scottieman said:
Hi all,
Suddenly have a question in my mind on CMOS technology. To have both NMOS and PMOS, we need a p-substrate for NMOS and a n-substrate for PMOS on the same silicon. That is why we do have a N-well in p-sub wafer.
However, why don't we do the opposite. Use n-sub with P-well to achieve the goal of CMOS.
Anyone can tell me the reasons behind it?
Thanks alot
Scottie
We try to use nmos in our design if we have option between nmos and pmos. Why? one of the reason is that, the mobilty of the carrier for nmos is higher than pmos. So, with smalll w/l of nmos we can get what pmos can give. That means small real estate for nmos in IC which mean lower cost for product. There are few more reason in term of performance in which nmos is better. In fact, before we have CMOS tech, circuitry was made up by nmos. So, I don't see any good reason to use n-sub instead of p-sub.