Plasma damage of SiCOH low-k films in an oxygen plasma is studied using a transformer coupled plasma reactor. The concentration of oxygen atoms and O-2(+) ions is varied by using three different conditions: (1) bottom power only, (2) bottom and top power, and (3) top power only. After plasma exposure, the low-k samples are characterized by various experimental techniques. It is shown that the ion bombardment induced by the bottom power minimizes the plasma damage by increasing the recombination coefficient of oxygen radicals. Contrary to the expectations, the densification of the top surface by ion radiation was limited. The increase in the recombination coefficient is mainly provided by modification of the pore wall surface and creation of chemically active sites stimulating the recombination of oxygen atoms. The results show that a reduction in plasma damage can be achieved without sealing of low-k top surface. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3372838]