THE ROLE OF RESIST FOR ULTRATHIN GATE OXIDE DEGRADATION DURING O-2 PLASMA ASHING

During ashing process, resist has been intuitively regarded as a prote ction layer and deliberately removed in previous studies by wet proces s prior to plasma exposure in an effort to amplify the damage effect, Recently, we found instead that resist does not simply act as a protec tion layer, This newly observed phenomenon cannot be explained by the well-known electron shading effect which should not affect the area-in tensive antenna structure used in our study, In this letter, we hypoth esize that this resist-related charging damage is determined by the pl asma potential adjustment difference between those devices with and wi thout resist overlayer, The experimental results show a good correlati on with our explanation, To be specific, severe antenna area ratio (AR R) dependent degradation of thin gate oxide is induced during the init ial ashing stage while the resist is still on the electrodes, not duri ng the overashing period.