Recovery of tungsten from the exhaust of a tungsten chemical vapor deposition tool

An ETC DryScrub plasma scrubber has been successfully tested fur the captur ing and recovery of metallic tungsten from the exhaust of a W chemical vapo r deposition (CVD) tool. The scrubber operation was completely transparent to, the upstream CVD process. The WF6 destruction removal efficiency of the scrubber was determined with a quadrupole mass spectrometer. The system ha d been tested with two different plasma frequencies: 100 and 40 kHz. With t he 100 kHz frequency, the destruction efficiency of WF6, reached an initial value of 98% at a nominal dissipated power of 1200 W. However, the layer o f W deposited on the scrubber electrodes contained hydrates of tungsten oxi des. Moreover the destruction efficiency of WF6, dropped to less than 70% a fter eight consecutively processed wafers ("memory effect"). introducing an intermediate H-2 plasma treatment ensured a continuously high efficiency, and improved significantly the purity of the deposited W layer in the scrub ber. With the 40 kHz power supply, the maximum efficiency reached is more t han 99% from a nominal dissipated power of 1100 W on. The purity of the dep osited W layer is high (>99%). No memory effect was observed. Successful ma rathon runs have been performed with each tested frequency. (C) 2000 The El ectrochemical Society. S0013-4651(99)12-050-0. All rights reserved.