AnandTech speculates N5 may be getting better yields than N7 due to increased use of EUV:
Part of what makes 5nm yield slightly better is perhaps down to the increasing use of Extreme UltraViolet (EUV) technology, which reduces the total number of manufacturing steps. Each step is a potential chance to decrease yield, so by replacing 4 steps of DUV for 1 step of EUV, it eliminates some of that defect rate.Graphs shown at the symposium indicate TSMC's N5 currently has about 0.10 to 0.11 defects per square centimeter and this is expected to drop under 0.10 when high-volume manufacturing starts ramping up in Q4 2020.
The first products with chips made on TSMC's N5 node, which will be smartphone chips, will hit the market later this year.