Absolute Contamination Standard

The Absolute Contamination Standard (ACS) is a bare silicon wafer that has nanometer range polystyrene latex spheres (PSL) or Silica spheres deposited on its surface. ACS are used to calibrate instruments that measure and count particles on wafer surfaces.


The polystyrene latex spheres that are deposited by CALMEPRO are highly spherical, have well characterized optical properties and a very tight monodisperse size distribution. These parameters make PSL spheres a metrology standard for the calibration and monitoring of instruments that measure and count particles.

CALMEPRO supplies these PSL standards in a wide variety of NIST traceable and non-traceable sphere sizes, typically between 0.010 μm and 5.0 μm.

For UV and DUV applications ACS can also be deposited with monodisperse Silica spheres.

CALMEPRO also performs custom depositions to provide characterization of surface contamination detection instruments. We accomplish this by precisely depositing a known size and distribution of polystyrene latex spheres onto customer-supplied substrates with films or defects present on the substrates. PSL’s are available in sizes that have traceability paths to the National Institute of Standards and Technology (NIST) as well as non-traceable sphere sizes.

Depositions can be performed on:
  • All bare wafers sizes
  • Patterned silicon wafers
  • Wafers with films
  • Hard drive plates
  • Reticles, pellicles and masks



The calibration certificate includes the approximate number of particles. This is not SI units traceable because the ACS is designed to calibrate particle size, and not particle count (capture rate) . Background contamination is kept at extremely low levels. The CALMEPRO process yields a highly monodisperse population of PSL spheres on the substrate. This can even be done at extremely low densities of approximately 1 particle per cm2.


Contact us for any questions.