High-Q Inductors on Locally Semi-Insulated Si Substrate by Helium-3 Bombardment for RF CMOS Integrated Circuits

Abstract

A helium-3 ion bombardment technique is proposed to realize high-Q inductors by creating locally semi-insulating substrate areas. A dose of × 1013 cm-2 helium-3 increases a Si substrate resistivity from 4 Ω · cm to above 1 kΩ · cm, which improves the quality factor of a 2-nH inductor with a 140-μm diameter by 38% (Q = 16.3). An aluminum mask is used for covering active areas, and at least 15-μm distance from the mask edge is required to avoid the p-n junction leakage. The proposed technique is applied to an 8-GHz oscillator, and an 8.5 dB improvement of the measured phase noise has been achieved.