High quality factor ( Q ) inductors were designed and fabricated on high-resistivity (2000 R.cm) Si substrates with multichip module (MCM) fabrication technology. A Q-factor of 30 was achieved for an inductor of 4 nH at 1-2 GHz. To enhance the Q-factor and reduce the parasitic coupling capacitance, a staggered double metal-layered structure was utilized by taking advantage of the double-layered metal lines in MCM. With electromagnetic simulation tools, computer-aided analysis was used to optimize the device characteristics. The skin effect and the lossy substrate effect on the performance of the radio frequency (RF) thin-film inductors were studied. The fabrication process used polyimide as the dielectric layer and aluminum as the metal layer. The use of the low dielectric-constant material, polyimide, reduces the parasitic coupling capacitance between metal lines and increases the quality factor and the self-resonant frequency for the RF integrated inductors.

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An optical sensor that simultaneously measures the concentration of the biochemical oxygen demand (BOD) and temperature in water based on a tapered microfiber is proposed for environmental monitoring. The sensor is characterized by a strong evanescent field, which is more sensitive to liquids with a low refractive index and a low transmission loss. The results show that as the BOD concentration increases, the interference spectrum shifts toward longer wavelengths, the spectral loss decreases, and the sensitivities of the BOD are 12.17 nm/mg/mL and − 2.387 d B / m g / m L in the range of 0.25–1 mg/mL, which indicates the extent of the water pollution. The detection limit for the BOD concentration is as low as 0.0016 mg/mL. As the ambient temperature increases, the interference spectrum shifts toward shorter wavelengths, the spectral loss decreases, and the temperature sensitivities are − 0.339 n m / ∘ C and − 0.031 d B / ∘ C in the range of 30°C–60°C. The matrix method can be used to achieve the simultaneous measurement of the BOD concentration and environmental temperature because the spectral interference peaks have different responses to these two parameters. The sensor can not only be used for detecting water pollution in rivers, drinking water, and groundwater but can also be utilized for other types of environmental monitoring. This sensor has great potential to act as a basic sensing unit in fiber-optic sensor networks for multiparameter measurements and intelligent monitoring.