Particles, Scratches and haze are normally measured on a system like a Tencor Surfscan 6420 pictured at the LEFT. These systems can sort for pits in the Silicon, tiny scratches and the smallest particles on the best most highly polished Prime wafers. Note: Even the newest particle counters need regular calibration using a traceable particle standard. At the most enhanced viewing levels, the surface of many films (like Silicon Nitride) can be rough or have other defects & features that can show up as particles on a un-calibrated system, even when there is No particulate present