We use 2D design and layout software to make the final designs for fabrication in the Marvell NanoLab. Microfabrication typically consists of a number of steps applied to a flat silicon wafer, where each step affects the surface in some two-dimensional way. Thus most designs are 2D geometry (for 3D robots, we break the robots apart into several flat 2D parts, construct the flat 2D parts, and assemble them into 3D afterward). A second reason most microfabrication designs are 2D is that many designs are too complex (to some extent, our electrostatic inchworm motors with arrays of thousands of fingers, but even more importantly, integrated circuit traces with thousands to millions of features) to quickly edit in 3D, even if we wanted to (e.g., Fusion 360 cannot quite handle a full microrobot design even before adding motors).

Most of the NanoLab tools (and most other microfabrication applications elsewhere!) take as input a GDSII file. This is the particular type of 2D file we almost exclusively use. These files have a number of layers, and each layer contains some number of polygons. For example, a photolithography tool like mla150 might expose a pattern on a wafer everywhere there is a polygon on either of two particular wafers in a given GDSII file.

Here's a screenshot of a GDSII file being edited in KLayout. The file represents a 6“ silicon wafer on which are fabricated many different designs. Each color represents a different layer of the GDSII file (sometimes, multiple GDSII layers are used in a single fabrication step).

Occasionally pages on this wiki may link to GDSII files. GDSII files can be large (megabytes to gigabytes), so we usually store them on Box or Google Drive. GDSII files can be large (megabytes to gigabytes) due to the sheer complexity of the designs they represent.

We typically use the software KLayout for creating and editing GDSII files for microrobot applications. KLayout is free, open source, fast, and has a number of handy features (e.g., design rule checkers (DRC) that can ensure certain manufacturability constraints are met). Drawing abilities are fairly basic (e.g., create rectangles, paths, polygons, and boolean operations) compared to drafting and 3D engineering programs (e.g., Fusion 360) but are sufficient for many tasks.

The KLayout website has good documentation on how to use the program here.

We have a number of DRC programs for KLayout included with our other custom 2D layout scripts at https://github.com/PisterLab/microrobot_library.

Tanner L-Edit is a widely used commercial layout editor with capabilities similar to KLayout.

We have also created software to programmatically generate GDSII files with full electrostatic inchworm motors, etc., given only a few basic parameters. This can drastically reduce design time.

This software and its documentation are currently stored at https://github.com/PisterLab/microrobot_library.

Cadence is a much more complex (than KLayout) piece of software in which one can define an electrical circuit, simulate its response, and semi-automatically create a 2D layout (e.g., in GDSII) implementing the circuit given 2D geometry for transistors, etc. Cadence is the industry standard for integrated circuit layout and is a commercial piece of software (with single licenses priced in the many thousands of dollars). We have a license via Berkeley used for designing SCμM, etc.