• Korean Journal of Metals and Materials
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• v.47 no.1
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• pp.26-31
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• 2009

The effects of $Ar/O_2$ ion-beam pre-treatment conditions on the interfacial adhesion energy of sputterdeposited Cu thin film to FR-4 substrate were systematically investigated in order to understand the interfacial bonding mechanism for practical application to advanced chip-in-substrate package systems. Measured peel strength increases from $45.8{\pm}5.7g/mm$ to $61.3{\pm}2.4g/mm$ by $Ar/O_2$ ion-beam pre-treatment with anode voltage of 64 V. Interfacial bonding mechanism between sputter-deposited Cu film and FR-4 substrate seems to be dominated by chemical bonding effect rather than mechanical interlocking effect. It is found that chemical bonding intensity between carbon and oxygen at FR-4 surface increases due to $Ar/O_2$ ion-beam pretreatment, which seems to be related to the strong adhesion energy between sputter-deposited Cu film and FR-4 substrate.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.75-78
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• 2005

Using a low-energy Ar+ ion-beam with and without reactive gases, polymers such as chemically stable poly(ether ether ketone) (PTFE) and poly(ether ether ketone) (PEEK) films were modified to have special surface features. The adhesion strength between the polymers and the copper was significantly improved because of both changes in the surface topography and chemical interactions due to polymer surface functionalization (oxidation and amination). The surface modification altered the failure mode from adhesive failure for the unmodified polymer/Cu interface to cohesive failure for the surface-modified polymer/Cu layer interface..

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.234-240
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• 2001

The diffusion barrier properties of TiN by using Cu(Mg) alloy film have been investigated. Cu(Mg) alloy film was deposited on air-exposed TiN film. Upon annealing, interfacial MgO of 100 $\AA$ has been formed due to the reaction of Mg with oxygen existed on the surface of TiN. Combined MgO/TiN structure prevented the interdiffusion of Cu and Si up to $800^{\circ}C$. To improve the adhesion of Cu(Mg) alloy film to the TiN, TiN layer was treated by $O_2$ plasma, followed by vacuum annealing at $300^{\circ}C$. It was found that increased oxygen on the surface of TiN film by plasma treatment enhanced segregation of Mg toward the interface, resulting in the formation of dense MgO layer. Improved adhesion characteristics have been formed through this treatment. However, increased power of $O_2$ plasma led to the formation of TiO$_2$ and decreased the Mg content to be segregated to the interface, resulting in the decrease in adhesion property. In addition, the deposition of 50 ${\AA}$ Si on the TiN enhanced the adhesion of Cu(Mg) alloy to TiN without deteriorating the TiN diffusion barrier characteristics.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.17-24
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• 2008

Thermal annealing and electromigration test were performed at $150^{\circ}C$ and $150^{\circ}C,\;5{\times}10^4\;A/cm^2$ conditions, respectively, in order to compare the growth kinetics of intermetallic compound(IMC) in Cu pillar bump. The quantitative interfacial adhesion energy with annealing was measured by using four-point bending strength test in order to assess the effect of IMC growth on the mechanical reliability of Cu pillar bump. Only $Cu_6Sn_5$ was observed in the Cu pillar/Sn interface after reflow. However, $Cu_3Sn$ formed and grew at Cu pillar/$Cu_6Sn_5$ interface with increasing annealing and stressing time. The growth kinetics of total($Cu_6Sn_5+Cu_3Sn$) IMC changed when all Sn phases in Cu pillar bump were exhausted. The complete consumption time of Sn phase in electromigration condition was faster than that in annealing condition. The quantitative interfacial adhesion energy after 24h at $180^{\circ}C$ was $0.28J/m^2$ while it was $3.37J/m^2$ before annealing. Therefore, the growth of IMC seem to strongly affect the mechanical reliability of Cu pillar bump.

• Journal of the Korean institute of surface engineering
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• v.38 no.3
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• pp.118-125
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• 2005

Low temperature plasma treatment with different gases and rf powers were performed to improve the adhesion strength between polytetrafluoroethylene(PTFE) and electroless deposited copper. According to the research, $H_2$ plasma having hydrogen radical was more effective in surface polarity modification than $O_2$ plasma due to the defluorination reaction. However, surface roughness of PTFE was more increased with $O_2$ than $H_2$ plasma. PTFE treated with $120W-O_2$ plasma and $250w-H_2$ plasma, consecutively showed rougher surface than single step $250w-H_2$ plasma treated one and more hydrophilic than single step $120W-O_2$ plasma treated one. And it showed 5B tape test grade, which is better adhesion property than 1B or 3B obtained by single step plasma treatment. In addition, adhesion strength between PTFE and Cu deposit is also deeply affected by residual water on its interface.

• Korean Journal of Materials Research
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• v.15 no.7
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• pp.458-464
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• 2005

In microelectronics packaging, the reliability of the metal/polymer interfaces is an important issue because the adhesion strength between dissimilar materials is often inherently poor. The modification of polymer surfaces by ion beam irradiation and rf plasma is commonly used to enhance the adhesion strength of the interface. T-peel strengths were measured using a Cu/polyimide system under varying $N_2^+$ ion beam irradiation conditions for pretreatment. The measured T-peel strength showed reversed camel back shape regarding the fixed metal-layer thickness, which was quite different from the results of the 90° peel test. The elementary analysis suggests that the variation of the T-peel strength is a combined outcome of the plastic bending work of the metal and polymer strips. The results indicate that the peel strength increases with $N_2^+$ ion beam irradiation energy at the fixed metal-layer thickness.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.42-46
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• 2005

In microelectronics packaging, the reliability of the metal/polymer interfaces is an important issue because the adhesion strength between dissimilar materials is often inherently poor. The modification of polymer sufaces by ion beam irradiation and rf plasma are commonly used to enhance the adhesion strength of the interface. T-peel strengths were measured using a Cu/polyimide system under varying $Ar^+$ ion beam irradiation pretreatment conditions. The measured T-peel strength showed reversed camel back shape regarding the fixed metal-layer thickness, which was quite different from the results of the $90^{\circ}$ peel test. The elementary analysis suggests that the variation of the T-peel strength is a combined outcome of the plastic bending work of the metal and polymer strips. The results indicate that the peel strength increases with $Ar^+$ ion beam irradiation energy at the fixed metal-layer thickness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.458-461
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• 2004

In order to improve the adhesion properties of copper, MPS(3-mercaptopropyltrimethoxysilane) organic film were employed. The plasma pretreatment in pure He or $He/O_{2}$ mixed gas environment greatly increased adhesion force. Adhesion force was measured by scratch test with nano indenter. Microstructures and surface roughness were observed with scanning electron microscope(SEM). The characteristics of MPS layer for pretreatment were studied with flourier transform infrared spectroscope(FT-IR) and contact angle tester. The heighest adhesion was achieved in the specimen pretreated with mixed plasma and NPS coating, which was 56mN. Other specimen showed lower value by $20{\%}$ to $30{\%}$. The roughness of substrate was not affected by the bonding strength of copper plating.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.204-210
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• 2008

$1.5\;{\mu}m$-thick copper films deposited on silicon wafers were successfully bonded at $415^{\circ}C$/25 kN for 40 minutes in a thermo-compression bonding method that did not involve a pre-cleaning or pre-annealing process. The original copper bonding interface disappeared and showed a homogeneous microstructure with few voids at the original bonding interface. Quantitative interfacial adhesion energies were greater than $10.4\;J/m^2$ as measured via a four-point bending test. Post-bonding annealing at a temperature that was less than $300^{\circ}C$ had only a slight effect on the bonding energy, whereas an oxygen environment significantly deteriorated the bonding energy over $400^{\circ}C$. This was most likely due to the fast growth of brittle interfacial oxides. Therefore, the annealing environment and temperature conditions greatly affect the interfacial bonding energy and reliability in Cu-Cu bonded wafer stacks.

• Journal of the Korean institute of surface engineering
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• v.33 no.4
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• pp.241-250
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• 2000

Popcorn cracking phenomena frequently occur in thin plastic packages during the solder reflow process, which are definitely affected by poor adhesion of Cu-based leadframe to epoxy molding compounds (EMCs). In the present work, in order to enhance the adhesion strength, a brown-oxide treatment on the Cu-based leadframe was carried out and the adhesion strength of leadframe/EMC interface was measured in terms of fracture toughness by using sandwiched double-cantilever beam (SDCB) specimens. After the adhesion tests, fracture surfaces were analyzed by SEM, AES, EDS and AFM to make the failure path clear. Results showed that failure path was closely related to the oxidation time and the interfacial fracture toughness.