Mechanism of the Reduction of Electron Shading Charge Build-up Using Pulsed Plasma

The effect of reduction of the electron shading charge buildup using pulsed microwave plasma was evaluated. The gate oxide voltage due to the electron shading effect was measured directly using a charging current measurement electrode on which a Si chip with a line-and-space (L&S)-patterned photoresist was mounted. The ratio of the electron saturation current to the ion saturation current (Ies/Iis ratio) in the open area and in the L&S area were also measured. In continuous wave (CW) plasma, the Ies/Iis ratio in the open area was larger than that in the L&S area, which causes the electron shading charge buildup. In pulsed plasma, the Ies/Iis ratio in the open area is equal that in the L&S area during the off-time period. This is the mechanism of the reduction of the electron shading effect by using pulsed plasma.