An Absolute Contamination Standard, appearing as a bare wafer to the naked eye.   A particle map and histogram of the same wafer acquired with a Scanning Surface Inspection System. SMALL OR LARGE, FIND THE PARTICLES THAT COUNT. The Absolute Contamination Standard (ACS) is used to calibrate instruments which size and detect particles for contamination control on the surface of bare silicon wafers. Use the Absolute Contamination Standard to characterize particles, before particles characterize products. Absolute Contamination Standards Product Description The Absolute Contamination Standard is built by depositing highly spherical polystyrene latex (PSL) spheres which have well-characterized optical properties and a very tight monodisperse size distribution. These parameters make PSL spheres a useful material for the calibration and monitoring of instruments that measure and count particles for contamination control. VLSI Standards supplies Absolute Contamination Standards with a wide variety of traceable sphere sizes in the range between 0.040 µm and 4.0 µm. Standards with smaller or larger sphere sizes may be special ordered. The calibration certificate includes the approximate number of particles deposited on the wafer. This is not a traceable value, as the Absolute Contamination Standard is designed to calibrate particle size, and not particle count. Background contamination is kept at an extremely low level and is defined on the measurement certificate. These characteristics of the standard ensure a highly monodispersed population of spheres on the substrate. Absolute Contamination Standards Product Specifications SEMI Specification Silicon Wafers 100 mm, 125 mm, 150 mm, 200 mm, and 300 mm diameter silicon wafers. Polystyrene Latex Spheres From 40 nm up to 4 micron * Traceability Traceable to SI Units through NIST * Sizes in other ranges may be available. Please check with VLSI Standards.