SEMATECH, Veeco work on AFM improvement

07/01/1997

Sematech, Veeco work on AFM improvement

SEMATECH will work to develop the critical dimension metrology capabilities of the Veeco Surface Metrology Dektak atomic force microscope (AFM), for both mask and wafer applications, under terms of a new agreement.

Karen Brown, director of lithography at the Austin, TX, consortium, said the impetus for the program originally came from the need to measure sub-quarter-micron dimensions on photomasks. However, she continued, "It turns out that many of the improvements for masks would also benefit wafer metrology, so it`s a two for one." AFM technology can precisely measure 3D features, without the need to cleave the wafer. Scanning electron microscopes, today`s leading edge tools, cannot be used on production wafers since the substrate must be broken for measurement.

"People are very worried about how far they can push CD-SEMs - they can definitely go to 0.18 ?m, but beyond that it`s unclear," said Brown. "Having a significantly improved AFM with higher throughput would benefit the industry."

Initial plans call for today`s 0.25-?m resolution to be improved to 0.2 and 0.18 ?m for mask features and 0.15-?m for wafer features. "The key things for masks have to do with throughput, tip lifetime, the ability to find features quickly, and the ability to measure chrome sidewalls," noted Brown.

The AFM tip is an extremely narrow probe, which is placed in such close proximity to the substrate being measured that it engages atomic-level forces. By scanning the tip and keeping the force level constant, a 3D surface map can be generated. Currently, said Brown, tips have a lifetime of just 32-40 hr; the program hopes to improve this substantially, ideally by a factor of 20 to 80. In addition, researchers hope to improve the dynamic precision of CD measurements from today`s 10- to 2-nm range. - P.N.D.