Jae Jeong Kim

Electrodeposited Ni dendrites with high activity and durability for hydrogen evolution reaction in alkaline water electrolysis

Different shapes of various nickel structures, including dendrite, particle and film are fabricated by electrodeposition under various conditions. The shape of nickel structures is definitely dependent on the deposition potential, leading to different electrochemical surface area and edge facets. The nickel particle which has a polycrystalline center and edge is obtained at high negative potential. On the other hand, the nickel dendrite deposited by relatively low negative potential exhibits large electrochemical surface area and a particularly active facet for hydrogen evolution reaction (HER) in alkaline water electrolysis. In fact the nickel dendrite shows the highest catalytic activity and stability for HER among the various nickel structures.

Investigation of various copper seed layers for copper electrodeposition applicable to ultralarge-scale integration interconnection

As a superior substituent for the chemical-vapor deposition and physical-vapor deposition (PVD) Cu processes in an ultralarge-scale integrated interconnection, electrodeposition on two kinds of electroless-plated Cu seed layers was investigated. Co(II) and formaldehyde were used as reducing agents for each electroless plating. Two samples of electroless-plated seed layers had relatively higher resistivity due to rough and irregular grains and weakly developed (111) texture, which are peculiarities of electroless plating. However, the Cu electrodeposited onto the electroless-plated seed showed reasonably good characteristics in resistivity, impurity level, crystalline structure, and surface roughness compared to those on the conventional PVD Cu seed. For the gap filling in the damascene structure, the electroless seed layer plating using formaldehyde and the subsequent electrodeposition on a patterned wafer showed an excellent filling profile without any voids or keyholes. After 400 °C annealing in a N2 at...

Improvement of Electrolessly Gap-Filled Cu Using 2, 2 ′ -Dipyridyl and Bis-(3-sulfopropyl)-disulfide (SPS)

The use of bis~3-sulfopropyl! disulfide ~SPS! in Cu electroless deposition resulted in Cu bottom-up filling. However, the high accelerating effect of SPS led to a poor electrical property of the film and generated many voids in the film by increasing the surface roughness and causing unstable deposition behavior. The addition of 2,28-dipyridyl together with SPS substantially improved the film quality of the gap-filled Cu maintaining the bottom-up filling behavior. It lowered the film resistivity by approximately 23% and enhanced the crystallinity. No voids were detected in the as-deposited Cu even after annealing.

Optimized Surface Pre-treatments for Cu Electroless Plating in ULSI Device Interconnection

We investigated the effects of under layer pretreatments on Cu electroless deposition to optimize the resistivity and morphology of the Cu. The pretreatments used in the Cu electroless plating process consisted of the removal of the titanium oxide layer on the barrier metal, TiN, and the deposition of Pd to activate the TiN diffusion barrier layer. Surface pretreatment using a 1%HF solution to remove the native Ti oxide formed on a TiN diffusion barrier layer showed a remarkable surface conditioning effect for the catalytic metal activation stage in Cu electroless plating, even in the absence of a wetting agent. Microcavities generated during Ti oxide etching are believed to be the key factor for the improved uniformity of the deposited catalytic metal on the pretreated TiN layer. Electroless plated Cu layers on non-uniform or rough Pd layers exhibited high resistivity and RMS roughness.

Electroless Cu Bottom-Up Filling Using 3-N , N-Dimethylaminodithiocarbamoyl-1-propanesulfonic acid

Cu bottom-up filling in Cu electroless deposition was attempted using 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid DPS . An accelerating effect on the planar surface was observed at low DPS concentrations, while a suppressing effect was found at higher concentrations. Co-addition of 2,2 -dipyridyl enhanced the surface morphology. Filling profiles were dependent on the concentration of DPS added, and Cu bottom-up filling was achieved due to a concentration gradient by diffusion of DPS between the top and bottom of the trench.

Formation of CoTi barrier and increased thermal stability of CoSi2 film in Ti capped Co/Si(100) system

We investigated the formation of CoSi2 for Ti capped Co on (100) Si substrate with emphasis on the Co–Ti interaction and its effect on thermal stability. A 15 nm thick Ti capping layer is shown to improve the interfacial roughness and thermal stability of CoSi2 film grown on Si substrate compared with TiN capping. The increased uniformity of silicide/Si(100) interface is speculated to result from retarded Co–Si reaction by the formation of CoTi binary phase. And the high thermal stability can be explained by the fact that the amount of Ti atoms in CoSi2 film for Ti capping is much higher than what is in TiN capping. It is likely that the surface Ti diffuses rapidly into CoSi2 grain boundaries and slows down the agglomeration process, thereby increasing thermal stability while Ti in TiN capping did not.

Investigation of copper deposition in the presence of benzotriazole

The effect of benzotriazole (BTA) on copper electroplating for ultra large-scale integrated circuits interconnection was investigated. BTA exhibited both strong suppressing and brightening effects by modifying the nucleation and growth steps. Electroplating in the presence of BTA followed a random deposition mechanism rather than a selective or preferential deposition mechanism. As a result, the crystal orientation intensity and mean aggregates size of the electroplated copper with BTA were much smaller than those of BTA-free, which resulted in an increase in resistivity. The increased resistivity of the electroplated copper in the presence of BTA was recovered to approximately 2 μΩ-cm through annealing at 400 °C in a nitrogen atmosphere by grain growth and recrystallization. The amounts of carbon and nitrogen impurities from the BTA were below the detection limit of Auger electron spectroscopy.

Characterization of 5-Aminotetrazole as a Corrosion Inhibitor in Copper Chemical Mechanical Polishing

In the Cu metallization process, it is important to prevent corrosion and recession of metal lines resulting from chemical reactions during the chemical mechanical polishing (CMP) process. In this paper, 5-aminotetrazole (ATRA) is investigated as a corrosion inhibitor for Cu CMP. In the wet etch test, it was found that the etch rate of ATRA decreased with concentration. The potentio-dynamic polarization test and chronoamperometry test results revealed that ATRA could inhibit the Cu surface against corrosion more effectively than benzotriazole (BTA) below 0.01 M. Fourier transform infrared and ultraviolet-visible analysis clearly demonstrated that ATRA dissociated more easily in all pH ranges and could be polymerized faster and more effectively than BTA. Therefore, both corrosion and recession could be considerably reduced after CMP by using slurry containing ATRA. Furthermore, from the results of defect review after CMP, it was found that defects such as slurry residue, pit corrosion, and particles were effectively prevented due to small molecular size and high solubility of ATRA.

Ruthenium Bottom Electrode Prepared by Electroplating for a High Density DRAM Capacitor

The possibility of Ru electroplating for application as the bottom electrode in high density dynamic random access memory (DRAM) capacitors was investigated. Prior to Ru electroplating on a TiN substrate, HF cleaning and Pd activation were performed. Removal of Ti oxide from the TiN substrate by HF treatment enabled Pd activation, which enhanced the nucleation of Ru on TiN substrate. Optimized pretreatments led to a continuous Ru film deposition. The surface roughness was measured to be 4.4 nm at 45 nm Ru film on the bare substrate. Moreover Ru electroplating method was also applied to a capacitor node-type TiN wafer. The deposition rate of Ru on the patterned wafer was the same as that on a bare wafer. The film showed 93% step coverage and good adhesion, comparable to CVD Ru films.

Additives for Superconformal Electroplating of Ag Thin Film for ULSIs

For Ag electroplating in a damascene structure, two additives were tried in the electrolyte composed of KAg(CN) 2 and KCN. One additive, thiourea, played a role as a suppressor and a brightener on a Ag seed layer. The other additive, benzotriazole, worked as an inhibitor on a Cu seed layer whereas it acted as an accelerator on the Ag seed layer. When these two additives were added to the electrolyte, the superconformal electroplating of Ag thin film for ultralarge scale integrateds (ULSIs) was accomplished successfully without defects in the damascene structure with a width of 400 nm and an aspect ratio was 4.