INDUSTRY NEWS

Behave yourselves

To hear Pam Ward tell it, plasmas often act like a gang of four-year-olds left at home without adult supervision. Only the home is a $3-million mansion and the kids have discovered the paint closet. Defects occur during plasma etch processing that can cost chipmakers millions of dollars in lost wafer lots, notes Ward, a scientist at Sandia National Laboratories in Albuquerque. She and other researchers have developed a method of process supervision that can keep the children, as it were, from giving mom and dad a very expensive headache.

Plasmas "don't always behave as they should," notes Ward. "Two or three gases may be involved, and manufacturers hope everything remains constant, but the mechanisms are temperamental." Among the problems? A leak that allows air to enter and form its own plasma, sticky flow controllers, and moisture in the chamber. Each affects plasma performance.

Sandia's solution is a "relatively inexpensive" computer program allied to a camera and laptop computer that allows chipmakers to spectroscopically analyze optical emissions from plasmas as they etch the wafer. The computer program permits virtually instantaneous analyses of emitted wavelengths "to detect if the plasma is misbehaving." The program, which controls up to 64 pieces of equipment, can sound an alarm and adjust plasma parameters.

The hot ionized gases "have a fingerprint," says Ward. "Our tool looks at that fingerprint, then compares it to fingerprints of known failure." It can't, however, deliver a stern tongue-lashing.

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