Measuring Gratings

Summary:

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

Measurement Example: 

In this example, we are measuring a grating etched into Indium Phosphide. 

To start, setup a line measurement on one line of the grating, as shown. 

grating 1

 

Note that for ProSEM 2.1.0, for your initial measurement, you need to start with 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 your intiial feature.

Next click the "Find Similar Features" button -- this is the bottom button in the Results Toolbar.  ProSEM finds 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

You can also see any individual measurement in the grating by selecting that element, either in the Image Tree or by clicking on the element border in the image.  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 you always have the full data available for review and export. 

Here's the Gratings Table for the above grating: 

 Grating Table 1

 

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

Grating Table 2