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====== Using Design CAD ======
[[http://imsidesign.com/Products/OtherProducts/DesignCADSeries/DesignCADv19/tabid/1138/Default.aspx|DesignCAD product website]]

===== Overview =====
Export your DesignCAD drawing in the .dxf format. All shapes in this file must be closed polygons. For example, a rectangle drawn with the rectangle tool is a closed polygon, however, 4 individual lines that touch at 4 corners do not form a closed polygon. If necessary, you can bind together a selection of lines with the key stroke shortcut "b", thereby creating a closed polygon.

===== Important features =====
  *The zero of the coordinate system can always be reset. Use the button in top left of window used to set the zero of coordinate system
  *DRAW:ARRAY
  *EDIT:SELECTION EDIT:ROTATE
  *EDIT:SELECTION EDIT:DUPLICATE (shortcut is N). 
  *EDIT:SELECTION EDIT:MOVE (shortcut is N). 
  *You can write text on a mask, you must use "save in vector" and "true type font"

===== Key stroke shortcuts =====
  *z = zoom
  *l = layer
  *g = grid (ctrl g = grid settings)
  *. = gravity, puts a handle on the nearest corner (now you can copy paste and use the x-y coordinate command for precision
  *: = allows you to type in an x-y coordinate rather using the mouse
  *b = bind together a selection of lines into polygons. 

===== General considerations =====

When creating a mask, here are some general considerations:
  *Our tube furnace inner diameter is about 22 mm. This means the overall chip dimension should be about 19~20 mm. When we cut the chips we need 1.5 mm padding of empty space around the electrode design. Therefore, working area for the electrodes is about 16 mm.
  *the contact aligner doesn’t perform consistently if features are less than 4 micron.
  *typical catalyst size is 4 micron
  *when you print multiple layers of a design, assume that alignment between layers could be 2~3 microns off.
  *nanotubes on SiO2 can grow 50~100 microns in unpredictable directions. Make sure that stray nanotubes won’t create unwanted short circuits.
  *contact pads should be > 150 x 150 micron.
  *Electrodes that will contact liquid should be kept to a minimal surface area to minimize Faradaic currents. 10 micron wide electrodes will work well.
  *Putting extra space between objects usually makes the photolithography more straight forward. After metal evaporation, lift-off of the photoresist is never perfect - metal features that are close together have a chance of getting short circuited. Another problem with close spacing can be "ghost exposure": photoresist which gets exposed by light bouncing around in the cracks.