The advantage of thin film technique in the application of spiral inductors and couplers [MCM]

Multi-chip modules for wireless communications in the microwave and mm-wave frequency range require carrier substrates with transmission lines of small size and well-controlled dimensions. RF multichip carrier substrates in thin-film technology allow realization of passive components like inductors and couplers off-chip from active circuits by direct integration on the substrate, thus reducing chip and substrate size and costs. Using at least two metallization layers, microstrip lines can be used as the line system, the properties of which are independent of the substrate due to the shielding effect. At the same time, the passives (inductors, couplers) are realized. Another advantage of the multi-layer thin-film scheme over single metallization-layer systems is the additional degree of freedom in line routing. Lange-type couplers, for instance, can be easily designed in a two-layer system without need for bonding. The paper provides an overview of some typical components which usually need bonding to join inner and outer connections and thus benefit from the two-metal-layer substrate.