How to understand the limit temperature of IC chip and is this value absolute?

While IC manufacturers cannot guarantee that a chip will work properly outside its rated temperature range, the chip will not suddenly stop working when its temperature range limits are exceeded. But if engineers need to use chips at other temperatures, then they must determine how well those chips work and how consistently the chips behave.

Some useful common rules

When the temperature is about 185 to 200°C (the exact value depends on the process), the increased leakage and reduced gain will make the silicon chip work unpredictably, and the accelerated diffusion of dopants will shorten the chip life to hundreds of hours, or in the best case, it may be only thousands of hours. However, in some applications, the lower performance and shorter life impact of high temperatures on the chip can be accepted, such as drilling instrumentation applications, the chip often works in high temperature environments. However, if the temperature becomes higher, then the working life of the chip may become too short to be used.

At very low temperatures, reduced carrier mobility eventually causes the chip to stop working, but certain circuits are able to operate normally at temperatures below 50K, even though the temperature is already outside the nominal range.

Basic physical properties are not the only limiting factor

Design trade-off considerations may result in improved chip performance over a certain temperature range, but the chip can fail outside that temperature range. For example, the AD590 temperature sensor will work in liquid nitrogen if it is powered up and gradually cooled, but will not start up directly at 77K.

Performance optimization leads to more subtle effects

Commercial-grade chips have very good accuracy over the temperature range of 0 to 70°C, but outside that temperature range, accuracy becomes poor. A military-grade product with the same chip is able to maintain slightly lower accuracy than a commercial-grade chip over a wide temperature range of -55 to +155°C because it uses a different trimming algorithm or even a slightly different circuit design. The difference between commercial-grade and military-grade standards is not only caused by different test protocols.

There are two other problems

The first problem: the characteristics of the packaging material, which may fail before the silicon fails.

The second issue: the effect of thermal shock. this characteristic of the AD590, which is able to operate at 77K even with slow cooling, does not mean that it will work equally well when suddenly placed in liquid nitrogen under higher transient thermodynamic applications.

The only way to use a chip outside its nominal temperature range is to test, test, and test again, so that you can be sure you understand the effect of non-standard temperatures on the behavior of several different batches of chips. Check all your assumptions. It is possible that the chip manufacturer will provide you with help on this, but it is also possible that they will not give any information on how the chip works outside of the nominal temperature range.