Derived mask in CMOS process.....

[kevin Park]

There is a question about layout. I am designing SRAM in 0.18 CMOS process.
Someone told me that there is a technique - drived mask - and it's possible to make nmos using only "ndiff" and poly except "n-implant".
Is it right? If so, what's the method?

 

[sunking]

why not contact the foundry?

 

[rfsystem]

Typically derived layers are used for device recognition or extraction. The logical AND of ndiff and poly define a NMOS. If you browse a extraction rule deck you will find typically more derived layers than orginal GDS layers. Some of the derived layers are used also for display in analog extracted view in Cadence or to monitor device extraction for other tools which could show GDS.