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Measuring Linewidth and Line Edge Roughness versus Exposure Dose


The linewidth and line edge roughness (LER) of a negative e-beam resist are measured as a function of e-beam exposure dose.



For this negative e-beam resist process, the linewidth varies with exposure dose of course, but from SEM observations it appears the line edge roughness (LER) also varies with dose.  Here, ProSEM is used to quantify this observation.

sample highest dose   Sample narrow line



example measurement


 The image filenames in this project include a relative exposure dose factor, here varying from 1.0 to 2.0. The absolute exposure dose is simply the Base Dose times this Relative Factor.  A ProSEM formula is used to extract the relative dose factor from the filename for each measurement, and a ProSEM value variable is defined to store the base dose for the exposure. 

base dose variable


exposure dose variable

The formula used here to extract the relative dose and calculate the exposure dose is: 

BaseDose * Number(/RelDos_([\d\.]+?)_/.exec(image.label)[1])

More details about formulas and Regular Expressions is found in other In Action examples detailing Formula Usage.

The measurement data, including the dose variables, measured CD and LER values, can be seen by selecting the "Lines & Spaces" Data Table tab. This data can then be exported to a .csv data file using the Export Current Table... button.  The data can then be plotted using an external program. 

data export

 When plotted, it is clearly seen that LER does indeed increase at very low exposure dose values.