High-performance electroplated solenoid-type integrated inductor (SI²) for RF applications using simple 3D surface micromachining technology

Electroplated solenoid-type integrated inductors (SI²s) have been demonstrated to have high performance and small area occupation for GHz applications, using a new, simple, and highly adaptable 3D surface micromachining technology. The method utilizes simply modified conventional photolithography and well-established electroplating at a low process temperature (<120 °C), so that the post-IC process and batch fabrication are possible. We have fabricated a 20-turn SI² with an inductance of 2.5 nH, a peak Q-factor of 19 at 5.5 GHz, and the surface area occupation of 800 μm by 90 μm excluding pads (50 nH/mm²), from the entirely unoptimized initial fabrication on a glass substrate. Also, a 10 nH and a peak Q of 12.5 at 2.3 GHz have been obtained from an 80-turn SI² (27 nH/mm²).