Wonbae Bang

An Approach to the Development of Organic Additives for Electrodeposition of Narrow Copper Interconnects

We have characterized the electrochemical properties and wetting effects of various organic materials, including selected accelerators, suppressors, and wetters, for the electrodeposition of submicrometer-wide copper interconnects. An additive composition consisting of the following organic chemicals was tested: bis(3-sulfopropyl)-disulfide, disodium salt as an accelerator, polyethylene glycol as a suppressor, and a cross-linked polyamide as a second suppressor (working also as a wetter). Copper films plated using this makeup exhibited a surface roughness of ∼35 nm after annealing, with grain sizes on the order of 0.1-0.5 μm, and an electrical resistivity of ∼ 1.9 μΩ cm. Using this made-up solution, 120 nm wide trenches were successfully gap-filled.

Planarity Improvement and Reduction of Coercivity by Organic Additives in Electroplated Ni – Fe Permalloy Thin Films

We studied the effect of organic additives on the surface planarity and magnetic properties of electroplated Ni-Fe Permalloy thin films. Compared to thin films prepared with a pure inorganic electrolyte, the Ni-Fe permalloy thin films electroplated with electrolytes containing additives showed changes in their crystalline orientations, surface roughnesses, and coercivities. The reduction in coercivity showed a strong correlation with the observed improvement of the surface planarity. We observed that the surface planarity of the thin films could be improved by 50-60% and that coercivity could be adjusted between 0.33 and 0.05 Oe by changing the concentration of additives.

Effects of Saccharine N-Propane Sulfonate on the Microstructures, Magnetic Properties, and Magnetoimpedance of Electroplated Ni – Fe Permalloy Thin Films

We have studied the effects of an organic additive, saccharine N-propane sulfonate, on the microstructures, magnetic properties, and magnetoimpedance of electroplated Ni-Fe Permalloy thin films. Compared to thin films prepared with a pure inorganic electrolyte, the Ni-Fe Permalloy thin films electroplated with electrolytes containing the additive have different crystalline orientation, grain size, surface roughness, coercivity, permeability, and magnetoimpedance. There is a strong correlation between the observed structural changes and the changes in the magnetic properties, such as in the coercivity and permeability. The changes are also dependent on the structure of the electroplating cells. By using an appropriate plating cell, the coercivity can be reduced from 0.36 to 0.08 Oe. These changes in the magnetic properties result in an increase in the magnetoimpedance by 31%.

Magnetoimpedance of Galvanostatically Electroplated Ni-Fe Permalloy Wires

We studied the magnetoimpedance of narrow Ni-Fe Permalloy wires prepared by electrodeposition. The wires were fabricated by lithographical patterning and chemical etching of electroplated thin films. The microstructure and magnetic property of the deposit were adjusted by using an organic additive added to the electrolyte. Aspect ratio of the wires was varied between 10 and 50 by changing the length of the wire while the thickness and width were fixed. The magnetoimpedance exhibited highest value at 30 MHz and was 18-25% depending on the aspect ratio. The magnetic fields for the highest magnetoresistance increased in proportion to the frequency in the range between 1 and 100 MHz.

Properties Change of Electroplated Permalloy Thin Films by Organic Additives

We investigated the changes of the magnetic properties in electroplated Permalloy thin films by a few organic additives added to the plating electrolytes. Under identical electroplating conditions, the crystalline orientations and the surface roughness of the plated thin films were different from those prepared with a pure electrolyte. These property changes reduced the coercivity and increased the magnetoimpedance ratio (MIR) up to 20%.

Interface between the Electroplated Copper-cobalt Thin Films and the Substrate

We electroplated copper-cobalt thin films on a silicon substrate, which had 150 nm thick copper seed layer. The adhesion between the two metallic layers could be increased by utilizing a proper organic additive, pulse plating technique, and high temperature annealing. The thin films exhibited columnar growth of the deposits and enhanced adhesion. This is attributed to the grain growth mechanism introduced by the additive and annealing.