The Moisture Dependence of the Electrical Sheet Resistance of Aluminum Oxide Thin Films with Application to Integrated Moisture Sensors
The measurement of moisture inside integrated circuit packages for reliability purposes involves either destructive mass spectroscopic tests, measurement of the impedance between interdigitated electrode pairs, or measurement of the capacitance of a parallel plate capacitor with a porous upper electrode and a dielectric of anodized aluminum oxide. This paper reports the use of an integrated circuit that combines interdigitated electrodes with a pair of matched field-effect transistors to permit sensitive, quantitative measurement of the moisture dependence of the sheet resistance of very thin filmis of oxidized aluminum. Data analysis is based on an equivalent circuit model for the device. It is found that the room temlperature sheet resistance of a 1500 Å film varies from 2 × 1015 Ohms/sq. at an ambient dew point of ¿43°C to 2 × 1010 Ohms/sq. at a dew point of +22°C. The device retains useful sensitivity below dew points of ¿60°C, and because of the absence of a porous upper electrode, exh ibits rapid response to changes in ambient moisture. Fabrication details, reproducibility, hysteresis, and aging of these devices is discussed.
The aging of hydrated aluminum oxide thin films
Abstract We report the results of aging on the electrical, structural and moisture-response characteristics of thin hydrated aluminum oxide films. The films, which have the pseudoboehmite structure, are produced by immersion of evaporated aluminum films into hot or boiling water. The sheet resistance, Rs, measured at room temperature using charge-flow-transistor techniques, is an approximately exponential function of dew point. This high sensitivity to moisture may be attributed to physisorbed moisture and the porous morphology of the film. Samples were aged at room temperature in 40% r.h. and in dry ambients. After 30 hours, Rs follows a power-law increase with time over two months. The aging rate decreases substantially for samples stored in dry ambient, suggesting that physisorbed water contributes to the aging rate. Three H2O components are distinguished by infrared spectroscopy coupled with isotope exchange using D2O: ‘physisorbed’ water, ‘chemisorbed’ water and ‘fixed’ water. The chemisorbed water can exchange rapidly with physisorbed water. However, in the absence of physisorbed water, the chemisorbed water does not exchange with ambient. This mechanism may be related to the hysteresis observed in aluminum oxide moisture sensors. After annealing films below 250 °C, the structure of the film is still that of pseudo-boehmite. However, above 250 °C, a gradual transition to alumina is observed.
Solitary Orbital Paget Disease: A Case Report
Purpose: To describe the clinical findings in a patient who had developed painless supraorbital prominence. Methods: Clinical and histopathological findings of the case are reviewed and presented. Results: The patient had an isolated histologically confirmed Paget disease of the orbit. Local excision of the lesion was performed. Conclusion: Paget disease can present not only as a diffuse process but also as a painless, solitary lesion of the orbit.