Abstract-Self-heating effects on integrated suspended and bulk spiral inductors are explored. A dc current is fed through the inductors during measurement to emulate dc and radio frequency power loss on the inductor. A considerable drop in by 18% at 36.5 mW is observed for suspended coils with 3-m aluminum metallization compared to reference inductors on bulk-Si. Simulations in Ansoft's ePhysics indicate that, due to the thermal isolation of the suspended coil, the power loss from resistive self-heating in the metal has to be transferred outwards through the metal turns. This also results in a thermal time constant. This time constant is measured to be 10 ms, meaning that it can affect power circuits operating in pulsed mode.Index Terms-Micromachining, radio frequency (RF) circuits, spiral inductor, suspended inductor, thermal effects.

An optimized Saddle-add-on metallization process is used on surface passivated high resistivity silicon substrate to implement very high quality (Q) factor inductors. Test inductors with 5 and 10 nH inductance values are realized and measured to have maximum Q values of 37 at 1.5 GHz and 32 at 900 MHz respectively.

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Abstract-An experimental study of the self-heating of micromachined spiral inductors operated under high-power conditions is presented. Typical suspended spiral coils are shown to develop highly elevated temperatures (up to several hundred degrees) under the flow of a moderate to high (> 60 mA) dc current, which often applies to inductors in radio frequency power circuits. This can lead to the degradation of quality factor and even device failure. The role of various heat dissipation mechanisms relevant for a suspended coil is discussed and analyzed by means of experiments and thermal simulations. Possible solutions to the self-heating issue are discussed and experimentally demonstrated.