New SRP metrology system eyes small/mid-tier sweetspot

by Debra Vogler, senior technical editor, Solid State Technology

Semilab SSM, a division of Semilab, announced at SEMICON West the SRP Express 170, a new member of its NanoSRP family of metrology products. The manual system offers density and resistivity depth profiling using spreading resistance profiling technology (SRP), which provides a direct measurement of the resistivity and carrier density profiles of electrically active dopants.

According to the company, small and mid-tier semiconductor and solar cell manufacturers have had to choose between high-end, high-throughput systems designed to support multiple samples at a time — or older obsolete low-end manual systems. The company is targeting this new product to fill that void.

The key technology in the SRP Express is a new piezoelectric table system, a third-party design made specifically for Semilab, according to Chris Moore, president of Semilab SSM. Contact probing, especially when moving the sample to probe at different points, has to do a number of things very well. “You have to get the probes to precise locations and there can be no vibration when taking the measurements,” he explained. “Very few XY stages have a mode where there isn’t some level of vibration induced by the table system itself, whether its servo system or a stepper system.” He noted that often end-users have to power down such systems and then lock and unlock them, which adds to the amount of work, and the results aren’t as good. “We’ve found that this particular [piezoelectric] table design is far superior to anything we’ve used in the past,” he told SST.

Advantages that a piezo drive has over other drive mechanisms, Moore said, include no jittering, no motion during power-off, and no electric holding force required to keep micro-position. “Keeping the position fixed during measurement is key for point-contact measurements,” he explained. There is no electronic interference during measurements and no heat dissipation, he added. Furthermore, sub-micron resolution and precision translates to better x-position repeatability and therefore measurement repeatability. — D.V.


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