Low-complexity MCM-D technology with integrated passives for high frequency applications

A silicon based technology for the integration of passive components into a MCM substrate is described. It is based on mature LSI technology, which makes it suitable for production in standard IC fabs. Using a double metal back-end process on isolated high-ohmic silicon and incorporating a resistor layer, thin film resistors, capacitors and inductors can be made with only 5 lithographic steps. By using thick gold as the top metal layer, good quality factors for the inductors are obtained, thus making RF applications feasible. This gold layer is also used for eutectic bonding of naked discrete silicon devices. A 1.3 GHz phase locked loop (PLL) module has been made as a demonstration of the combination of a passive integrated substrate and active dies mounted on top, thus forming a RF MCM-D. Mounting technology is based on the combination of standard IC mounting and discrete device mounting. The module contains a passive integration substrate with 55 integrated passives, 1 synthesiser IC and 3 discrete semiconductor devices.