Mechanical Enhancement of Low-k Organosilicates by Laser Spike Annealing

Low-k organosilicate films are considered essential for meeting the material needs of interconnect dielectric layers in present and future semiconductor devices. These materials, whether deposited by chemical vapor deposition or spin-on processes, are mechanically inferior as compared to undoped silicate glass or fluorine doped silicate glass. The introduction of porosity to further lower the dielectric constant diminishes the mechanical properties even more. For this reason, post-porosity treatments such as E-beam and UV curing have been explored. In this paper, we describe the use of laser spike annealing (LSA) to achieve similar results. Infrared analysis coupled with Rutherford backscattering, forward recoil, and X-ray photoelectron spectroscopy were used to study the effect of varying laser power and dwell time on the structural changes of both a dense and porous organosilicate, indicating removal of hydrogen and some carbon from the samples. These changes were interpreted in terms of oxidative and bond redistribution transformations. As a result of the structural changes, significant increases in Young's modulus were achieved. Properties such as k, refractive index, film shrinkage, and water contact angle were also correlated with laser power and dwell time. LSA compares favorably with both E-beam and UV curing and three times improvements in modulus without significantly affecting k were observed.