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The Dimensional SEM/FIB

Display Industry: Nanostructures on glas

   

In a flat panel display production process small structures in glass samples are produced by a laser. The following sketch gives an overview about the lateral dimensions of these structures:


Flat structures on glass generated with a laser, scaled in mm

The SEM image shows the medium sized structure but the SEM alone cannot resolve the 3D information:


Biggest pattern with 5 um linewidth generated with a laser

 

The 3D-image of the circle area and a part of the line array generated with the "Dimensional SEM" is shown in the next picture. All axes are scaled and traceable to international standards:


Biggest pattern with 5 um linewidth generated with a laser

 

The grooves in the 3D-scan appear deeper than they are, because the vertical (depth-) axis in the upper picture has a higher magnification than the two horizontal axes. A zoom into a small area of such a structure is shown in the next image including more details:


One line and its fine structure

 

In any area of the sample structure linscans can be measured. The following single linescan was made over an area of 5 linear grooves (big pattern). The depth of the grooves is measured with 217 nm, a value that is already below the wavelength of light. The distance between the grooves (periodicity) is measured with 10.200µm:


Biggest pattern: single linescan over the area of 5 linear grooves

 

The next 3D surface scan was made over a complete medium sized pattern. The single linescan was made within the area of 5 linear grooves:


3D scan of the medium sized pattern together with a linescan

The lateral image size is 80 µm x 80 µm. The depth of the grooves is measured with 218 nm. The distance between the grooves (periodicity) is measured with 6.050µm. The linescan presents the fine structure of the lines and circles quantitatively and informs about the side effects of the structuring method, e.g. the small peaks beneath the grooves.

The next 3D scan was made over a small structure that is nearly invisible in the light microscope and can laterally only be resolved with the SEM:


3D scan of the small sized pattern together with a linescan

The lateral size of the whole image is 50 µm x 50 µm. The single linescan was made within the area of 5 linear grooves and shows that the lines are different in depth. The maximum depth of the grooves is measured with 255 nm, the minimum depth is measured with 238 nm. The distance between the grooves (periodicity) is 4.032 µm. The precision of this measured data is already in the range of Scanning Probe Microscopes. But SPM's cannot compete in range and functionality.

The upper measurements could not be performed with other machines in the market. And the next measurement is even more unique: The surface roughness measurement WITHIN a single of these grooves:


Linescan within a single groove of the big pattern for surface roughness detection


Calculated roughness values for this measurement:
Ra: 8.0 nm, Rq: 8.8 nm, Rz: 20.1 nm, Rt: 35.5 nm

Parameters:
Lambda cut-off: 30 000 nm, Measuring length: 12 694 nm, Single measuring length: 2 549 nm

That's what we call a Dimensional SEM!

Summary:
The Dimensional SEM offers traceable 3D topography data with nm precision, inner and outer contour measurements as well as roughness detection inside of a SEM/FIB.
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