Thomas H. Baum

Laser chemical vapor deposition of copper

The first laser‐induced deposition of copper has been demonstrated using a volatile copper coordination complex. The technique is characterized by reasonable rates and by the high quality of copper produced.

Laser chemical vapor deposition of gold

High quality gold spots and lines have been deposited from gaseous dimethyl (2, 4‐pentanedionato) gold (III) using a focused argon ion laser. Growth rates of 1 μm/s at power densities of 4×105 W/cm2 were obtained. Resistivity, threshold writing power densities, and deposition rates were measured and their relationship to the physical and chemical properties of the gaseous complex are explored.

Chemical vapor deposition of copper from 1,5‐cyclooctadiene copper(I) hexafluoroacetylacetonate

We have studied the chemical vapor deposition of copper from 1,5‐cyclooctadiene Cu(I) hexafluoroacetylacetonate, a moderately volatile yellow cystalline solid. It yields pure copper by pyrolytic decomposition at 150–250 °C, produces copper films with near bulk resistivity, and has the advantage of being air stable at room temperature.

LCVD of copper: Deposition rates and deposit shapes

Laser chemical vapor deposition of copper has been performed under a variety of conditions. The results are interpreted using the kinetic model of Ehrlich and Tsao. We find that the kinetics of the process are limited by the rates of surface reactions and not by diffusion of reactant molecules to the surface. Furthermore, we find that deposit shapes are quite sensitive to laser intensity and scan rate.

Laser‐induced chemical vapor deposition of aluminum

The laser‐induced deposition of high‐purity aluminum metal has been achieved by pyrolytic decomposition of trimethylamine aluminum hydride. The chemical structure of the precursor affords a high ambient vapor pressure which results in rapid rates of aluminum film formation. In addition, the precursor is nonpyrophoric, in contrast to other trialkylaluminum precursors. These combined chemical and physical properties make trimethylamine aluminum hydride an ideal precursor for laser‐induced chemical vapor deposition of aluminun films.

Aerosol flow reactor production of fine Y1Ba2Cu3O7 powder: Fabrication of superconducting ceramics

An aerosol flow reactor operating at 900–1000 °C is used to prepare high‐purity Y1Ba2Cu3O7 powders with a uniform chemical composition and a submicron to micron average particle size by thermally decomposing aerosol droplets of a solution consisting of the nitrate salts of Y, Ba, and Cu in a 1:2:3 ratio. The powders were at least 99% reacted based on thermogravimetric analysis, and the x‐ray diffraction pattern is essentially that of Y1Ba2Cu3O7. Magnetic susceptibility measurements showed the powders to be superconducting with a transition at 90 K even for average reactor residence times as short as 20 s. Sintering cold‐pressed pellets between 900 and 1000 °C provides dense, fine grained (average size on the order of 1 μm) superconducting ceramics with sharp 90 K transitions. The grain size and shape of a final sintered part could be varied depending on powder production, processing, and sintering conditions.

Photochemical generation and deposition of copper from a gas phase precursor

The photochemical generation and deposition of copper metal from a volatile copper coordination complex are described. Pulsed and cw ultraviolet light sources were used to induce deposition. The chemical compositions of the films are compared for all methods.

Chemical Vapor Deposition of Copper for IC Metallization: Precursor Chemistry and Molecular Structure

In the microelectronics industry, integrated circuit (IC) device performance is continually increasing while the critical feature sizes are rapidly decreasing. Since this trend is expected to continue for future generations of ICs, areal density constraints often require that circuit designs utilize multilevel structures with vertical interconnects. It was recently demonstrated that the resistivity of the metal interconnects may limit device performance in multilevel thin-film structures. Although Al metallurgy (Al/2 wt.% Cu alloy) is extensively used for IC metallization today, lower resistivity metals, such as gold, copper, and silver may be necessary for designs requiring feature sizes of 0.25 μm or less. Chemical vapor deposition (CVD) is an attractive technique for the conformal filling of submicron vertical interconnects. For CVD to be generally applicable to IC fabrication, volatile precursors with adequate stability must be designed and optimized. Lastly, IC metallization typically requires that both uniformity and conformality be achieved simultaneously in a single process step.

Kinetics of laser‐induced chemical vapor deposition of gold

Rates of photothermal gold deposition onto alumina substrates heated by a focused argon‐ion laser beam were measured by determining the time required for deposits to grow through the focal spot of a HeNe laser probe beam directed parallel to the substrate. Deposition rates from 0.25 to 6 μm/s were measured for deposits with heights ranging from 5 to 100 μm. Rates of gold deposition using dimethyl gold hexafluoroacetylacetonate as a precursor depend linearly on the gold precursor partial pressure and for a wide variety of conditions do not depend on the laser power or focal spot diameter. A theory is presented to describe reactant mass transfer‐controlled deposition with and without buffer gas. Comparison of measured with calculated growth rates showed that gold deposition rates using dimethyl gold hexafluoroacetylacetonate as a precursor were transport limited for the conditions studied. Theory and experiment also showed that the deposition rate decreases inversely with increasing buffer gas pressure abov...

Laser chemical vapor deposition of gold: Part II

The laser‐induced pyrolytic deposition (LCVD) of high purity gold metal is discussed. The effects of laser flux and cell temperature are examined for the deposition process. Rates of deposition, resistivities, and deposit quality are highlighted.