Thin film interaction between low-k dielectric hydrogen silsesquioxane (HSQ) and Ti barrier layer

The interaction between low-k dielectric hydrogen silsesquioxane (HSQ) and Ti barrier layer has been studied using four-point-probe sheet resistance m easurement, X-ray diffraction, conventional Rutherford backscattering spect rometry (RBS), nuclear resonance analysis (NRA), elastic recoil detection ( ERD), secondary ion mass spectrometry (SIMS), Auger electron spectroscopy ( AES) and thermal desorption spectroscopy (TDS). The conventional intermetal dielectrics SiO2 and plasma-enhanced tetraethylorthosilicate (PETEOS) have been studied also for the purpose of comparison with HSQ. In the low tempe rature regime (300-550 degrees C), a considerable amount of oxygen atoms, f rom various sources, diffuses into Ti film to form a Ti(O) solid solution, raising the resistivity of Ti significantly and causing the expansion of th e Ti lattice. A good correlation between the oxygen composition in the Ti f ilm, the sheet resistance variation of Ti and the chance of Ti lattice para meter Cu have been observed. Ar the same temperature, there are more oxygen atoms incorporated into the Ti film in Ti/HSQ than those for Ti/PETEOS, su ggesting that additional HSQ-related oxygen sources, such as the moisture u ptake and the conversion reaction of HSQ, may be attributed to this. In the high temperature regime (550-700 degrees C), HSQ reacts with Ti to form a final TiO/Ti5Si3/HSQ stack structure. It is assumed that a few competing re actions occur in this regime. At 550-650 degrees C, HSQ reacts directly wit h Ti; in the meantime, part of HSQ undergoes conversion reactions, with the reaction products SiO2 and SiH4 reacting with Ti to form Ti silicide. At 6 50-700 degrees C, HSQ is almost completely converted into SiO2, so the domi nant mechanism is Ti reaction with SiO2, Before HSQ is completely turned in to SiO2, the Ti/HSQ system is more reactive than both Ti/PETEOS and Ti/SiO2 . The initiating temperature for the Ti/HSQ reaction exhibits no obvious Ti thickness dependence. (C) 2000 Elsevier Science S.A. All rights reserved.