Instability of Metal Barrier with Porous Methyl Silsesquioxane Films

Abstract

Integration of porous ultralow-dielectrics into advanced copper interconnect scheme has been a challenge. Among other issues, metal diffusion/drift into interconnected pores consequently leading to the degradation of dielectrics is a concern. In the present work, the electrical stability of the metal-insulator-semiconductor ͑MIS͒ capacitors with various metal electrodes on porous methyl silsesquioxane ͑MSQ͒ on thermal oxide/n-type silicon was investigated. Our results suggest that the tendency of various metal, Pt Ͻ Cu Ͻ Ru Ͻ Ta Ͻ Al, drift into porous MSQ under bias-temperature stress ͑BTS͒ corresponds to the order of metal oxidation tendency at the interface. It is noted that the metal barrier materials such as Ta and Ru perform worse than Cu itself. This behavior is similar to metal drift in organosiloxane polymer reported earlier ͓Appl. Phys. Lett., 79, 1855 ͑2001͔͒. Furthermore, as-prepared MIS capacitors with Cu electrodes show stable capacitance-voltage characteristics under a moderate BTS of 150°C and 0.5 MV/cm. Under the same BTS, a deterioration of the MIS capacitors with increasing exposure time in air is observed. The electrical stability is fully restored after being annealed at an elevated temperature of 350°C in a reducing ambient. The degradation of the MIS capacitors over time is attributed to the permeation of oxygen and moisture through interconnected pores, which consequently facilitate the formation of interfacial Cu oxide. The electrical stability of MIS capacitors with Ta electrodes however does not exhibit improvement by such annealing because of their greater heat of oxide formation. The MIS capacitors with Al electrodes on N 2 O-plasma treated porous MSQ show less metal drift than Al on porous MSQ, suggesting that the intrinsic property of metal oxide determines whether the oxygen contained in the dielectrics assists or inhibits the metal-related activities.Continuous device shrinkage beyond the 90 nm node results in interconnect delay becoming increasingly important in limiting the performance of integrated circuits ͑ICs͒. Industry has shifted to copper instead of conventionally used aluminum as the interconnect metal because copper has better conductivity and is less susceptible to electromigration. However, to significantly increase the performance of the future generation devices, copper needs to be integrated with ultralow-dielectrics ͑ Ͻ 2.5͒. 1 The shift of interlayer dielectric has been from silicon oxide ͑ = 4͒ to low-dielectrics ͑ Ͻ 3͒ and is proposed to go finally to ultralow-materials ͑ Ͻ 2.5͒. Each generation of dielectric materials has different characteristics thus creating various challenges associated with IC fabrication and device reliability. Ultralow-dielectrics are generally porous and scalable, i.e., their value can be reduced by increasing the porosity without changing the material. 2 Though, some issues can be addressed by the use of the ultralowdielectrics, these materials introduce their own set of challenges. Molecules, atoms, and ions placed anywhere within th...

In Situ XPS Chemical Analysis of MnSiO3 Copper Diffusion Barrier Layer Formation and Simultaneous Fabrication of Metal Oxide Semiconductor Electrical Test MOS Structures

“…In contrast, for the Cu/MnSiO 3 /SiO 2 sample, there are no measurable changes in the CV profile following the atmosphere anneal at 300 °C. Previous reports have suggested that excess metallic Mn resulting from the incomplete conversion of Mn into MnSiO 3 could diffuse through the deposited Cu film to the surface, resulting in the formation of Mn oxide layer thereby preventing Cu oxidation and hence inhibiting Cu diffusion into the dielectric. − Thus, in order to ascertain whether the MnSiO 3 barrier at the metal/SiO 2 interface or a surface localized Mn oxide is responsible for the stability of the MnSiO 3 sample, XPS measurements of both samples were performed to determine the surface chemical composition post atmosphere ambient anneal. The survey spectra for both samples, shown in Figure a, reveal that the only elements present in the top surface of the samples are copper, oxygen and traces of adventitious carbon, within XPS detection limits.…”

Preparation of a Preplated Bismuth Film on Pt Electrode and its Application for Determination of Trace Aluminum(III) by Adsorptive Stripping Voltammetry

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Thermal Stability Study of Pore Sealing Using Parylene N

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