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CD-SEM

A workhorse for imaging and metrology.
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Description:

A scanning electron microscope, or SEM, takes measurements by sending out an electron beam, which interacts with electrons in the material being scanned. That sends back signals, which are mapped by the equipment. The more critical dimensions that need to be mapped, the greater the amount of data that needs to be processed and stored.

CD-SEM files are measured in tens or hundreds of gigabytes. Just being able to decipher this much data requires a higher level of abstraction. There is no equipment powerful enough to process it within a reasonable time frame, and no way to retrieve that data quickly. In data terminology, it has to be mined just to be useful.

This problem grows worse with finFETs, which has stretched CD-SEM to its limits. About 75% of the inspection on a 3D transistor can be done using conventional CD-SEM, according to IBM. But that still leaves a large amount of information for which there is no solution using an image-based tool. As device geometries continue to shrink, and as more features and functionality are added onto a die, that becomes increasingly troublesome.

This has led to a search for new approaches, such as atomic-force microscopy and some hybrids of different inspection approaches.

  • Other names: critical dimension scanning electron microscopy
  • Type: Manufacturing

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