UV assisted curing of plasma damaged porous ultralow-k material after a k-restore process: Influence of UV-wavelength and curing ambient

Low dielectric constant materials (low-k) are widely used for isolation within the interconnect system to lower RC delay and crosstalk. During plasma processes like ashing, etching and cleaning these films are facing heavy damage effects, which increase their k-value. With k-restoration by silylation silanol groups formed at dangling bonds are substituted by Si(CH3) 3 and Carbon content of the damaged surface near area can be increased. The k-restore process can be combined with an UV-assisted thermal curing step to enhance repair effects. In this study we evaluated two repair chemistries and show by FTlR analysis that besides finding a working restore-solution choosing the right UV wavelength for curing is essential. High energy radiation turned out to be destructive to the material and reverses a successful repair achieved by the restore-liquid by breaking Si-C bonds and generating H-Si-O. Additional the modification of the material's structure by using varied process times and curing ambients has been studied.