Ellipsometer Standard Operating Procedure

Taking measurements with the ellipsometer

1. 

   Ellipsometer components needed for operation.

   Turn the keyswitch on the back-right clockwise to turn the tool on.
2. Start the software:
   1. On the ellipsometer computer, open up the "GEMP" program on the desktop.
   2. Go to the menu option Ellipsometer > Waferskan Mapping, OR click on the toolbar icon resembling an ellipsometer.
      • 
3. Align the table tilt and height:
   1. Place any piece of flat reflective substrate on the table.
   2. Ensure that the laser beam stop is pushed in to protect your eyes.
      • It is silver, knurled, and pointing out at the user from the body of the laser to the left of and above the sample table.
   3. Look through microscope and us vertical XY knobs on the black round plate to center the two crosshairs with the microscope.
4. Place either a calibration standard, or the sample to be measured on the center of the ellipsometer table.

   

   Ellipsometer GEMP control software.

5. Z adjust procedure:
   1. Click "Adjust Sample Table"
   2. Unlock the Z lock screw.
      • It is silver, knurled, and pointing out at the user from under the sample table.
   3. Pull out the beam stop to allow the red laser beam to strike the sample table.
   4. Use the 3" knurled ring under the sample table to adjust the table height
      • Do this while monitoring the Table Height Adjustment view in the software until the table position is centered.
   5. Lock the Z lock screw and ensure the table alignment has not shifted.
   6. Click OK to exit the table adjustment dialog.
6. Check the ellipsometer function with a calibration standard for your film(s) if available:
   1. In this example, we will use the SiO2 1990 Angstrom standard from Gaertner.
   2. Return to the Waferskan Mapping window.
   3. Load a model:
      1. Click "Load New Model File" in the "Thin Film Model" pane.
      2. Select a TFM file and click "Open."
         • i.e., "Thin Oxide.tfm" for SiO2.
   4. In the field "Thickness 1" in the "Measurement and Calculation" pane, enter the expected thickness of the sample (in Angstroms)
      • i.e., 1900
   5. Know which wavelength the tool is using in the "Thin Film Model" frame of the Waferscan Mapping window.
      • This will either be 4050, 6328, or 8300 Angstroms.
      • This wavelength can be changed between the available options by clicking on the "Wavelength" button
      • The wavelengths can also be disabled by unchecking the box for that wavelength.
   6. Click "Meas & Calc" in the "Measurement and Calculation" pane.
      • Note that there are separate buttons for these steps as well:
        1. The "Measure" step:
           • This will get new values for the Psi and Delta fields.
           • i.e., Psi=33.341, Delta=279.711
        2. The "Calculate" step:
           • This will display a thickness under the "Thick1" field, and an index of refraction under the "Nf1" field, as well as any other layers present in the model.
           • i.e., Thick1=1976.951, Nf1=1.4706
   7. If the measurement is OK and matches the expected standard thickness, proceed to measure your samples.
7. Switch over to your sample on the sample table and measure:
   1. Ensure that the laser beam stop is pushed in to protect your eyes.
   2. Adjust table tilt and table height again.
   3. Pull out the beam stop.
   4. Enter expected thickness of the film
   5. Enter expected index of refraction of the film
   6. Change to the desired measurement wavelength.
   7. Click "Meas & Calc" as before to acquire the calculated thickness.
8. Wrap up:
   1. Close the software
   2. Turn off keyswitch on the back-right

Creating thin film models for the ellipsometer

1. On the ellipsometer computer, open up GEMP program, then go to the menu option Ellipsometer > Waferskan Mapping
2. Look up the indices of refraction for your sample substrate and films for the wavelengths 4050, 6328, and 8300 Angstroms.
   • These may be found in a table in the green-bound ellipsometer manual.
   • These may be measured on the F20 tool.
   • https://refractiveindex.info/ is also good resource.
3. Click "Save New Model File" in the "Thin Film Model" pane.
4. Save the name of your new model in the model directory, descriptively titled in the format "[film material] on [substrate material].tfm"
   1. You can also specify the source for your constants in the filename.
5. Check which wavelength the tool is using in the "Thin Film Model" frame of the Waferscan Mapping window.
   • This will either be 4050, 6328, or 8300 Angstroms.
   • This wavelength can be changed between the available options by clicking on the "Wavelength" button
   • The wavelengths can also be disabled by unchecking the box for that wavelength.
6. Enter data into the model file:
   • Enter estimated thicknesses under the "Thick" field. index of refraction active wavelength under the "Nf" and "Kf" fields
   • For the thin films, enter data in the numbered rows, starting at the top row in the "Thin Film Model" pane, up to 4 films possible.
   • For the substrate, enter data at the bottom row in the fields "N_s" and "K_s"
7. Cycle through each of the three wavelengths, repeating data entry for each.
8. Save again the name of your new model in the model directory, overwriting the same file you created earlier.
9. The model can now be used for measurement and recalled when needed.