Interdiffusions and reactions in Cu/TiN/Ti/thermal SiO₂ and Cu/TiN/Ti/hydrogen silsesquioxane multilayer structures

Interdiffusion and thermal reactions in the Cu/TiN/Ti/thermal SiO₂ and Cu/TiN/Ti/hydrogen silsesquioxane (HSQ) multilayer structures on silicon wafers, as-deposited and after annealing in vacuum at 400-800°C, have been investigated by using sheet resistance measurement, scanning electron microscopy, glancing incident angle X-ray diffraction (GIAXRD), and Auger electron spectroscopy. The sheet resistance values of both systems decreased after annealing up to 600°C and began to increase after annealing at 700°C. The decrease in sheet resistance occurred in conjunction with grain growth of the copper films, while the increase of sheet resistance was related with oxygen incorporation into the TiN-Ti layers. After annealing at 800°C, the surfaces of both systems consisted of Cu-color area and gray dots. Microvoids were seen on the Cu-color areas of both systems. Both microvoids and gray dots existed in greater number and larger sizes for the HSQ sample, and GIAXRD revealed the existence of Cu₃Si phase in the 800°C annealed HSQ sample. The interdiffusion and reaction characteristics of the two multilayer structures upon vacuum annealing are discussed.