Contact hole distortion in dielectric etching was investigated and it is found that the contact hole distortion is mainly caused by low mask selectivity, poor mask surface control (roughness, striation, pitting or pin hole) before and after etching. The surface roughness and mask selectivity have been studied to overcome the problem of pattern deformation of photoresist (PR) and C-rich materials as the mask. By using the polymer deposition process (PDP), the mask degradation is improved and the contact profile is well controlled. This paper focuses on the discussion of PDP chemistry selection, PDP time decision, and PDP used at before or after BARC (bottom anti-reflective coating) open step