this post was submitted on 18 Oct 2023
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Also bleeding-edge processes mean smaller, thinner gates. That's what gives them the fast switching speeds, but it reduces the max allowable voltage. For parts that need to handle more than 1.8V or so a modern 5nm process will just end up using bigger gates than the process is optimized for. May as well go with an older process (bigger minimum gate size) that's better suited to switching the voltage needed. For Bosch (automotive parts, power tools, etc) they're making a lot of parts with really big output transistors (switching 14V, 48V, etc) and not super high-performance processors.
The big disadvantage with particularly old processes is that they used smaller wafers. So fewer chips per wafer processed, meaning lower overall yields and higher price/chip. The switch from 200mm wafers to 300mm in 1999 meant the wafer area increased by a factor of 2.25! 300mm wafers also required fully-automated factories due to the weight of a wafer carrier (a front opening wafer pod, or FOUP, is 7-9kg when loaded with 25 wafers), which save on labor costs. So processes older than 1999 (around the 180nm node) are sometimes not worth it even for power electronics.