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.
Estimation of thickness, complex bulk permittivity and surface conductivity using interdigital dielectrometry
Theoretical techniques for deducing continuum parameters from the gain-phase response of interdigital electrodes provide a basis for experiments that demonstrate the use of 50- mu m or 1-mm-wavelength interdigitated electrodes for the absolute measurement of: (1) the thickness and voltage of a layer formed by the sedimentation of 41- mu m particles in transformer oil; (2) the thickness and high-frequency bulk permittivity of plasma-deposited bromobenzene and vacuum-deposited parylene, the former in situ; (3) the complex permittivity of transformer oil without and with a parylene layer for passification against adsorption of water; (4) the dispersion of oil-impregnated paper having a finite thickness; and (5) the surface conductivity due to adsorption of water on a silicon dioxide substrate. The frequency range for (3)-(5) is 0.005 Hz to 10 kHz. Difficulties apparently due to charging effects on the integrated circuitry are discussed.<<ETX>>
INFRARED ABSORPTION HYGROMETER
Abstract A recording infrared absorption hygrometer which measures the absolute humidity in a 1-meter light path is described. Record is obtained on a remote self-balancing potentiometer. Use is made of the 1.37 µ water vapor absorption band and a 1.24 µ reference band. Isolation is by means of transmission type interference band-pass light filters. Infrared detection is by means of a lead sulfide photocell and amplifier. Isolation filters are contained on a sector wheel which is rotated to chop an infrared beam. A self-balancing null system is employed whereby the energy in the absorption band is kept equal to the energy in the reference band at all times. Balance is maintained by automatically varying the temperature of the lamp supplying the infrared energy, and the temperature of the lamp is a measure of the water vapor in the sensing path. An index of the lamp temperature is obtained by means of a monitor photocell, and meter or recorder. Included is a discussion on the calibration and field tests ma...