| Cell phones and laptop computers have important roles in our everyday lives, and the demand for more portable electronic devices continues to increase rapidly. This is currently driving the use of integrated or embedded passive components to replace off-chip, discrete, modular assemblies. However, the poor properties of integrated inductors have been a critical factor limiting the overall performance of radio-frequency (RF) circuits. As a result, this factor has also limited the realization of system-on-a-chip (SoC) or system-in-package (SiP) circuits for portable electronics.;The use of a magnetic core with high permeability in the integrated inductor was proposed decades ago to significantly increase the inductance by the relative permeability of the magnetic material used. However, the inductance enhancements reported so far have been limited and not well understood. In addition, the use of a magnetic core results in magnetic power losses. These losses and how to minimize them must be well understood in order to make the magnetic inductor practical and useful.;In this dissertation, I report the results of my assessment of high-performance, integrated inductors that use a solenoid design with a magnetic layer. A set of analytical models was developed to describe the properties of integrated solenoid inductors. Using the models, design parameters were optimized to achieve a high inductance while maintaining the lateral device area less than 1 mm2 and the coil resistance less than 1 O. The integrated inductors were fabricated on Si wafers using copper as the conducting layer and CoTaZr alloy as the magnetic core layer. A polyimide planarization process was developed as the preceding step for the formation of the magnetic core.;The inductance of the fabricated inductor was as high as 70.2 nH measured at 10 MHz with a DC resistance of 0.67 O and a device area of 0.88 mm 2. The inductance was enhanced by a factor of 34 compared to an air core inductor with identical geometry, and the resulting inductance density was 80 nH/mm2. By decreasing the lateral dimensions while leaving the vertical dimensions unchanged, the inductance density increased to 219 nH/mm2 without significantly affecting the coil resistance. The measured properties of the device and the results obtained from analytical models were in good agreement. The resistance of the magnetic inductor increased significantly as frequency was increased due to the introduction of magnetic power losses at high frequencies. The frequency-dependent resistance and quality factor of the magnetic inductor were also in excellent agreement with the analytical results.;The properties of integrated magnetic inductors are well understood, and the available analytical models predict these properties quite accurately. Therefore, integrated magnetic inductors can now be reliably designed, fabricated and optimized for applications and frequency ranges of interest, which enables the realization of RF integrated electronics. |
