• 마이크로전자및패키징학회지
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• 제27권1호
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• pp.17-24
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• 2020

As an interconnect scaling faces a technical bottleneck, the device stacking technologies have been developed for miniaturization, low cost and high performance. To manufacture a stacked device structure, a vertical interconnect becomes a key process to enable signal and power integrities. Most bonding materials used in stacked structures are currently solder or Cu pillar with Sn cap, but copper is emerging as the most important bonding material due to fine-pitch patternability and high electrical performance. Copper bonding has advantages such as CMOS compatible process, high electrical and thermal conductivities, and excellent mechanical integrity, but it has major disadvantages of high bonding temperature, quick oxidation, and planarization requirement. There are many copper bonding processes such as dielectric bonding, copper direct bonding, copper-oxide hybrid bonding, copper-polymer hybrid bonding, etc.. As copper bonding evolves, copper-oxide hybrid bonding is considered as the most promising bonding process for vertically stacked device structure. This paper reviews current research trends of copper bonding focusing on the key process of Cu-SiO₂ hybrid bonding.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.55-60
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• 2020

최근 참단 반도체 패키징 기술은 고성능 SIP(system in packaging) 구조로 발전해 가고 있고, 이를 실현시키기 위해서 구리 대 구리 접합은 가장 핵심적인 기술로 대두되고 있다. 구리 대 구리 접합 기술은 아직 구리의 산화 특성과 고온 및 고압력 공정 조건, 등 해결해야 할 문제점들이 남아 있다. 본 연구에서는 아르곤과 질소를 이용한 2단계 플라즈마 공정을 이용한 저온 구리 접합 공정의 접합 계면 품질을 정량적 접합 강도 측정을 통하여 확인하였다. 2단계 플라즈마 공정은 구리 표면에 구리 질화막을 형성하여 저온 구리 접합을 가능하게 한다. 구리 접합 후 접합 강도 측정은 4점 굽힘 시험법과 전단 시험법으로 수행하였으며, 평균 접합 전단 강도는 30.40 MPa로 우수한 접합 강도를 보였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.34-36
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• 2005

Copper wire bonding is an alternative interconnection technology that serves as a viable and cost saving alternative to gold wire bonding. In this paper, ultrasonic wedge bonding with $25{\mu}m$ copper wire on Au/Ni/Cu metallization of a PCB substrate was performed at ambient temperature. The central composite design of experiment (DOE) approach was applied to optimize the copper wire wedge bonding process parameters. After that, pull test of the wedge bond was performed to study the bond strength and to find the optimum bonding parameters. SEM was used to observe the cross section of the wedge bond. The pull test results show good performance of the wedge bond. Additionally, DOE results gave the optimized parameter for both the first bond and the second bond. Cross section analysis shows a continuous interconnection between the copper wire and Au/Ni/Cu metallization. The diffusion of Cu into the Au layer was also observed.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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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).

• 소성∙가공
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• 제6권2호
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• pp.136-144
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• 1997

(Ag-10%Ni)/Cu clad metals for electric contact switch were fabricated by cold-roll bonding process. 2 or 3 passes of cold-rolling was carried out for each process to investigate the effect of the rolling passes on the bonding property. The effect of the annealing temperature of copper before the cold-roll bonding on the bond strength was also studied. The specimen bonded with copper annealed below 30$0^{\circ}C$ before roll bonding showed good bond strength. This is because high stored energy in copper promoted the short range diffusion and the grain refinement of copper by the static recrystallization increased the degree of the interfacial coherency. The maximum peel strength of clad metals bonded with Cu annealed below 30$0^{\circ}C$ was 120N.

• 한국세라믹학회지
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• 제38권11호
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• pp.1000-1007
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• 2001

진공관형 태양열 집열기에서는 열관(heat pipe)과 붕규산염 유리관의 안정된 접합이 이를 장시간 사용하는데 매우 중요하다. 구리와 유리는 그 물리.화학적 성질에 큰 차이가 있어 접합하기가 어려움으로 구리관 표면에 유리와 화학적 결합이 용이한 산화막을 생성시켜 접합하도록 구리의 산화상태, 접합계면 및 접합강도를 XRD, SEM, EDS 및 인정시험기로 측정하였다. 순수 구리는 $600^{\circ}C$ 이하로 열처리하였을 때 Cu$_2$O 산화막을 생성하였으나 그 이상의 온도에서는 CuO 산화막을 형성하였으며 후자의 산화막은 구리와의 접합력이 매우 불량하였다. 그러나 붕사로 표면 처리를 하였을 경우에는 80$0^{\circ}C$에서도 Cu$_2$O 산화막 만이 발견되었다. Cu$_2$O 산화막을 생성시킨 구리관과 붕규산염 유리관을 Housekeeper법으로 접합하였을 경우 354.4N의 접합강도를 얻을 수 있었으며 열충격 저항성도 매우 뛰어났다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.6-9
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• 1996

The Joining of copper rod and zirconia tube was carried out in Ar gas atmosphere. There are two type of the joining. The one is the reaction bond consisting of Cu and zirconia was dominated by surface reaction wi th a undetctable very thin layer. It was found that copper elements were diffused to zirconia side, but that most of Z $r^{4+}$ ions were not diffused to copper side. This result means application of a DC voltage to migrate oxygen to the copper/zirconia interface can oxidize metal at the copper /zirconia interface, and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result means application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cr.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.511-512
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• 2006

Tungsten coatings with different interlayers onto the oxygen-free copper substrates were fabricated by atmosphere plasma spraying. The effects of different interlayers of NiCrAl, NiAl and W/Cu on bonding strength were studied. SEM, EDS and XRD were used to investigate the photographs and compositions of these coatings. The tungsten coatings with different initial particle sizes resulted in different microstructures. Oxidation was not detected in the tungsten coating, but in the interlayer, it was found by both XRD and EDS. The tungsten coating deposited directly onto the copper substrate presented higher bonding strength than those with different interlayers.

• 연구논문집
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• 통권24호
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• pp.63-79
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• 1994

This article reports a experimental study of the method to achieve a bond joint at lower temperature in a short time. DC magnetron sputtering of Sn, Sn/Pb, Sn/In and Sn/Cu on copper substrate was provided as an interlayer for Cu to Cu bonding under the air environment. Various examination was conducted and investigated on the effect of experimental parameters such as coating materials, coating time(or coating thickness), bonding temperature and bonding time etc. Bonding was performed at the temperature of $210^\circC-320^\circC$ for 0sec and interfacial reaction between the coated layer and copper substrate was examined using optical, scanning electron microscope and x-ray diffractometer. From the obtained results, it was found that intermetallic compounds layer consisted of $\eta-phase(Cu_6Sn_5)$ and $\beta-phase(Cu_3Sn)$ was formed at the joint interface for almost all coating materials. But the dominant phase formed in the preetched Cu substrate coated with Sn was $\beta-phase$. A characteristic morphology looks like a reaction ring, which was believed as the strong interconnecting regions between two substrates, was found to be formed on the reaction surface of copper substrates. The morphologies and compositions of the intermetallics, which depends on the regions of the reaction surface, was appeared as greatly different. Based on above results, the new bonding process to make the joint at lower temperature for short time can be admitted as a feasible process.

• 한국재료학회지
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• 제16권9호
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• pp.592-597
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• 2006

A deoxidized low-phosphorous (DLP) copper was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two copper sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles (${\varepsilon}{\sim}6.3$). TEM observation revealed that ultrafine grains were developed after the 4th cycle, and their size decreased at higher cycles. Tensile strength of the copper increased with the equivalent strain, and it reached 547 MPa which was 3 times higher than that of the initial material. It is concluded that the ARB process is an effective method for high strengthening of the DLP copper.