Direction of topography dependent damage current during plasma etching

We have studied the electron shading or topographical effects on charging damage by measuring the damage current directly using newly developed probes set on the wafer surface. By using the probe to model the end point of metal etching with high-aspect-ratio patterns, positive current flowing from the antenna to the substrate was observed. On the contrary, with the second probe for overetching of low-aspect-ratio patterns, negative current flowed from the antenna to the substrate. The negative damage current and charging voltage for the second probe increased with increasing space width and electron temperature. These results explain the recently reported complex phenomena in device damage measurement and give more insight into electron shading effects