ZDot Contact Profilometry Technology and Applications

Contact profilometry was likely one of the first techniques designed for measuring the roughness of a material’s surface by physically making contact with a surface or surface forces.

Stylus profilometers equipped with a diamond-tipped probe are the most common contact profilometers. Atomic force microscopy (AFM) uses the same concept for operation, but on a much smaller scale.

Novel measurement techniques that can perform measurements without making contact with the material surface are preferred in advanced systems and processes. Zeta-20 Optical Profilers are an innovative system from KLA, featuring ZDot™technology. The versatility, excellent cost of ownership, and speed of the Zeta-20 Optical Profiler make it an ideal replacement for the traditional stylus profilers in various applications.

Comparison of Stylus Profiler, AFM and ZDot™ Technology

The following table compares the capabilities of ZDot™ technology with the stylus profiler and AFM:

  Stylus Profiler AFM ZDot™
Measurements Stylus Profiler AFM ZDot™
Line scan roughness Yes Yes Yes
Line scan step height Yes Yes Yes
Area-based roughness and step height Slow (must combine multiple line scans) Slow (must combine multiple line scans) Fast
Large area measurements Slow, Minutes to Hours NO Fast, Seconds
Thinfilm thickness measurement Requires a film edge Requires a film edge Option for transparent films; no edge required
Characterization of buried surfaces No No Yes (if top layer is transparent)
True color or False Color False Color False Color True and False Color
Simultaneous 2D and 3D Analysis No No Yes (cross sections + area roughness)
Method and Limitations
Contact (does the sample get ‘touched’ by a probe?) Contact Contact Non-contact
Artifacts (false readings) due to size of the probe? Yes, stylus shape and size can affect measurements; knowledge of the sample, the tip and some
Experience is all needed to identify artifacts.
AFM No probe artifacts (no probe)
Large step height capability (> 150 µm) No No Yes
Cost of Ownership
Consumables to buy? Yes, periodic replacement of expensive diamond stylus probes Yes, very frequent replacement of AFM probe tips No consumables
Requires skilled operator? No Yes No
Calibration frequency? Frequent calibration due to tip change Frequent calibration due to tip change None
Total cost of ownership Medium to high Medium to high Low

Zeta-20 Optical Profilers feature standard objectives, fixed to a standard turret to offer endless customization options to users. Various attachments are offered by third party suppliers, including AFMs (Figure 1).

Customer Testimonial

We use our KLA nearly every day and rely on it for quick measurements and sample characterization. It suits our needs perfectly. We were especially impressed by KLA's willingness to customize. We had a unique need, and they jumped at the opportunity to make it work for us. We’ve also been impressed by the level of customer service we’ve received.

Dr. Rebecca Krone Kramer, Assistant Professor, Purdue University, USA

An AFM attachment available from multiple suppliers

Figure 1. An AFM attachment available from multiple suppliers

Other accessories of  Zeta-20 Optical Profilers include:

  • Diamond scribe to mark defects
  • External dark field illumination
  • Edge inspection fixture with dark field illumination
  • Through transmissive illumination
  • SWIVEL head option

Applications of Zeta-20 Optical Profilers

Given below are the major applications of  Zeta-20 Optical Profilers:

  • Unlike stylus profilers that do not provide information on buried layers, Zeta-20 Optical Profilers can characterize both upper film and the layers beneath (Figure 2).
  • Probes may take a longer time to characterize large areas, and their tip shape can vary during scans, leading to inaccurate measurements. Zeta-20 Optical Profilers allow fast large area scans (Figure 3).
  • Zeta-20 Optical Profiler exhibits true film colors (Figure 4). Rough surfaces are not a problem and no wear or replacement as there is no stylus
  • Unlike a probe, the ZDot™ technology is capable of imaging aromatic oil droplets in Rosemary leaf (Figure 5)

Measurement of layers beneath the material’s surface

Figure 2. Measurement of layers beneath the material’s surface

Large area measurement

Figure 3. Large area measurement

eta optical profilers exhibit true film colors.

Figure 4. Zeta-20 Optical Profilers exhibit true film colors.

Dot™ technology can image a Rosemary leaf, showing the aromatic oil droplets.

Figure 5. ZDot™ technology can image a Rosemary leaf, showing the aromatic oil droplets.


With ZDot™ optical profiling technology, the concept of confocal microscopy is extended with the additional benefit of true-color imaging. It allows imaging of complex surfaces at ease and provides exceptional metrology capability required for challenging production and R&D applications in the high brightness LEDs, microfluidics, solar cells, advanced semiconductor packaging, and several other sectors.

This information has been sourced, reviewed and adapted from materials provided by KLA Corporation.

For more information on this source, please visit KLA Corporation.


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