WYKO Rough Surface Tester White Light Interferometer

WYKO Rough Surface Tester White Light Interferometer Setup at Nanomanufactoring Laboratory

The WYKO Rough Surface Tester (RST) Light Interferometer is a non-contact optical profiler capable of very sensitive 3D surface profilometry and surface roughness characterization. The RST Light Interferometer operates in two measurement modes, i.e., the optical phase-shifting mode and the vertical-scanning mode. The optical phase shifting mode is used for reflective, mirror-like samples while the vertical-scanning mode is used for measurements of samples with rough surfaces.

The following tables describe the technical specifications for the system, magnification, performance, environment, direction, and power requirements of the WYKO RST non-contact optical instrument:

System Specifications

Measurement Technique 1) Optical phase-shifting
2) Vertical scanning interferometry
Measurement Capability Three-dimensional surface profile measurements
Objective Lenses 2.5X, (20X)
Field Lenses 0.5X, 1.0X, 2.0X
Field of View Variable (up to 4.9 mm - See table below)
Array Size
Selectable (128 x 128 to 739 x 484)
Light Source Tungsten halogen lamp
Stage ±6° tip/tilt, ±90° rotation, ±2 inches x,y
Video Display 9 inch black and white monitor
Computer System PentiumTM Class PC
Signal Output CCIR
Active Pixels 739(H) x 484(V)
Alignment System Fringe viewing and twin spot alignment
Software WYKO VisionTM software running under Microsoft WindowsTM


Magnification Objective 2.5X 10X 40X
Interferometer Type Michelson Mirau Mirau
Numerical Aperture 0.075 0.25 0.50
Working Distance (mm) 2.0 4.0 3.9
Field of View (mm) 4.9 x 3.7
2.6 x 1.9
1.3 x 1.0
1.2 x 0.9
0.6 x 0.5
0.3 x 0.2
0.3 x 0.2
0.2 x 0.1
0.08 x 0.06
High Resolution Spatial Sampling Interval (Aµm) 7.6
Standard Resolution Spatial Sampling Interval (Aµm) 15.2


Total System (including vibration isolation table) 60 in. W x 34 in. D x 57 in. H
Vertical Resolution <1 Å Ra

Power Requirements

Input Voltages 110/220 VAC, 60/50 Hz
Power Consumption 300 W


Vertical Measurement Range 0.1 nm to 500 µm
Vertical Resolution <1 Å Ra
Scan Speed 3.6/7.2 µm/sec


Temperature Range 0.1 nm to 500 µm
Humidity Range <80%, non-condensing

The following figures show some examples of measurements obtained from the WYKO RST White Light Interferometer. The figure below displays a cross-sectional evaluation of two nanometric cuts on a silicon workpiece under different scratch conditions1.

Cross-sectional evaluation (X profile in the right side) of two parallel nanometric cuts (left side)

The 3D scratch profile shown below, obtained with the WYKO (RST) White Light Interferometer, allows the visualization of the cut along its length. In this figure, the well defined groove edges in the left cut helped characterize the cut of a silicon workpiece as more ductile when compared to that of the right1.

3-D scratch profiles of two parallel nanometric cuts on a silicon workpiece.

1The Effect of Laser Heating on the Ductile to Brittle Transition of Silicon

Manufacturing Engineering

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