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Data Conversion

Table of content

  1. Vistec EBPG5000 overview
  2. What is an electron beam (ebeam) lithography system?
  3. Electrons, resists and substrates
  4. Process Flow for Ebeam Lithography
  5. Data conversion
  6. Running the ebeam

Data Conversion

The ebeam machine does not understand gdsii, DWF or any other design or CAD format directly. Your design needs to be translated into the format the machine uses. You will need to have your design in gdsii format, you will then transfer this to the data conversion computer, convert your pattern, and then transfer to the computer that controls the ebeam machine. The data conversion computer is call CAD026 and the software used for the conversion is called CATS. Some simple instructions for using CATS are given below. You should put your design in the ebeam drop box here: \\sti1files\cmi-transfert\ebeam_dropbox for easy transfer to the CAD026 machine.


During training you will get a working area on the cats machine which is where you need to move your gds files to be converted. This will also be where the converted files created by cats and writefile (another conversion program) will be stored. On the destop of the CAD026 machine right click and select open terminal.

enter the name of your user area. If you have sub-directories move into the place you want to work.

type cats to run the program. 4 screens will appear. The flying CATS graphics screen will be blank at the moment. commands in CATS are mostly issued in window 4 at the Command: prompt. Window 3 can be used to change options when viewing the layout.

NOTE: CATS is pre-configured to have the correct parameters for our machine, therefore DO NOT ADJUST ANY SETTINGS IN WINDOW 2

Basic CATS commands


Below is a table listing the basic CATS command set. This will cover almost everything you want to do (later there will be a more advanced set of instructions). The instructions are in the approximate order that you would normally use them, although this can change depending on your design and what you want to process. There are two tables split into process commands and infomation commands

Process Commands

input mygds.gds

Name of your gds pattern (=Open in windows)
structure mycell Name of the cell you want to fracture
layer 1-3,7 selects the layers you want to fracture
resolution 0.1 In microns. The minimum pixel size your pattern will be split into. For well defined features this should be ≈x10 smaller than your critical dimension.
limits and extent all

The graphics window will remain blank until CATS knows how much of your design you want to see. This is set by the limits or extent all command.

The extent all command sets the limits of the pattern to the maximum on all layers in the selected structure regardless of whether they are selected with the layer command or shown in the graphics window.

The limits command allows you to set the limits of your design manually. You can do this by specifing an area bounded by a box given by the coordinates from the bottom left had corner to the top right hand corner in the format x1,y1 x2,y2 eg limits -5000,-5000 5000,5000.

output Name of the CATS files to be created (.cflt and .cinc ) (=Save As in Windows)
do produces the .cflt and .cinc CATS files with the output name. NOTE: nothing you do in CATS is "saved" or more accurately processed until you issue the do command.
exit Leave CATS

Information Commands


Shows the top cells (unreferenced) in your design. This is often the cell you want to process
tree Shows all the cells referenced (or instanced) within your design. You can add a number to the tree command to produce a listing of the selected level in the heirachy. If you do not put a number then this will most often be a useless command as there are usually many cells within the design and there is no way to stop the structure list scrollling off the top of the screen
datalayers Tells you the layer numbers in your design


Once you have got the .cflt files you want you still haven't finished. There is one more step to convert the CATS cflt file to gpf format which is the format the ebeam machine needs to write your design. This conversion is easy though. Open a new terminal window and move to your working enviroment and directory. At the command line type

writefile mycfltfile.cflt

you will then get a dialogue box asking whether the file found is the correct one, answer y. Your cflt file is then converted into gpf with the same file name but with the extension .gpf