Specific Process Knowledge/Lithography/EBeamLithography/JEOL 9500 User Guide: Difference between revisions

*No users, not even authorised users, are allowed to load a cassette into the automatic cassette transfer system.

*The maximum frequency of the deflector scanner is 200 MHz, i.e. the minimum beam dwell time is 5 ns.

 

 

==Sample mounting==

Operation screen of the automatic cassette transfer system / auto stocker.

*Toggle the system to '''Local''' operation mode

*Use the '''shelf selector''' to choose that number

*Once the robot is done, click '''Open''' to unlock the door

*Click '''Close''' to lock the door

*Set the system back to '''Remote''' operation

Samples can be loaded into appropriate cassettes on the cassette preparation table.

Nanolab staff member loading the 4" wafer cassette to the automatic cassette transfer system.

*Always wear face-mask and a new pair of gloves

*Never put cassettes directly on the table, use lint-free cleanroom tissues

*Never touch the reference planes, i.e. the six polished areas on the front side of the cassette

*Never lift the cassette in the hook

*Always check the wafer for loose parts or flakes before loading. In case of loose parts or flakes, stop mounting, discard or rework the sample and rethink your process.

*Always check the cassette for loose parts, dust and particles.

*When exposing chips, make sure the chip size is at least 2 mm larger than the slot opening. Be careful when mounting the cover plate, it will get stuck easily if mounted at a slight tilt. '''Never push the cover into place,''' it must fall in by itself.

*When mounting a wafer, hold the spring (wafer securing pin) back when putting the wafer and the cover into the cassette, especially on the 2" cassette (the spring can lift the wafer). Tighten the leaf spring first, then release the spring and tighten the rotation lock lever.

*Inspect the front side of the cassette carefully after mounting the chip/wafer; a small gap between substrate and cassette will lead to a failure in HEIMAP and no exposure is thus possible.

==Cassette transfer==

==System calibration==

After cassette transfer the system has to be calibrated with the chosen beam current condition profile. This is done in a mostly automated sequence with only minute input from the user. The sequence is explained in detail in the following but in overview it is

===Select and restore the system to the chosen beam current profile===

The SDF specifies which system condition file to use for the exposure, this determines the beam current. Condition files are named according to beam current and beam aperture, for instance '''6nA_ap5''' which will expose at 6 nA using aperture 5. Restoring a condition file for use is done from the '''Calibration''' window, if it is not open it can be opened from the '''EBX Menu'''.

*Browse and select the condition file to use and click '''OK'''  

'''Calibration''' and '''RESTOR''' windows.

===System self calibration===

With the correct condition file restored the next step is to measure beam current and verify that it is close to the expected value.  

The stage moves to the faraday cup to measure beam current. This takes 15 seconds and the '''Calibration''' window will display the measured beam current. Note this down for the Labmanager usage log. If the value is more than 5% off the expected beam current call the e-beam responsible for assistance.

Result display of current measurement.

Correct result of '''INITAE''' (left) and '''INITBE''' (right).

=== Auto calibration ===

Load the '''daily''' batch command and execute it.

During calibration the system will measure and display the beam position at 49 locations of the writing field. The position error (in nm) can be read of the matrices during execution, an example is shown below. At the end of the process the '''Calibration''' window will display '''Finished BATCH CALIB'''.

===Measure stage drift===

Comparison of two drift measurements.

In this example the two drift measurements are made a bit more than 1 minute apart (look at timestamps). The x-axis drift has changed from 65.4 nm to 64.2 nm, i.e. a change of 1.2 nm in about 1 minute. The y-axis drift has changed from 85.3 nm to 86.8 nm, a shift of 1.5 nm in about 1 minute. Thus the drift is about 1-1.5 nm/min in this particular example. This is a typical value. If you experience drift of 5-10 nm/min, give the system 10 min to thermally equilibrate and try again. If drift is above 10 nm/min please call the e-beam personnel for assistance.

===Measure height profile of sample===

Parameter window of the '''HEIMAP''' subprogram.

The example above will create a 3x3 matrix of height data with a pitch of 1 mm in x and y. After execution the system will display a matrix with height measurement data in µm. Verify that there are no outliers and that variation is less than 100 µm from top to bottom.

===Save condition file===

Acquire the calibration data and then apply the data to save.

===Job execution===

'''Expose''' window with .mgn file loaded for exposure. Notice that the '''Progress''' part of the window still shows the previous exposure information. This field will not update until exposure is started.

The system will now carry out initial and cyclic calibration as defined by the path in the JDF file and then exposure will start. The pattern writing can be observed in the SSP window (top left) once it starts. Progress can be monitored in the '''Expose''' window which will give a completion percentage and completion time for the current sequence. Once exposure is completed the system will confirm this with the '''Pattern writing completed''' window.