EBeam Computations

EBeam Computations:
Expose Time Approximation

Given some exposure conditions and information about the pattern and layout,
provides an ESTIMATED write time. See notes below for more details.

Inputs

EOS Mode:
Beam Current:		pA
Shot Pitch:		pixels
Dose:		μC/cm²
Area Per Die:		μm²
Fields Per Die:
# Die in Job:
Field Shift/Multi/Overlap:
Global Alignment Time:		secs/wafer
Die Alignment Time:		secs/die
Include Load/Unload/Calibrate Time?:		(est 20 min/wafer)

Limitations:

This simple estimator calculates only some components of the total machine time needed for a complete exposure. The factors considered are:

Beam-On Time -- The time the beam is unblanked and writing. This is an estimate, as only a single dose value can be entered. If there are multiple doses in your pattern, this will affect the accuracy of the estimate.
Stage Move Time -- Estimate based only on the number of fields and chips on your wafer, and an average time per stage move. Longer or shorter stage moves will affect the accuracy.
Alignment Time -- Enter the amount of time, in seconds, for wafer/global alignment, and for each chip on the wafer. These can vary depending on the substrate type and size, prealignment accuracy, etc. Leave 0 for no alignment. For a well pre-aligned wafer with good cross marks, estimate 120 seconds for wafer alignment, and 5 seconds for die alignment.
Load / Unload / Calibrate Overhead -- If checked, adds 20 minutes to the estimate for wafer loading, pumpdown, system calibration, and unload.

Other Factors Not Included in this Simple Estimator:

Column settling time, if changing EOS conditions. Changing current, same lens, add 10 minutes. Changing final lens (4th to 5th, or 5th to 4th), add 40 minutes.
Periodic system drift checks during your write (see: PATH)
Shape handling overheads. If your pattern contains many tiny shapes, this can become a significant!! In extreme cases, this can multiply your pattern write time by a factor of 2 or even 3 times! So for patterns of many tiny shapes, such as small arrays of dots, this time estimator can underestimate the actual time really badly!!

E-Beam Computations, Time Estimate, v1.5

Disclaimer: Although I've checked these computations carefully, I can't guarantee the results are always correct. Please double-check any results, and tell Rick about any problems. Thanks!