T. Mizuno et al., EXPERIMENTAL-STUDY OF THRESHOLD VOLTAGE FLUCTUATION DUE TO STATISTICAL VARIATION OF CHANNEL DOPANT NUMBER IN MOSFETS, I.E.E.E. transactions on electron devices, 41(11), 1994, pp. 2216-2221
Threshold voltage fluctuation has been experimentally studied, using a
newly developed test structure utilizing an 8 k-NMOSFET array. It has
been experimentally shown that both V(th) and the channel dopant numb
er n(a) distributions are given as the Gaussian function, and verified
that the standard deviation of n(a) can be expressed as the square ro
ot of the average of n(a), which is consistent with statistics. In thi
s study, it has been shown that V(th) fluctuation (deltaV(th)) is main
ly caused by the statistical fluctuation of the channel dopant number
which explains about 60% of the experimental results. Moreover, we dis
cuss briefly a new scaling scenario, based on the experimental results
of the channel length, the gate oxide thickness, and the channel dopa
nt dependence of deltaV(th). Finally, we discuss V(th) fluctuation cau
sed by the independent statistical-variations of two different dopant
atoms in the counter ion implantation process.