Measuring vacuum ultraviolet radiation-induced damage

Abstract

During plasma processing of semiconductors, ultraviolet (UV) and vacuum ultraviolet (VUV) radiation are present, but their effects can be difficult to separate from those due to charged particles incident on the wafer. The contribution of VUV photon irradiation to gate-oxide damage, and damage to dielectric materials in general, was examined using two measurement techniques that can predict the possibility of damage. They are (1) surface potential measurements and (2) electrically erasable read-only memory transistors (CHARM-2 wafers). To isolate the radiation effects, unpatterned oxide-coated wafers and CHARM-2 wafers were exposed to VUV synchrotron radiation. VUV exposure of dielectrics and conductors results in an accumulation of positive charge due to photoemission. As a result, it can become difficult to distinguish the photoemitted from the plasma-deposited charge. In addition, it was determined that the UV monitors on CHARM-2 wafers did not respond to VUV radiation.