SF-100 maskless lithography system

Standard Operating Procedure (beta version)

Author

Rev. 01: Chang Ge, 2017

Exposure procedure:

  1. If the “Auto Stage” program is not already running:
    1. Double-click its icon on desktop.
    2. Input the user name and password.
    3. A dialog box will pop up to select the correct profile (select “4x Profile.txt” for 4x objective and select “20x Profile.txt” for 20x objective).

Note: you must not make any edits in the “4x Profile.txt” and “20x Profile.txt” files.

  1. If the “Auto Stage” program is already running:
    1. Click on “Load Setting” button from the top right side of the “Auto Stage” program.
    2. A dialog box will pop up to select the correct profile. Brows to “C:\Program Files\Auto Stage”. (select “4x Profile.txt” for 4x objective and select “20x Profile.txt” for 20x objective)

Note: you must not make any edits in the “4x Profile.txt” and “20x Profile.txt” files.

  1. From “Motion Controls” section, click “Home” button, then a dialog box will pop up. Select “X”,”Y”, and “T” and click “OK”. Make sure not to click “Z” so the stage does not crush the objective.
  2. To make chip alignment more convenient, rotate the stage 45ᵒ counter clockwise in steps of 5ᵒ.
  3. From “Image Controls” section, click “Load Image” button and select the DXF file that to be used.
  4. Click the “Image” tab and then double-click on any row in the “Layers” section, select “Default” and then click “OK”.
  5. From “Light/filter” tab, click on “OFF” button that has “Lamp Power” label to turn the UV light on. It is recommended to let the turn the lamp on for 30 minutes before exposing the chip.
  6. From “Image Controls” section, slide the “Horizontal Mirror” to the “Mirror” side to mirror the mask horizontally so it will be exposed correctly.
  7. From “Image Controls” section, click “Draw” button to show the part of your layout highlighted with red rectangle.
  8. From “Motion Controls” section, click “Load” button. This will move the stage near the machine door so you could load the chip.
  9. Load the chip and click “OK” to indicate that you loaded the chip. This will take the stage back to its original location.
  10. From “Motion Controls” section, click “ON” under “Chuck Vac” label. This will turn the vacuum on to fix the chip on the stage.
  11. Using the “Motion Controls”, move the stage until you see the projected light is on the chip surface.
  12. Move the stage in Z-direction in small steps until you can see the projected image and the chip in the camera window.

Note: you need to watch the stage while it is moving to make sure that the stage will not crush the objective.

If the chip looks very bright or very dark, go to “Camera” tab, and change one or both of “Gain” and “Shutter Speed” in the “camera preview settings”

  1. From “Motion Controls” section, click “Focus” button.
  2. If you have features on the chip and you would like to align them with the mask to be exposed then follow the instructions in the “Alignment section”.
  3. If you don’t have features to align with the mask, then move the stage where the top right side of your mask (before mirroring) will be exposed.
  4. From “Exposure” tab, click on “Auto Exposure Setup” to move back the red box to the top left corner of the mirrored mask. If you move the stage after this step for any reason, you need to redo steps 17-18.
  5. From “Exposure” tab, insert the desired exposure time in “Exposure Time” text box
  6. From “Exposure” tab, click “Start/Stop Auto Exposure”.
  7. A dialog box will pop up, make sure that “Perform surface modeling” check box is checked so variations in the height of the substrate will be taken into account. Then click “Continue”. Once you do that, make sure not to touch the system and not to use the computer to avoid any vibration or occupying the computer resources during the exposure process.
  8. Once the exposure is finished, from “Motion Controls” section, click “Load” button. This will move the stage near the machine door so you could unload the chip.
  9. Unload the chip and click “OK”. This will take the stage back to its original location.
  10. From “Motion Controls” section, click “OFF” under “Chuck Vac” label. This will turn the vacuum off.
  11. From “Light/filter” tab, click on “ON” button that has “Lamp Power” label to turn the UV light off. If you need to turn the lamp on again, you need to wait at least for 10-15

 

Level-to-Level Manual Alignment:

  1. Do the steps 1-16 from “Exposure procedure” above.
  2. Get the center coordinates of the alignment marks you like to use.
  3. Go to “Level-to-Level” tab, and insert these coordinates in the “X mask” and “Y mask” columns in the rows “Mark 1”, “Mark 2”,….
  4. Make sure that the button in the “Enable” column showing “Enabled” for the rows you have filled.
  5. Click on any cell in the “Mark 1” to highlight it, then click on “Display Mark”. This will make the part of your mask that contains this this alignment mark projected.
  6. Move the XYZ-stage until you can see both the projected alignment mark and the feature to be aligned with on the chip. You may need to refocus to make both visible, refer to steps 14-15 in “Exposure procedure above”.
  7. Move the stage until you align the chip with the projected alignment mark. You don’t have to have a perfect alignment from first round, so you can redo this procedure few times to get the desired alignment accuracy.
  8. From “Level-to-Level” tab, click “Mark is Aligned” and “Register”
  9. Click on any cell in the “Mark 2” to highlight it, then click on “Display Mark” and then click “Go to Mark”. This will move the stage to the location where the next feature to be aligned with second alignment mark. Also, it will project the Mark 2 region of your mask.
  10. Redo steps 6-8.
  11. Redo step 9 for “Mark 3” and “Mark 4” if you have them.
  12. From “Level-to-Level” tab, click “Get Corrections”
  13. We recommend clicking “Correct Theta” only to correct the rotational error. Other corrections may be made if you think there is a scale and/or shear errors.
  14. Redo steps 9-13 but not for all alignment marks you have (including “Mark 1”).
  15. Once you are satisfied with alignment accuracy, go to “Exposure” tab, click on “Auto Exposure Setup” to move back the red box to the top left corner of the mirrored mask.
  16. From “Level-to-Level” tab, click on any cell in the “Initial” row to highlight it, and then press “Insert” button on the keyboard.
  17. From “Level-to-Level” tab click on “Display Mark” and then click “Go to Mark”.
  18. Then do steps 19-25 “Exposure procedure” above.