A compatible MOS-bipolar device technology for low-power integrated circuits

A major problem in the design of low-power integrated circuits occurs in the need for high-value resistors occupying a small area. Another problem area exists in the need for active devices capable of operation at extremely low current levels. This paper consists largely of an attack upon these problems. The relative merits of various resistor structures, including the MOS resistor, are discussed, and their electrical characteristics are compared. Active device design for low-power circuit operation is also discussed, and the design of a bipolar transistor structure is described which optimizes the current gain at low current levels. Next, a process technology is described which allows MOS resistors, double-diffused planar epitaxial NPN transistors, and diffused junction isolations to be realized within the same integrated cricuit structure.