The ever growing market for computing and communication technology drives a similar growth in demand for semiconductor wafers. During production, the surface of these wafers are closely monitored for defects known as “features” that cause inconsistency in final product. As the wafers get smaller so do these features and following “Moores law”, the ability to measure them accurately, quickly and at smaller scales is becoming ever more important.
To measure these features quickly without contact, laser speckle is used. By looking at the interference pattern created when illuminated by long coherence lasers, the surface features can be resolved into 3 dimensions and to a high resolution.
The key parameters for the successful use of speckle are high stability in the bandwidth and beam pointing. Any movement in either of these key parameters will result in false measurements, causing a good wafer to be rejected. Together with the need for long term reliability, typically 24/7 operations with only annual shutdowns to perform servicing, and a high temperature control without the use of water or forced air cooling, the laser head has to be cleverly designed.
The finesse and opus lasers are ideal choices for semiconductor wafer inspection due to their high power, stable and reliable performance allowing a “fit and forget” placement.