Embedded thin film resistors, capacitors and inductors in flexible polyimide films

The High Density Electronics Center (HiDEC) at the University of Arkansas is working with the Sheldahl MCM-L Consortium and Rensselaer Polytechnic Institute (RPI) to develop low-cost embedded resistors, capacitors, and inductors in flexible polyimide films under an ARPA contract. Embedding thin-film passive devices into polyimide layers as part of a Multichip Module (MCM) system is new. The design concept allows fabrication and testing of embedded passive devices before assembling them into an MCM-L substrate. Embedded passive devices are needed as an enhancement to present day MCM-L and MCM-D technologies. The ability to remove devices such as terminating resistors and decoupling capacitors from the surfaces of PCB boards and MCMs into a flexible film, at low cost, would be a break-through for MCM technology. The devices are made into a flexible MCM package using a 2 layer interconnect system called the Interconnected Mesh Power System (IMPS) developed and patented at the University of Arkansas. The IMPS interconnection topology incorporates fine line lithography and batch via generation to allow planar power and ground distribution, and dense signal interconnection, on only two metal layers. The materials being used are NiCr, TaN, and CrSi for the resistors and Ta_xO_y and BaTiO_x for the capacitors. Contacts, interconnecting signal lines, and power lines are made with Cu metallurgy. The devices are made on a 25 μm or 50 μm thick polyimide film and are encapsulated with the same polyimide