X-ray photoelectron spectroscopy investigation of sidewall passivation films formed during gate etch processes

We have used x-ray photoelectron spectroscopy (XPS) to investigate the comp osition of sidewall passivation films formed during the plasma patterning o f 0.1 mum silicon gates in a high density plasma source, as a function of p lasma operating conditions for HBr, Cl-2, and O-2 based chemistry. XPS anal yses clearly show that sidewall passivation films SiXxOy (X = Br, Cl, x + 2 y less than or equal to 4) are formed during the main step of the gate etch process and become oxidized at the early stage of the overetch step leadin g to an oxidelike layer after halogen desorption. Sidewall passivation film s are thicker under HBr based chemistry than under chlorine containing chem istries. In addition, the film thickness seems to be highly sensitive to ox ygen dilution in HBr based plasma. These results are discussed in view of t he critical dimension deviation budget bearable in sub-0.1 mum gate fabrica tion. (C) 2001 American Vacuum Society.