Monolithic silicon fabrication technology for flexible circuit and sensor arrays

A novel monolithic batch fabrication method produces arrays of silicon islands containing conventional integrated circuit components and supported by a flexible polyimide substrate. Islands are interconnected by photolithographically defined gold leads embedded in the polyimide. Because no bonding pads are necessary at island boundaries, lead density between islands is at least twice as high as with hybrid techniques. The technology has been used to fabricate thermometer arrays for temperature profile measurement during hyperthermia treatment of cancer. An array consists of twenty silicon islands; each island contains one p-n diode, which is used as a thermometer. These linear arrays are 1 mm wide by 0.4 mm thick, with 20 micrometer wide by 1 micrometer thick gold interconnects on 40 micrometer centers. The flexible array technology is currently being modified to fabricate two-dimensional arrays of micromechanical sensors for robotic and biomedical uses.