Specific Process Knowledge/Lithography/EBeamLithography/JEOLPatternPreparation: Difference between revisions
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Content and illustration by Thomas Pedersen @ DTU Nanolab unless otherwise noted. | Content and illustration by Thomas Pedersen @ DTU Nanolab unless otherwise noted. | ||
= Rough estimation of exposure time = | |||
The writing time should always be estimated prior to an exposure session. The writing time ''t'' [s] is a function of exposure dose ''Q'' [C/cm<sup>2</sup>], pattern area ''A'' [m<sup>2</sup>] and beam current ''I'' [A], as given below: | |||
''t = QA/I'' | |||
As a rule of thumb and easy extrapolation exposure of an area of 1.000.000 µm<sup>2</sup> at 1 nA and exposure dose of 100 µC/cm<sup>2</sup> takes 17 min. A simple Excel sheet to estimate writing time is [[:File:WritingTimeEstimator.xlsx|available here.]] | |||
The e-beam scanning frequency f (Hz) is a function of the e-beam scanning step, p (shot step), as shown below: | |||
f = I /(Qp2) | |||
The e-beam writer has scan speeds up to 100 MHz available. The dose, Q, shot step, p, and current, I, is chosen to meet the requirement of the pattern to be written, the writing time available, and also to meet the requirement f < 100MHz. | |||
Based on the equations above, a rough estimate of the exposure time is easily calcualted. In the second sheet of the e-beam logbook, a simple program for calculating the scan speed frequency and an estimation of the exposure time can be found. Note, that the actual writing time will exceed this estimated exposure-time, as the exposure-time calculation does not include pre-calibrations and stage movement during exposure. | |||
The area of your pattern can easily be found in L-edit by selecting all of your structure and use the area calculator in Tools/Add-Ins. If your pattern contains instances, you have to flatten your pattern (Cell/Flatten) before you use the area calculator; notice, however, that the flattening cannot be undone. | |||
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|Beam diameter versus Beam current: The machine have three operating objective apertures (no. 15 on above illustration of the column) in order to obtain different beam diameters in different current ranges. The available apertures are called 'aperture 5' (60 µm), 'aperture 6' (100 µm) and 'aperture 7' (200 µm). | |||
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=Pattern preparation for exposure on JEOL 9500 = | =Pattern preparation for exposure on JEOL 9500 = | ||