Inductors in High-performance Silicon Radio Frequency Integrated Circuits

Download or read book Inductors in High-performance Silicon Radio Frequency Integrated Circuits written by Richard D. Lutz and published by . This book was released on 2005 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spiral inductors are a key component of mixed-signal and analog integrated circuits (IC's). Such circuits are often fabricated using silicon-based technology, owing to the inherent low-cost and high volume production aspects. However, semiconducting substrate materials such as silicon can have adverse effects on spiral inductor performance due to the lossy nature of the material. Since the operating requirements of many high performance IC's demand reactive components that have high Quality Factor's (Q's), and are thus low loss devices, the need for accurate modeling of such structures over lossy substrate media is key to successful circuit design. The Q's of commonly available off-chip inductors are in the range of 50- 100 for frequencies ranging up to a few gigahertz. Since off-chip inductors must be connected through package pins, solder bumps, etc., which all contribute additional loss and thus lower the apparent Q of an external device, the typical on-chip Q requirement for a given RFIC design is generally lower than that for an off-chip spiral solution. However, a spiral inductor that was designed and fabricated originally in a low loss technology such as thin-film alumina may have substantially worse performance in regard to Q if it is used in a silicon-based technology, owing to the conductive substrate. For this reason, it is imperative that semiconducting substrate effects be accurately accounted for by any modeling effort for monolithic spirals in RFICs. This thesis presents a complete modeling solution for both single and multi-level spiral inductors over lossy silicon substrates, along with design considerations and methods for mitigation of the undesirable performance effects of semiconducting substrates. The modeling solution is based on Spectral Domain Approach (SDA) solutions for frequency dependent complex capacitive (i.e. both capacitance and conductance) parasitic elements combined with a quasi-magnetostatic field solution for calculation of the frequency dependent complex inductive (i.e. both inductance and resistance) terms. The effects of geometry and process variations are considered as well as the incorporation of Patterned Ground Shields (PGS) for the purpose of Q enhancement. Proposals for future extensions of this work are discussed in the concluding chapter.