Research On The Automatic Interconnect Reliability Modeling For Power Amplifier

With the amazing development of wireless communications,power amplifiers(PAs)are playing an irreplaceable role for various applications in various walks of life.The interconnect is become thinner and narrower with the development of CMOS technology.Electromigration(EM)induced interconnect failure has become a major reliability issue due to higher current density in the interconnect as the feature size in CMOS technology continues to shrink.Moreover,lower power added efficiency(PAE)restricted by the lossy substrate of CMOS results in higher heat generation from CMOS PA transistors,which aggravates the interconnect and circuit reliability.To evaluate the interconnect reliability of a PA,several reliability modeling and simulation approaches were proposed.In particular,3D circuit modeling is preferred because this method is able to integrate various driving forces(such as current,temperature,stress,etc.)in EM diffusion process.However,3D circuit model is accomplished manually in ANSYS Workbench according to the PA layout from Cadence.Drawing is a tedious process for a complicated PA.When the layout structure changes,the 3D circuit model must be reconstructed,which makes it more time consuming.Therefore,an automated modeling approach for the PA interconnect reliability which considers the heat generation from transistors is quite desired.Parametric modeling with ANSYS parametric design language(APDL)is used to construct the 3D PA model automatically,by embedding the geometrical parameters in the codes,different 3D PA models can be constructed by defining different geometrical variables,which makes the tedious modeling procedure a significant time-saver.Automated model generation(AMG)algorithm is an advanced method to automate the process of developing neural network models.In addition,AMG algorithm is applied in an effort to work with the simulation data from ANSYS to predict the reliability data quickly.A dynamic sampling method is adopted to speed up the simulation by reducing the training data.Therefore,a fully automated methodology is achieved to analyze the interconnect reliability without a waste of time and physical labor.In this paper,we made a comparison between AMG and the Artificial neural network(ANN)modeling to verify the feasibility of AMG.By using AMG,a reduction of 49.2% simulation time is achieved by using the dynamic sampling method.A series of experiments have been performed with different layout structures and operating conditions.The simulated reliability results offer a guideline to choose the PA layout based on the real RF performance and EM reliability during design stage.