I am laying out a precision poly resistor... I would like to have the most flexibility in selecting tap points so I have filled the entire length with contacts (each contact is 0.24um apart) with overall length 300um so more than 1000 taps.  Will having so many taps alter the R/sq of the poly ?

Thanks

"precision poly resistor"

No such thing.

+/- 20% variance on process needs to be accounted for.

even if you are trying to get matched resistors you will have matching errors and contact resistance vaires widely.

What is the problem you are trying to solve with this magic resistor? There are probably better ways to solve the problem.

Also, I'm not changing the length, just the tap point on the divider.  Contact resistance doesn't matter because there is no DC current flowing through the contacts/tap point.

Hi jiesteve,

What are you working on? A resistor ladder or just a divide-by-2?

What type of resistor do you use? Poly with silicide or without silicide?

What is the resistance of the all resistors?

What's the accuracy/error you are seeking? If you need a 10+ bit DAC, there is an good example in VERMA and RAZAVI's paper. JSSC Nov. 2009.



Best Regards,
Yawei

Taking your numbers

16 Ohms/sq & 1.6KOhm and 11 Bit accuracy of the 0.5 divider ratio makes 50sq+50sq but the tap should be stepped at 50/2048 sq =1/40 sq

You should have a very wide poly to make tap adjustments by 1/40sq with single contacts. I would also layout two interwinded snakes of poly because otherwise the poly and silicide thickness gradient are violating 10-11bit. If you want to have a selectable tap by less than a contact size I propose to use a second resistor connected at 0.525 and 0.475 positions and having a higher resistor and being longer to place the taps.