"Please note that actual wafer starts per month (WSPM) output of a fab depends on multiple factors, including process technologies used. As a result, all the WSPM capacity numbers are relative and may not reflect actual performance. Keep in mind, that as foundries and IDMs increase usage of multi-patterning techniques, their effective WSPM output drops as wafers spend more time in the cleanroom. Hence, to keep the wafer starts per month capacity, chipmakers need to add equipment (which may, or may not, involve physical expansion of the cleanroom space)." by Anandtech
Gondolom ez lehet az oka.
