A methodology is introduced to investigate the effects of ion and photon fluences on dielectrics during plasma exposure. Ion and photon fluences were separated using a capillary-array window. The fluences can be varied separately by varying the plasma parameters. Most of the charge accumulation came from the ion fluence, while the photon fluence introduced most of the defect-state modifications. It was further shown that during plasma exposure, UV photons can penetrate through the dielectric layer and cause modifications of the defect states. Based on the results, optimized conditions were found to minimize both the charge accumulation and the defect-state formation during plasma exposure. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3524403] All rights reserved.