Integrated Circuit Chips

NASA Glenn's durable, extreme-temperature, integrated circuit chips begin with the replacement of conventional silicon IC transistors with n-channel SiC junction field effect transistors (JFET) and resistors that can reliably function above 500°C. JFETs with the necessary high-temperature stability and electrical gain are fabricated from commercial 4H-SiC wafers with epilayers using dry etching and a self-aligned n-type ion implantation. An innovative circuit approach creates digital logic gates from these normally-on n-channel JFETs and resistors. Using two levels of 500°C durable metal to interconnect numerous SiC gates, complex circuits enabling a variety of control, operation and sensing functions for intelligent systems in harsh environments can be implemented in physically small chips. The challenge of getting electrical signals to and from the chip in a harsh environment is overcome by the use of the iridium interfacial stack (IrIS) that acts simultaneously as a bond metal and diffusion barrier, and can be used on an ohmic contact to the SiC. Combined with Glenn-developed high-temperature durable ceramic chip packaging and harsh environment sensor technology, this revolutionary durable integrated circuit technology is game changing for harsh-environment applications of all types. Innovators at NASA's Glenn Research Center have developed a new generation of silicon carbide (SiC) logic and mixed signal integrated circuits (ICs), unprecedented in the field of high-temperature electronics. Previously, SiC ICs could not withstand more than a few hours of 500°C temperatures before degrading or failing. Now, NASA Glenn has successfully fabricated prototypes that consistently exceed 1,000 hours of continuous operation at 500°C. The superior performance stems in part from previous Glenn advancements, such as the iridium interfacial stack (IrIS), a bondable and durable metallization stack that enables electrical packaging connections to SiC integrated circuits operating above 500°C. The enhanced stability of these components will enable important improvements in sensing, control, and operation of harsh environment systems, by providing analog and digital circuit functionality directly where it is needed. This advancement in the manufacturing of SiC-based electronics revolutionizes and broadens the opportunities for intelligent systems by providing ICs that operate well beyond the current temperature limits of conventional (silicon) ICs.