Specific Process Knowledge/Lithography/EBeamLithography/JEOLJobPreparation: Difference between revisions

===SDF header section===

The SDF starts with specifying the name of the job. The name must be uppercase alphanumeric and limited to 9 characters. First character must be a letter. The name will appear in the exposure job list upon execution, but it is hardly important what it is. We recommend using your initials. In the example above the job will be named “MYWAFER”.

===SDF sequence section===

Specification of the cassette number to expose, i.e. from which slot of the autoloader the cassette is loaded from. This must naturally be the cassette your substrate is loaded into. In the above example the exposure will be carried out on the cassette from autoloader slot number 8.

Some cassettes have multiple substrate slots. This designates which slot of the cassette to expose. 6” and 8" cassettes only have a single slot but one must still designate that slot. In the example slot 4A will be exposed. This is slot A of a 4” wafer cassette.  

This specifies the name of the JDF for the exposure and the layer number of the JDF to use. The JDF can be set up to have multiple layers typically used to specify different beam currents to various designs. Please note this “layer” has nothing to do with layers of the pattern file. We advise users to name their JDF with user initials followed by exposure date. In the example the JDF called is “thope220101.jdf” using layer 1.

This designates the acceleration voltage to be used, unit is kV. While the system can in principle run at other acceleration voltages the stabilization time is prohibitively long and thus the system is only used at 100 kV. This must always be stated as ACC 100 as in the example.

The calibration parameter command designates which calibration file to use for the exposure. This sets the exposure current and aperture used. In the example exposure will be done at 2 nA using aperture 4. It is important to stress that one cannot simply choose another beam current by writing another number here. The command references a pre-defined calibration file on the system and only a selected set of calibration files exist. These can be found and listed in the CALIB window on the system.

This parameter determines if the system writes in 2 deflector mode or 1 deflector mode. In 2 deflector mode the primary deflector positions the beam within the main writing field with the subdeflector positions the beam with each 4 x 4 µm subfield. Writing speed is significantly higher in 2 deflector mode and the system should always be used in mode 2.

This determines the exposure dose in units of µC/cm2. The beam dwell time is automatically adjusted to achieve this area dose based on the latest beam current measurement. In the example a dose of 240 µC/cm2 is used. In many cases it can be necessary to perform a dose test to get the optimum result. A dose test can be set up in several ways, please consult with the dose testing section in Labadviser.

The SHOT A command determines the beam pitch, i.e. the distance between beam positions when filling in a pattern. The beam pitch grid is 0.25 nm and hence the number stated here signifies the beam pitch in units of 0.25 nm. In the example a beam pitch of 16 units will result in a beam pitch of 4 nm.

The OFFSET command can be used to shift the position of the entire content of the referenced JDF, unit is µm. In the example the pattern specified in the JDF is shifted 5000 µm left and 1000 µm up. For first print (unaligned) exposures one can use the offset command to move patterns as wanted. For exposure with alignment this is however not the case, for aligned exposures the offset command must be used to state the offset of the pattern from the substrate center as determined by the optical pre-aligner.

===SDF footer section===

The END command serves two purposes. First of all it tells the software that this is the end of the job. Secondly, the number after the END command determines which cassette to load from the autoloader to the stage after job execution. In the example a pattern is written on cassette 8 and since the END command also ends with 8, no cassette change is made. If it had terminated with '''END 1''', cassette 8 would be transferred out and cassette 1 would be transferred in after pattern writing. If the job terminates with an END command without a number, the current cassette will be unloaded and the stage left empty. This is not allowed since the stage will loose position tracking after extended time without a cassette on stage. Always either leave the current cassette on stage or transfer another cassette.