during ion-beam mixing and rapid thermal annealing (RTA). The influences of As and Ge implantation energy and dose were investigated in the range of 50 to 200 keV and 1–1014 to 5–1015 cm2. The annealing temperature was varied between 700° C and 1100°C.

It could be demonstrated that the Co concentration in SiO2 rises with increasing Ge and As energy and dose up to values of 5·1015 cm2 compared to 2·1012 cm2 in unim-planted, annealed samples. The Co profiles in SiO2 were also studied by secondary ion mass spectroscopy (SIMS) and compared with Monte-Carlo simulations indicating pure ballistic mixing. Plan-view and cross-section transmission electron microscopy (TEM) were used to examine the SiO2 surface as well as the Co-SiO2 interface. These investigations revealed that ion-beam mixing with doses at or above 5·1014 cm2 and subsequent annealing does not damage the SiO2 unlike to unimplanted, annealed samples which show a rather severe structural change of the SiO2 surface increasing with rising annealing temperatures.

To meet the needs for vertical integration in microelectronic devices, metalization should not only provide required conducting properties, but should also be suitable for further epitaxial growth so that multilayer structures or heterostructures can be formed. For Si based electronic devices, this has been hindered by the amorphous nature of SiO2. SiO2 layers have been extensively used to passivate the Si surfaces and act as dielectric insulators for forming integrated circuits. In this study, we show that high quality, oriented, metallic nickel disilicide (NiSi2) thin films can be formed on SiO2/Si by combining both ion implantation and e-beam evaporation techniques. The orientation of the Si substrate is maintained in the NiSi2 film as if the SiO2 is not present. RBS/ion channeling and TEM were used to characterize the structures formed and the results indicated that the metallic NiSi2 films were comparable with the films made directly on Si under the same deposition condition. This method should, in general, be applicable to other suicides that have been epitaxially grown on Si.

An investigation of the stability and electrical characteristics of Aluminum-Copper bilayer films on SiO2 has been carried out. In this investigation, a thin layer of sputtered aluminum is used as a diffusion barrier/adhesion promoter between the copper and SiO2. The electrical performance of these structures when subjected to thermal cycles and applied biases is determined. The interactions and diffusion of copper through aluminum into SiO2 was investigated using both blanket films and MOS capacitors. Results are compared with those obtained from structures of Al and Cu metallization on SiO2. Samples were annealed at various temperatures in the range of 200°C to 500°C. Analysis using four-point probe resistivity measurements, X-ray diffraction, and Rutherford Back Scattering were carried out. MOS capacitors are used to establish performance under applied bias. Capacitance-Voltage characteristics of formed alloys are discussed. These results will be presented and discussed in view of the applicability of aluminum as the adhesion promoter for copper interconnections on SiO2.

Co-evaporated Au-Ti thin films deposited onto sapphire and silicon dioxide substrates were thermally treated over a temperature range of 300–900°C in both vacuum and reactive amb ients. Vacuum annealing produced negligible reaction between the oxide substrate and film, the Au-Ti, however, reacted to form intermetallic compounds with little net elemental redistribution in the film. Heat treating in oxygen resulted in segregation of titanium to the surface where it formed both rutile and anatase structures. In addition, the high interfacial energy between the gold and the oxide phases led to the formation of large (5 micron diameter) gold particles on the film surface or voids at the titania-gold interface. Annealing in Ammomia produced an oxynitride surface in addition to the Ti-Au separation, Au particulate formation, and/or interfacial voiding already observed. The extent of surface degradation observed during these reactive ambient anneals varied with Ti concentration and temperature. The film did not react with SiO2 under any circumstances, however, at temperatures above 650°C in reactive ambients the titanium accumulated at the Al2,O3 interface. These results were obtained by RBS, X-ray diffraction, TEM and SEM.

Electrical characterization has demonstrated dramatic differences in the amount of heat treatment time required to convert the ohmic contact metallizations from Schottky to ohmic behavior, depending on the layering sequence of the Al, Ge, and Ni metals. Additional time differences were found to be dependent on the doping concentration of the contact layer of the GaAs and on the heat treatment temperature. For samples with Ge at the metal-semiconductor interface, the time required to convert from Schottky to ohmic behavior varies inversely with the doping concentration of the contact layer and directly with heat treatment temperature. Samples with Ni at the metal-semiconductor interface converted from Schottky to ohmic behavior much faster and had a much smaller dependence on the doping concentration and the heat treatment temperature. Models to explain these observations in terms of interdiffusion of the components and phases formed will be proposed.

Differential scanning calorimetry (DSC) has been used to study the temperatures, kinetics and phase formation mechanisms in Cu/Mg multilayer thin films. When the Cu:Mg layer thickness ratio was 1:4, CuMg2 was the only phase that formed. Cu/Mg films with a layer thickness ratio of 1:1 first form CuMg2 at 215°C with an activation energy of 1.0 ± 0.04 eV and then Cu2Mg at 380°C with an activation energy of 0.73 ± 0.04 eV. The temperatures at which the two phases form decrease as the layer thicknesses decrease due to the shorter reaction times needed in thinner films. The constant scan rate DSC data from films with a layer thickness ratio of 1:1 show three exothermic peaks. The first peak is extremely sharp and results from the formation of isolated nuclei of CuMg2 at the Cu/Mg interface. The formation of CuMg2 is thus shown to be nucleation controlled. The second peak is a growth peak due to the heat released during the growth of CuMg2. The third peak corresponds to the formation and growth of Cu2Mg.

We have demonstrated that aluminum can be grown epitaxially on H-terminated Si(100) substrates under modest vacuum conditions using thermal deposition. The effect of 1 keV to 4 keV ion bombardment during deposition was found to be either minimal or detrimental. Preliminary results from sputter-deposited Al films show very different behavior, with the films tending to relax from the epitaxial (110) texture to a (111) texture.