Multilayer interconnections

Majid, N. Dabral, S. McDonald, J. F., The parylene aluminum multilayer interconnection system for wafer scale integration and wafer scale hybrid packaging, J. Electron. Mater. 1989, 18, 301 311... 

Copper/Polyimide Thin Film Multilayer Interconnect Structure... 

Figure 15. Packaging structures incorporating thin-jilm multilayer interconnections. (Reproduced with permission from reference 79. Copyright 1988 Materials Research Society.)...

Material Options for Thin-Film Multilayer Interconnections... 

A typical polyimide (BDTA-ODA-MPD) for thin-film multilayer interconnections... 

Thick Film Multilayer Interconnection from Chip Pad to Pins... 

The increase of the density of electronic circuits has been an area of active development over the past several decades. The primary reason for this interest is that the cost of an electronic component is roughly proportional to the total length of wire in the circuit[1]. The dielectric properties of materials used as insulators in multilayer interconnection structures determine the wiring density and total wire length in the finished part. 

Because multilayer interconnecting networks are an important element of advanced chips and parallel processors, it is essential that an understanding of the corrosion processes that affect their reliability be developed. Needed are methods to quantify metal corrosion and ion transport in polymers and means to identify electrochemically reliable metal-polymer systems. 

The prime function of adhesives is to mechanically attach or bond devices, components, heat sinks, wire, connectors, and other parts onto a circuit board or an interconnect substrate. Adhesives are also used as pastes or films to attach lids in sealing cavity packages and as dielectric films in fabricating multilayer interconnect substrates. The most important consideration in obtaining a reliable adhesive bond is the ability of the adhesive to flow and wet the surfaces. For a reliable bond, strong adhesion to both surfaces and strong cohesion within the adhesive are necessary. 

The interconnect section of the IC has similarly seen continuous innovation in feature scaling as well as in materials. Pure aluminum single-layer interconnect was replaced by Cu-doped aluminum multilayer interconnect with tungsten vias, followed by the widespread implementation of damascene Cu metallization in the 1990s. A useful figure of merit for the speed of the interconnect is 1/(RC), where R is the resistance of the interconnect line and C is the capacitance associated with the interconnect. The introduction of Cu metallization improved interconnect speed, since the lower resistivity of copper... 

Bauer, Charles E., and Bold, William A.,Tektronix, Inc., U.S. Patent 4,566,186, Multilayer Interconnect Circuitry Using Photoimageable Dielectric, January 28,1985. 

J. 1. Steinberg, S. J. Horowitz, and R. J. Bacher, Low Temperature Co-Fired Tape Dielectric Material Systems for Multilayer Interconnections, Solid State Electronics, pp. 97-101, January 1986. 

H. S. Hartmann and C. L. Booth, Development of a CrystalUzable, Low-K, Low-Loss, Low Temperature Multilayer Interconnection System, Proc. Int. Microelectronics Conference, May 1990. 

In all but the simplest electronic circuits, it is necessary to have a method for fabricating multilayer interconnection structures to enable all the necessary points to be connected. The thick film technology is limited to three layers for all practical purposes because of yield and planarity considerations, and thin-film multilayer circuits are quite expensive to fabricate. The copper technologies can produce only a single layer because of processing limitations. 

Ceramic-glass composite materials may be used to economically fabricate very complex multilayer interconnection structures. The materials in powder form are mixed with an organic binder, a plasticizer, and a solvent and formed into a slurry by ball or roll milling. The slurry is forced under a doctor blade and dried to form a thin sheet, referred to as green tape or greensheet. Further processing depends on the type of material. There are three basic classes of materials high temperature cofired ceramic (HTCC), low temperature cofired ceramic (LTCC), and aluminum nitride. 

Base Metal Conductors. Copper conductors have gained some acceptance over the past decade because of their relatively low metal cost, low resistivity, good adhesion on AljOj substrates, excellent solder leach resistance, and low migration tendency. Advances in compatible thick film dielectric formulations have resulted in significant use of Cu in multilayer interconnect boards, primarily for military applications. Also, uses of Cu conductor materials have included power hybrid and microwave-related applications. Their applications in more complex systems and networks have been limited by the availability of state-of-the-art nitrogen-firable resistor systems. However, there are additional factors that complicate the widespread usage of this versatile material. 

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