Title :
Rotational Driven RF Variable Capacitors With Post-CMOS Processes
Author :
Gu, Lei ; Li, Xinxin
Author_Institution :
Shanghai Inst. of Microsyst. & Inf. Technol., Chinese Acad. of Sci., Shanghai
Abstract :
A ring-shaped on-chip tunable capacitor is proposed and fabricated with CMOS-compatible micromachining processes for radio frequency integrated circuits (RFICs). The rotationally driven variable capacitor features a much higher axial mechanical stiffness compared to its conventional straight-line-driven counterpart, and therefore, can effectively depress the instability caused by environmental vibration when the varactor is used in mobile systems. Meanwhile, the rotationally driven intedigitated capacitor is designed to be very flexible for wide range of electrostatic tuning. Near-room-temperature micromachining techniques are developed for post-CMOS integrating the tunable capacitors into RFIC chips. The fabricated varactor is measured with a tuning ratio of 2.1:1 under an actuation of 12 V. Q-factor is measured as 51.3 at 1 GHz and 35.2 at 2 GHz, while self-resonance frequency is as high as 9.5 GHz. The rotationally driven tunable capacitor shows about two orders of magnitude higher antivibration capability compared to the conventional straight-driven one. Therefore, the high-performance CMOS-compatible tunable capacitors are promising for practical RFIC applications in mobile electronic telecom systems.
Keywords :
micromachining; radiofrequency integrated circuits; varactors; Q-factor; RFIC chips; actuation; axial mechanical stiffness; electrostatic tuning; frequency 1 GHz; frequency 2 GHz; frequency 9.5 GHz; micromachining; mobile systems; post-CMOS processes; radio frequency integrated circuits; rotational driven RF variable capacitors; self-resonance frequency; varactor; voltage 12 V; Capacitors; Electrostatic measurements; Frequency measurement; Micromachining; Radio frequency; Radiofrequency integrated circuits; Semiconductor device measurement; Tunable circuits and devices; Tuning; Varactors; Radio frequency integrated circuit (RFIC); rotational comb structure; tunable capacitor;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2007.914106