Autostep 200 Mask Making Guidance

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WIP

[null Mask Layout / Alignment Marks]

1)   Alignment marks in exposure field, Global, Local (DFAS).  To learn more about how these alignment marks work with the system, see the reticle handbook.  In our system we mainly use manual global alignment to get +/- 0.25 or better alignment tolerance. Local alignment can be used but needs some characterization for each process.

  • Global alignment marks:  These marks and how to place them on the mask are described on page 5-44 to 5-47 of the reticle handbook and are included as an attachment to this document (attach document). The difference of our system from the manual is that the objectives are 63.5 mm apart, not 76.2 mm as indicated in the manual.  The distance of this mark (or marks) to the center of the cell in X and Y should be noted, this is the key offset and will be required when exposing a job.  (Positive offset values are left for X and up for Y)
  • Local alignment marks:  These marks and how to place them on the mask are described on page 5-33 to 5-34 of the reticle handbook and are included as an attachment to this document.  If possible use one of each type if you desire to try to use local alignment. These can be light or dark field in nature.  The distance of the center point of this mark (or marks) to the center of the cell in X and Y should be noted, this is the key offset and will be required when exposing a job.

2)   Vernier Scales: These can be included to quantify the alignment offset after an exposure is done.  The reticle handbook has an example of vernier scales on pages 5-49 to 5-53.  You should include them for any layers that require critical alignment.

 3)   Resolution:  If you have room in the mask layout, it is good to have features that can give the resolution of a given exposure.  The resolution should show both “pillars” and “trenches” in the resist so that you can see whether the focus or exposure needs some tweaking for your particular process.