Reduction of Plasma Induced Damage in an Inductively Coupled Plasma Using Pulsed Source Power

Pulse-time-modulated plasmas have been proposed to overcome charging problems due to electron shading in ULSI patterning. In this paper, we report the effectiveness of pulse-power-modulation of a commercial, inductively coupled plasma system in reducing topography-dependent charging, sensed by the reduction in the shift in the threshold voltages of MOS transistors. This plasma-induced damage during metal etching can be significantly reduced by turning the 13.5 MHz radio frequency (rf) power to the transformer-coupled coil antenna on and off, while maintaining a continuous rf bias power at 13.5 MHz. At an optimum condition of 50 mus on and 50 mus off, the severity of the device damage is reduced to nearly 1/5 that of continuous wave plasma. Thus, the use of pulse-time-modulated plasma is an effective and promising technique for suppressing topography-dependent charging during metal etching in a commercial reactor.