Creating a fully coupled multiphysics model is one of the holy grails of MEMS modeling. If you can automate the creation of a MEMS model, it opens the door to design and process exploration via Monte Carlo analysis, Design of Experiments (DOEs), Design Optimization, and even Genetic Algorithms.
In a recent blog post, we described how to create a 3D solid model for FEA (Finite Element Analysis) using just a layout file and a process description. CoventorMP® 2.1, which has just been released opens the door to even more automation during model creation.
When creating a MEMS model, the story always starts with a layout file and a process description. Next, we need a tool that can provide fully coupled multiphysics models. CoventorMP is just such a tool. In this article, we will show how to leverage a new “automatically add components” feature in the MEMS+® portion of CoventorMP, using its Component Library approach, to automate the construction of 3D and compact models.
Imagine you have a GDS file of your favorite MEMS device. For illustration, Figure 1 displays the layout of a reversed engineered STMicroelectronics gyroscope obtained from a TechInsights teardown. As you can see, different portions of the gyroscope have been displayed in different colors, using a feature in MEMS+ to regroup polygons by functionality. For example, all comb rotors, stators, suspensions, and other components are on different design layers based upon our modeling considerations (Figure 2).
To create a compact model for this gyroscope, we will use the Construct 3D Model feature in MEMS+. We need to link the different GDS layers to specific components in our design. In the following example, we will tell the software to take every rectangle found on a specific GDS layer (L5D61) and turn that into a Rectangle of type “Side Gap Rotor Right” (Figure 3). This allows us to simplify and efficiently build a complete design without having to mechanically replicate similar components throughout the design.
Why are we using a rectangle named “Side Gap Rotor Right”? The idea here is to represent some irregular combs with pairs of rectangular / side gap fundamental components. Because the gyroscope comb fingers vary in length in the design, we will create a component that allows us to modify the length of the comb fingers. In this case, we made a modeling choice where we assumed that fingertip fringing fields (with different size comb lengths) did not play a significant role in the function of the device.
We are now two clicks away from having a simulation-ready 3D model.
In CoventorMP 2.1, we introduced the ability to create a subcomponent each time its parent is instantiated. This option lets a user create a tree of components with a single action. Used in conjunction with the Construct 3D Model capabilities, it allows a designer to create a fully functional device from a layout file, including non-geometrical components that would not be part of the original layout file per se.
From the screenshot of the Component Library, we can see that each time we – or the Construct 3D Model software – create a Side Gap Rotor Right, a Side Gap child component will also be created (Figure 4). For this device, 144 Side Gap Rotor Right and 144 Side Gap components will be created automatically. This greatly accelerates the process of building our model. Figure 5 shows a comparison of the 3D model that we created, with and without the AutoAdd option.
The AutoAdd feature provides a time-saving and an error-free solution when you are creating devices that share systematic properties. This feature increases the usability of CoventorMP and allows users to be more confident in their designs, allowing them to quickly go from GDS Layout File to Simulation Ready MEMS Model.
To learn more about MEMS component libraries in CoventorMP, please visit our MEMS+ Component Library page