Flexible circuit and sensor arrays fabricated by monolithic silicon technology

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 that available using hybrid techniques. The technology has been used to fabricate thermohaeter arrays for temperature profile measurement during hypertherminal treatment of cancer. An array consists of 20 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-µm-wide by 1-µm-thick gold interconnects on 40-µm centers. The flexible array technology is currently being modified to fabricate two-dimensional arrays of micromechanical sensors for robotic and biomedical uses.