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| Introduction |
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Preventing Defects from Printing: Mask Inspection
The photomask is one of the most important elements in photolithography. It contains all structural information that is required in the process of pattern transfer that is necessary for the manufacture of integrated circuits, or “chips”. Modern micro-electronic devices are complex and may contain up to forty differing layers, each having an associated photomask.
Even minute defects in the layout of a single mask used in this process can render all chips on the exposed wafer unusable resulting in enormous losses. That is why it is crucial to inspect all masks for defects, understand their impact on the photolithography process, and eliminate them before the mask is used in a stepper, or scanner. The best way to reliably control quality at this stage is to optically emulate the photolithographic process using the  Aerial Image Measurement, or AIMS™ technique.
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