Low Resolution Mask Making Procedure

NOTE: An older version of this document (25 micron features) using L-Edit to generate cif, psmask to convert to postscript, and printing locally, is available here.

The following are instructions for preparing low resolution (7 micron minimum feature)

UPDATE MAY 2011: Direct write to 4" soda-lime chrome mask now available for features down to 3-5 microns ($225 ea), or in a "best effort" mode 2-3 microns ($337). Typical corner radius 2 microns. No more than 3 defects >5 microns per square inch.

UPDATE (Oct 2010): Photoplot store is back, with production by www.fineline-imaging.com. You can use fineline directly or go through photoplot (Richard Sayer is at photoplot is helpful with questions and tips).

photoplot FAQs and minimum feature sizes (this link is useful but may eventually break; photoplot store is no longer in business).

Prepare file in LEDIT

Check for updated information at the FineLine-Imaging and/or Photoplot Store site.
Be sure to include alignment marks if you have more than one mask level.
No circles ("flashes"); polygon "circles" in GDS are ok.
Best to limit polygon size (a hundred verticies seems ok).
A template is available:
Tell your browser to save one of the linked files below (right-click or ctrl-click on them):
- MASKtemplate.tdb (for use with L-Edit V13) or
- 8MASKtemplate.tdb(for use with L-Edit V8) or
- MASKtemplate.cif (may also be used in MAGIC)
- MASKtemplateflat.dxf (for import into other CAD)
- 8MASKtemplate.pdf (for visual reference - not full resolution)
The mask plate is 4" square, the exposure is 3" diameter, but best not to use the outer 1/4" of a wafer if possible. There are two circles on the template which do not print; one at 3" diameter, and one at 2.5".
To avoid confusion, best to use Only one cell--create single cell as follows:
- copy data (mycell) to a new cell (myflat) and flatten
- copy that to a new file (temp:myflat), and delete cell0 in that file.
- export to a GDSII stream file
- Complete Fineline Imaging order form, or see photoplot store online ordering.
  - Mylar mask (we can easily transfer mylar to chrome/glass, and you have realestate for up to four masks on mylar for about the same price. We have not tested their chrome option. They also now have a much more expensive chrome direct write option which could be used for higher quality (lower defects) masks.
  - Suggest 8.5X11 inch film output if you use the template. This is under the minimum order price.
  - Resolution options as of 2010: 8 micron min feature: 40,640 DPI 63.4¢ /Sq. In. $95.00 Minimum 6 micron min feature: 50,800 DPI $ .965 /Sq. In. $125.00 Minimum 5 micron min feature: 65,024 DPI $ 1.25 /Sq. In.$150.00 Minimum
  - Ask them to convert from GDSII (cost: $15)
  - BRIGHT field: If you want the features you drew to be dark and the area around them "field" to be transparent, specify this option. Used, for example, with positive photoresist when features are to be etched in a film.
  - DARK field: If you want the film to be mostly black with the features you drew as clear windows in this. Frequently used with negative photoresist such as SU-8, or with positive resist and "lift-off".
  - RRED: Right read down. Important only if you care about whether your design shows up as drawn or as a mirror image of that drawn. Transfering the film onto the chrome mask, the emulsion (ink) side will be down facing the chrome, so RRED will result in a chrome mask which is as designed (readable if it has text). However when you transfer the mask pattern to a sample, the mask chrome will be placed down and the result on your sample will be a mirror image of what you designed.
  - RREU: The opposite of RRED: results in a mask which is mirror image and a sample created from that mask which is readable.
  - Follow up with a phone call to the company.
Processing the film into a chrome mask is detailed in this document

Christopher.G.Levey@ dartmouth.edu