Mitigation of accumulated electric charge by deposited fluorocarbon film during SiO2 etching

SiO2 contact-hole etching with a high-aspect ratio is a key process in fabricating ultra-large scale integrated devices. However, charge accumulation in contact holes during plasma etching causes serious problems, such as charge-build-up damage, etching-stop, and microloading effects. Therefore, understanding the mechanism behind this electric charge accumulation and controlling the plasma etching processes would be very important to achieve the next-generation semiconductor devices. We found, through our previous research, that deposited fluorocarbon film in contact holes had high electric conductivity because of ion bombardment. In this experiment, we investigated the build up of charging potential during plasma processes by in situ on-wafer monitoring to control charge accumulation in the contact holes. We developed an on-wafer monitoring device to measure the charging potential in SiO2 contact holes (aspect ratio=5.7). The dc potential of the SiO2 contact hole top and bottom surfaces were measured during plasma exposure with/without deposited fluorocarbon film in the holes. The results revealed that the sidewall deposited fluorocarbon film has high electric conductivity that may mitigate electric charge accumulation at the bottom of contact holes during SiO2 etching processes