S-parameters-based high speed signal characterization of Al and Cu interconnect on low-k hydrogen silsesquioxane-Si substrate

In this study, hydrogen silsesquioxane (HSQ) thin films are employed as the intermetal dielectric, and the high frequency characteristics of Al-HSQ and Cu/Ta-HSQ system are investigated and compared with those of Al-SiO₂ system. The S-parameters of the interconnect are measured for insertion loss and crosstalk noise. The interconnect transmission parameters are extracted from the S-parameters. A figure of merit (FOM) is employed to evaluate the characteristics of the interconnect system at high frequencies (100 MHz ~ 20 GHz). It is found that the insertion losses are 2.01 dB/mm, and 1.50 dB/mm, 2.73 dB/mm, 2.44 dB/mm, and 1.66 dB/mm at 10 GHz, and 2.16 dB/mm, 1.64 dB/mm, 3.08 dB/mm, 2.62 dB/mm, and 1.82 dB/mm at 20 GHz for Al-SiO₂, Al-HSQ, Al-HSQ (O₂ plasma), Cu/Ta-HSQ, and Cu/Ta-HSQ (NH₃ plasma), respectively. The Al/HSQ system has better performance than the other ones do from 100 MHz to 20 GHz. The high frequency characteristics of Al and Cu interconnect with HSQ dielectrics are discussed.