Experimental characterization of an inductively coupled plasma discharge using a shape-adjustable coil

We report the results of experimental studies of an inductively coupled pla sma (ICP) source that employs a shape-adjustable coil to maximize the sourc e's operation window With this novel concept, the plasma density uniformity can be maintained over a wider operation window as the system's parameters , such as gas pressure, chemistry, and chuck RF bias power, are varied, as compared to the conventional fixed coil design. To reduce the uneven shape deformation, which may degrade the plasma's uniformity, the adjustable coil design uses two sets of windings connected in parallel. Experimental measu rements using a 2D RF compensated Langmuir probe show that the radial profi le of the plasma density changes as the coil is deformed. This effect is mo re evident at higher gas pressures where the electron's mean free path beco mes shorter and the distribution of RF power plays a more dominant role in determining the plasma density profile.