Reactive spraying of nickel aluminides was accomplished via reaction synthesis techniques in which nickel and aluminum powders were fed through a direct-current plasma torch onto carbon steel substrates. The as-sprayed coatings obtained by reactive spraying were characterized by x-ray diffraction and microscopic techniques. Reactive spraying of nickel and aluminum resulted in coatings consisting of Ni, Al, Ni3AI, NiAl3, NisAI3, NiAi, and AI203, depending on the experimental conditions. Nickel aluminide phases observed in plasma spray depositions were compared with the phases obtained by combustion synthesis techniques, and the formation of phases in reactive spraying was attributed to the exothermic reaction between splats of aluminum and nickel. Primary and secondary reactions leading to the formation of nickel aluminides were also examined. The splat thickness and the reaction layer suppressed the formation of desired equilibrium phases such as Ni3AI and NiAI. As-sprayed coatings were annealed to enhance the diffusional reactions between the product phases and aluminum and nickel. Coatings obtained by reactive spraying of elemental powders were compared with as-sprayed and annealed coatings obtained with a bond coat material in which nickel was deposited onto aluminum particles.

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Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 "C. High purity (>99.5 wt% pure A1,0,) alumina powders were plasmasprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 "C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the importance of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.THERMAL SPRAYING is attracting considerable interest as a method for depositing economical high performance dielectric coatings for semiconductor applications. One such application that has gained increasing attention over the past several years is the development of thermal spraying for manufacturing electrostatic chucks (ESCs). ESCs can lower semiconductor manufacturing costs by reducing wafer bowing, particle contamination, and other disadvantages associated with mechanical clamping [ 1,2]. ESCs for etching, implantation, physical vapor deposition (PVD), and chemical vapor deposition (CVD) have been explored and implemented with varying degrees of success [3,4]. A particular challenge is the development of dielectric coatings that will allow ESCs to function in higher temperature wafer processing environments (up to 600 "C).In the simplest ESC design, an insulating layer such as a ceramic coating applied to the lower electrode controls the charge separation between the wafer and chuck, Electrical properties that determine the effectiveness of this layer are the dielectric constant, electrical resistivity, and the dielectric strength. Dielectric constant should be high enough that the applied voltage requid to sustain the needed clamping pressure does not result in dielectric breakdown. Electrical resistivity is particularly important relative to high temperature performance, as the resistivity for most ceramics typically decreases exponentially with increasing temperature, while the dielectric constant increases very slowly.In alumina, -a desirable candidate ESC coating material -volume resistivity can be as high as about 10" 0-cm at room temperature [5]. The presence of impurities (particularly alkaline metal ions such as sodium) significantly lowers electrical insulating ability, especially as temperature increases. In the temperature range of i...

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Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 °C. High purity (>99.5 wt% pure Al2O3) alumina powders were plasma-sprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 °C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the importance of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.