• Advances in materials Research
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• 제1권2호
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• pp.109-113
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• 2012

Electromigration-induced void evolutions in typical upper and lower layer dual-inlaid Copper (Cu) interconnect structures were simulated by applying a phenomenological model resorting to Monte Carlo based simulations, which considers redistribution of heterogeneously nucleated voids and/or pre-existing vacancy clusters at the Copper/dielectric cap interface during electromigration. The results indicate that this model can qualitatively explain the electromigration-induced void evolutions observations in many studies reported by several researchers heretofore. These findings warrant need to re-investigate technologically important electromigration mechanisms by developing rigorous models based on similar concepts.

• 한국결정성장학회지
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• 제14권2호
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• pp.58-62
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• 2004

The shape evolution of the interface void of copper metallization for intergrated circuits under electromigration stress is modeled. A 2-dimensional finite-difference numerical method is employed for computing time evolution of the void shape driven by surface diffusion, and the electrostatic problem is solved by boundary element method. When the diffusion coefficient is isotropic, the numerical results agree well with the known case of wedge-shape void evolution. The numerical results for the anisotropic diffusion coefficient show that the initially circular void evolves to become a fatal slitlike shape when the electron wind force is large, while the shape becomes non-fatal and circular as the electron wind force decreases. The results indicate that the open circuit failure caused by slit-like void shape is far less probable to be observed for copper metallization under a normal electromigration stress condition.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.86-86
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• 2003

Copper has attracted much attention in the deep submicron ULSI metallization process as a replacement for aluminum due to its lower resistivity and higher electromigration resistance. Electroless copper deposition method is appealing because it yields conformal, high quality copper at relatively low cost and a low processing temperature. In this work, it was investigated that effect of the microstructure of the substrate on the electroless deposition. The mechanism of the nucleation and growth of the palladium nuclei during palladium activation was proposed. Electroless copper deposition on TiN barriers using glyoxylic acid as a reducing agent was also investigated to replace toxic formaldehyde. Furthermore, electroless copper deposition on TaN$\sub$x/ barriers was examined at various nitrogen flow rate during TaN$\sub$x/ deposition. Finally, it was investigated that the effect of plasma treatment of as-deposited TaN$\sub$x/ harriers on the electroless copper deposition.

• 한국재료학회지
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• 제17권1호
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• pp.56-59
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• 2007

Recently, requirement for the ultra thin copper foil increases with smaller and miniaturized electronic components. In this study, we evaluated the surface morphology, crystal phase ana surface roughness of the copper film electrodeposited by pulse method without using additives. Homogeneous and dense copper crystals were formed on the titanium substrate, and the optimum condition was 25% duty cycle. Moreover, the surface roughness(Ra), $0.295{\mu}m$, is the smallest value in this condition. It is thought that this copper foil is good for electromigration inhibition due to the preferential crystal growth of Cu (111)

• 한국진공학회지
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• 제9권3호
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• pp.267-272
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• 2000

electroplating(EP)법을 이용하여 ULSI용 Cu 박막을 제조하였다. seed Cu는 sputtering으로 증착하였으며, 확산방지막으로 TaN를 사용하였다. 제작된 EP Cu 박막은 seed Cu의 영향으로 열처리 조건에 관계없이 Cu(111)방향으로 강하게 우선 배향 하였다. 열처리 온도와 시간이 증가함에 따라 Cu박막의 미세조직이 non-columnar structure에서 약 2배 이상 결정립 성장하여 columnar structure로 바뀌었으며, 또한 as-deposit시 관찰되었던 stacking fault, twin, dislocation들이 상당히 줄어드는 것이 관찰되었다. Cu의 확산에 의하여 생기는 copper-silicide는 관찰할 수 없었으며, 이것은 두께 45nm의 TaN막이 $450^{\circ}C$, 30분 열처리시 확산방지막으로 충분한 역할을 한 것으로 판단된다. Cu(111)우선 배향과 열처리에 의한 결정립 성장 및 defect감소는 Cu 박막의 결정립계에서 발생하는 electromigration 현상을 상당히 줄일 수 있을 것으로 판단된다.

• 한국재료학회지
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• 제16권11호
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• pp.710-714
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• 2006

The purpose of this study is to identify the effect of additives and composition on copper surface morphology and mechanical characteristics by copper electrodeposition. Additives such as hydroxy ethyl cellulose(HEC), chloride ion were used in this study. Electrochemical experiments allied to SEM, XRD, AFM and four- point probe were performed to characterize the morphology and mechanical characters of copper in the presence of additives. Among various electrodeposition conditions, the minimum surface roughness of copper foil was obtained when electrodeposited at the current density of 200 mA/$cm^2$ for 68 seconds with 2 ppm of HEC. The minimum value of surface roughness(Rms) was 107.6 nm. It is copper foil is good for electromigration inhibition due to preferential crystal growth of Cu (111) deposited in the electrolyte containing chloride ions(10 ppm) and HEC(1 ppm).

• 마이크로전자및패키징학회지
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• 제20권3호
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• pp.11-18
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• 2013

Interest in copper nanoparticles has increased as an alternative for substituting silver nanoparticles because of its lower cost and less electromigration effect than silver. In this paper, the recent research trends and main results in wet-chemical synthesis of sub-100 nm Cu nanoparticles were summarized. The characteristics of synthesis were discussed with a classification such as modified polyol synthesis, modified hydrothermal synthesis, solvothermal synthesis, and the others, focussing on effects of capping agents, reductants, and pH. Information on the oxidation of synthesized copper nanoparticles were additionally commented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.136-139
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• 2003

Copper has attractive properties as a multi-level interconnection material due to lower resistivity and higher electromigration resistance as compared with Alumina and its alloy with Copper(0.5%). Among a variety of agents in Copper CMP slurry, $H_2O_2$ has commonly been used as the oxidizer However. $H_2O_2$ is so unstable that it requires stabilization to use as oxidizer Hence, stabilization of $H_2O_2$ is a vital process to get better yield in practical CMP process. In this article the stability of Hydrogen Peroxide as oxidizer of Copper CMP slurry has been investigated. When alumina abrasive was used, $\gamma$-particle Alumina C had a better stability than $\alpha$-particle abrasive. As adding KOH as pH buffering agent, $H_2O_2$ stability in slurry decreased. Urea hydrogen peroxide was used as oxidizer, an enhanced stability was gotten. When $H_3PO_4$ as $H_2O_2$ stabilizer was added, the decrease of $H_2O_2$ concentration in slurry became slower. Even though adding $H_2O_2$ in slurry after bead milling lead to better stability than in advance of bead milling, it had a lower dispersibility.

• 한국진공학회지
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• 제18권3호
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• pp.203-207
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• 2009

반도체 공정에서 기존 금속배선으로 사용되던 Al을 대체하여 사용되는 금속배선으로는 Cu가 그 대안으로 인식되고 있다. 이는 비저항값이 Al ($2.66{\mu}{\Omega}$-cm)보다 Cu ($1.67{\mu}{\Omega}$-cm)가 더 작아 RC 지연 시간 (RC delay time)을 극복하기 때문이다. 그러나 Cu의 녹는점은 $1085^{\circ}C$로 높지만 저온에서 쉽게 Si기판과 반응하는 특성을 가지고 있고, 또한 Si과의 접착력이 좋이 않는 것으로 알려져 있다. 이러한 이유로 Cu와 Si과의 반응을 방지하고 접착력을 높이기 위하여 확산방지막의 연구가 꾸준히 진행되고 있다. 본 연구그룹에서는 Cu의 확산을 방지하기 위하여 W-C-N의 확산방지막에 대하여 연구하여 왔다. 지금까지 보고된 연구 결과에 의하면 W-C-N (tungsten-carbon-nitrogen) 확산방지막은 고온에서도 Cu와 Si과의 확산을 효과적으로 방지하는 것으로 보고되었다. 이 논문에서는 W-C-N 확산방지막에 질소(N) 비율을 다르게 증착하여 지금까지 진행한 연구 결과를 기반으로 새로이 Cu의 전자거동현상(Electromigration)에 대하여 연구하였고, 고온 열처리 과정에서 박막의 표면강도 (Surface hardness)를 Nano-Indenter system을 이용하여 연구하였다. 이러한 연구를 통하여 박막내 질소가 포함된 W-C-N 확산방지막이 Cu의 전자거동에 더 안정적이며, 고온 열처리 과정에서도 표면 강도가 더 안정한 연구 결과를 획득하였다.

• Corrosion Science and Technology
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• 제9권6호
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• pp.276-280
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• 2010

Copper(Cu) as an interconnecting metal layer can replace aluminum (Al) in IC fabrication since Cu has low electrical resistivity, showing high immunity to electromigration compared to Al. However, it is very difficult for copper to be patterned by the dry etching processes. The chemical mechanical polishing (CMP) process has been introduced and widely used as the mainstream patterning technique for Cu in the fabrication of deep submicron integrated circuits in light of its capability to reduce surface roughness. But this process leaves a large amount of residues on the wafer surface, which must be removed by the post-CMP cleaning processes. Copper corrosion is one of the critical issues for the copper metallization process. Thus, in order to understand the copper corrosion problems in post-CMP cleaning solutions and study the effects of DC biases and post-CMP cleaning solution concentrations on the Cu film, a constant voltage was supplied at various concentrations, and then the output currents were measured and recorded with time. Most of the cases, the current was steadily decreased (i.e. resistance was increased by the oxidation). In the lowest concentration case only, the current was steadily increased with the scarce fluctuations. The higher the constant supplied DC voltage values, the higher the initial output current and the saturated current values. However the time to be taken for it to be saturated was almost the same for all the DC supplied voltage values. It was indicated that the oxide formation was not dependent on the supplied voltage values and 1 V was more than enough to form the oxide. With applied voltages lower than 3 V combined with any concentration, the perforation through the oxide film rarely took place due to the insufficient driving force (voltage) and the copper oxidation ceased. However, with the voltage higher than 3 V, the copper ions were started to diffuse out through the oxide film and thus made pores to be formed on the oxide surface, causing the current to increase and a part of the exposed copper film inside the pores gets back to be oxidized and the rest of it was remained without any further oxidation, causing the current back to decrease a little bit. With increasing the applied DC bias value, the shorter time to be taken for copper ions to be diffused out through the copper oxide film. From the discussions above, it could be concluded that the oxide film was formed and grown by the copper ion diffusion first and then the reaction with any oxidant in the post-CMP cleaning solution.