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what are the options to route the guard ring?

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padmanabanks

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hello friends,

i got a question in an interview...

after you done the layout for an inverter, DRC says that you need to put a guard ring for pmos and nmos????

option 1: we can stretch p-cell and n-cell...then put a guard ring for both..
option 2: without stretching the both cell, simply put a guard ring then wherever the
metal short there flatten the guard ring then chop the metals.
option 3: ?????????????

recently they are using option 3....

can you tell me anyone? how to route the guard ring??
 

what do you mean p-cell and n-cell, PMOS and NMOS?
i think if you tied n-tap (N-well for PMOS) and p-tap (p-sub for NMOS) to VDD and GND, respectively, you've done with the inverter.
 

no..i meant p-cell as pmos, n-cell as nmos...

actually what is the my question is, after u done the layout for an inverter...the DRC says that..u need to put a guard ring (well guard ring for pmos transistor, p guard ring for nmos) what you'll do? and how you'll route the guard ring for both transistor...

u can see the options in above...
did u get? my question
 

i did not get option 2.
as i know, if you can make sue you have tied the p-sub and n-well well, there is no DRC error, at least for us, this is the case.
 

well...
if we put the well contact for pmos and p-contact for nmos..u wont be get any drc error....ok...

in my interviewer asked me...u need to keep only the guard ring...what r the options r there after u done the layout for an inverter...

option 2 : we can route the guard ring around the pmos and nmos..without stretch the layout..at that time ull get short in the routing area by the guard ring..right?
show by enable the flatten, we can chop the metal only from the guard ring.. so there wont be short between guard ring metal and routing metal...am i right?

i need third option what will be and how will be the guard ring routing?

he said, recently they found and they r using......
 

put guard ring around the inverter not separetly for Pmos and NMOs and connect either VDD or VSS but it will be guard ring not BULK for these transistors (well for one of them it will be bulk as well)
 

yes, pickup ring is different from guardring.
for NMOS, pickup ring is p+ well tap, for PMOS, pickup ring is N+ well tap.
for NMOS, guard ring is N+ tap surrounding NMOS; for PMOS, guard ring is P+ tap surrounding PMOS.
 

prcken said:
for NMOS, guard ring is N+ tap surrounding NMOS; for PMOS, guard ring is P+ tap surrounding PMOS.
Click to expand...

Did you mean dummy transistors with power connection on P-substrate when you say N+ tap and dummy transistor with power connection on N-well when you say P+ tap?

prcken said:
yes, pickup ring is different from guardring.
Click to expand...

What exactly is a pick-up ring? And how it is different from guard ring?

prcken said:
yes, pickup ring is different from guardring.
for NMOS, pickup ring is p+ well tap, for PMOS, pickup ring is N+ well tap.
Click to expand...

What do you mean by "P+ well tap" and "N+ well tap"?
 

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