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

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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

*Execute pattern writing

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'''.

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

Correct execution will look like above. '''INITAE''' uses the beam to scan a PN-junction which the system uses to determine beam position and shape. '''INITBE''' uses the beam to scan a gold marker on the stage which the system uses for position and distortion correction of the beam placement within the writing field. The top row shows the signal, the following rows shows the 1st and 2nd derivative, respectively.

The system can auto calibrate itself using the AE and BE stage marks. The system will automatically measure beam position at various locations of the writing field to determine position errors. A correction matrix will be applied and the beam position will be remeasured to validate the result. The sequence takes about 8 minutes to execute. This should be done every time beam current is changed, i.e. a new condition file is restored. The procedure is

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The next step is to measure stage drift. This is done from the '''Calibration''' window.

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.

The height of the sample surface must be known to focus the electron beam properly at the surface. This can be done using 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.

For the calibration data to have effect during exposure the data must be saved into the calibration profile. This is done via the '''SAVE''' subprogram from the '''Calibration''' window.

All of the calibration data is now saved and the system is ready for exposure.

The job and the system is now ready to execute the exposure.