
IC DfM for Devices and Products 131
TABLE3.13
Categories of Mask Defects and Their Impact on a 10-Point FMEA Scale
Category
FMEA
Size No.
On Mask On Wafer Impacts Severity Occurrence Detectability RPN
Smallest to Largest
1 Not printable Not printable Write time 2 5 2 20
2 May peel Potential
repeaters
Inspectability 10 5 8 400
3 Marginal CD control Not printable Write time 4 5 5 100
4 Poor CD control May peel Hot spots 8 4 5 160
5 In spec Marginal Poor CD control 7 3 2 42