Inductor for integrated circuit

Abstract

An inductor is integrated in VLSI and ULSI technology products for very high frequency applications. The inductor is in a microstrip transmission line configuration which can be designed in a form of straight line, spiral line or Meander line. The inductor is formed by shorting the microstrip center conductor to the lower level ground plane at one end of the transmission line. This results in an inductance which, for a given design of transmission line, and in a specified frequency range, is independent of frequency, within the operating design range. The microstrip transmission line provides an inductance which could be used on any type of substrate, with either low or high resistivity. The microstrip transmission line could utilize two or all of the metal wiring levels of the technology, allowing a wide range of inductance and quality factor design tradeoffs. An important feature in this trade-off is the ability to utilize lower (below the inductor) metal wiring levels, as well as lower silicon and polysilicon areas for other than inductor design purposes, without affecting the operation of the inductor. This is because of the isolation properties of this inductor system. By utilizing isolation layers with low relative dielectric constant, Further enhancements of the system are achieved. The inductance of this system is constant within 10% over a frequency range extending from about 8 GHz to about 35 GHz This inductor system allows the design to be optimized, through several parameters, to achieve the desired performance.

Description

technical field [0001] The present invention relates to the enhancement of inductors for use in integrated circuit technology, and more particularly to structures and methods for fabricating inductors which do not substantially disrupt conventional semiconductor fabrication techniques. Background technique [0002] Fabrication of on-chip inductors in combination with modern integrated circuits is highly desirable for many applications. [0003] A major disadvantage of integrated inductors, especially on low-resistivity substrates, is the significant electric and magnetic field coupling between the inductive element and the conductive substrate. First, this will reduce the resulting inductance since any induced current in the substrate will result in a magnetic field oriented opposite to that of the inductor (Lenz's law). This magnetic field opposing the inductor's field causes the overall field to weaken as frequency increases, producing a varying eff...

AI Technical Summary

Problems solved by technology

[0014] In summary, there are several problems with the prior art: making the inductor requires a particularly complex and expensive process, requires a high-resistivity substrate to reduce coupling to the inductor, and the inductance is not constant over a fairly wide frequency range

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