Wafer level processing of integrated passive components using polyimide or polybenzoxazole/copper multilayer technology
Focus of this work was the development and optimization of process techniques for the application of Polyimide ( PI) or Polybenzoxazole (PBO) to act as dielectric material together with semi-additive copper as conductive material in a thin film multilayer buildup, which is suitable for the integration of all three types of passive components. A thin film set up including seven layers was used to create integrated coils with values between 1 and 80 nH, integrated resistors with values between 100 Omega and 100 k Omega as well as integrated radio-frequency (RF) filters for application between 2 and 5 GHz. As substrate material both low resistivity silicon and glass (Borofloat 33) was used, which influences the quality factor of the coils as well as the filter performance substantially. The fabricated structures performed well in thermal cycling tests, where no critical failure could be observed after 3000 thermal cycles for all examined components. The RF components have shown no critical deviations between initial measurements and measurements performed after thermal cycling. The resistor values have shown no deviations between the measurements, which have been taken before and after thermal cycling. Thus Polyimide/Polybenzoxazole/copper multilayer wiring represents a reliable and versatile base technology for the fabrication of passive components at wafer level.