MLA150 - Troubleshooting

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Revision as of 09:38, 7 June 2021 by John d (talk | contribs) (Out of Focus exposures - problem + solutions)
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Look below for the issue you're experiencing, to see if we have a workaround or solution.

Make sure you record your problem and solution in the log book! This is very important for allowing us to improve system stability and make repairs.

Known Bugs & Workarounds

Stage not centered during Substrate Load

When the system moves the stage to place your sample under the lens, the center of the stage is not under the lens!

WARNING: Do NOT continue if this occurs - there is significant danger of crashing the lens into a sample.

  • Cancel the substrate load process.


In the software Menu, choose Tools > Initialize Stage, then retry your Job.

If that does not solve the problem, please reboot the computer (instructions below), which will also reinitialize all motor controllers.

Exposure Logs / Reports

You can find a detailed log file of each exposure in the folder C:\HIMT\LogFiles\ExposureLogs. At the end of this file you can find final statistics from Field (Local) Alignment. You can copy the appropriate log file into your Nanofiles user folder to make it accessible via FTP.

If you run into an unusual error, please let us know the Job Name, so that we can locate this log file if needed.

Defocus: unable to enter ±25 full range

In the Setup screen, Editors for Resist or Series templates, you are limited to only ±10 defocus, even though the system is capable of ±25.


  1. During Job Setup, Make sure you choose one of the staff-made Resist templates, which enable the extended defocus software option.
  2. In the Exposure screen - after wafer load etc. - you may still edit the defocus range, and in this screen you are able to type in the full range ±25. For a Series exposure (focus-exposure matrix, FEM), you can choose the "_Manual" template during Setup, and on the Expose screen you can edit the Series array to your needs with full defocus range.

Unexpected Behavior

If the software is acting unusual (eg. black screen), or stage is moving to an incorrect location, or Convert software unable to launch, it could be due to the computer running out of RAM memory. A computer restart typically resolves this. Run the restart procedure further down this page to resolve.

Convert software is unable to launch

  1. Check whether the XWindows software is available in the Windows Start bar - sometimes the window lands behind the MLAMenu software.
  2. If an error window is indicating some error with launching convert, then perform the computer reboot procedure below.

Out Of Focus Exposures

After developing, you find that some of all of your pattern is extremely out of focus. Small features (less than ~20µm) don't show up at all, and large features are extremely rounded, often with rainbows at the PR edges indicating extremely slanted photoresist.


There are multiple possible causes for this issue:, all of which have to do with the Optical Autofocus' confocal surface detection:

  1. The Optical AutoFocus laser is starting the write on an extremely non-uniform part of the photoresist spin (eg. corner of quarter-wafer), which causes it to drive out of focus before the write starts.
  2. Very dark (low reflection) areas of the wafer can also cause the OptAF surface detection to lose signal, and lose the feedback signal needed to maintain focus during a write.

Solutions for small substrates

For Samples that are less than ~1 or 2 inches:

  • Make sure the ORIGIN (0,0) coordinate of your CAD file is placed in a relatively uniform area of your sample. Do not place the Origin at the corner or on PR edge-bead, as the Optical AF laser will do an initial measurement at this location.
  • Remove thick photoresist edge-bead prior to exposure (eg. with razor blade, or a little EBR100 on a cotton swab).

Solution for 3-4 inch wafers

  • For large substrates, switching to Pneumatic Autofocus works well. PneuAF causes a few-mm of edge-bead area to expose out-of-focus, which is acceptable for full-wafers, but often too large exclusion for smaller samples.
  • Contact the supervisor for info on switching to Pneumatic AF. Do NOT use PneuAF without first asking Staff! There is significant crash potential if performed incorrectly.
  • PneuAF will usually have a slightly different defocus offset compared to OptAF. You should run a new FEM/Series with PneAF.

Focus Depth Motor Not Initialized

After an exposure has been initiated, but before exposure has actually begun, you get an error window stating the the "Focal Depth Motor is not initialized."

Notify staff

We can reinitialize that motor remotely, which will allow you to start your exposure.

Nanofiles folder not showing up on SFTP

Problem: When you log into the Nanofiles FTP server, you don't see an "MLA_Heidelberg" folder to upload your CAD files.

Reason: After your user's folder is created in the Users_Nanofiles folder on the MLA computer, our FTP server only creates the corresponding folder on the Nanofiles FTP site once per day around 00:00 midnight.

Wait until the next morning and your folder should be available. If you need immediate access, please email the tool supervisors, and one of us can upload your file into our Staff folder on the tool.

You can find more troubleshooting info about the Nanofiles FTP at the corresponding Frequently Asked Questions section.

Rebooting the Computer

Restarting the computer can resolve errors due to the system running out of memory (RAM), and also force the reinitialization & homing of motors.

Restart Procedure

  • In the MLAMenu (main) software, go to File > Exit.
    • It takes a minute or so to close everything. It will also close the camera viewer (SharkVision).
  • Reboot the computer via Windows Start > Power > Restart
    • It takes a few mins for the computer to reboot.
  • On the Windows login screen (Looks like "Heidelberg instruments" background), start typing to log in. Login info is written at the computer.
  • After logging back in, wait ~1 min until the 2 icons appear next to the Time in the start bar. (SiiPlus and XMing)
  • Then launch MLAMenu.exe, wait ~1 min until it has completed initializing.
  • Make sure the "Hardware" section of the software shows all components as "OK" or "Initialized"

System is ready to run exposure jobs.