by Debra Vogler, senior technical editor, Solid State Technology
Oct. 21, 2008 – KLA-Tencor recently introduced the PlasmaVolt X2 for measurement of plasma chamber conditions in semiconductor wafer processing systems. The new sensor wafer measures above-the-wafer effects in a plasma chamber, downloading the data after it is returned to the FOUP.
“Other tools used to evaluate plasmas, such as Langmuir probes, are single-point measurements…that do not provide insight at the wafer-level,” Rangesh Raghavan, director of marketing, SensArray division at KLA-Tencor, told SST. With an increased number of independent embedded sensors (14) over the previous monitoring system and improved spatial resolution, the new sensor wafer is sensitive to changes in various parameters such as radio frequency (RF) power, gas flows, magnetic fields, and chamber design. “The new tool measures RF current, which is a proxy for all the parameters that affect plasma health,” he said. Aside from fitting the electronics into a package that mimics a product wafer, another enabling innovation is a “very good” Faraday cage that surrounds the sensors, which allows signals to be extracted within the chamber environment without noise.
The previous-generation PlasmaVolt had a Y shaped layout with fewer sensors and did not have enough sampling at the edge of the wafer, Raghavan told SST (see figure). The X2 has a redesigned layout to give a better characterization of the wafer edge, and being able to maintain uniformity as close as possible to the wafer’s edge is key to achieving yield.
According to Raghavan, the new sensor wafer has been adopted by two of the largest DRAM and logic microprocessor manufacturers. It is also being used by three of the top four etch chamber OEMs, and a fourth is in the process of evaluating it. The new plasma behavior measurement and characterization system enables chamber-to-chamber matching, tool qualification, system troubleshooting, and process development for production environments. When the new system is paired with KLA-Tencor’s PlasmaTemp G4, which is designed for temperature measurements, the complete plasma chamber is mapped. — D.V.
A new sensor layout pattern from the previous generation enables the PlasmaVolt X2 to provide increased spatial resolution. (Source: KLA-Tencor)