When should I use Dummy Transistors?

[ryusgnal]

when should i apply this?

is it only for even number of fingers or should apply everytime we use multifinger? Help please....

 

[Vabzter]

dummy transistor layout

Hi,
To minimize the etch effects during fabrication. If they are not placed then it can so happen that one side is slightly more parameter(Vth e.g) then the other transistor. Hence the matching will not be identical for all the devices. For a good matched layout dummy devices must be used. Generally dummy devices are added to resistors as well so that they surround the complete resistor.
BR
Vabzter

 

[dabing]

dummy transistors

is it only for even number of fingers or should apply everytime we use multifinger? Help please....[/quote]

The dummy structure is not only for even fingers, but also for odd fingers or you think you should use the dummy for immunity orther fabrication influence:diffusion imp and so on.
I think you can get two mirrors. and take the two mirrors under the sun. You should see the different between the mirrors and the sides of the mirrors.
If you want to get the same shallow, i think you can take more mirrors, maybe 4. and take the four mirrors under the sun, you can get the same shallow. The trasnsitor is the same while fabrication.
Or, you can info for a process engineer. The above is my opion.

I think the dummy is not only use for immunity fabrication, maybe some other surroundings we can use.

And the more fundamental about dummy, you can refer to <<The Art of Ananlog Layout>> or other books.

Best wishes for you

 

[ryusgnal]

transistors for dummies

If I put dummy transistor in my layout, is it will effect my LVS (Layout Versus Schematic) Result?

 

[jfyan]

dummy poly structure

If I put dummy transistor in my layout, is it will effect my LVS (Layout Versus Schematic) Result?

hi,
yes, i think it will take effect, so you should add the dummy tansistor in the schemetic.
goo luck
jeff

 

[jagadeesh2k1]

transistor for dummy

Dummy poly alone is enough no need for the dummy transistor.

 

[hung_wai_ming@hotmail.com]

dummy poly

This dummy transistor layout is better than just putting poly without diffusion.
This is a typical dummy layout for those RF design or highly sensitve analog layout design. Just putting poly will have profile not flatten around the edge as the diffusion is already missed out there, so therefore, don't be lazy to put a real dummy transistor at both ends. This is a practical situation that I have saw it from some layout designers working over 20 years in the field.

Also, dummy is added whenever you feel comfortable from design point of view and you need to add dummy transistors in the schematic to make LVS passed.

Dummies are much required when your transistor's device size is very small, tending to have more rupture effect during fabrication.

 

[ayanbur]

How can I add dummy transistor to schematic even layout?

 

[ayanbur]

How can I add dummy transistor to schematic even layout?

I have solved the problem about LVS. Thanks