On the Chemical Dry Etching‐Induced Critical Dimension Loss in VLSI Submicron Contact/Via Etching

In this study, we examined the effect of critical dimension (CD) loss as the result of chemical dry etching (CDE) in VLSI submicron contact/via etching. We found that during chemical dry etching of oxide, the top layer of photoresist is fluorinated and, consequently, it etches faster than the un‐fluorinated resist, leading to contact/via CD loss in the subsequent anisotropic etching. Using electron spectroscopy for chemical analysis, in a surface analysis technique, we were able to identify the mechanism of the observed CD loss as the reduction of hydrogen in the resist by fluorine from the plasma. The CD loss is dependent on the extent of the fluorination and the presence of oxygen in the subsequent anisotropic etch process gas chemistry. When a non‐oxygen‐containing gas chemistry in the subsequent anisotropic etching is used, the CD loss can be prevented, regardless of the extent of CDE exposure during the first isotropic etch step.