San Jose, California - June 10, 2002 - Applied Simulation Technology is announcing the release of a hybrid simulator. ApsimFDTD-SPICE is a 3D-full wave electromagnetic field solver and non-linear circuit simulator for IC design. As the technology and speed of semiconductors continues to rapidly evolve the characterization of the IC interconnect system has become a major focus point. As the semiconductor devices themselves become faster the major contributor to delay becomes the interconnect system. Moreover the interconnect system is also a major cause of noise, which by itself can alter timing or cause functional failure. The need to accurately account for the interconnect system gives rise for the need to do electromagnetic simulation. ApsimFDTD-SPICE uses the full wave accuracy of Maxwell's equations combined with the industry standard transistor level simulator SPICE in a time stepping manner. This means that the FDTD field solver and SPICE communicate at every time step. This is a more direct way than conventional two step methods that need equivalent circuit generation using a field solver before nonlinear circuit simulation. This combination gives a level of accuracy never before achieved for non-linear time domain analysis.
The current set of tools used for characterization of the interconnect system in an IC is fast becoming obsolete. Such tools use systems based on the Quasi-TEM mode to approximate the propagation velocity and extract RC or RLC circuit elements assuming silicon substrate as a ground reference conductor. At very high speeds this approximation is no longer accurate. The Slow Wave Mode, Skin Effect Mode and Quasi-TEM Modes all need to be accounted for. These depend on the silicon substrate resistivity and frequency and need to be taken into account in order to get an accurate scenario even for nonlinear circuit simulation. ApsimFDTD-SPICE accurately accounts for all three modes using full wave electromagnetic analysis and nonlinear circuit analysis in the time domain. In order to efficiently take care of both electromagnetic and nonlinear effects specialized for IC structures, newly developed special techniques such as irregular meshing, auto-initial conditions and auto-spatial boundary conditions have been implemented. Since ApsimFDTD-SPICE uses general 3D full wave electromagnetic field solver, lossy conductor, dielectric, and magnetic materials can be modeled. This allows users to evaluate the effect of thin magnetic adhesion layer for copper traces in ICs. Once integrated with the process transistors it allows design and process engineers to accurately characterize new layouts and technology without many months of empirical analysis.
The program reads in technology and layout information compiles the files such as GDSII and runs a SPICE like net-list. There are a variety of output functions available that include real time animation of the 3D spatial voltage, current, electric and magnetic fields in time domain as well as S, Y, and Z parameters in the frequency domain. It also can be interfaced with the Electromagnetic Interference simulator ApsimRADIA. The traditional time domain plotting supported by SPICE is also done. The application of ApsimFDTD-SPICE is intended for the analysis and electrical characterization of high performance IC cells with transistor and/or behavioral models for both digital and analog designs. Although ApsimFDTD-SPICE uses its own ApsimSPICE which has more than Berkeley SPICE models, it can read Table_SPICE format accurately converted from the original native SPICE. It allows engineers to characterize new layout and technology changes that may impact a design's electrical performance. It can account for accurate delay, cross talk, signal degradation, power/ground bounce and simultaneous switching output noise (SSO) due to the electromagnetic interactions of the interconnect system with the IC design technology. ApsimFDTD-SPICE can also be used for IC package and printed circuit design with a layout system interface. It can be applied to all levels of design from IC, IC package to PCB as a unified tool. ApsimFDTD-SPICE is most accurate hybrid simulator for 3D-fullwave electromagnetic and nonlinear circuit simulation. It accounts for more than traditional inductance effect and silicon substrate resistive effect.