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3D Planar EM Software for Custom Microwave Design Flows

Fullwave electromagnetic (EM) model extraction has become an essential part of high frequency IC design flows and has become invaluable for extracting highly accurate models for inductors, baluns, MIM capacitors, transmissions, coupled lines, interconnects and even on-chip grounding busses. However, EM model extraction based on full 3D volume meshing can be computationally prohibitive to apply to such processes because physical features of these structures can vary by four orders of magnitude or more. The most stressing feature of this technology is the extremely thin dielectrics in a multi-layer IC process, which may be on the order of 0.1 or even 0.01 microns separating lateral conductors with dimensions on the order of 1000s of microns. It is in this area that 3D planar high frequency EM simulators based on the 3D planar Method of Moments (MoM) find a niche because they mesh only the conductor surfaces and not all of the volume. In this way, 3D planar EM simulators are relatively immune to the difficulties presented by fullwave EM analysis of today's multi-layer silicon and CMOS process stackups.

Sonnet Software has released a new version of its high frequency 3D planar EM software, the Sonnet Suites. Prominent in this new release are features intended to streamline Sonnet's capability to efficiently solve demanding microwave and mm-wave frequency structures on challenging IC processes and to become a more "push-button," on-demand 3D planar EM extraction client to popular high frequency EDA design environment such as Cadence Virtuoso, Agilent EEsof EDA's Advanced Design System (ADS) and the Microwave Office Suite from Applied Wave Research. Sonnet also announces a new MATLAB toolbox, SonnetLab, which is freely available to all Sonnet and Sonnet Lite customers.

Faster Fullwave 3D Planar EM Simulation

In Release 13, Sonnet's flagship High Performance Solver (HPS) engine increases CPU core utilization to up to 12 physical cores in parallel on high-end computation platforms, decreasing solver run time by an order of 30 percent for workstations with dual hex core processors. The conservatively priced Desktop Solver (DTS) Engine has increased parallel CPU core utilization from 2 to 3 cores – appropriate for the average single-CPU office desktop PC. In addition, the Sonnet Professional matrix solvers have undergone further algorithm improvements for handling large jobs on 64-bit operating systems. Matrix fill is now fully parallelized for large jobs (4 GB), and customers are reporting simulation time reductions by as much as a factor of seven for very large circuit analysis.

New Via Modeling Features for Efficient RFIC and MMIC EM Model Extraction

Sonnet now provides separate metal definitions for vias, which are more appropriate to the way in which via metals are typically specified in foundry process design kits (PDK). Via metals may now be specified in terms of volume metal or surface impedance characteristics and specified to have either a solid fill or a predefined wall thickness.

New via meshing controls are provided to achieve faster results with fewer descritizations. Vias can now be simulated using filled meshing throughout the via cross-section, meshed with a ring definition for the outline of the via, use mesh elements at only the corners or a single mesh element in the middle of the via. In all cases, the metal loss computation is corrected in the simulator for the meshing that is employed. The mesh definition can be easily and quickly changed for via definitions when the designer wishes to shift between rapid prototyping and minimum-error simulations.

In Release 13, micro via array simplification technology is introduced to accurately model via array interconnects in a highly efficient composite manner. The simplification comes in the form of a new via fill type defined for the EM solver. The simplification is automated and accessible in its GDSII, DXF and Gerber imports, as well as in its RF EDA framework APIs. Multi-layer planar metal stacks (such as those used in silicon RFIC inductors, baluns and transformers) can now be efficiently simulated in Sonnet without manual model adjustments, providing accurate simulation results for kHz through THz frequencies.

Figure 1 Sonnet Suites EM model extraction window in Cadence Virtuoso.

A Flexible EM Extraction Client for Custom High Frequency IC Design Flows

As independent high frequency 3D planar EM software, Sonnet is capable of standalone use, free of a larger framework, or it can be used as an entirely integrated EM model extraction client for the abovementioned high frequency EDA RFIC and MMIC design environments. The Sonnet API for Cadence Virtuoso (see Figure 1) can now read process stackup and drawing layer map information from a variety of sources, including Assura process files, Helic Veloce/RF technology files, Agilent technology (.tch) files as well as existing Sonnet Material (.matl) and pre-existing Sonnet project files. Complete process stackup and layout-to-material associations can be imported with a single import for any given structure within a process technology. Often these process files come with the technology PDK supported by the parent EDA framework. Alternatively, a stackup definition may be created and stored in the Sonnet API by the EDA tool flow manager for use in all structures simulated for a given process technology.

The Sonnet API for Virtuoso now includes the ability to display an internal simulation progress bar, implementation of Sonnet's unique Co-calibrated Port technology for internal port group calibration and de-embedding, single-click access to show circuit descritization, "simulate and release" capability to allow EM simulation to continue without locking out the Virtuoso framework and the ability to automatically create a symbol for the Cadence Schematic Composer in the form of a layout look alike instance. Sonnet provides both frequency domain model extraction in the form of S-, Y- or Z-parameters, as well as the ability to provide a Spice model extraction using the Sonnet Broadband Model extractor.

Figure 2 Example balun schematic.

Once the EDA tool flow manager has an optimal setup for Sonnet model extraction appropriate for a given process technology, the settings can be saved in the form of an API State. State settings can include model simulation options, sub-sectioning control options, frequency plans, grid controls, layer mapping and process information. By loading an API state, the user obtains an automated EM model extraction starting from a Virtuoso PCell, without having to touch the EM project. This automation makes it possible for RFIC designers in the Cadence Virtuoso environment to generate a schematic symbol ready for use in downstream electrical simulation based on Sonnet's fullwave EM modeling capability in an easy, one-step process (see Figure 2).

Sonnet's APIs for both Agilent ADS and AWR Microwave Office have also been enhanced to result in a smoother, more tightly integrated use. Starting in Release 13, designers will find it less necessary to open the EM project in the Sonnet Project Editor in order to set advanced Sonnet options. Process technology for MMIC or RFIC design can be loaded directly from within ADS or MWO using existing process stackup or substrate definitions already located within the frameworks, often already inherited from a foundry PDK. The API for ADS and MWO will also have the ability to set States with full Sonnet translation and simulation settings for a given process technology, enabling one-click configuration of Sonnet EM model extraction processes. As with the API for Virtuoso, these APIs can also help users who are not familiar with Sonnet to leverage Sonnet's distinctive accuracy without expert-level tool knowledge.

The new SonnetLab toolbox makes it possible to use MATLAB scripts to automate the construction of a Sonnet project, launch the EM simulation and extract the resulting output model for further processing. It is possible also to use MATLAB for sophisticated control and optimization of Sonnet planar EM projects for a variety of design automation and analysis processes. The SonnetLab toolbox is available for download from the Sonnet website free of charge, and is compatible with all Sonnet Suites, including Sonnet Lite.

Expanded Capability for Entry-Level Sonnet Suites

Sonnet offers a number of entry-level suites, aimed at students and customers with less demanding structures involving fewer circuit layers and ports. All of the Sonnet entry-level Suites – Lite, LitePlus, Level2 Basic, Level2 Silver and Level3 Gold – have received at least a doubling of allowed memory, making them able to simulate larger problems than before. The Sonnet Level3 Gold Suite has been expanded to allow unlimited circuit ports and a memory use increase of a factor of eight.

Easier to Fit to Real Circuitry

The Sonnet Release 13 environment has also received additional improvements for flexibility and usability. Some of these features include:

  • Rotated edge ports and internal ports, enabling arbitrary entry directions with de-embedding.
  • Any port may have an independent reference plane or may share a reference plane with other parallel lines. Shared reference planes enable the de-embedding of parallel line coupling to the reference plane.
  • A new visual continuity checker in the user interface that shows DC continuity in the meshed model. This is an error-checking feature that is particularly useful in checking the simulation models for model translation errors prior to simulation.
  • A new Conductor Surface Roughness loss model, developed in conjunction with researchers from Rogers Corp., has been introduced to provide loss and transmission line phase velocity changes due to the roughness of conductors on microwave laminates and substrates.
  • Heat Flux computation and display for lossy conductors and planar resistors. The data may be exported for post-processing in thermal analysis tools.
  • A new Example Browser makes it possible for learners to quickly and easily search for applicable examples and load them into the Sonnet Project Editor for personal observation and experimentation.

The Sonnet Suites Release 13 provides further capability and enhancements in Sonnet's industry-leading 3D planar high frequency EM software and now enables a smooth integration of shielded domain method of moments (MoM) model integration within major high frequency EDA design environments.

Sonnet Software Inc.,
North Syracuse, NY
(877) 776-6638,

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