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[Giorgio Aguilar]

TheJEOL JBX-9500FS electron beam lithography system is a spot electron beam lithography system designed for use in writing patterns (10 nm - 1 m) in electron sensitive resists. The JEOL JBX-9500FS was purchased in 2012 and is installed in E-1 and E-2 at DTU Nanolab. The main console of the e-beam writer is installed in E-2 which is a class 10 (ISO 4) cleanroom with tight temperature and moisture control. The computer controlling the e-beam (EWS/9500) and the computer supporting the conversion of e-beam files are located in E-1 which is a class 100 (ISO 5) cleanroom.

If a cassette has been used recently it might be found on the cassette preparation table already, otherwise it will have to be retrieved from the cassette transfer system. This is done from the operation screen of the cassette transfer system.

Once the cassette is placed up-side down on the preparation table the slot cover can be removed by pressing down and rotating the spring loaded locking mechanism. The substrate can be placed in the slot using the vacuum tweezer found on the table. As the cassette is up-side down, the substrate must be loaded with resist side down.

The system is fitted with an auto stocker system that can store 10 cassettes. It is thus possible to prepare multiple substrates and define an automated job to execute exposure of several substrates across several cassettes. After sample loading the cassette must be placed in the automatic cassette transfer system. Users are NOT allowed to do this. Only Nanolab staff who are members of the E-beam Loading Team may place cassettes into the automatic cassette transfer system. Hence users must always contact the Nanolab E-beam loading team prior to exposure to have their cassette loaded into the cassette transfer system. The E-beam loading team can be contacted at [email]. Upon loading a cassette Nanolab staff will visually verify the sample has been installed and secured correctly. Incorrect sample mounting can lead to severe damage to the internal parts of the JEOL 9500 exposure system.

The Loader window shows available cassettes in the automatic transfer system and which cassette is currently inside the writing system. In this example cassette 10 is inside the writing system. Cassettes can be moved between the writing system and the transfer system with the Carry in and Carry out buttons. Carry in will move the selected cassette to the writing system while Carry out will move the selected cassette to the selected shelf in the transfer system. In order to move a particular cassette into the writing system the current cassette must naturally be moved out first.

The EXCH EVAC switch must always be left unchecked as in this example. If it is toggled on the exchange chamber (load lock) will be pumped down after a carry out operation and the next carry in operation must then wait for the pump down (15 min) before it can be executed. Always leave EXCH EVAC off.

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

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.

The bottom line of the Calibration window will now display Received an intermediate result RESTOR(DEMAG) to indicate it is working. Setting up for the new condition file takes about 1 minute and the bottom line will say Finished subprogram RESTOR when done.

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.

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

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.

The system will scan the drift mark (BE mark) to determine drift since last drift reset. The absolute value is not important since it is unknown when the drift subprogram was last reset. The time variation of the drift measurements is however important thus one should compare two drift measurements taken 1-2 minutes apart. Luckily the dayli batch command ended with a drift measurement, having made one manually we can now compare the result, see the example below.

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 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 m. Verify that there are no outliers and that variation is less than 100 m from top to bottom.

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.

Below is a brief explanation of some of the most important subprograms found in the Calibration window. The subprograms listed in the blue part of the table are a part of the 'daily' batch of programs.

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