Establishing a bipolar fabrication service for analog circuit realization at the Rochester Institute of Technology

A bipolar fabrication service has been developed at the Rochester Institute of Technology to service students and faculty from the Microelectronic, Electrical and Computer Engineering departments wanting to realize designed integrated circuits. The fabrication technique combined Implanted N-Well and double diffusion processes. Phosphorous was implanted into a p-type substrate, oxidized for eight hours and diffused in nitrogen for another 40 hours to create isolated n-wells. Devices were then fabricated using a double diffusion process. The CAD tool used for the service is the Integrated Circuit Editor, ICE, which has campus wide accessibility through the RIT VAX system. Designed standard cells include resistors, bipolar and MOS transistors, a current mirror, a differential amplifier, a Darlington circuit and an operational amplifier. Full custom circuits can also be designed using ICE. Maskmaking files generated from circuit designs are sent to the Microelectronic Engineering department for circuit fabrication, and the completed circuits are returned to the designer for testing. The RIT N-Well process has provided vertical NPN and PNP transistors with common emitter current gains of 100 and 40 respectively, Early voltages greater than 50 volts, and breakdown voltages higher than 15 volts. Differential amplifiers and current mirrors have alos been successfully designed, fabricated and tested