An inspection system has been developed that uses high-speed electron- beam imaging combined with digital image processing to automatically locate defects on semiconductor wafers. The system inspects wafers using a low beam energy of 0.8 KeV and a scan speed that is as much as 1000 times faster than traditional SEMs. This paper describes the system and presents characterization testing results of the system's ability to find defects on advanced integrated circuits. Three unique applications for the new automated scanning electron microscope inspection system (SEMSpec) have been found. First, the high resolution of the electron imaging microscope allows the tool to find much smaller defects than optical inspection systems can find. The SEMSpec system found defects smaller than 0.1 micrometers in size, even on densely packed, sub-quarter micron, high aspect ratio, multilayer geometries. Second, wafers that are late in the fabrication process are much easier to inspect at high sensitivity by SEMSpec than by optical means. This is because SEMSpec images are much cleaner than optical images when viewing grainy poly, metal, or other interconnect layers. Third, the SEMSpec system can sometimes find electrical problems by observing charge-induced voltage contrast differences. Voltage contrast occurs when some of the IC features are electrically defective and they charge up differently under the electron beam than they normally would. The SEMSpec system can then identify them as defective even though they might otherwise appear to be perfectly formed.

Characterization of a new automated electron-beam wafer inspection system

The status of x-ray mask inspection and repair at the IBM Advanced Mask Facility is presented. Defect classification and sources are presented along with some preliminary results from a defect printing study done at the Advanced Lithography Facility.

O. De Hodgins

Papers

Status of x-ray mask inspection and repair