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.