Effect of channel dopant uniformity on MOSFET threshold voltage variability

The effect of the dopant uniformity in an MOSFET channel on the threshold voltage variability is studied with a simple model and the test MOSFET array which includes many MOSFETs with different channel length and width. The simple model shows that the channel uniformity in channel length direction affects the threshold voltage variability. Takeuchi coefficient as a function of the channel length is calculated from the measured threshold voltage data. The electrical channel length as a function of the gate voltage is extracted using channel resistance method. It is found that those data show the similar degree of the channel dopant uniformity for MOSFETs having various channel structures.

► We studied how the dopant uniformity in a channel affects on VTH (threshold voltage) variability.
► We show that the non-uniformity in channel length direction affects VTH variability.
► We found both VTH variability and electrical channel length similarly depend on the dopant uniformity.
► This fact explains why VTH variability for N-MOSFET is larger than that for P-MOSFET.