Stepper Mask-Making Guidelines (Generic)

Generic Stepper Mask Parameters

Tutorial: If you are not familiar with the difference between designing Contact Litho Masks and Stepper Litho Masks/Reticles, please review this short tutorial:

• Demis D. John - Stepper Reticle Layout vs. Wafer Layout.pdf
  

  Reticle Patterns (“images”) are independent of wafer-layout.  The reticle could contain 20 variations while the wafer could have only a few of the Images actually exposed, in any desired location on the wafer, determined buy the Job Programming.

For the stepper you are designing for, make sure you know:

1. The maximum exposure field size, and
2. The minimum gap between adjacent patterns/images that must be dark chrome (for the system's reticle shutters to block adjacent images)
3. Either the quoted product number from our photomask vendor quotes, or reticle size/thickness/material (eg. 5" x 5" x 0.090", Soda-Lime glass)

These values will vary depending on the stepper you're designing for. Contact the Stepper's Process Expert or Tool Supervisor to find out these values.

Generic Stepper design/programming CAD files & spreadsheets

• Example Toppan Order Form via Digidat
  • Academic users may request the UCSB Nanofab's quotes from various photomask vendors.
• Fill out this Spreadsheet before programming your job on the machine, using your CAD file:
  • UCSB_Stepper_-_Programming_Worksheet.pptx - New version of the spreadsheet below, that also includes the wafer-layout info needed to generate a basic stepper exposure program.
  • Stepper Reticle Programming Params - MASKJAN2020 v1.xlsx (example for fictional barcode "MASKJAN2020") - Spreadsheet form of the above PPT. Faster to fill out for "expert" stepper users.
• On-wafer alignment marks:
  • This pattern is usually available on a system reticle - you are not required to include the alignment mark pattern in your own designs.
  • Please check for the specific Stepper you are using.

Example CAD File and Programming

Using an Example CAD file, here is the corresponding Mask Order Form & Spreadsheet:

• Example CAD file from Utilities > CAD Layout > Example CAD File, designed in KLayout.
• Example "Stepper Reticle Programming Params" spreadsheet for reticle "DEM-2020-03"
• Example Reticle Order Form for reticle "DEM-2020-03"

CAD Tips

• By default, Wafer flat is Down (–Y) with respect to your CAD file.
• Utilize the "Cell" and "Cell Instancing" functionality in your CAD layout program! (aka. a "Block" in AutoCAD). Highly recommended to use KLayout, not AutoCAD. See Calculators + Utilities > CAD Design Tips for tutorials.
• Center your entire design around the coordinates (0,0). (0,0) should always be the center of your device, wafer and/or photomask/reticle. Photomask vendors should then NOT "auto center" your designs on the plate.
• Inside each sub-Cell, also design around the cell's (0,0) origin.
• Create a Cell called "reticle_layout" or similar, that is an exact representation of what the printed reticle patterns should look like (typically at 1x wafer-scale, if not including the outer templates for the stepper system). Instance the Device's Cells into reticle_layout, and reference this Cell on your mask order form. (You can also Instance the same cells into "device_layout" and "wafer_layout" cells during design/verification.)

If you follow the above rules, your printed "reticle_layout" Cell will have Instances of each of your design's Images/patterns, and the coordinates/sizes of these Cells are exactly what you use to write your Stepper program.

See the example CAD Files here:

• Calculators + Utilities > Example CAD File