High resolution sensors are supporting improvements in semiconductor metrology and inspection at vital points in the production process. Because the fabrication of semiconductor wafers may require hundreds of steps and weeks of manufacturing time, early-stage defects that go undetected can have costly downstream consequences. Plus, because semiconductor processing always requires a high degree of precision, advances in fabrication methods seem to require ever-finer measurements in a never-ending quest.
Today’s metrology instruments are incorporating high resolution sensors for automated wafer inspection. Resolution, the smallest measurement that a sensor can reliably indicate, may be given in dimensional units such as nanometers (nm) or micrometers (microns). The advantage of using a dimensional unit instead of volts or percent of scale is that it indicates the smallest displacement measurement a sensor can provide. Displacement, a vector whose length is the shortest distance from the initial to the final position of a point undergoing motion, quantifies both distance and direction.