• Journal of the Korean Vacuum Society
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• v.13 no.2
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• pp.72-78
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• 2004

Cu seed layers deposited by magnetron sputtering onto tantalum nitride barrier films were treated with ECR plasma and then the copper films were electroplated and rapid thermal annealed in an argon or nitrogen atmosphere at various temperatures ranging from 200 to $500^{\circ}C$. Changes in the microstructure and physical properties of the copper films electroplated on the hydrogen ECR plasma cleaned copper seed layers were investigated using X-ray diffraction (XRD), electron back-scattered diffraction (EBSD), and atomic force microscopy (AFM) analyses. It was found that the copper film undergoes complete recrystallization during annealing at a temperature higher than $400^{\circ}C$. The resistivity of the Cu film tends to decrease and the degree of (111) preferred orientation tends to increase as the annealing temperature increases. Theoptimum annealing condition for obtaining the film with the lowest resistivity, the smoothest surface and the highest degree of the (111) preferred orientation is rapid thermal annealing in a nitrogen atmosphere at $400^{\circ}C$ for 120 s. The resistivity and the surface roughness of the electroplated copper film annealed under this condition are 1.98 $\mu$O-cm and 17.77 nm, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.55-59
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• 2012

Defects such as voids or seams are frequently found in TSV via filling process. To achieve defect-free copper via filling, organic additives such as suppressor, accelerator and leveler were necessary in a copper plating bath. However, by-products stemming from the breakdown of these organic additives reduce the lifetime of the devices and plating solutions. In this research, the effects of levelers on copper electrodeposition were investigated without suppressor and accelerator to lower the concentration of additives. Threelevelers(janus green B, methylene violet, diazine black) were investigated to study the effects of levelers on copper deposition. Electrochemical behaviors of these levelers were different in terms of deposition rate. Filling performances were analyzed by cross sectional images and its characteristics were different with variations of levelers.

• Journal of the Korean institute of surface engineering
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• v.16 no.4
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• pp.199-214
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• 1983

Up to this date, numerous methods of analysis of electroplating solutions are published. Some, however, need lots of works before reaching final results, or require high technique and special instruments, and also some are unaccurate due to unclearnes of end point. Like our undevelope countries, technicians of electoplating shops are most high school gradutes or under, and have not much knowledge on chemistry. Furthermore, those technicians have to control their plating solutions by themselves without having enough analytical laboratory equiIJment. Therefore, in this paper the simplest, besides accurate method is investigated after comparing nu.merous methods published. Among the methods of 'copper determinations from acid and alkaline copper plating baths, EDT A titration method are chosen, due to these methods are the simplest and fastest for the evaluation of metal content, without requiring any special instrument. For acid copper solutions, chelate titrations were accurate enough. Since the end point of titration of chelate method is variable according to the kind of .indicators androther metal's coexsistence as well as solution comIJonent, many difficulties were encountered from cyanide' copper, on the contrary of acid copper bath. PAN, PV, and MX indicators were tried, but it is found that MX is the best. In cyanide solution, due to cyanide is the masking reagent, elimination of this component is essential, and finally found that elimination eN- by precipitation with AgN03 solution was the simplest and the most accurate way among others. This method was very accurate for the new plating solutions even coexistence with organic brightners. However used solutions for long months running have to be predetermined the accurate copper value by thiosulfate method from time to time, before chelate titration by means of AgN03 precipitation. Always some constant deviatioJ;ls will be seen according to the solutions nature. Therefore those deviation values have to be compensated each time.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.123.1-123.1
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• 2017

Hybrid solar cells have intensively studied in recent years due to their advantages such as cost effectiveness and possibility of applications in flexible and transparent devices. It is critical to fabricate individual layer composed of organic and inorganic materials in the hybrid solar cell at low cost. Therefore, it is required to manufacture cheaply and enhance the photon-to-electricity conversion efficiency of each layer in the flexible solar cell industry. In this research, we fabricated pure Cu metal mesh electrode prepared by using electroplating and/or electroless plating on the Ni mold which was manufacture through photolithography, electroforming, and polishing process. Copper mesh was formed on the surface of nickel metal working master when pulsed electrolytic copper deposition were performed at various plating parameters such as plating time, current density, and so on. After electrodeposition at 2ASD for 5~30seconds, the line/pitch/thickness of copper mesh sheet was $1.8{\sim}2.0/298/0.5{\mu}m$.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.740-747
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• 2009

The purpose of this study is to identify the effect of electrolyte compositions on electrodeposited copper foil. First of all, the polyimide substrate was pretreated with plasma. Finally, copper foil was deposited on a Cu/Ni/Polyimide substrate using the electroplating technique. As the quantity of Cu increased, preferred orientations changed into (111). Increasing sulfuric acid, on the other hand, brought down the preferred orientation of (111). The lowest sheet resistance, surface roughness, and fine adhesion were detected when the ratio of $Cu^{2+}$ and $H_2SO_4$ is 50:50(g/l).

• New & Renewable Energy
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• v.1 no.1 s.1
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• pp.37-43
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• 2005

High-efficiency silicon solar cells have potential applications on mobile electronics and electrical vehicles. The fabrication processes of the high efficiency cells necessitate com placated fabrication precesses and expensive materials. Ti/Pd/Ag metal contact has been used only for limited area In spite of good stability and low contact resistance because of Its expensive material cost and precesses. Screen printed contact formed by Ag paste causes a low fill factor and a high shading loss of commercial solar cells because of high contact resistance and a low aspect ratio. Low cost Ni/Cu metal contact has been formed by using a low cost electroless and electroplating. Nickel silicide formation at the interface enhances stability and reduces the contact resistance resulting In an energy conversion efficiency of $20.2\%\;on\;0.50{\Omega}cm$ FZ wafer. Tapered contact structure has been applied to large area solar cells with $6.7\times6.7cm^2$ in order to reduce power losses by the front contact The tapered front metal contact Is easily formed by the electroplating technique producing $45cm^2$ solar cells with an efficiency of $21.4\%$ on $21.4\%\;on\;2{\Omega}cm$ FZ wafer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.123-127
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• 2009

In order to get more higher integration density of devices, it is getting to be used more and more micro via interconnection lines for interconnecting layers or devices. However, it is very important to enhance the electrical characteristic by reducing the electrical resistivity of micro via interconnection line because it affects the reliability of packaging. In this paper, Micro vias were patterned with a diameter from 10 to 100 um by increasing the step of 10 um and 100 um height and were fabricated by micromachining technology to investigate the electrical characteristic of micro via interconnection lines. These micro vias were filled with copper by electroplating process with appling pulse current mode. And the electrical characteristics of micro via interconnection lines were measured. The measured value of electrical resistivity shows with a range from 20 to $26\;m{\Omega}$. This value from micro via interconnection lines fabricated by pulse current mode electroplating process shows better result than the resistivity from than micro via interconnection lines fabricated by DC mode ($31\;m{\Omega}$).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.102-102
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• 2018

Electronic industry had required the finer size and the higher performance of the device. Therefore, 3-D die stacking technology such as TSV (through silicon via) and micro-bump had been used. Moreover, by the development of the 3-D die stacking technology, 3-D structure such as chip to chip (c2c) and chip to wafer (c2w) had become practicable. These technologies led to the appearance of HBM (high bandwidth memory). HBM was type of the memory, which is composed of several stacked layers of the memory chips. Each memory chips were connected by TSV and micro-bump. Thus, HBM had lower RC delay and higher performance of data processing than the conventional memory. Moreover, due to the development of the IT industry such as, AI (artificial intelligence), IOT (internet of things), and VR (virtual reality), the lower pitch size and the higher density were required to micro-electronics. Particularly, to obtain the fine pitch, some of the method such as copper pillar, nickel diffusion barrier, and tin-silver or tin-silver-copper based bump had been utillized. TCB (thermal compression bonding) and reflow process (thermal aging) were conventional method to bond between tin-silver or tin-silver-copper caps in the temperature range of 200 to 300 degrees. However, because of tin overflow which caused by higher operating temperature than melting point of Tin ($232^{\circ}C$), there would be the danger of bump bridge failure in fine-pitch bonding. Furthermore, regulating the phase of IMC (intermetallic compound) which was located between nickel diffusion barrier and bump, had a lot of problems. For example, an excess of kirkendall void which provides site of brittle fracture occurs at IMC layer after reflow process. The essential solution to reduce the difficulty of bump bonding process is copper to copper direct bonding below $300^{\circ}C$. In this study, in order to improve the problem of bump bonding process, copper to copper direct bonding was performed below $300^{\circ}C$. The driving force of bonding was the self-annealing properties of electrodeposited Cu with high defect density. The self-annealing property originated in high defect density and non-equilibrium grain boundaries at the triple junction. The electrodeposited Cu at high current density and low bath temperature was fabricated by electroplating on copper deposited silicon wafer. The copper-copper bonding experiments was conducted using thermal pressing machine. The condition of investigation such as thermal parameter and pressure parameter were varied to acquire proper bonded specimens. The bonded interface was characterized by SEM (scanning electron microscope) and OM (optical microscope). The density of grain boundary and defects were examined by TEM (transmission electron microscopy).

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.667-673
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• 2010

Copper filling into TSV (through-silicon-via) and reduction of the filling time for the three dimensional chip stacking were investigated in this study. A Si wafer with straight vias - $30\;{\mu}m$ in diameter and $60\;{\mu}m$ in depth with $200\;{\mu}m$ pitch - where the vias were drilled by DRIE (Deep Reactive Ion Etching) process, was prepared as a substrate. $SiO_2$, Ti and Au layers were coated as functional layers on the via wall. In order to reduce the time required complete the Cu filling into the TSV, the PPR (periodic pulse reverse) wave current was applied to the cathode of a Si chip during electroplating, and the PR (pulse-reverse) wave current was also applied for a comparison. The experimental results showed 100% filling rate into the TSV in one hour was achieved by the PPR electroplating process. At the interface between the Cu filling and Ti/ Au functional layers, no defect, such as a void, was found. Meanwhile, the electroplating by the PR current showed maximum 43% filling ratio into the TSV in an hour. The applied PPR wave form was confirmed to be effective to fill the TSV in a short time.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.84-84
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• 2012

소자가 고집적화 됨에 따라, 비저항이 낮고 electro migration (EM), Stress Migration (SM) 특성이 우수한 구리(Cu)를 배선재료로서 사용하고 있다. 그러나, 구리는 Si과 $SiO_2$의 내부로 확산이 빠르게 일어나, Si 소자 내부에 deep donor level을 형성하고, 누설 전류를 증가시키는 등 소자의 성능을 저하시킬 수 있는 문제점을 가지고 있다. 그러나, electroplating 을 이용하여 증착한 Cu 박막은 일반적으로 확산 방지막으로 쓰이는 TiN, TaN, 등의 물질과의 접착 (adhesion) 특성이 나쁘다. 따라서, Cu CMP 에서 증착된 Cu 박막의 벗겨지거나(peeling), EM or SM 저항성 저하 등의 배선에서의 reliability 문제를 야기하게된다. 따라서 Cu 와 접착 특성이 좋은 새로운 확산방지막 또는 adhesion layer의 필요성이 대두되고 있다. 본 연구에서는 이러한 Cu 배선에서의 접착성 문제를 해결하고자 Metal organic chemical vapor deposition (MOCVD)을 이용하여 제조한 코발트(Co) 박막을 $Cu/TaN_x$ 사이의 접착력 개선을 위한 adhesion layer로 적용하려는 시도를 하였다. Co는 비저항이 낮고, Cu 와 adhesion이 좋으며, Cu direct electroplating 이 가능하다는 장점을 가지고 있다. 하지만, 수소 분위기에서 $C_{12}H_{10}O_6(Co)_2$ (dicobalt hexacarbonyl tert-butylacetylene, CCTBA) 전구체에 의한 MOCVD Co 박막의 경우 탄소, 산소와 같은 불순물이 다량 함유되어 있어, 비저항, surface roughness 가 높아지게 된다. 따라서 구리 전착 초기에 구리의 핵 생성(nucleation)을 저해하고 핵 생성 후에도 응집(agglomeration)이 발생하여 연속적이고 얇은 구리막 형성을 방해한다. 이를 해결하기 위해, MOCVD Co 박막 증착 시 수소 반응 가스에 암모니아를 추가로 주입하여, 수소/암모니아의 분압을 1:1, 1:6, 1:10으로 변화시켜 $Co/TaN_x$ 박막의 특성을 비교 분석하였다. 각각의 수소/암모니아 분압에 따른 $Co/TaN_x$ 박막을 TEM (Transmission electron microscopy), XRD (X-ray diffraction), AES (Auger electron spectroscopy)를 통해 물성 및 조성을 분석하였고, AFM (Atomic force microscopy)를 이용하여, surface roughness를 측정하였다. 실험 결과, $Co/TaN_x$ 박막은 수소/암모니아 분압 1:6에서 90 ${\mu}{\Omega}-cm$의 낮은 비저항과 0.97 nm 의 낮은 surface roughness 를 가졌다. 뿐만 아니라, MOCVD 에 의해 증착된 Co 박막이4-6 % concentration 의 탄소 및 산소 함량을 가지는 것으로 나타났고, 24nm 크기의 trench 기판 위에 약 6nm의 $Co/TaN_x$ 박막이 매우 균일하게 형성된 것을 확인 할 수 있었다. 이러한 결과들은, 향후 $Co/TaN_x$ 박막이 Cu direct electroplating 공정이 가능한 diffusion barrier로서 성공적으로 사용될 수 있음을 보여준다.