The characteristics of a low pressure inductively-coupled plasma (ICP) source which employs a novel coil design to maximize the source's operation window will be described. A uniform plasma density over an area larger than the wafer size is one of the most important requirements for the plasma sources used in ULSI processing tools. By making the coil deformable, the plasma density uniformity can be maintained over a wider operation window as system's parameters, such as gas chemistry, gas pressure, and chuck RF bias power, are varied to meet different process requirements, as compared to the ICP sources based on conventional fixed coil design. The other feature of the new coil design is that it has two sets of winding connected in parallel but 180 degrees opposite azymuthally. This arrangement in principle provides a better azymuthal symmetry than the conventional single winding planar coil. The system was characterized with several plasma diagnostic tools: a 2D RF-compensated Langmuir probe, a B-Dot probe, a heterodyne interferometer and spectroscopy/imaging of plasma-induced emissions. A wafer-type grided ion energy analyzer has also been developed to measure ion energy distribuition at different locations on the wafer. Experimental results show that the radial profile of plasma density changes as the coil is deformed. The effect is more pronounced at higher gas pressures where electron's mean free path becomes shorter and the plasma density profile is basically determined by the distribution of RF power deposition. The detailed experimental results will be presented.