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Product Briefing Outline: KLA-Tencor has introduced SURFmonitor, a module that extends the Surfscan SP2 unpatterned surface inspection system beyond traditional defect inspection to also monitor process variation and drift. The SURFmonitor system is designed to measure variations in surface morphology of bare wafers or blanket films, which correlate to a broad array of process parameters such as surface roughness, grain size, and temperature. SURFmonitor, is claimed to create detailed, full-wafer parametric maps with sub-Angstrom repeatability in under a minute--while defect information is being collected--enabling fabs to monitor both process variability and defectivity simultaneously. It is also claimed to have the ability to detect atomic-level roughness variations that allows it to replace AFM's to a large extent.

Problem: Advanced integrated circuits rely on films only a few atomic layers thick. The quality of the film--its surface roughness and uniformity--has become critically important to the performance and reliability of the device. While metrology systems can supply the resolution, precision and repeatability required, their discrete sampling strategy may miss
localized parametric variations.

Solution: The SURFmonitor module uses low spatial-frequency, low amplitude
scattering signals from the defect scan to generate high resolution, full wafer maps. With sub-Angstrom height resolution, the maps resemble high quality digital photographs of the surface. SURFmonitor then analyzes these maps for within-wafer or wafer-to-wafer spatial variations, and applies the results for statistical process control. The SURFmonitor data, according to the company has shown excellent correlation to several parameters such as film thickness, surface damage, surface temperature variations, and AFM measurements of surface roughness for copper, tungsten and poly-silicon films. The SURFmonitor also provides sub-threshold defect detection capability, finding defects such as watermarks and stains that can be difficult to detect in traditional defect channels.

Applications: Bare wafers and blanket films.

Platform: Built on the Surfscan SP2 platform.

Availability: July 2007 onwards.

Caption 1: CMP process monitor wafer with circular signatures that reveal slurry residue issue

Caption 2: Wet clean process monitor wafer with streak signature that reveals the presence of known yield-impacting wet bench issue