The limitation of the use of HF-based chemistry for the cleaning of submicron high aspect ratio features is discussed. In this paper we describe the post-dry-etch cleaning of contact holes on TiSi2. This cleaning process is a combination of the use of oxidizing agents to remove residues consisting of fluorinated polymers and titanium fluorides. and HF-last cleaning to remove SiO2 on TiSi2. The HF-last cleaning is necessary to reduce the contact resistance. Two issues are pointed out : a very narrow process window for the KF etch time, and a strong hole size dependence of the contact resistance. These issues are not seen when soft sputter etching is used instead of HF-last cleaning. Concerning the narrow process window, the contact resistance decreases with increasing HF treatment time but increases again after passing through a minimum value. The kinetic study of TiSi2 etching shows that a preferential etching of the C49 phase takes place during an HF treatment. As a result, the TiSi2 surface becomes porous, which is thought to decrease the contact area. The hole size dependence is discussed in view of transport of chemical species in the contact hole. It is shown that the size dependence can be explained by assuming an abnormally small diffusion coefficient. HF-SiO2 chemistry at the sidewall surface of narrow hydrophilic features can explain this abnormally small diffusivity.