hello everyone!
i want to body baise my NMOS and PMOS devices , but someone told me that i can not use body biasing for NMOS because of p- substrate; which is common for NMOS and PMOS, is there any suitable way to do that?
Dear Akil,
To give a specific answer on your question one needs to see a drawing of the cross section of your CMOS structure. Could you display it?
Respected Abdelhalim ,
i added cross section drawing in the attachment. it is NMOS nominal 1.8v, 180um process. please guide me if i can use its body terminal for body biasing?
Dear Akeel,
Concerning the control of the threshold voltage by the back gate bias voltage, the only available way is to have a separate bulk or substrate terminal for the transistor as the case in your cross section. Then you can apply different Vbs values such that the bulk to source junction is reverse biased.
The cost of the intentional back gate bias is the conducting paths or buses to the back gate bias terminals and an extra power supply. Normally, substrate is connected to the source terminal and the threshold voltages are adjusted by technological means such as ion implantation. Before the advent of the ion implantation, the threshold voltage of the nmos transistor is adjusted by boron implantation.
The p mos transitory will lay out of the p well in the n substrate, The pn junction between the p well and n substrate isolates the two transistors provided it is zero or revere biased.
I wish you success.
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