In a new article, ExtremeTech explains there's also another issue that's driving shortages. The site notes there's been insufficient investment in 200mm wafer production capacity over the past decade or so. With a lot of the industry switching to 300mm, demand for older technology like 200mm was expected to decline. Foundries were expected to switch to 450mm but that technology never made it to market. So instead of the expected decline in demand for 200mm capacity, demand for this wafer format has actually been growing since 2015.
Larger wafers are considered better as it's more efficient to manufacture 300mm wafers, but a lot of customers that don't make cutting-edge products. Many IoT sensors and similar products are made using these extremely mature technologies and the growing demand plus the slow uptick in 200mm capacity has resulted in 200mm utilization getting very high at a lot of fabs.
Porting designs to new fabs is often not an option as it's too expensive:
I don’t want to give the impression that literally every foundry with 200mm capacity is running all-out, but it takes a significant amount of time and money to port designs to a new fab. A company with a chip designed for Foundry A’s manufacturing line would likely face significant costs to port the same chip to Foundry B. In some cases, a company would pay more to port a chip to a new foundry/node than it would ever make back from selling it. Not literally every 200mm fab is full, but the pure-play foundries with significant amounts of 200mm capacity aren’t having much trouble filling it.So basically, there's not a single big factor that's driving the shortages we've seen this year. It's a combination of a lot of factors like an increase in laptop demand for the stay-and-work-at-home-economy, the new console releases, two big GPU launches the COVID-19 pandemic, the Huawei situation, and also the 200mm capacity shortages.