(111) uniquely oriented large crystalline grain Al thin films have been grown on amorphous substrates such as glass or fused quartz. Al has been evaporated by means of an electron beam in a vacuum of 10-7 mbar which was obtained by a conventional oil diffusion pump in conjunction with a titanium sublimation pump and a series of shields cooled at the liquid nitrogen temperature. By studying the variation of the grain size as a function of the growth temperature, a large increase in the grain size has been found at a substrate temperature 100°C below the Al melting point. This has been interpreted as due to the beginning of the metal surface melting and, as a consequence, to the quasi rheotaxial growth of the metal on itself. When the growth has been carried out at a substrate temperature close to the Al melting point (625°C), the grain size has been found out to increase exponentially as a function of the film thickness with a slope which slows down at a thickness of about 1 pm. (111) oriented columnar grains with a size of 50 – 100 pm, hitherto unreported, have been obtained on glass substrates kept at a maximum temperature of 655 °C. The surface morphology of the Al films has been studied by SEM microscopy while the film structural properties have been studied by an X-ray powder-diffracto-meter and by computer - controlled pole figure goniometer.

A new x-ray diffraction method is developed to determine the full elastic strain tensor and its distribution about a strain center in single crystal materials. It is based on the recently developed Computer Aided Rocking Curve Analyzer and is particularly well suited for analysis of thin film structures common to electronic materials. This technique will be described in detail, and its application in measuring the non-uniform strains in InGaAsP epitaxial film on InP substrate will be presented. Also, possibility of using this method to measure the uniformity of film thickness will be discussed.

A Seemann-Bohlin X-ray diffration attachment has been developed recently. In addition, two new intensity factors are introduced to existing intensity formula of Seemann-Bohlin diffractometer. Its characteristic is that the glancing angle is rather small and that no crystal monochromator is put in the incident path. Compared with the conventional diffractometer, it is superior in many aspects: (1). Very high sensitivity in identifying the structures of solid surfaces and thin films, with the intensities being 7–20 times those of the conventional method. For example, in analysing a gold film of 70 Å thick by 1KW X-ray, a fairly good pattern was obtained up to 2θ=120° with the scanning speed of 4°(2θ)/min. (2). All diffraction peaks obtained give the information of the surface layer in nearly the same depth. It thus enables one to study the variation of the composition, the lattice constants, and the structures with depth. (3). It can also be used for thick polycrys-talline samples, and the intensities are 3–20 times those of the conventional diffractometer. This method can be used for various ordinary diffractometers.

A computer code (BASF) has been constructed to perform automatic iterative fitting of smoothed Rutherford Backscattering Spectra using only the experimental spectrum and the parameter set defining the experiment. The code may be used to analyze anywhere from two to five elements. The code output consists of the total amount of each element present and a composition versus depth profile.

The code's performance was verified experimental backscattering spectra. Samples consisting of nickel substrates onto which layers of nickel and aluminum have been alternately evaporated were used to produce backscattering spectra. These spectra, when analyzed, demonstrated that the code was able to determine the total aluminum content to within 5% and the ratio of aluminum to nickel within 1% of the thickness monitor readings taken during evaporation. The code has also shown the ability to recognize sharp interfaces in well resolved spectra. The ultimate limits on the code's accuracy are the resolution of the spectrum and the accuracy of the computed stopping powers.

A dual ion gun system has been proposed (D.E. Sykes et al, Appl. Surf. Sci. 5(1980)103) to reduce texturing and improve depth resolution during Auger sputter depth profiling. We have evaluated this ion gun configuration by profiling a variety of multilayer structures. With careful alignment of the guns, we have obtained a dramatic decrease in ion-induced texturing often seen when a single ion gun is used. This effect was particularly pronounced for polycrystalline Al films on Si where an order of magnitude improvement in depth resolution was achieved. Further refinements of the technique include the use of low energy (IkeV) grazing incidence xenon ions and a small electron beam probe area. Depth profiles obtained from Ni/Cr, W/Si, and GaAs/GaAlAs multilayer structures will also be discussed.

As solid state device features continue to decrease in size, it has become more important to characterize dopant concentrations within the first several hundred angstroms of the surface. Secondary ion mass spectrometry (SIMS) is the technique of choice for dopant depth profiling due to its high sensitivity and good depth resolution. In order to increase the sensitivity of SIMS, electropositive elements (e.g. oxygen) or electronegative elements (e.g. cesium) are used as primary ion species to enhance positive or negative secondary ion yields, respectively. This has the disadvantage, however, of causing secondary ion yields to vary by up to several orders of magnitude over the first few hundred angstroms of a depth profile as the implanted primary ion concentration increases [1,2]. Secondary ion yields stabilize once the primary ion reaches a steady state concentration, which occurs at a depth proportional to the range of the primary ions in the solid. This ion yield transient artifact hinders quantification of dopant concentrations until the primary ion concentration reaches steady state.

The low pressure pyrolysis of alkylmetals on resistively heated substrates was studied using multiphoton and electron ionization mass analysis. The activation energy for the production of gas phase methyl radicals from the decomposition of trimethylgallium under single collision conditions was found to be 26 ± 3 kcal/mol, which is to be compared to 13 ± 2 kcal/mol previously observed for trimethylaluminum. No evidence could be found for any surface radical reactions leading to the production of CH4 or C2H6. A proposed deposition mechanism accounting for these observations was tested by pyrolyzing trimethylgallium in the presence of hydrazine. No change in methyl signal was observed, supporting the theory that radical reactions do not occur on the surface under the conditions employed.

The roles of Ar and H2 on the decomposition of SiCl4 1n cold plasma were Investigated by Langmulr probes and mass spectrometry. Decomposition of the reactant by Ar only has been found to be very slow. In presence of H2 in the plasma SiCl4 is decomposed by fast radical-molecule reactions which are further enhanced by Ar due to additional 1on-molecule reactions in which more H radicals are produced. A model for the plasma-surface Interactions during deposition of pC-S1 1n the Ar + H2 + SiCl4 system is presented.

The use of CVD W as a diffusion barrier between Al and Si is becoming widespread. The initial stage of the deposition involves the Si reduction of WF6 according to the following reaction:

The reaction is thought to be self-limiting, since once a sufficiently thick W film forms, WF6 and Si are no longer able to be in contact. We have studied the effects of implanted dopant and damage on the rate of this reaction and the thickness of the self-limiting W film. To study the mechanism of W film growth, Si wafers were implanted with As, P or Sb. These wafers were either left in the as-implanted state (amorphized surface layer) or were annealed to drive-in the implant and recrystallize the Si. The reactivity with WF6 of these wafers, as well as unimplanted Si wafers, was then studied as a function of temperature between 210° C and 700° C. Si-WF6 reactivity is shown to have a strong temperature dependence, with maximum reactivity occuring at 340 °C, at which temperature a 960A thick film of W can form. Enhanced diffusion of Si through the growing W film is thought to be the mechanism responsible for thick film growth. At higher temperatures, thinner films form, due to the cessation of enhanced diffusion. Lower temperature films are also thinner, probably due to a nucleation barrier, not a kinetic barrier, to growth. Implantation lowers the temperature of the onset of enhanced reactivity between Si and WF6, when the wafers are reacted in the as-implanted state.

Secondary or abnormal grain growth has been observed in ultrathin films of silicon (<120nm) that were heavily doped with phosphorous or arsenic. This grain growth leads to grains which are much larger than the film thickness (>50x) and which have uniform (111) texture. This abnormal grain growth is believed to be driven, in part, by surface energy minimization and hence is termed surface-energy-driven secondary grain growth.

It was found that n-type dopants, phosphorous and arsenic, markedly enhance the rate of secondary grain growth as seen through a lowering of the temperature required for significant growth. On the other hand, boron (a p-type dopant) appears to neither markedly increase nor decrease the rate of grain growth. Enhancement caused by phosphorous or arsenic is thought to stem from increases in the mobility of the grain boundaries. Enhancement of grain boundary mobility was found to be compensated (reduced or eliminated) by additional doping with boron.

The power of VLSI circuits is, to a large measure, derived through an extensive network of fine-line metalization interconnects used to wire up various components on the chip. For example, the 1Mb DRAM utilizes three levels of conductors to interconnect over one million each of transistors and capacitors on a chip. The combination of larger chip dimensions and finer scaling generates several technology concerns that must be addressed by a variety of measures, including an optimum choice of metalization processes. These concerns are related to parasitics, defect density and generic reliability.

This talk will review trends in materials/processes to control RC time constants, series resistances, fine-line metal defects during pattern transfer, control of topography-related defects and generic reliability related issues such as contact electromigration and ∝-particle sensitivities.

Several silicon wafers were implanted with 58Ni+ at an energy of 170 keV and a current density of 12 μA cm-2 to doses between 5 × 1015 and 1.8 × 1018 ions cm-2. The substrates were phosphorus doped n-type <100> Czochralski grown silicon wafers. The wafers were water cooled during implantation and the surface temperatures was monitored with an infrared pyrometer and controlled to < 70°C. Samples were subsequently furnace annealed at 900°C for 30 min in nitrogen. The as-implanted and annealed samples were analyzed using cross-sectional transmission electron microscopy (XTEM), Rutherford backscattering (RBS) spectroscopy, spreading resistance depth profiling (SRP), and scanning electron microscopy (SEM). Micro-crystallites of NiSi2 (2–5nm) buried within an amorphous matrix formed during the 1.5 × 1017 ions cm-2 dose implantation. For higher doses above 3 × 1017 Ni+ cm-2, ion beam sputtering occurred. After annealing, rapid diffusion of nickel and solid-phase recrystallization of the amorphous regions occurred.

The formation of titanium suicide over polycrystalline silicon has been investigated after rapid thermal annealing treatment in nitrogen and argon ambients. After rapid thermal annealing 300 Å thick titanium overlayer at 900°C for 10 seconds, the sheet resistance of about 3 Ω/□ was achieved, which decreased to 2 Ω/□ after 1100°C / 10s treatment. The TiSi2 Phase was found to be stable after RTA treatments up to 1100°C /10s with no or negligible migration of titanium along the grain boundaries in polycrystalline silicon. In the nitrogen ambient, an external layer (titanium rich, mixture of titanium oxide and nitride) was observed to form after the RTA treatment, but the surface was found clean in the argon ambient.

A strong correlation has been found between the electrical, compositional and structural properties of the polysilicon contact and its interface with the heavily doped pol isi 1-emitter of a transistor. The integrity and thickness of the oxide interface is a major factor for improving the observed performance. Transistors for which the polysilicon was also the diffusion source for the emitter were studied.

Si samples, with and without masking oxide films, implanted with various doses of As, P, or BF2 have been evaluated on the formation of titanium suicides from titanium films. In all cases, suicide reaction for implantation with masking oxide films is more difficult than that for implantation without masking oxide films. Suicide reaction becomes more difficult with decreasing implant energy in the range over a critical dose. In the case of implantation with masking oxide films, knocked oxygen has been found at the surface of Si substrate. Suicide formation after removing the surface layers containing considerable amount of knocked oxygen with argon back-sputtering is as easy as suicide formation for implantation without masking oxide. The difficulty of Ti silicidation for implantation with masking oxide films is believed to be due to the effects of interference from knocked oxygen.

PtSi films have been formed using sputtered Pt and different annealing sequences and ambients. A clear dependence on the annealing sequence and ambient is observed for both the PtSi films and the passivating oxide layers formed. The single-temperature process at 550°C using forming gas (N2-H2 9:1), nitrogen and oxygen shows incomplete reactions between Pt and Si, with a surface oxide layer of poor resistance against etching in aqua regia. A three-temperature process using forming gas is shown to provide complete reactions between Pt and Si, with a surface oxide layer of excellent resistance against aqua regia. The three-temperature process using nitrogen or oxygen, however, fails to provide films of high quality, and the results are similar to those obtained by the single-temperature process in various gases.

An n+ /i/p /i/n amorphous silicon bipolar transistor has been successfully fabricated with a current gain of 12 and a response speed of 30 yS This new structure of bipolar transistor has a very thin base (200Å), therefore, high gain and high speed is obtainable. This device has a very promising applications as a flat panel display transistor and a phototransistor in photosensing element/array and photo coupler. Electrical and optical characteristics have been extensively investigated. Theoretical model and experimental results are plausibly in good agreement.

Variation from the fundamental structure is also been developed, such as the Schottky emitter Al/i/p /i/n bipolar transistor.

The specific contact resistance between any two interconnecting layers is of vital importance in determining the total interconnection resistance of these layers. We present here an experimental technique to obtain the specific contact resistance when both of the conducting layers have finite conductivities of similar magnitudes. This structure is then used to obtain practical information on the poly to single crystal interconnection system, details of which are present. Finally a modification to this system is proposed and its status reviewed.

It is required for the reliable semiconductor to control high junction quality in wire bonding.

It is expected that the Al film properties may considerably affect the junction quality. Yamamoto et al. studied the effects of Al film properties on the bondability in wire bonding by thermocompression bonding system, and disclosed that the breakability of oxide film on the Al is a key factor. [1]

In this report, effects of fabrication condition, properties and bond-ability of Al thin film were investigated in wire bonding by thermosonic bonding system. As a result, it has clarified that concentration of impurities in the Al film is an extremely influential factor for the stability of adhesion and the expansion of alloying region in the junction boundary, that is, for the improvement of junction quality.

Decohesion of thin films from ceramic or semiconductor substrates is strongly influenced by internal stresses in films and stress concentrations from edges or flaws as well as by interfacial fracture energy. Residual stresses can cause spontaneous delamination, splitting and curling of films under tension or delamination, buckling and spal ling of films under residual compression, even with good interfacial bonding. Delamination behavior is considered using simple fracture mechanics models, supplemented with preliminary measurements of interfacial fracture energies. Formation conditions largely control internal stresses in films; whereas fracture energies are dictated by interfacial chemistry and mechanical factors such as plasticity.