Semiconductors electromigration

Electrical Properties. Generally, deposited thin films have an electrical resistivity that is higher than that of the bulk material. This is often the result of the lower density and high surface-to-volume ratio in the film. In semiconductor films, the electron mobiHty and lifetime can be affected by the point defect concentration, which also affects electromigration. These effects are eliminated by depositing the film at low rates, high temperatures, and under very controUed conditions, such as are found in molecular beam epitaxy and vapor-phase epitaxy. 

Figure 9. The electric fields and directions of positive ion electromigration in the near-surface region of both n- and p-type semiconductors under anodic and cathodic...

Copper is going to replace aluminum as the material of choice for semiconductor interconnects due to its low electrical resistance and high electromigration resistance (1-4). An inlaid interconnect is used for copper metallization in which the insulating dielectric material is deposited first, trenches and vias are formed by patterning and selective dielectric etching, and then diffusion barrier and copper seed layer are deposited into the trenches and vias (5). 

This paper describes the application of three fundamental conservation laws for continuous media, to three aspects of semiconductor technology device modeling, electromigration, and laser annealing. 

The frequency dependence of for sinusoidal excitation was studied by Haberland, Karmann and Repp (1970). An example is shown in Figure 6.6 (Sieja (1966)). At high frequencies drops because of the finite recovery time tj discussed in a later section. The low frequency and d. c. region is at the present time accessible only for switches which have carbon electrodes and whose amorphous semiconductor films are free of loose ions which would be able to electromigrate. The failure to assure this made earlier switches d. c. unstable. 

In a recent work, Calo et al. exploited the electromigration upon dewetting to fabricate ultrathin and highly oriented films of a discotic liquid crystal [DLC] semiconductor (Fig. 14.14). They show... 

It is also suggested that the electrodes could be the main source of fluctuations. An obvious first step is to relinquish Au - a material non grata in semiconductor fabrication - and use less diffusive metals such as Pt, Pd, Ti or Cr. Well-defined small gaps are, however, more difficult to achieve in these materials and involve challenging fabrication methods, such as electromigration [45]. 

A1 alloys often contain some percents of Cu. Vapor-deposited films of this composition range have been used in the semiconductor industry for conductive connections in integrated circuits. The Cu content is used to reduce electromigration, which leads to failure of the metallic connections. Cu can cause corrosion problems on a small scale. Electrolyte residues together with moisture and voltage supply of 5-18V may lead to corrosion phenomena. Cu-rich inclusions are widely known to be detrimental to the corrosion resistance of A1 alloys used in the ship building and airplane industry. 

In the sputter deposition of aluminum conductor materials for semiconductor devices, it has been shown that a small partial pressure of nitrogen during sputter deposition can have an effect on the electromigration properties of the deposited aluminum film. In the case of reactive deposition, the residual gas partial pressure is high and has a major effect on the surface mobility and the development of columnar morphologies, even at high deposition temperatures. 

Lattice defects in the film can affect the electrical conductivity and electromigration in metallic films, and carrier mobility and lifetime in semiconductor materials. Generally high defect concentrations result in poor electromigration properties. Lattice defects have been shown to be important to the properties of the high transition temperature superconductor films. 

Adhesion to semiconductor materials generally requires a high nucleation density and the formation of a diffusion or compound type of interface. Often the system has a requirement for a low electrical contact resistance and good resistance to electromigration in addition to good adhesion, This can often be accomplished using a layered structure. 

Electromigration (semiconductor) The movement of atoms in a metallic conductor stripe under high current conditions (>10 A/cm in aluminum). 

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