Dielectric spectroscopy was used to probe the relaxation dynamics of dilute and semidilute polyisoprene solutions in a moderately good solvent. The concentration dependences of both the terminal relaxation time and the dielectric spectrum exhibit universality over a wide range of molecular weights. The terminal relaxation time in the limit of infinite dilution scales with [ ] and is consistent with partially draining Rouse-Zimm behavior. Terminal times are exponential in concentration tx/t\ = exp(cA), where the concentration scaling parameter A has a somewhat different molecular weight dependence than intrinsic viscosity [jj]. The terminal times show no transition in behavior with increasing concentration that would indicate the onset of entanglement. The spectrum of relaxation times appears to be a universal function of cA or c[t;]. At low concentrations, c[rj] < 1, the spectrum is consistent with Rouse-Zimm theory. At higher concentrations (up to c[ij] = 8), loss peaks are much broader than the Rouse-Zimm prediction and, along with coil dimensions, become comparable to those seen in the melt for both entangled and unentangled polyisoprenes. Both the shape of the dielectric loss peaks and the dependence of characteristic concentration on molecular weight suggest that relaxation dynamics are controlled by the degree of overlap between polymer chains but not by intermolecular hydrodynamic interactions or by entanglements as they are usually defined.

Scaling analysis and finite element modeling of the governing transport equations are used to show that in the submicron features of damascene ultralarge scale integrated interconnect structures, diffusion of cupric ion and trace additives is the only transport process that affects plating uniformity. Potential variations in solution or in the metal film, while important on wafer (dm) length scales, are completely negligible on feature (m) length scales. Convection is also unimportant in submicron features. As a result, changes in process parameters such as fluid flow rate, barrier film conductivity or thickness, or solution conductivity are unlikely to result in significant changes in plating uniformity or void formation inside trenches and vias. On the other hand, changes in plating current density, feature geometry, or additive concentration in the plating bath will have a large impact on filling profiles. The impact of diffusive limitations on feature filling is described by a dimensionless parameter D . Low values of D indicate that for typical damascene structures and plating conditions, cupric ion depletion is only on the order of a few percent, indicating that copper plating is essentially conformal. Only very deep or high-aspect features will pinch off as a result of cupric ion depletion. For additives that are depleted at the metal surface, values of D can be large, indicating the potential for substantial additive depletion inside trenches and vias. D scales with L 2 /w. As a result, deeper features (larger L) plate less uniformly, as do more narrow features (smaller w). However, if aspect ratios (L /w) are held constant as critical dimensions decrease, beneficial effects of additive depletion will diminish in future device generations.

The relentless miniaturization of integrated circuit (IC) feature sizes has pushed mainstay aluminum alloy interconnects into a regime where electromigration failure and interconnect resistance-capacitance (RC) delays are becoming significant concerns. Primarily for these reasons, as well as potential cost and yield benefits of a copper/damascene process, efforts to develop copper interconnect capability have accelerated dramatically in recent years. Integrated circuits containing copper interconnects are now being manufactured, 1 and will be widely employed in the 180 nm technology generation. 2 Most current development work focuses on electroplating as the primary means for depositing copper films onto patterned dielectrics. 2 While this work can successfully draw on decades of industrial experience with copper deposition onto printed wiring boards (PWBs), there are factors that make IC metallization fundamentally different from PWB metallization. First, the wafers entering the plating process are several orders of magnitude more valuable than are circuit boards. This means that the equipment required to minimize yield loss due to handling errors, wafer contamination, or process variations is very expensive, and that the number of process steps should be kept low. Second, copper contamination can destroy the functionality of silicon devices. This means, among other things, that conductive barrier films must be used to keep copper from diffusing into either the dielectric or the device contacts. Finally, there are large differences in length scales, making the phenomena that control plating uniformity very different. For example, IC linewidths and via diameters are several hundred times smaller than PWB through-hole diameters. As a consequence, metal film thicknesses are at least 20 times smaller in ICs than they are in PWBs, making film resistance an important contributor to plated film thickness nonuniformity.A drawback to electrolytic Cu deposition on insulators is that a conductive layer, generally copper, must be deposited first by nonelectrochemical means to allow electronic current to be carried to all surfaces where plating is desired. This layer is usually deposited by electroless deposition, or by sputtering for semiconductor applications. The sputtered copper films provide good blanket coverage, but sometimes offer poor sidewall coverage of high-aspect trenches and vias. However, in semiconductor applications there is an alternative to sputtering. Because of the extreme sensitivity of silicon devices to copper contamination, a barrier film such as Ta or TaN is required to encapsulate the copper conductors. Since barrier films are somewhat conductive, it may be possible to eliminate the extra step of depositing a conduction layer by plating directly onto the barrier film.High sheet resistance is a major obstacle to electroplating onto barrier films. The films are less conductive than copper, and are very thin, typically about 500 Å thick. Under conventional plating conditions, extreme potential variati...

ABSTRACT:An alkali-hydrolysable surfactant,(1-tetradecyloxycarbonylmethyl)trimethylammonium chloride, was used as an emulsifier for emulsion polymerization of styrene in water. The polymerization yielded a high molecular-weight polymer almost quantitatively. Addition of a small amount of NaOH to the resulting latex solution precipitated the polymer immediately. Analysis of the centrifuged solid indicated almost perfection of both recovery of the polymer and removal of surface-active species from it. Minimization of ionic species in the polymer solid was confirmed by a high contact angle of the polymer film with water.

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