Optimization of process and device characteristics for MOSFETs by using the BFGS method

This paper proposes an improved process/device optimization technique, which effectively determines the optimum process conditions for realizing the desired MOSFET performance. The BFGS method, which is the best quasi-Newton method now available, is introduced to save computational time. Furthermore, upper and lower boundaries are also implemented to facilitate the search for more realistic solutions. In order to demonstrate the practicality of the present simulator, channel doping conditions, such as implanted boron dose and annealing temperature, were optimized. Optimization within constraint boundaries was successfully carried out using the relationship between measured drain current and drain voltage characteristics. Consequently, it was verified that the optimization works well for a wide range of initial values and that CPU time is less dependent upon the initial values than that was obtained by using the previous method. Owing to optimization improvements, the computational time has been significantly reduced. Therefore, the present simulator is expected to become an important tool for device design.