An investigation of the electrical behavior of thermally-sprayed aluminum oxide

Abstract

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...

Review of Functionally Graded Thermal Sprayed Coatings

“…The dielectric properties of thermally sprayed ceramic coatings have been frequently tested. The electrical breakdown strength and dielectric constant of APS, SPS, and HVOF sprayed alumina were determined to be in the range 9-40 kV/mm and 5.3-8.3 respectively [257][258][259][260][261]. The breakdown strength of alumina was the highest for HVOF sprayed alumina coatings.…”

Influence of conditions of plasma spraying of aluminum oxide powder on the porosity and electrical resistance of a coating

“…Оптимальное Данные по влиянию параметров напыления на электрические свойства покрытий оксидом алюминия весьма ограничены. Так в работе [11] представлены результаты исследования влияния температуры подложки и мощности плазменной струи на диэлектрические свойства покрытий оксида алюминия на нержавеющей стали. Показано, что с ростом температуры подложки электрическое сопротивление покрытия снижается, тогда как влияние мощности плазменной струи имеет экстремальный характер, проходя через минимум при значении мощности около 30 кВт.…”

Comparative Study of the Electrical Properties and Characteristics of Thermally Sprayed Alumina and Spinel Coatings

“…The dielectric strengths/dielectric breakdown voltages of the plasma-sprayed Al 2 10)). APS spinel coatings presented the lowest dielectric strength value; this result was also confirmed by Pawlowski (Ref 9).…”

“…Thermally sprayed alumina coatings with suitable dielectric properties have been prepared and tested for manufacturing of electrostatic chucks, discharge devices, ozonizer tubes, and insulating coatings for reliable high-temperature heater systems (Ref [1][2][3][4][5][6]. The electrical resistivity of sintered alumina (a-Al 2 O 3 , corundum) at 20°C is stated to be on the order of magnitude of 10 12 -10 13 X m ( Ref 7,8).…”