Real-time monitoring of charge accumulation during pulse-time-modulated plasma

The authors investigated real-time monitoring of charge accumulation during pulse-time-modulated plasma processes by using their developed on-wafer monitoring chip. The charge accumulation potential between the top surface and the bottom in a SiO2 contact structure was measured during pulse-time-modulated plasma exposure with an on-wafer monitoring device. In conventional plasma with rf bias, the electron shading effect could be clearly observed as the potential difference between the wafer surface and the contact-hole bottom. Conversely, the accumulated charge in the pulse-time-modulated operation was drastically decreased. Time-resolved electron and ion flows to the SiO2 contact hole were clarified by the on-wafer monitoring. Accordingly, it was confirmed that the on-wafer monitoring is a very effective tool for investigating the local charge accumulation in actual device structures