Monitoring variability of channel doping profile in the 45nm node MOSFET through reverse engineering of electrical back-bias effect

We propose a non-destructive, sensitive, and computationally efficient method for the determination of planar MOSFET channel doping profile from electrical measurements of back-bias effect. This method is superior to the physical measurements techniques in its ability to collect statistical and design relevant data. The concentration profile of electrically active dopants is determined within the channel region that controls the deviation of threshold voltage shift observed in the design range of forward/reverse back-bias conditions. The principle and sensitivity of the method are validated in 45 nm node against process and device simulation. Then we apply the method to experimental data for statistical characterization of doping profile at a depth ranging from 30 nm to 60 nm from oxide/silicon interface; average doping over depth, and its slope are proposed as two variability indicators for which statistically relevant data are reported, including spatial, intrawafer, and interwafer distributions from 1 lot.