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PATH definition

Initial and Cyclic Calibrations

The PATH specification in your Job Deck (JDF) file(s) specifies which calibrations are to be carried out within your job execution. You don't directly specify which calibration routines should be executed, instead you give the name of a pre-defined PATH. It is that PATH definition that defines which Calibration Subroutines will be executed. You can see a list of the available PATHs defined here.

For any Path definition, there are two distinct sections:

INITIAL calibrations

Calibration routines listed in the INITIAL segment of a PATH definition will be executed at the start of the PATH segment within your job. As described in the overview of calibration, there is some flexibility about how you calibrate the system before your exposure. It is possible to run some, many, or all of the calibration routines manually, outside of your job, before you being the execution of your compiled job. Running the calibrations manually gives you more control to review the calibration results, make decisions, handle errors, etc. When running calibrations inside a compiled job, the job runs uninterrupted from start-to-finish without any opportunity for operator interaction. If an error condition occurs, the entire job is aborted, and must be restarted from the very beginning. The choice of operating mode is, however, ultimately yours.

CYCLIC calibrations

The system can also periodically perform certain calibration subroutines at present intervals during your exposure. Practically, there are only two calibration routines that are commonly used in mid-exposure:

CURRNT - measures the actual beam current, and adjusts the exposure clock to keep the exposure dose at the specified value. This compensates for drift in the beam current, which is mostly caused by drift in the electron gun.
DRIFT - measures the position of the beam at a reference point, usually either the BE mark, or if writing an aligned-wafer Direct Write, at the P-Mark.

Note!

Normally, the calibrations specified in a PATH definition will NOT interrupt the writing within a chip (pattern file). If the specified interval timing is up during a pattern write, the system will wait until the end of that chip/pattern before doing the specified calibrations and corrections. This avoids adjustments to dose or position within a pattern, which is often, but not always, the best practice. You will notice in the list of defined paths, however, that some paths include the ",F" option appended to the CYCLE time definition. If the ",F" is there, these cyclic calibrations WILL interrupt within a pattern exposure, at the next Field boundary after the specified time has elapsed. This may the desired option if, for example, you are writing one very large pattern, such as often the case when writing a mask plate.