Characterization and integration of silver metallization and low-dielectric-constant materials

A model of silver grain growth and texture evolution in Ag/Ti/SiO ₂ scheme has been presented. Low resistivity of the silver films is still maintained after the encapsulation due to a negligible amount of residual titanium in the silver. A residual tensile stress of ∼320 MPa in the film plane is determined in the encapsulated thin silver film.; Good etch effect has been achieved by conducting reactive ion etching in 50-watt-powered oxygen plasma for 5 min to fabricate 10-μm-linewidth silver patterns. The etch mechanism is that silver oxidizes in oxygen plasma and silver oxides exfoliate layer by layer due to the strain-induced cracking caused by the volume expansion of oxides. By performing encapsulation anneal, a thin TiN(O) layer forms on the surface of silver patterns, and a Ti(O)/Ti ₅Si₃ stack structure is produced at the initial Ti/SiO ₂ interface due to the interfacial reaction. The electromigration failure of bare silver lines is dominated by the surface atomic diffusion. After the encapsulation, the electromigration lifetime of silver lines is improved by at least one order of magnitude due to the inhibition of the surface diffusion by TiN(O) layer.; An ion-beam technique has been applied to characterize low-dielectric-constant (k) dielectric hydrogen silsesquioxane (HSQ). The interactions between HSQ and a variety of diffusion barriers (Ti, TiN, Ta, TaN, and W ₂N) used for the integration of HSQ have been investigated by various techniques. It is shown that Ti, Ta, chemical vapor deposited (CVD) TiN, and CVD W₂N are better barriers to maintain the integrity of HSQ than physical vapor deposited (PVD) TaN and PVD TiN. A “nitride effect” mechanism has been proposed to account for this finding. Of all barrier/HSQ systems investigated in this work, Ti/HSQ is the only reactive system. In the low temperature regime (300–550°C), oxygen atoms originating from various sources are dissolved into the titanium film to form a Ti(O) solid solution. Good correlation has been established between the oxygen composition, sheet resistance, and lattice constant C₀ of titanium films. For the high temperature regime (550–700°C), a final TiO/Ti₅Si ₃/HSQ stack structure forms due to the reaction of HSQ with titanium. This is assumed to proceed through two competing modes: a direct reaction of HSQ with titanium, and HSQ decomposition into SiO₂ with a subsequent reaction of SiO₂ with titanium. Due to the difference in stoichiometry, HSQ is more reactive with titanium than SiO₂. A model has been developed to describe the thickness dependence of the sheet resistance of annealed Ti/dielectric structures. The simulations generated by this model agree well with the experimental observations. (Abstract shortened by UMI.)...