Computer-Aided Design

Computer-Aided Design (CAD) utilizes a computer to assist in the creation, modification, analysis, and optimization of a design. Specifically for e-beam lithography, CAD is used to define areas which will be exposed by the electron beam. Ideally, we want pattern data drawn in the CAD to be replicated by the machine. In reality, the machines have design and physical limitations which influences the fidelity of the printed pattern. Fortunately, there are some CAD softwares that are sophisticated enough to automatically compensate for machine errors and process effects by adjusting the pattern. However, these CAD programs are generally too expensive to be used in academia.

A free CAD software that can be used to create patterns for e-beam lithography is KLayout. KLayout supports only the creation and modification of patterns. Furthermore, it cannot export the patterns in a machine compatible format. Patterns drawn in KLayout, or any CAD program, must be saved in GDSII format. GDSII is a standard format that is supported by all machines designed for micro-fabrication and nano-fabrication. The machine should have a program to convert the GDSII data to a machine compatible format. Usually, the user will need to learn and implement design rules to ensure that the conversion from GDSII to machine format is successful.