Inductors are vitally important for efficient power converters. Through the integration of inductors and other converter components onto a chip or into a package, integrated power conversion can be realized to save space and power. However, previously reported integrated inductors for integrated power conversion usually have unsatisfactory performance and account for a relatively large power loss. Therefore, technologies for integration of high-performance power inductors need to be developed. In this thesis, new inductor integration technologies will be proposed and demonstrated for integrated power conversion.

First, an interposer-embedded inductor integration technology for large inductance applications is proposed. An inductor integration process is designed to embed air-core induc...[ Read more ]

Inductors are vitally important for efficient power converters. Through the integration of inductors and other converter components onto a chip or into a package, integrated power conversion can be realized to save space and power. However, previously reported integrated inductors for integrated power conversion usually have unsatisfactory performance and account for a relatively large power loss. Therefore, technologies for integration of high-performance power inductors need to be developed. In this thesis, new inductor integration technologies will be proposed and demonstrated for integrated power conversion.

First, an interposer-embedded inductor integration technology for large inductance applications is proposed. An inductor integration process is designed to embed air-core inductors into the back of a silicon interposer and then integrate the inductors with converter ICs and loads in a 2.5D package. The inductor achieves a small DC resistance by implementing thick windings inside the interposer. As a demonstration of the proposed integration technology, a 4.2 μH inductor is fabricated and integrated with a buck converter IC and LED loads. The inductor achieves a good power efficiency of 89% for use in a buck LED driver application.

Second, a fan-out-package-embedded inductor integration technology for small inductance applications is proposed. The inductor with a large winding thickness is implemented in the unused fan-out space. To demonstrate the inductor integration technology, a 2.4 nH inductor is fabricated and integrated with a chip in a fan-out package. Compared with prior arts, it shows a very small DC resistance and many times higher quality factors. Additionally, coupled fan-out-package-embedded inductors are also designed and fabricated for a buck converter application. Benefitting from the superiority of the fan-out-package-embedded inductors, a high converter efficiency of 90.4% is achieved, which is significantly higher than that of the converter implemented using other inductor approaches.

Finally, a suspended thick-winding inductor integration technology for on-chip, low substrate loss, and small inductance applications is proposed. A novel silicon molded metal transfer process is developed for the on-chip integration of suspended thick-winding inductors. The suspended structure minimizes the substrate loss at high frequencies. At the same time, the thick winding enables a small DC resistance. For demonstration purposes, a 25 nH inductor is designed and fabricated for integrated voltage regulator applications. The fabricated inductor achieves a peak inductor efficiency of 97.8% for 1.8–1.1 V voltage conversion.