Influence of Oxide Hard Mask on Profiles of Sub-100 Nm Si and Sige Gates

Oxide hard mask was found to have a profound effect on sub-100 nm Si and SiGe gates profiles. The gates patterned with hard mask only (photoresist is stripped after hard mask patterning) exhibit considerable profile distortion. It has been found that the distortion is caused by the ions deflection due to the charge accumulation on the hard mask. The distortion can be avoided by using either a thinner (15 nm–20 nm) hard mask (that accumulates less charges) or by increasing the ion energy, using higher (above 150 W) bias power (ions impinging the surface with higher speed are less likely to be deflected).