Evaluation of charging damage test structures for ion implantation processes

Control of charging damage is a critical issue in both current and future ion implantation systems. The development of sub-0.18 mu m devices will make control of wafer charging more difficult and more important. In addition, sub-0.18 mu m devices will require novel doping technologies such as ultralow energy ion implanters or plasma doping, PLAD. Here, we examine the efficacy of two, very distinct, charging monitors. They are Varian Research Center's, VRC, antenna-MOS devices, and CHARM-2 devices. Some of the limitations and advantages of each test device are examined. In addition, results from implantations using both PLAD and a traditional beamline system are reported. It is found that the results from the VRC devices are consistent with production results while correlations with CHARM-2 results are less clear. It is shown in this article that these differences are due to the fundamental nature of the CHARM technique combined with how modern ion implanters operate. It is also noted that CHARM is well suited for examining charging damage in steady state processes, but these same concerns for the reliability of predictions based on CHARM-2 data will arise for any ion/plasma process in which the current to the surface undergoes rapid variations. (C) 1999 American Vacuum Society. [S0734-2101(99)09104-6].