The electrochemical behavior of levelers was studied and compared for two commercial Cu plating chemistries in an effort to correlate the electrochemical behaviors with their impacts on bottom-up filling, impurity incorporation, and grain structures. While a strong complexing between leveler and accelerator resulted in a leveler-sensitive bottom-up filling rate and low impurity level in the deposit, a traditional non-interacting leveler showed little impact on the filling performance and yielded a high impurity incorporation. An oscillatory behavior was reported for the strongly-interacting leveler chemistry during galvanostatic plating, this oscillation manifested itself in both the potential and impurity incorporation. High impurity incorporation is known to inhibit the Cu grain growth; a laminated structure with alternating layers of big and fine Cu grains was obtained by annealing the Cu films plated with the oscillatory behavior.

The effects of suppressor and accelerator on the superfilling of copper are studied for two commercial chemistries. The potential transients during galvanostatic plating were obtained for injections of the industrially recommended dose of accelerator and various doses of suppressor. The potential increase immediately after the injection was found to be strongly dependent on the type of suppressor as well as the amount of suppressor injected. While the transient of the full dose of suppressor represents what happens at the mouth of the feature and the field outside the feature, the bottom of the feature can be simulated by the case in which a fraction of suppressor is injected. The filling results in sub-100 nm lines are well correlated with the differences observed in the potential transients.

The impurities incorporated in the electrodeposited 40 nm Cu lines as well as in blanket Cu films were studied. Two different levelers were used in the study. While the impurity in the blanket films were found highly dependent on the leveler and its concentration, the leveler had no impact on the impurity in the narrow lines. Furthermore, the concentrations of suppressor and chloride showed little to no impact on the impurity in the narrow lines. An increase of accelerator concentration resulted in higher S and Cl contents in the lines. The increase in S incorporation was also observed for blanket wafers plated with incremental concentrations of accelerator. In addition, the impurity in the narrow lines was also found to increase with the increase of the applied plating current density. A correlation between a slow Cu grain growth and high impurity content was established by using Cu blanket films plated with different leveler concentrations or Cu films ion-implanted with different doses of impurities.

Qubit information processors are increasing in footprint but currently rely on e-beam lithography for patterning the required Josephson junctions (JJs). Advanced optical lithography is an alternative patterning method, and we report on the development of transmon qubits patterned solely with optical lithography. The lithography uses 193 nm wavelength exposure and 300-mm large silicon wafers. Qubits and arrays of evaluation JJs were patterned with process control which resulted in narrow feature distributions: a standard deviation of 0.78% for a 220 nm linewidth pattern realized across over half the width of the wafers. Room temperature evaluation found a 2.8 − 3.6% standard deviation in JJ resistance in completed chips. The qubits used aluminum and titanium nitride films on silicon substrates without substantial silicon etching. T1 times of the qubits were extracted at 26 µs -27 µs, indicating a low level of material-based qubit defects. This study shows that large wafer optical lithography on silicon is adequate for high-quality transmon qubits, and shows a promising path for improving many-qubit processors.

Cu films with low impurities were electroplated on pure Cu, CuCo alloy and electrodeposited Co seed layers to study the room temperature grain growth behavior. As-evaporated Cu and CuCo alloy seed layers showed a significant enhancement effect on the Cu recrystallization compared with sputtered Cu seed layers and post-annealed evaporated seed layers. The impact of the electrodeposited Co seed layer on the Cu grain growth was found to be dependent on the Co plating chemistry and on the thickness of the Co film. Co films plated in the absence and presence of saccharin showed a crystal structure of fcc and hcp, respectively. While the former showed little to no impact on the Cu recrystallization, the later was found to enhance or hinder the Cu recrystallization depending on the thickness of the Co. Studies on a Cu/Co sandwich stack structure showed that the recrystallization started at the top Cu layer, proceeding to the middle layer and then to the bottom layer.