hello everyone.
now i got a RF CMOS process PDK, there are 4 types RF MOSFET: nominal vt, low vt, zero vt, and native vt. but i don't know what differences are there among these MOSFETs, especially between the nominal vt Mosfet and the latter 3 Mosfet. so anybody can help to explain them or give me some references?
thanks a million.
Basically during fabrication you cant precisely control the subsrate doping , due to this there might be shift in Vt.
And hence Different kinds of Vt arises. Fabs gives models for transistors for all the
situation that can be encountered.
For Rf CMOS. if speed is the criteria then you need to the reach the specifications in high Vt process, as this the slowest of all. And if low power is the blocking criteria then you need to reach the spec in Low Vt process.
Definitions of the different Vt you asked for is as said by before post.
In my opinion, Native Vt is similar to nominal Vt process.
i have another question, that is, how to realize the low vt mosfet in process. i had searched in google and IEEE paper database, but can't find some valuable imformations. in the RF CMOS PDK, the low vt mosfet add an extra process step: the low vt implant, shown in figure below, but i donot know the effect of this process step. so who can tell me?