Metal routing in the CMOS layout?

katrin said:

Hello, I have some questions regarding the routing in the CMOS layout. I am always not sure about these problems, or if it should be avoided to do it like this way.

1, In general the power supply plane and the ground plate should be as large as possible, to form a big capacitor between to stabilize the power supply?
Ans. The Power and Ground line thickness depends on the highest current of your block. Make sure you double check and compute your current density according to your design rule.
Also for uniformity purposes if some block used i.e 10u width for power and ground then you can use it as well but then again you have to compute your current density limitation for particular metals.

2, Is it OK to route signal metal line over the power supply metal layer?
It depends..if you don't have a choice then go over the power or ground line. If it is a noisy signal then you must shield the signal lines.

3, Can I route signal metal line over the poly resistor?
If the poly resistor does not require matching then it is ok...but the rule of thumb..if you can route the signal outside the poly the better.

4, Can I route the power supply metal over the devices?
Again if the devices that you are going to route with the power lines does not have any matching then you cannot do it...

5, Can I route the higher layer signal metal line over the transistor devices?
Again and again if the devices does not need matching you can do it...but as a good layout practice even if there's no matching required you really don't have to pass the signal lines of power/ground lines over the devices..esp. if it needs matching.

Click to expand...