Downstream characterization of 20-cm diameter 915MHz/2.45 GHz multipolar electron-cyclotron-resonant plasma source

Among different types of commercially available electron cyclotron resonant (ECR) microwave plasma sources, the microwave plasma disk reactor (MPDR) is a compact and easy to operate plasma source. It consists of a ring of permanent rare-earth magnets surrounding a quartz disk discharge volume. These rare-earth magnets create multipolar, ECR zones inside the discharge volume which provide the mechanism and region for efficient microwave energy coupling at low pressures. Depending on the application, the diameter of the plasma disk can vary from 5-cm to 25-cm. Disk sizes of 20-cm or above are ideal plasma sources for single 5 to 8-inch wafer processing, especially ULSI fabrication because of its lower ion energy and high plasma density. The experimental evaluation of two MPDR designs i.e., a 20 cm MPDR excited with 915 MHz and a 25 cm MPDR excited with 2.45 GHs, is presented. Single and double Langmuir probes and a multi-grid energy analyzer are employed to measure properties of argon gas discharges. In particular electron and ion densities, average electron energies, electron and ion energy distributions, etc. are measured as a function of position in the plasma processing region of the discharge. Measurements are performed over a range of experimental variables: (1) input power 150W-800W, (2) pressure 0.4mT-2mT, and (3) flow rates 15-50 sccm. The measured performance of the two large ECR reactors will be compared with each other and smaller ECR discharges.