There are two ways to calibrate the scale (if no calibration is carried out, nm/pixel ratio will take the default value of 1). You can directly change the nm/pixel ratio by single clicking on it and inputting a new value, or you can also get the nm/pixel ratio from the known distance of two points (a scale bar) on the image.
How are the result values calculated?
Assume that we have detected n edges, the number of points on ith edge is Ni (i = 1,...,n) , and Δxij is the edge residual of point j on edge i.
In lithography metrology, a set of lines and spaces are often created in the same orientation. For this reason, the orientations of the fitting lines on each edge are considered to be the same in all the following calculations with only one exception when calculating Mean-LER*.
Line edge rough is defined as 3 times the standard deviation σ (LER = 3*σ).
where N0 is the total number of all points N0 = N1 + N2 + ... + Nn, and µ is the average of Δxj.
2) Mean LER
Line edge roughness of the ith edge LERi is defined as 3 times its standard deviation σi. LERi = 3*σi.
where µi is the average of Δxij.
Mean LER is then defined as the average of LERi (i = 1,...,n).
3) Mean LER*
Mean LER* is defined the same way as Mean LER, except that that the orientations of the fitting lines are different and are best fitted to each edge. In a typical line-space pattern, the values of Mean-LER and Mean-LER* are expected to be very close.
4) Odd LER
Odd LER is the average of odd-numbered edges, i.e. the ones on the left in the case of vertical lines or the upper in the case of horizontal lines.
5) Even LER
Even LER is the average of the right-side edges (or the upper in horizontal lines).
6) Mean CD
Mean CD is the average of the linewidths of the lines.
Pitch is the average of the pitches of the lines and spaces.