Ui-Hyoung Lee

In situ observation of the grain growth of the copper electrodeposits for ultralarge scale integration

The grain growth which occurs during the self-annealing in copper electrodeposits was investigated by in situ observation with an electron backscattered diffraction technique. From these observations, it was found that a newly created twin was initiated on the front interface of growing twin and that the transverse direction for the growth was ⟨110⟩. Most of the twins had the Σ3 twin boundary of {111}⟨110⟩. The formation of the twin and its peculiar growth direction could be explained quite well based on the hypothesis that the growth front interface is one of the {111} planes.

A Study of Copper Electroplating of the Submicrometer Scale Patterns

The effect of an accelerator on the morphological evolution during copper electrodeposition was investigated with the designed one-directional (1-D) pattern which has a seed layer only at the bottom of the pattern. Field-emission scanning electron microscope images showed that there was no superfilling found in the pattern with 0.2 μm width trench and no reduction in the surface area during electroplating. This indicates that superfilling in a damascene pattern results from the accumulation of the accelerator. It was found that copper damascene electroplating for ultralarge-scale integration is a simple electroplating system that is controlled by the activation overpotential of adhered organic additives, not by the concentration overpotential of copper ions.

Microstructure and Pattern Size Dependence of Copper Corrosion in Submicron-Scale Features

The effects of grain size and pattern geometry on the etching rate were investigated by using our invented pattern, and each pattern has a same height of electrodeposits regardless of pattern size after electroplating. It was found out that the logarithmic value of the etching rate is inversely linear with the pattern width at self-annealed specimen. In other words, as the pattern width decreases, the etching rate increases exponentially. Such tendency of the etching rate is owing to the result that the interfacial energies of pattern surface and grain boundary per unit volume increase by the decrease of pattern width. In contrast, the as-deposited sample shows a flat etching rate for pattern sizes. In addition, at the narrow patterns with a pattern width of below 220 nm, the etching rate in the nanocrystalline structure of the as-deposited sample is lower than in the grain grown structure of the self-annealed sample. It can be surmised that the stresses caused by interfacial energies may be relaxed by the nanocrystalline structure in the as-deposited sample.

Control of Impurity Concentrations in Copper Electrodeposits by Using an Organic Additive

Copper was electroplated using plating baths containing various concentrations of Janus Green B (JGB, C30H31ClN6) from 0 to 1 mM. The electrical resistance, microstructure and impurity concentration were investigated by using four point probe, electron backscattered diffraction, and glow discharge spectroscopy analyses, respectively. The initial sheet resistance of the Cu films was increased by increasing the JGB concentration, and the impurity concentrations of C, H and N also linearly increased. At 0.2 mM of JGB, while the sheet resistance decreased by 7% for the initial resistance, crystal growth did not occur. The initial decrease in electrical resistance was due to the redistribution of impurities, and grain boundary migration was inhibited by solute dragging. As a result, we were able to retard the recrystallization of Cu electrodeposits using the impurities from the JGB additive. †(Received April 4, 2016)

Effect of Microstructural Evolution on Electrical Properties of the Copper Electrodeposits for ULSI

Copper electrodeposits annealed at 80 °C were investigated by electrical resistance measurement, X-ray diffraction and electron backscattered diffraction analyses. The decrease of electrical resistivity had a linear relationship with the re-crystallized area. Interestingly, the texture coefficient of (200) orientation increased as the re-crystallization occurred. Such appearance of (200) texture during annealing seemed to be related to the residual strain in the copper electrodeposits. It is possible to evaluate the progress of grain growth by measuring the electrical resistivity or texture coefficient in copper electrodeposits. †(Received July 23, 2013)