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Profile Measurements

Display Industry: Back Light Modules

   

Topography and dimensional measurements at back light modules for TFT LCD displays:

Different light reflecting and distributing patterns were developed within the TFT Display industry, starting from V-grooves in different size up to 3 or 4 facet pyramid patterns. The following 3D-Nanfinger measurements were made together with our customer METAL INDUSTRIES RESEARCH & DEVELOPMENT CENTRE, Kaohsiung, TAIWAN who also arranged the samples.

Sample 1: 4-facet pyramids

The following sketch describes the design of a 4-facet pyramid pattern and the parameters to be measured:


Schematic diagrams of 4 facet pyramid patterns

The 3D topography of the 4-facet pyramid sample is measured with the 3D-Nanofinger®:


3D-surface image of the metallic 4-facet pyramid structure, measured with the 3D-Nanofinger®.

 

Within this dataset Linescans can be displayed to analyze the dimensional features of this sample. The periodicity, pyramid angles, structure height as well as the surface roughness can be analyzed:

Distance:


Single Linescan over the surface, specified as "section A-A" in the upper schematic diagram.

The length of the Linescan is 250µm, the distance between the measured points is 100nm.
Calculated height value of the pyramids: 19.13µm
Calculated total width for 2 pyramids: 138.28µm

 

Angle:


Same Linescan used for angle determination

The two red interpolation lines for the angle calculation are shown in the lower display. They are specified by the two magenta resp. blue cursors shown in the upper display. The vertical scale of the lower display is stretched.
Calculated angle between the two facets of one pyramid: 120.1°

 

Roughness


Surface roughness graph for sample 1

The upper display shows the area where the roughness analysis was carried out. Lower display, white color: measuring length, magenta color: sample length. For this Linescan the surface roughness on one facet was determined. The roughness values were calculated as follows:
Ra = 12.0 nm
Rq = 15.9 nm
Rz = 70.6 nm
Rt = 109.6 nm

Parameters:
Lambda cut-off: 4 000 nm
Measuring length: 16 100 nm
Sample length: 4 000 nm.

 

 

Sample 2: 3-facet pyramids

The following sketch describes the design of a 3-facet pyramid pattern and the parameters to be measured:


Schematic diagrams of 3 facet pyramid patterns

The 3D topography of the 3-facet pyramid PMMA sample is measured with the 3D-Nanofinger®:


3D-surface image of the PMMA 3-facet pyramid structure, measured with the 3D-Nanofinger®.

 

Again the periodicity, pyramid angles, structure height as well as surface roughness are analyzed

Distance:


Single Linescan over the surface, specified as "section A-A" in the upper schematic diagram.

The length of the Linescan is 500 µm, the distance between the measured points is 100nm. On two slopes of the scan, some surface defects or contaminations are visible.
Calculated height value of the pyramids: 65.00 µm
Calculated total width for 2 pyramids: 299.67 µm

 

Angle:




Within one Linescan three different angles are determined

Three angles were determined, by placing linear fits into the Linescan. From top to down, the calculated values are:
Angle 1: 90.27°
Angle 2: 70.36°
Angle 3: 88.58°

 

Roughness


Surface roughness graph for sample 2

The upper display shows the area where the roughness analysis was carried out. Lower display, white color: measuring length, magenta color: sample length.
For this Linescan the surface roughness on one facet was determined. The roughness values were calculated as follows:
Ra = 24.5 nm
Rq = 27.7 nm
Rz = 109.1 nm
Rt = 137.4 nm

Parameters:
Lambda cut-off: 6 000 nm
Measuring length: 24 000 nm
Sample length: 6 000 nm

 

 

 

Summary:
Neither a standard Profilometer nor a Coordinate Measuring Machine can deliver the results presented here.
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