A CMOS embedded RF-MEMS tunable capacitor for multi-band/multi-mode smartphones

Abstract

This paper reports on 1-chip RF-MEMS tunable capacitor that equips CMOS driver circuit in the underlying layer. A Wafer Level Chip Scale Package (WLCSP) optimized for RF-MEMS is employed to minimize the module size.The MEMS actuation voltage is generated by an Actuation Voltage Generator (AVG). The boost mechanism employed in the AVG enables instant high voltage generation and reduction of the dielectric charging. The measured noise at RF frequencies is less than -120dbm, thanks to a shield metal layer formed between MEMS and CMOS layers.To achieve high power handing and high creep immunity, we employ the previously reported techniques, the Quadruple Series Capacitor (QSC) [1] and the SiN springs [2]. The quality factor measured in the WLCSP is larger than 100 at 1GHz. The capacitance can be changed from 1.4pF to 5pF by a step of 0.45pF.

CMOS-embedded high-power handling RF-MEMS tunable capacitor using quadruple series capacitor and slit with dielectric bridges structure

“…RF-MEMS tunable capacitors are more suitable for these systems than any other devices such as p-i-n diodes, silicon-on-insulator (SOI) switches, [9][10][11] or barium-strontium-titanate (BST) type tunable capacitors, 12) thanks to their low loss and excellent linearity. [13][14][15][16][17][18][19] In order to use a MEMS tunable capacitor in a transmitting system, high-power handling is needed. For example, power handling of up to +35 dBm is required in the global system for mobile communications (GSM).…”