Enhanced dielectric-constant reliability of low-k porous organosilicate glass (k = 2.3) for 45-nm-generation Cu interconnects

The mechanism of the dielectric-constant increase in porous organosilicate glasses (OSGs) under electric-field stress has been revealed for the first time, where the dielectric-constant increase is caused by the oxidation of methyl groups in porous OSGs. By optimizing the methyl content, the authors developed a highly reliable, novel low-k porous OSG (k =2.3) with a dielectric-constant lifetime of 10³ years for 45-nm-generation copper interconnects. The newly developed porous OSG was successfully integrated into 240-nm-pitch copper interconnects, where the line-to-line capacitance shows a much longer lifetime than the case of conventional porous OSGs.