Updated PDK Vth Delta

Dear illaoi,

illaoi said:

On the new PDK (mature) for a given process node, selecting op of a given FET and then Vth shows more than 60% delta (~150mV), foundry verified that they see <1mV delta, this remained a dilemma for us to understand the discrepancy. 

In the netlist the LDE (SA,etc.,) are on, if that helps! I have attached ID-VGS, and gm-VGS, which I do not see that Vth delta!

There are a couple of points to consider from my perspective.

1. The definition of the threshold voltage is not standard. It is necessary to specify exactly how the parameter is measured. Hence, I would initially verify that the conditions you are simulating the parameter have been verified to be identical to those your PDK vendor is using.

2. Usually, a PDK vendor takes measurements on only specific device sizes. As you know, smaller devices will show greater amounts of threshold variation than larger devices. Hence, please verify that the device you are simulating has the same topology and is the same device type (i..e., low or high threshold, core or I/O device, etc) as was used by your PDK vendor. In your specific case, my guess is your device is much larger than that used by the PDK vendor.

Shawn