Tham khảo tài liệu 'mosfet modeling for vlsi simulation - theory and practice episode 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Optimization Method 577 11. Minimization and maximization of the performance function under the nonlinear constraint given by Eq. gives the slow and fast z vectors respectively. The procedure outlined above was carried out using the same data as was used for generating WCF discussed in section . The results of optimization using drive as the performance function are shown in Table . Note that the values for only few important parameters are shown. Since fdrive is a function of the model parameters and device w and L the optimization was carried out using w 3 tm and L 1 pm. It should be pointed out that the parameters were obtained using two steps of optimization. In the first step parameters pertaining to the threshold voltage model were optimized. These parameters were then fixed and other parameters for drive were then optimized. In Table the numbers in the bracket show standard deviation times the amount of the shift in the parameter value from their respective mean typical values. Note that the change in the parameter value is less than 3ơ for the so called four independent parameters AL A IT Cox and Vfb. This is understandable because overall change for Idrjve is the effect of other parameters too. The optimized DC parameter values shown in Table are then used to calculate drive bounds. These bounds are shown as dotted line in Figure . Clearly the optimization technique results in a more realistic WCF compared to the principal factor method. The histrogram of drive for Wm Lm 1 n-channel devices based on data collected from 3 different lots 117 die locations from different wafers for a typical 1 pm CMOS technology is shown in Figure . The vertical lines designated as TS and TF are the slow and fast bounds respectively generated by the principal factor method while the corresponding bounds generated by the optimization method discussed above are designated as OS and OF respectively. Note from this figure that the bounds
