Hongqing Shan

Magnetic field optimization in a dielectric magnetically enhanced reactive ion etch reactor to produce an instantaneously uniform plasma

The effect of magnetic field on plasma uniformity was investigated for a capacitively coupled plasma in a dielectric etch chamber and a tool to measure the dc bias uniformity across the high-powered cathode (e.g., 1200 W) was developed. At that power, the dc bias can be as high as 1500 V at 50 mT. A 5% variation in the dc bias across the cathode corresponds to a 75 V potential drop across the wafer, which may in turn cause degradation or breakdown of gate oxide structures. Therefore control of the instantaneous plasma uniformity is important to minimize device damage. The primary effect of the magnetic field on instantaneous plasma uniformity is through the E×B drift force which, because of the strong electric field at the cathode surface at high powers, dominates the other magnetic field effects on the plasma. dc bias measurements show that the plasma nonuniformity can be optimized by adjusting the gradient of the magnetic field, and thus the E×B drift force, across the cathode over a wide range of magne...