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Gate direction of mos transistor in layout

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John Xu

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Hi,
I have a question on the gate direction of mos transistor in layout. We know, in layout, for the matched transistor/device, they are asked to place in the same orientation to keep matching. But for those unneedded transistors, are they needed to place in the same orientation? Place them in different orientation will afect the product yield?


Thanks in advance
 

vbhupendra said:
definately it will !
Click to expand...

hi,vbhupendra
Thanks for the reply! Would you like to elaborate it a bit more? We passed the design in full case. So for the mos transistor, we confirmed it with typ,ss,ff,sf and fs. It can not guarantee all the corners fall into this range?

thanks
 

In general practice the matched devices should be placed in the same orientation.If differs the mobility og=f the caarriers changes inturn mobility related to the gain,current....All these quantities will change. u can place other devices which requires no matching in different orientation.
 

    J

    John Xu

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John Xu said:
Hi,
I have a question on the gate direction of mos transistor in layout. We know, in layout, for the matched transistor/device, they are asked to place in the same orientation to keep matching. But for those unneedded transistors, are they needed to place in the same orientation? Place them in different orientation will afect the product yield?


Thanks in advance
Click to expand...

Devices that don't have matching requirements needn't be in the same direction.
BTW, what are unneeded transistors?
 

    J

    John Xu

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If you are talking about horizontal poly and vertical poly then...generally we like to keep safe and matched transisitors are oriented in same direction. topologies of common centroid are followed. but in case you have a very stable process where the foundry guarantees proper construction you can have exceptions that is very rare to my knowledge...but it does happen atleast in digital core of your chip...yeild to size tradeoffs do exist...
 

    J

    John Xu

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Hi,

My opinion is that it will not affect anything. However, take for another case that you have two groups of matching transistors, but the two groups need not be matched. It is still good to put the transistor in both groups in the same orientation because it allow the process engineer to optimise the fabrication process to achieve better yield.

Regards,
Eng Han
www.eda-utilities.com
 

    J

    John Xu

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[quote="Hughes
Devices that don't have matching requirements needn't be in the same direction.
BTW, what are unneeded transistors?[/quote]

Hi,Hughes,
Sorry for the typo,.The "unneeded transistors"means those unneeded matched transistors.

regards
 

John Xu said:
vbhupendra said:
definately it will !
Click to expand...

hi,vbhupendra
Thanks for the reply! Would you like to elaborate it a bit more? We passed the design in full case. So for the mos transistor, we confirmed it with typ,ss,ff,sf and fs. It can not guarantee all the corners fall into this range?

thanks
Click to expand...

I would have thought u r talking of dummy (as unconnected transitors) !!!
 

some process doesnt allow orientation of transistors in both directions

but some will allow in all the directions i.e in vertical & horizontal direction
 

    J

    John Xu

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For deep submicron technology such as 65nm or 45nm, in general only one poly(active) direction is allowed. But for other not so deep submicron technology, it maybe OK for using 2 poly directions to those non-critical circuitry.
 

    J

    John Xu

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i think that the direction of the poly depend up on the pdk of the fab that we are using....

correct me if i am wrong...
 

Hi,
The basic rule for matching is the orientation, but we may not follow the orientation for the whole chip. But if you follow orientation throughout the chip, the performance of your chip will be better ( It meets what designer wants ), Please refer to the ion implantation effects in razavi (last chapter). And think urself what happens to other transistor functionality if you dont follow orientation.
Thanks & REgards,
Shiva.
 

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