Memories, both volatile and non-volatile, are an essential element in various computing and logic devices because it is where the data being processed resides. Mass market memory technologies serve consumer, industrial, and enterprise applications (including data centers), but computing at extreme temperatures, both at very cold temperatures and at extreme temperatures very high, is important for quantum computing (usually at very cold temperatures) and for extreme temperatures. and environmental applications.

I have written in the past about possible technologies to enable quantum computer memories. In this article, we will talk about memories for extreme temperature applications.

This article is based on a recently published Nature Reviews Materials article, Materials for high temperature digital electronics. This review article delves deeper into the various factors that go into creating volatile and non-volatile memories for extreme temperature applications, particularly high temperature applications.

Consumer memory begins to lose performance around 85°C, begins to degrade around 150°C, and degrades rapidly at 210°C. These temperatures are acceptable for most computer applications, but not in extreme environments.

The table below from the article provides an overview of applications with temperatures up to 1000°C. Electronic packaging containing organic materials only works up to around 150°C, beyond this temperature various ceramic packaging technologies are required. These applications include logic and computing devices for automotive, oil and geothermal exploration, interplanetary exploration, nuclear reactors and aerospace applications.

Regarding non-volatile memory, NVM, for very high temperature applications, the figure below shows several important memory characteristics as a function of temperature for the memory technologies most likely for higher temperatures. These are data retention, in seconds), read endurance, in cycles, and on/off ratio.

Magnetic random access memory (MRAM) and phase change memories are limited by their Curie temperatures and phase change temperatures, although MRAM products are now available as embedded memory for automotive applications. The best non-volatile memory candidates for high temperatures, the green regions in the figures below are special types of NOR flash memories, ferroelectric memories and resistive memories.

In particular, ferroelectric nitride NVM, especially in wurtzite-structured nitrides and oxides, appears to be the most promising technology. However, there is still work to be done on these memories, particularly in terms of the on/off ratio.

It should be noted that for these high temperature applications, traditional silicon substrates will not work. For these applications, wide bandgap semiconductor materials are required, such as SiC and GaN, particularly to support device operation at 850°C or higher.

The chart below shows feature size scaling trends for conventional commercial semiconductors and high-temperature semiconductor devices. Packaging and interconnection as well as technical issues and especially low demand for high temperature electronic devices limit the feature size and therefore the density achievable for semiconductors operating at very high temperatures.

It is evident that high temperature devices tend to lag behind silicon devices operating at lower temperatures, on a logarithmic scale. The various problems associated with manufacturing high-temperature semiconductor devices limit their use to applications in aerospace, avionics, automotive, oil/gas exploration, and nuclear power. The low volume of these applications slows down the miniaturization and performance of these applications compared to higher volume applications.

High-temperature volatile and non-volatile memories are important for aerospace, avionics, automotive, oil/gas exploration, and nuclear power applications, but these applications require new materials , interconnections, packaging and manufacturing processes.