Strong off-axis illumination at contact hole level is used to improve the process latitude and the imaging contrast. As consequence the circularity of the contact can be affected and its shape can become elliptical. Aim of this work is to investigate the impact of film thickness and resist formulation on the lithographic performances of contact holes when printed by a dipole illumination. Using a commercially available ArF photoresist as a baseline, after the process window, the main focus was on the circularity of the contact hole, which is defined as the CD-ratio between Y- and X-directions as measured by top-down CD-SEM. We observed that a different resist thickness can modify the circularity of the contact hole. Besides, when using a resist formulation with changed absorbing photo acid generator (PAG) we observed a similar effect. We looked further into the impact of the anion size of the PAG and a PAG which combines both different absorbances with different anion size. We continued this study with an investigation of the effects of base quencher loading level, polymer type and solvent.