Zero-Temperature-Coefficient (ZTC) is the point at which the performance of a transistor becomes independent of temperature changes. Normally, when the temperature increases, we see two main effects: the mobility of carriers (like electrons in nMOS transistors) decreases, and the threshold voltage (the voltage needed to switch the transistor on) also drops slightly.
However, at the ZTC voltage, these two effects cancel each other out. So, as you increase the temperature, the speed of the circuit doesn’t change. I find it fascinating because it means we can design circuits that are more stable and reliable across a wide range of temperatures.
What is the Narrow-Channel Effect?
This ZTC behavior becomes especially important as we continue to scale down to smaller technology nodes, like 45 nm and beyond. In these modern transistors, the temperature effect is becoming less predictable, and worst-case and best-case performance simulations need to be reconsidered. High-temperature doesn’t always mean slower performance anymore. For example, in a chip with both high-VT and low-VT cores, some cores may slow down with heat, while others may speed up.
As you can see, the temperature effect on MOS transistors is complex, and as technology evolves, it requires more careful analysis to ensure optimal performance under various conditions.
