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

Abstract

The International Technology Roadmap for Semiconductors (ITRS) predicts that by 2010 over one billion transistors will be integrated into one chip [Semiconductor Industry Associations, International Technology Roadmap for Semiconductors, 2004. Available from: < http://pubic.itrs.net/Files/2004UpdateFinal/2004Update.htm >]. The interconnect system of this one billion transistor chip will provide the required high-speed signal and power to transmit each transistor on the chip. This system will deliver high frequency signals to various circuits, and the parasitic effects associated with interconnect will become evident and cannot be ignored. Small parasitic capacitance (C) between interconnect are required to reduce the crosstalk, power consumption, and RC delay associated with the metal interconnect system. Therefore, interconnect with low dielectric constant (k) materials is required. In this study, hydrogen silsesquioxane (HSQ) thin films prepared under various conditions are employed as the intermetal dielectric and the high frequency characteristics of Al-HSQ system are investigated and compared with those of Al-SiO2 system. The S-parameters of the Al 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 Al-HSQ system at high frequencies (100 MHz-20 GHz). It is found that Al interconnect with HSQ films annealed at 400 degrees C has an insertion loss of 1.64 dB/mm, a coupling of -13.3 2 dB at 20 GHz, and a propagation delay of 0.121 ps/mu m, while those of the PECVD SiO2 films are 2.01 dB/mm (insertion loss), -13.40 dB (coupling), and 0.149 ps/mu m (propagation delay). The Al-400 degrees C-annealed-HSQ system has better performance than the Al-SiO2 system does from 100 MHz to 20 GHz. However, specimens with 350 degrees C-annealed HSQ films or plasma-treated HSQ films exhibit larger insertion losses and higher crosstalk noises than those with PECVD SiO2 films do. Both annealing temperature and O-2 plasma treatment of the HSQ films affect the high frequency characteristics of the Al-HSQ system. (c) 2005 Elsevier B.V. All rights reserved.