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Semiconductor Wafer Defect Inspection

Illustration Example of Semiconductor Wafer Inspection Machine

When it comes to precision linear and rotary positioning stages, the semiconductor wafer inspection industry is one that demands high precision.

Metrology and inspection are important for the management of the semiconductor manufacturing process.  There are 400 to 600 steps in the overall manufacturing process of semiconductor wafers, which are undertaken in the course of one to two months.  If any defects occur early in the process, all the work undertaken in the subsequent time-consuming steps will be wasted.  Metrology and inspection processes are therefore established at critical points of the semiconductor manufacturing process to ensure that a certain yield can be confirmed and maintained.

High speed wafer defect inspection systems detect physical defects (foreign substances called particles) and pattern defects on wafers and obtains the position coordinates (X, Y) of the defects.  Defects can be divided into random defects and systematic defects.

Patterned wafer inspection system
There are many types of patterned wafer inspection systems, including the electron beam, brightfield, and darkfield inspection systems.  Each of these has its own features, but the basic detection principles are the same.

On a semiconductor wafer, electronic devices of the same pattern are made side by side.  Random defects are often caused by particles such as dust and occur in random positions.  The possibility that they will occur repeatedly in a specific position is extremely low.  Patterned wafer inspection systems can therefore detect defects by comparing the pattern images of adjacent chips (also called dies) and obtaining the difference.  If numerous defects occur on the surface of a wafer, the circuit patterns are not created correctly, causing patterns to be missing.  If there are numerous defects, they prevent the electronic circuit from operating correctly, thereby making the wafer a defective product.  Detecting defects and specifying their locations (position coordinates) are the primary role of a wafer inspection system.