About Photomasks at SNF
The high quality and competitive pricing of many local commercial services gives labmembers several options for making photolithography masks. To make a mask:
First, decide which aligner to use and the resolution required.
Soda-Lime Glass/Chrome masks. These are a good, economical solution for contact aligners, in applications where resolution at 4 microns and above are desired.
Quartz (Fused Silica)/Chrome masks. The higher transparency, more stable substrate makes these best for applications where high quality imaging is required. The costs can vary widely, depending on the quality desired. Quartz masks are also recommended for contact aligners where high resolution is needed. For the ASML stepper, only quartz masks from approved suppliers (Compugraphics, Benchmark) are allowed.
Transparency masks. Transparencies from a high-resolution printer can be used as a contact mask in place of a standard photolithography mask. Transparency films don't wear well and have limited resolution, but they are cost-effective for patterning larger structures. A caveat: office laser printers don't print densely enough to sufficiently block UV illumination; only film plotters with print density of at least 3800 dpi will work. Go <here> for a list of film plotter providers.
Second, layout your design.
Some good references are listed below.
Contact Mask Design Principles, by Alissa Fitzgerald, AFM Associates, (Process considerations for layouts -- applicable to steppers as well)
Photomask Basics, by Bill Martin (or "all that mask terminology explained" -essential for filling out any Mask Order Form)
The E341 Guide to Tanner LEdit, by Sung-Jin Park (cool tricks with LEdit)
"Tips and Tricks for using LEdit", contributed by several labmembers.
The file format commonly accepted by most mask suppliers is GDSII. Layouts can be done in AutoCAD or other programs, but be aware that there are some technical bugs and extra costs associated with DXF formats. The CAD room (Allen 151) houses two dedicated desktop CAD systems with Tanner LEdit. The left-side PC also has utilities which allow file conversion between DXF (for die-hard AutoCAD users), GDSII, and PostScript (for printer later or for creating Transparency Masks). These are available for anyone to use; instructions and guidelines for their use are posted above each system. SNF also has several Tanner LEdit portable license keys, which Stanford researchers can check out. Contact Staff for more info. Other layout editors, some of them shareware, can also be used.
When using LEdit, make sure to review the "Tips and Tricks for using LEdit" section. This page lists the optimal program settings and ways to get the most from your layout with minimal cost and confusion. If you have comments and suggestions to add to this or any other page, contact staff.
Third, order your mask.
Some Commercial service providers recommended by SNF labmembers are listed here.
Special Academic Pricing is available to SNF academic labmembers (SUNet ID required.) Non-Stanford academics are also eligible for academic pricing and may contact Staff for information.