The minimum laser fluences required to planarize interlevel vias in a two‐metal‐level test structure have been measured as a function of via size and sample temperature. Generally, the minimum fluence required increases as the via size increases, resulting in larger operating process windows for smaller vias. Under some circumstances, however, the planarization dynamics may be dominated by features associated with groups of vias. While required fluences for planarization and sample damage both decrease as the sample temperature increases, the relative insensitivity of the damage threshold generally results in larger process windows at higher temperatures.