It's hard to convey just how ridiculously complex and expensive 5nm is compared with 90nm.
5nm is a multi-billion dollar fab, absurdly high running costs, and very expensive wafers.
As a data point: 5nm lithography equipment is > $100M/unit, needs megawatts of power to run, and they handle about 60-80 wafers per hour.
90nm lithography equipment is ~ $1M/unit, needs kilowatts of power to run, and they handle about 60-80 wafers per hour.
So a wafer scanned on 5nm equipment that could have been scanned on 9nm equipment is carrying a very large capital and operational cost burden that's pointless.
5nm is a multi-billion dollar fab, absurdly high running costs, and very expensive wafers.
As a data point: 5nm lithography equipment is > $100M/unit, needs megawatts of power to run, and they handle about 60-80 wafers per hour.
90nm lithography equipment is ~ $1M/unit, needs kilowatts of power to run, and they handle about 60-80 wafers per hour.
So a wafer scanned on 5nm equipment that could have been scanned on 9nm equipment is carrying a very large capital and operational cost burden that's pointless.