The proposed work covers an initial feasibility analysis of high temperature tolerant memory cells. Additionally, the proposed work covers an exploratory set of small-scale experiments and a proof-of-concept demonstration. The project targets a well-rounded approach of “design for manufacturing” and “design for reliability” for temperature hardened memory electronics.
A high temperature tolerant memory technology is needed for sensing and logging operations in harsh environments. To this end, silicon carbide offers a mature semiconductor technology that is akin to silicon in many aspects of its processing.
A dynamic random-access memory (DRAM) is a crucial part of many silicon electronics. It provides a fast high-capacity storage solution in many applications due to its relatively small cell structure. The most compact DRAM array is based on one capacitor one transistor (1C1T) memory cell.
Even though the 1C1T memory cell is volatile in silicon due to the relatively high leakage currents at its p-n junctions, it is speculated that such a cell would be “practically” non-volatile and static if fabricated in silicon carbide. This is due to the fact that the reverse biased leakage currents in SiC p-n junctions is minimal, drastically cutting the loss rate of the stored charge, or increasing the time constant of the charge storage system.
The longest possible time that DRAM holds onto its data before losing it to leakage is called the charge retention time. Charge retention times in silicon are small, requiring constant refresh cycles, which are not very power-aware. The initial experiments in silicon carbide indicate such times are very long in SiC, making its 1C1T cell “practically” a non-volatile and static memory unit.
In this project, we plan to design and fabricate SiC DRAM and SRAM memory cells, and investigate their potential for use in harsh environments, to pave the way for advanced logging and metrology in extreme environments.
Exploration of inner planets such as Venus and Mercury require electronics that can operate at high temperatures. The peak temperature on Mercury is as high as 430 C, while the lowest temperature is as low as -180 C. Additionally, even though Venus is further away from the Sun, it is significantly warmer than Mercury. Lastly, gas giants (for example Jupiter) and some solar probes also require electronics that can operate at temperatures above the reach of silicon electronics. The proposed work provides a high temperature electronics solution.
High temperature electronics include components ranging from the drill logging and sensing devices needed for the commercial oil, gas, and geothermal exploration activities to the active components, controls, and sensors needed for jets and hypersonics. Temperature hardened electronics are a gamechanger for energy exploration, energy conversion, and propulsion to name a few technical areas.