Post‐CMOS micromachined nickel tunable‐capacitors with a large tuning‐range under low actuating voltage

Abstract

AbstractA novel metal micromachining technique is presented, with which both area‐tuning and gap‐tuning variable capacitors are designed and fabricated. Mainly comprising nickel electroplating and gaseous isotropic etching, the developed micromachining technique can be processed in low resistivity silicon substrate under low temperature (max. 120°C). Thus, the micromachined tunable‐capacitors can be on‐chip integrated into RF (radio‐frequency) ICs by means of post‐CMOS compatibly process. The fabricated tunable‐capacitors are measured, generally resulting in a larger tuning‐range than 200% (namely 3:1) under 4‐V actuation voltage. The Q‐factor for the area‐tuning capacitor (C0 = 0.28 pF) is measured as 169 at 1 GHz and 46 at 2 GHz, respectively, while the gap‐tuning style capacitor (C0 = 0.37 pF) is with the Q measured as 87 at 1 GHz and 35 at 2 GHz. With the successful application in the tunable‐capacitors, the developed post‐CMOS compatible metal micromachining techniques are promising for high‐performance on‐chip RF/microwave passives. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2469–2472, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23645