Nonuniformities isolated

U. Landau, R. T. Galasco, and J. Tang, Current Distribution in Pattern Plating of Nonuniformly Spaced and Isolated Lines, Extended Abstracts of the 174th Meeting of the Electrochemical Society, 88-2, No. Abstract No. 330, 484-485, The Electrochemical Society Inc., Pennington, NJ (1988). 

In this section, three example applications intimately related to the pattern dependent behavior of CMP are briefly discussed. First, we note the relative importance of die-level effects with respect to typical wafer-scale nonuniformity. Second, we describe recent application of the integrated density and step height model to the run by run control of ILD CMP. Finally, we summarize issues in the application of density models to prediction of shallow trench isolation. 

The diffusion boundary layer of any given drop in chain interacts with the diffusion wake of the previous drop (located upstream). The concentration field in it is substantially nonuniform and is depleted because of the absorption of the solute at the surfaces of all preceding drops. By virtue of such interaction, the inner mass exchange will be appreciably retarded (the shielding phenomenon) compared with the case of isolated drops. 

At this point you might ask how S can achieve a maximum value if U and V are fixed, since the specification of any two intensive variables completely fi.xes the values of all others. The answer to this question was given in Chapter 4, where it was pointed out that the specification of two intensive variables fixes the values of all other state variables in the uniform equilibrium state of a single-component, single-phase system. Thus, the equilibrium criterion of Eq. 7.1-5 can be used for identifying the final equilibrium state in a closed, isolated system that is initially nonuniform, or in which several phases or components are present. 

Results from these and other laboratories indicate that coke is ubiquitous on any metal surface (that has not been recently atomically cleaned). At low coverages, i.e., less than half a monolayer, coke exists as isolated 2-dimensional islands. As the coverage increases, these islands may coalesce into nonuniform graphitic clumps. Even at monolayer coverages of C, the adsorption of, say, benzene is noticeable. This is in contrast to the behavior (described below) when sulfur is adsorbed very small coverages of sulfur may render the surface incapable of adsorption, probably because the sulfur is uniformly distributed while C is present in 3-dimensional clumps. Clearly, qualitatively different selectivities are to be expected during the deactivation by coke and by poisons. 

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