SURFACE MODIFICATION OF POSITIVE PHOTORESIST MASK DURING REACTIVE ION ETCHING OF SI AND W IN SF6 PLASMA

This paper reports the results of a preliminary study concerning the surface modification of a diazoquinone-novolak photoresist (HPR 204)1 during reactive ion etching of Si and W in SF6 plasmas. X-ray photoelectron spectroscopy analyses provide the following information: the C1s spectrum reveals various bonding states of carbon with fluorine such as CF3, CF2, and CF which proves the fluorination of the carbon network. The existence of CO-CF(x) and C-CF(x) species is also most probable. A loss in the oxygen content is the main degradation observed. Sulfur residues are present and discussed in relation to the nature of the cathode material. In the case of a W cathode, the identification of tungsten fluorides on the photoresist surface is correlated with the etching of the cathode. Ion bombardment-induced effects are investigated, in particular concerning the presence of metallic tungsten sputtered from the cathode.