Measuring Gratings


One-Dimensional Line/Space Gratings are common lithographic patterns.  ProSEM can measure these gratings and report statistics of the gratings.



  • Use of Find Similar Features to measure a Line/Space Grating.
  • Line Edge Roughness (LER) measurement and Power Spectral Density display


Measurement Example: 

In this example, agrating etched into Indium Phosphide will be measured. 

To start, first a measurement of a single line is setup, as shown here: 

grating 1


Note that for ProSEM 2.1.0, the initial measurement must be a feature on the left side for a vertical line/space grating or on the bottom for a horizontal line/space grating, as ProSEM 2.1.0 only searches to the right and upward from the intiial feature.

Next the "Find Similar Features" button, the bottom button in the Results Toolbar, is used to have ProSEM find the other elements of the grating. 

After finding the similar features, ProSEM then fits the grating, and reports fitting statistics about the grating. When the "Group_n" label is selected in the Images tree, the information displayed is for the entire grating.   

Grating 2


   Grating Pitch[nm] :     Mean = 220.7 Min = 216.9 Max = 226.9 StdDev = 2.6 N = 22
   Grating Line[nm] :      Mean = 111.5 Min = 108.0 Max = 115.5 StdDev = 2.2 N = 12 
   Grating Trench[nm] :    Mean = 109.3 Min = 108.5 Max = 111.4 StdDev = 0.8 N = 11 
   Grating Rotation[deg] : Mean = 91.46 Min = 91.33 Max = 91.56 StdDev = 0.07 N = 24

Any specific individual measurement in the grating can be shown by selecting that element, either in the Image Tree or by clicking on the element border in the image (when the cursor changes to a pointing finger).  When an individual element is selected, the Results Area shows the specifics of that selected element.  

   CD[nm] :        Mean = 108.8 Min = 101.7 Max = 117.5 StdDev = 2.8 n = 1152
   Rotation[deg] : 91.56 91.35

Grating 3

Line Edge Roughness

When a grating is selected and the Line Edge Roughness button is clicked, the roughness is calculated for each individual line edge as well as the collective length of line in the full grating.  By evaluating LER over the longer length of all grating edges combined, a less noisy PSD results.  

Grating LER


Data Tables

For a grating measurement, each grating group will be output to a line in the Gratings Table, and each individual element will be output to a line in the Lines & Spaces Table, so the full data is always available for review and export. 

The Gratings Table for the above grating is shown here: 

 Grating Table 1


And here is the Lines & Spaces Table for the grating, showing each individual line in the grating. 

Grating Table 2