Improved Microwave Modeling of CMOS Spiral Inductors with Metal Dummy Fills

Abstract

In advanced CMOS technologies, the insertion of metal dummy fills is unavoidable due to stringent metal density process requirements. Therefore existing compact models for on-chip components need to be updated to accurately account for the effect of these metal dummy fills in CMOS RFIC designs. This paper proposes a simple but accurate method to predict the microwave behavior of on-chip spiral inductors with metal dummy fills. Experimental results show that the increase in the dioxide capacitance C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</inf> is the dominant factor leading to the decrease in Q <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> and f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> . Two methods are adopted to calculate the change in the dioxide capacitance of on-chip inductors due to the metal dummy fills. Good agreement is achieved between the predicted and measured performance of inductors with metal dummy fills by updating C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</inf> in the conventional models.