Design of radio frequency metal-insulator-metal (MIM) capacitors

RF components such as inductors and capacitors are now common on deep submicron CMOS circuits because of their low cost and reasonable performance. The performance however depends on the design of those components. In this paper, we propose guidelines for improving the high frequency capacitance and quality factor, Q, of integrated capacitors. We present measured data showing how the quality factor is improved when the number of vias is increased.

1. Introduction

The demand for RF metal-insulator-metal (MIM) capacitors, which can offer low parasitic capacitance, low voltage coefficient, and high quality factor, was triggered by the increase in wired and wireless communications [1], [2]. Key performance attributes of an MIM capacitor for wireless applications include: high linearity, low series resistance, high capacitance density, low temperature coefficient of capacitance, excellent matching and low parasitic capacitance [3]. A MIM capacitor is usually composed of an aluminum bottom plate with Ti/TiN liners, a silicon nitride dielectric, and a titanium nitride top plate. Unfortunately, the titanium nitride top plate has high sheet resistance.