Mary Kathryn Haas

Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing

Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size.

Porous low k structural design to meet next generation interconnect needs

As porous low k films are integrated for 45nm/32nm and extend into 22nm/16nm technology nodes, there is a need for more rigorous structural design of porous low k films to meet the integration challenges. This paper demonstrates the ability to tune porous low k films and discusses the impact of these choices to subsequent integration steps such as etch, ash and wet clean processes. Balancing carbon content in the film to minimize damage needs to be coupled with improving mechanical properties for packaging compatibility. By tuning the porous low k deposition process, these properties can be balanced.