Naoki Okamoto

Formation Factor of Nodule by Copper Electrodeposition

Copper electrodeposition has been used in the formation of the signal line in cellular phones, liquid crystal TVs and digital cameras. Recently, the formation of nodules and large knot deposits became a serious problem because of the downsizing of signal lines pitch in electronic devices. The nodules cause short circuits in the signal lines. In our previous work, we have investigated the origins of the nodules formation. The nodules grow as the growth of the copper electrodeposits and tiny hemispherical deposits are the nucleuses of the nodules. However, numerous unknown factors remain, such as the formation mechanism of the nodules nucleuses. In this report, we further discuss the factors of the nodule formation.

Shape Evolution of Electrodeposited Bumps with Shallow and Deep Cavity

For aspect ratio of 0.25, the initial bump shape is flat for the 0 rpm rotating disk electrode. The bump shapes have humps on the upper stream sides for the 10 and 20 rpm. The hump on the upper stream side shifts to the down stream side for the 100 rpm. The vortices form both at the cathode and photoresist corners on the upper and lower sides. The upper stream side has humps both for the 10 and 20 rpm and the hump shifts to the down stream side at 100 rpm. For aspect ratio of 3.3, the cross section of the initial bumps became flat for all the rotating disk electrode rotation speeds of 0, 10, 20 and 100 rpm. Two vortices were generated at all the rotation speeds. The vortices did not reach the cathode. The bump cross section became flat because the transport is controlled by diffusion.