This paper reports the results of a study to integrate a metal-parylene interconnection system. The advantages and issues are highlighted. Fabrication steps for packaging geometries as well as proposed fabrication steps for VLSI applications are discussed. The relevant material properties for interconnection system design have been compiled.

A driving force in the semiconductor industry has been the reduction in feature size to increase the speed and functionality per unit area. As the minimum feature size has been reduced to the submicron regime, the benefit of further reduction of device size will be increasingly offset by the interconnect or resistance capacitance (RC) delay. 1 With the intensified search for ultra-low dielectric-constant materials ( < 2.2), fluorination of polymeric materials is an option to reduce the dielectric constant of hydrocarbon polymers while still retaining a dense dielectric. To be compatible with copper-damascene processing, the low-interlayer dielectric (ILD) must possess a robust interface with copper-diffusion barriers, adhesion layers, or dielectric liners, depending on the back end of the line-metallization scheme. The presence of fluorine in the ILD, however, presents reliability concerns as any fluorine instability might seriously undermine diffusion/adhesion liners and copper wires. The present work investigates the stability of two fluorinated-parylene polymers before and after oxygen reactive-ion etching (RIE) in contact with Al, Al 2 O 3 , and TaN X overlayers. It is important to understand the chemical interaction between the fluorinated ILD and the barrier overlayer because trench formation in Cu-damascene architecture could be undertaken via oxygen RIE of the ILD.With the primary goal to improve adhesion, numerous research papers have devoted attention to the interface between metal films and surfacemodified fluoropolymers. Surface modification has been achieved by low-energy ion beams; 2,3 argon plasma; 4 water-vapor plasma; 5 remote-hydrogen plasma; 6,7 oxygen plasma; 8 filament-assisted watervapor modification; 9,10 strong bases, such as KOH and LiOH; 11,12 solution-borne reducing agents, such as benzoin dianion/DMSO and NaBH 4 ; 13,14 and solvated electrons. 15,16 Further, a book and a review article discuss the surface modification of polymeric surfaces via plasmas. 17,18 However, it is the particular interest here to study how fluorocarbons interact with oxidizing plasmas.There are two components of a typical plasma that can damage or etch a polymeric surface, the The fluorine stability of two parylenes, aliphatic-fluorinated AF-4 (␣, ␣, ␣Ј, ␣Ј poly(p-tetrafluoroxylylene) and aromatic-fluorinated VT-4 (2, 3, 5, 6 poly(p-tetrafluoroxylylene), were investigated underneath Al, Al 2 O 3 , and TaN X overlayers with and without exposure to oxygen reactive-ion etching (RIE). No fluorine diffusion was observed for Al films deposited onto the as-received parylenes. However, after oxygen RIE, x-ray photoelectron spectroscopy (XPS) depth profiling detected fluorine diffusion throughout Al and to a lesser extent Al 2 O 3 but in contrast to Ta 2.67 N. Metal-fluoride bonding was evident at the metal/parylene interface for all the overlayers after the parylene was exposed to oxygen RIE and annealed.

Ion beam analysis techniques have become very useful for characterization of low k materials. Studies on several ion beam analysis techniques will be discussed. Rutherford Backscattering Spectrometry (RBS) provides a very powerful analytical technique for the thickness and porosity measurements on porous Si0 2 films. Nuclear Reaction Analysis (NRA) techniques for hydrogen and fluorine profiling are very useful to characterize fluorinated polymer and fluorinated oxide films. Examples of low k materials including Si02:F, Parylene-AF and Teflon-AF will be discussed. Fluorine diffusion in to metals and various interface effects between metal and low k materials will be presented.

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