For wafers to become a worthy substrate for integrated circuits to be built on, it has to possess certain properties. If you’re planning to use a Si wafer to make integrated circuits, here are some things to look out for in choosing good quality wafers:
The wafer you’re looking for must be flawless. Always check for any scratches, stains, residues, smudges, mounds, and streaks on the surface of the Si wafer.
Your Si wafer must have a flatness of 1-3 microns unless you specify otherwise. Flatness is a wafer’s maximum change from peak to valley in contrast with a reference plane. This is measured through an industry-approved method.
This can be in the form of a saw mark during the slicing stage. This impurity can be removed through lapping.
This refers to the sum of particles present per unit area of the wafer. As much as possible, a wafer must have little to no particle density present on its surface.
This type of defect is brought about by chemical etching, oxide stripping, and other wafer fab processes. These defects are usually small and shallow. Any densities less than 100 per sq.cm is acceptable.
A good quality wafer must have no fissures or cracks.
Haze is a result of microscopic distortion or roughness on the topmost layer of the wafer. This defect is determined through a small beam of tungsten light.
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