Thin films of W were grown using the low pressure chemical-vapour deposition technique in WF6/SiH4 flow on a TiN layer obtained by annealing in nitrogen atmosphere Ti films for different times. The investigation of W nucleation was followed by Atomic Force Microscopy in air. The Atomic Force images taken after fixed time of exposure of the TiN layer to the WF6/SiH4 flow show, on the surface of the W films, the presence of columnar structures only when the TiN films were obtained with forming times below 100 minutes. To investigate this effect X-ray Photoelectron Spectroscopy depth profile and X-Ray Diffraction measurements were performed on the obtained W/TiN films. The results show the deeper penetration of the nitrogen into the titanium layer with the longer forming time and a non stoichiometric composition of TiN interfacial layer which strongly influences the W nucleation.

The nucleation and growth characteristics of CVD-W on Ti/TiN barrier layers with SiH4 and H2 reduction chemistries are presented. In particular, the reaction between WF6 (precursor used for depositing W) and the underlying Ti of the barrier stack was studied to better understand the chemistry of ‘volcano’ formation - a phenomena that causes severe defects in the deposited W film. Ti/TiN processing parameters and stack thicknesses were varied, along with the CVD-W deposition chemistry (gas flows, pressures, temperatures and times), to evaluate film properties and characteristics after SiH4 passivation, nucleation and full W plug deposition. The analysis was augmented with cross-sectional Scanning Electron Microscopy (SEM) on short-loop testers and films were characterized using Rutherford Backscattering Spectroscopy (RBS), Secondary Ion Mass Spectroscopy (SIMS), X-ray Diffraction (XRD) and Auger Electron Spectroscopy (AES) techniques. Several processing conditions are recommended for ‘volcano-free’ and ‘defect-free’ CVD-W films.

The behavior of Cu and Si in the Al-alloy / TiN interface has been demonstrated by techniques of SIMS, GDS, XRD and AES. Cu and Si were observed to segregate at the AlSiCu / TiN interfaces just after sputtered. This segregation occurred to form a layered structure, not an island one. As these materials at the interface remained to exist even after annealing, the distribution of Cu and Si after annealing would be governed by that just as sputtered. The segregation behavior of Cu in A1Cu / TiN structure was the same as that of AlSiCu / TiN.

Very thin films of cadmium, with a mean thickness between 1 Å and 500 Å, were deposited by thermal evaporation in ultra-high-vacuum on a Si(100) 2×1 surface held at room temperature. In situ X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy were performed in order to investigate the interaction between the silicon substrate and the deposited cadmium. In samples with deposited mean thickness up to 3 Å, cadmium and silicon are found to be strongly interacting. In fact both XPS and AES spectra show evident changes in shape and energy position leading to the conclusion that a chemical compound between Cd and Si is formed. No diffusion between cadmium and silicon is observed, so the cadmium atoms deposited after the first 3 Å show a bulk character. The analysis of the first derivative intensity of the Si L23VV and Cd M5N45N45 Auger signals, varying the amount of deposited Cd, indicates the formation of islands in the early stage of the Cd growth. These islands show an amorphous structure as observed by using the LEED spectroscopy.

We present results on the evolution of Co/Ge films on Si(100) substrates. Room temperature deposition of 18 nm thick Ge films followed by 5 nm thick Co films was done by Molecular Beam Epitaxy (MBE) and then post-deposited annealing was done at 700 C. Using combinations of Scanning electron microscopy, Auger electron spectroscopy and Rutherford backscattering spectroscopy, we determine that the Co and Ge are clustering on the Si surface at these annealing temperatures. During the clustering, the Co is diffusing into the Si substrate leaving a Ge-rich clustered morphology. To test the effect of the Si substrate on the evolution of the films, Co films were deposited on Ge(100) substrates and annealed at 700 C. Clustered morphologies are seen on the Ge substrates and Co in-diffusion is also occurring. The morphologies on the Ge substrates are significantly different from those on the Si substrates.

The specific contact resistance, pc, of Au/Zn/Au, Ni/Zn/Ni/Au, Pd/Zn/Pt/Au and Pd/Mln/Sb/Pd/Au contacts to p-In0.47Ga0.53As/ InP has been measured as a function of layer thickness of Zn or Mn. All of the as-deposited contacts were ohmic, with pc = 1−2 × 10−5 Ω cm2. Increasing thickness of the Zn layer above 200 Å in the Au/Zn/Au contacts resulted in a minor decrease in pc while producing no change in the Ni/Zn/Ni/Au metallization. For the as-deposited Pd/Mn/Pd/Au contacts, the value of pc was independent of thickness of the Mn layer but differences in pc emerged at annealing temperatures of ≥ 250°. The analysis of these structures by RBS has shown an extensive intermixing of the metal layers at an annealing temperature of 450 °. In the Pd/Zn/Pt/Au contacts, the value of pc was reduced to a minimum value of 8 × 10−6 Ω cm2 by annealing at a temperature of 500 °. An examination of the Pd/Zn/Pt/Au configuration by RBS has shown that the Pt layer acted as a barrier for the indiffusion of the Au.

Interfacial microstructure and phase composition of PtTiGePd ohmic contacts to heavily C doped AlGaAs were investigated as a function of annealing temperature. Results of the material analyses were used to explain the specific contact resistances measured for each thermal treatment. Evidence of interdiffusion and compound formation between AIGaAs and Pd was visible in a Ga rich Pd-Ga-As reaction zone prior to heat treatment. This phase is critical for the formation of Ga vacancies, which upon heating are occupied by in-diffusing Ge. As the annealing temperature was elevated, from 530 - 600°C, As began to out-diffuse. This As out-diffusion, which is critical to the formation of good p-type ohmic contacts, contributed to the creation and development of the two phase TiAs/Pd12Ga2Ge5 interfacial region overlying the AlGaAs substrate. In response to the enhanced As out-diffusion at 600°C, the interfacial region became laterally continuous, compositionally uniform, and the specific contact resistance achieved its minimum value. Athigher annealing temperatures, ∼650°C, the electrical measurements degraded in response to intensive chemical diffusion and development of a broad, non-uniform multi-phased interfacial region.

ONO (SiO2/Si3N4/SiO2) structures with thickness less than 10 nm were deposited onto silicon wafers by successive steps using two different method. The effects of the forming time and temperature on the stoichiometry of the single layers and of the whole sandwich have been studied using X-ray Photoelectron Spectroscopy (XPS). This paper demonstrates that the “Auger parameter method” is highly suitable in quantifying the composition of very thin insulating structures.

The standard Transmission Line Model (TLM) is an electrical network that is commonly used to model planar two-layer (metal-semiconductor) ohmic contacts. More complex multilayered planar structures have led to the development of more complex models. A Tri-Layer Transmission Line Model (TLTLM) was recently proposed in order to more accurately represent an alloyed ohmic contact. The TLTLM also enables other layered planar contact structures such as non-alloyed n+/n, heterojunction and metal-silicide-silicon contacts to be analysed. In this paper, it is shown that when the TLTLM is combined with a modified TLM network, important device properties such as contact and parasitic resistance can be derived for device structures using several epilayers such as FET's. An example is given of the current distribution in an FET and the calculation of the parasitic resistance in the gate-drain channel and the contact resistance of the drain.

Al-.5Cu is used as an interconnect conductor in ultra large scale integration (ULSI) devices. The specific use investigated in this study is as a gate electrode deposited directly on extremely thin 6 nm TCA SiO2. Changes in microstructure and reactions between the AI-.5Cu and SiO2 following heat treatment were characterized using analytical electron microscopy. When Al-iSi or AI-.5Cu are used as gate electrodes in a metal oxide Si field effect transistor (MOSFET) a conducting diffusion barrier layer of TiN or heavily doped poly-Si is usually deposited between the AI alloy and the SiO2. The addition of this relatively high resistivity barrier layer increases the power consumption of a MOSFET constructed with this gate electrode, increases the operating voltage necessary and decreases the frequency at which the MOSFET can be switched.1 An Al-.5Cu metal oxide silicon (MOS) device maintained a high break down voltage without a diffusion barrier following heat treatment by forming an Al-Cu intermetallic at the silica/metal interface.

Thin metal layers play an important role in the development of electronic devices. The thin metal films deposited at low temperature (LT=77K) showed some unique properties which enhanced device performance. The micro-structural properties of thin metal films formed at room temperature (RT) and LT were investigated. An insulating substrate was used for Au, Pd Al and Ag metal deposition. The metal films were deposited by vacuum evaporation with thickness ranged from 100 Å to 100 Å. The surface morphology of the metal films was determined by transmission electron spectroscopy (TEM). The resistance of the films was insitu measured as a function of film thickness and temperature. Electrical measurement found that these films shown several orders lower resistance compared to the film obtained at room temperature at very thin thickness, which, implies potential application of these films on electronic and optoelectronic devices. It is found that the LT films showed much lower densities of grain boundaries than the RT samples. This is consistent with the resistivity measurement results.

In this article we report the first nanoparticle-derived route to smooth, dense, phase-pure CdTe thin films. Capped CdTe nanoparticles were prepared by injection of a mixture of Cd(CH3)2, (n-C8H17)3 PTe and (n-C8H17)3P into (n-C8H17)3PO at elevated temperatures. The resultant nanoparticles 32-45 Å in diameter were characterized by x-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy, thermogravimetric analysis and energy dispersive x-ray spectroscopy. CdTe thin film deposition was accomplished by dissolving CdTe nanoparticles in butanol and then spraying the solution onto SnO2-coated glass substrates at variable susceptor temperatures. Smooth and dense CdTe thin films were obtained using growth temperatures approximately 200 °C less than conventional spray pyrolysis approaches. CdTe films were characterized by x-ray diffraction, UV-Vis spectroscopy, atomic force microscopy, and Auger electron spectroscopy. An increase in crystallinity and average grain size as determined by x-ray diffraction was noted as growth temperature was increased from 240 to 300 °C. This temperature dependence of film grain size was further confirmed by atomic force microscopy with no remnant nanocrystalline morphological features detected. UV-Vis characterization of the CdTe thin films revealed a gradual decrease of the band gap (i.e., elimination of nanocrystalline CdTe phase) as the growth temperature was increased with bulk CdTe optical properties observed for films grown at 300 °C.

A capacitance relative humidity (RH) sensor is described that has a design, construction, and material composition that result in an inexpensive and robust sensor. This sensor has a multilayer, free-standing film construction. It consists of a humidity sensitive polyimide (PI) dielectric core and conductive layers consisting of carbon filled polysulfone on each side of the polyirnide film to form a capacitor. The polyimide used is a BPDA-ODA type, and replaces a PMDA-ODA type polyimide used in a previous version of this sensor. The BPDA-ODA sensor has a nominal capacitance of 200 pF and a nominal sensitivity of 13% at 100% RH. The characteristics of this humidity sensor are discussed and compared to the characteristics of the PMDA-ODA type sensor. Characteristics considered include the PI film moisture uptake and water vapor transmission, and the sensors' sensitivity to relative humidity, frequency response, and aging at 85°C/85% RH. The dual-state sorption model and free volume calculations are used to demonstrate that observed differences in the film are due to differences in chemical composition between the films.

A nicrofabricated silicon-based chemical gas sensor with a discontinuous film of Pt / TiOx, as the active sensing component has been characterized by atomic force microscopy, environmental scanning electron microscopy, and transmission electron microscopy. A study of the device's multilayer structure and of the thin sensing film is undertaken to understand and control the sensing properties of the metal / semiconducting materials. The purpose of this research is to advance the understanding of the conduction mechanism and provide a basis for optimizing the sensing properties and microstructure of the sensing device.

We have performed the investigations of temperature dependencies of dark conductivity σd(T) in a-Si:H films deposited on different substrates (glass, oxynitride, polyimide film) at the temperature range of 20 °C to 250 °C. The temperature dependence of dark conductivity of a-Si:H on glass and oxynitride demonstrates the “kink” at 80 –160 °C. This “kink” wasn't observed in σd(T) measurements of a-Si:H on polyimide. It has been shown that the appearance of “kink” is connected with substrate material, value of applied electric field and its polarity. The relaxation nature of the “kink” is also suggested. Two transport mechanisms of charge carriers are proposed - transport via material bulk and transport via a-Si:H/substrate interface. It is shown that “kink” occurs when transport via interface becomes predominant. The mathematical simulation of this process is also presented.