One Design, Multiple Simulation Options
Every MEMS+ design is compatible with multiple simulation environments, including the built-in MEMS+ simulator, along with MATLAB®, Simulink® and the Cadence Virtuoso® environment.
The MEMS+ design process starts with the entry of material and process description information for the proposed design. Layout data can be directly entered in MEMS+, or imported into MEMS+ using a GDS2 format file. IC layout artwork, including custom shapes and geometries, can be imported into MEMS+ from many 3rd party design tools. Using layout data, along with material and process descriptions, MEMS+ can generate a 3D schematic of a MEMS device.
Key Features
- 3-D design entry is tied to the manufacturing process
- Built-in, parametric material database and process description
- The material data, process file and Innovator schematics are stored in separate text files using the standard XML format
- Graphical variable definition and exposure
- Easy setup of mechanical boundary conditions and electrical ports
- Interactive, graphical design entry, and
- Python scripting interface allows scripted design entry
- GDSII or 3D ACIS SAT files can be imported into Innovator for comparison with a MEMS+ model
- Standard output filters include GDSII layout and ACIS SAT 3D solid models
Process Aware
While MEMS and IC design share aspects related to manufacturing, they differ in the impact manufacturing has on their design flows. IC components are standardized within a fabrication process while MEMS components are not. For instance, a transistor (an IC component) is created out of specific layers deposited on the silicon substrate during the fabrication process, and these layers cannot be changed by the IC designer; but a mechanical suspension beam that is part of a MEMS design can be placed on any of several “mechanical” layers, and that layer is a design choice.
In addition, it is often necessary to tailor the fabrication process to a particular MEMS device in order to achieve the design goals for the device. Thus, the fabrication process is an important “free parameter” in MEMS designs that may be changed as development progresses. The flexibility to change the description of the fabrication process is required for MEMS design, but is missing from conventional IC design environments.
The MEMS+ environment addresses the specific needs of MEMS designers by providing two integrated editors for specifying all process-specific data: the material editor and the process editor.
Linking Processes and Library Components
A relationship between the library components in MEMS+ “Innovator” (the parametric component design area) and fabrication data is included using a common layer property. With this layer property, a designer can establish a relationship between a component structure and one of more layer names.
What are the benefits of MEMS Parametric Design?
In the MEMS+ “Innovator” tab, a designer can select parametric components from the MEMS Component Library to include in their design. These parametric components are like MEMS-based “building blocks”. Users assemble a design in Innovator by combining parameterized components into a larger assembly . This is somewhat analogous to creating an IC layout by inserting pre-defined parametric layout cells into the layout. The main difference betweeen MEMS+ and IC design is that the MEMS+ design is done in a 3-D environment. This 3D design is more natural for MEMS designers, who are used to working in 3D CAD environments.
Unlike 3D CAD environments, there is a sophisticated behavioral model associated with each MEMS+ component. Each of these component models can also be automatically connected by a wizard. Users can control which parameters and electrical and mechanical “pins” are exposed in the models during simulation. Users can also define a hierarchy of symbolic variable names and use those names in place of literal values, or combine them in algebraic expressions, to define any material property, any process parameter (e.g. layer thickness), or any component parameter (e.g. width of a suspension). A combination of variables and algebraic equations allows for properties to be mutually dependent on other properties, upon environmental variables (e.g. temperature and pressure) or even based upon abstract variables such as the equipment settings for a given fabrication process. This flexibility enables development of highly complex behavioral models, without the time and expense of custom-built MEMS model development.
Most importantly, MEMS+ models are entirely parametric. These advanced parametric design features, coupled with extremely fast simulation times, provide the ability to quickly and accurately explore a broad design space. This capability is not available using conventional finite element modeling techniques, due to excessive simulation time requirements.
