Advanced Microelectronic Packaging, Emerging Interconnection Technology and Pb-free Solder: 3D Microelectronic Packaging and Emerging Interconnects I
Sponsored by: TMS Functional Materials Division, TMS: Electronic Packaging and Interconnection Materials Committee
Program Organizers: Christopher Gourlay, Imperial College London; Kazuhiro Nogita, University of Queensland; David Yan, San Jose State University; Mike Wolverton; Babak Arfaei, Ford Motor Company; Andre Delhaise; Mehran Maalekian, Mat-Tech; Mohd Arif Salleh, Universiti Malaysia Perlis
Tuesday 2:00 PM
February 25, 2020
Room: Palomar
Location: Marriott Marquis Hotel
Session Chair: David Yan, San Jose State University; Babak Arfaei, Ford Motor Co.
2:00 PM
Mechanical Reliability of Cu-filled Through Si via under Annealing and Thermal Cyclic Loading Conditions: Dipali Sonawane1; Praveen Kumar1; 1Indian Institute of Science
Cu-filled-TSV is subjected to thermal expansion mismatch induced stresses during fabrication and service that can compromise structural integrity of microelectronic packages. Here, we comprehensively report effects of thermal stresses under annealing and myriad of thermal cycling conditions. Extrusion of Cu relative to Si, grain-boundary sliding, and failure of TaN barrier-layer leading to Cu-Si reaction were observed during thermal cycling between -50 and 150 oC, whereas such effects were observed only at significantly higher temperatures (250-650 °C) during static annealing. Cu-Si reaction led to nucleation of micro-cracks in Si that propagated during subsequent room temperature storage, suggesting slow crack growth in Si. Post-annealing microstructural analysis, including elemental mapping, and stress measurement using Raman spectroscopy suggest that oxidation of Si at the crack-tip and residual thermal stresses can be driving force for the slow fracture of Si. Insights gained into mechanics of the observations using finite element analysis will be discussed.
2:20 PM
Different Electroplating Temperature Affecting on Mechanical Strength of Highly (111) Preferred Orientated Nanotwinned Copper (TMS 2020): Chen Fu-Chian1; Chih Chen1; 1National Chiao Tung University
Recently, highly (111) preferred orientated nanotwinned copper (nt-Cu) has been studied for potential applications in electronic packaging and lithium ion batteries. The mechanical strength of nt-Cu is almost the same as commonly used Cu alloys, but nt-Cu provides better electrical conductivities, which is a great advantage for application in electronic devices. Some applications in 3D-IC require high strength, high thermal stability and well electromigration resistance. It is reported that nt-Cu possesses all the characteristics. In this study, three different electroplating temperatures are used to electroplate nt-Cu: 15°C, 25°C and 35°C. We used a tensile tester to measure the UTS (Ultimate tensile strength) and elongation of each sample. By controlling the electroplating parameters, we can electroplate nt-Cu with different strength, ranging from 700MPa after 150 °C annealing for 1h.
2:40 PM
Formation of Cu-Cu Direct Bonding by Green Synthesized Approaches: Wei Liu1; Kuo-Shuo Huang1; Wen-Chih Lin1; Jim Wang2; Albert T. Wu1; 1National Central University; 2SHENMAO Technology Inc.
Cu to Cu direct bonding is considered as a new packaging technique for power device module. The Cu particles with different sizes are chemically synthesized in organic acidic solution. The Cu particles aggregate in the solution and form Cu paste. Cu particles are sintered at temperatures below 150 oC for different duration of times in ambient. The Cu particles in the paste are prevented from oxidation. Sintering of the Cu particles occurs continuously. Cu paste is applied between two Cu coupons, and the morphology of the sintered bonds are examined by optical and scanning electron microscopy. The Cu paste is also applied between Cu wires for measuring resistivity. Detail bonding mechanism is investigated by using transmission electron microscope. The effect of particle sizes on bonding ability is assessed.
3:00 PM
Effect of a Metallic Cap Layer on the Magnitude, Statistical Variation and Mechanism of Through-Silicon Via Extrusion: Golareh Jalilvand1; Tengfei Jiang1; 1University of Central Florida
The statistical variation of via extrusion is an important reliability issue for TSV-based 3D-IC, as the overall reliability of the device is limited by the weakest link, i.e. a small number of vias with the highest extrusion.In a novel approach, an effective reduction in the statistical variation of TSV extrusion is demonstrated by the application of a metallic cap layer on the top surface of the vias. Furthermore, using focused ion beam, electron backscatter diffraction and white light interferometry, we investigate the correlation between the microstructure and the magnitude of via extrusion and show how this correlation is affected by the presence of the cap layer. Results from the uncoated vias reveal a direct microstructure-extrusion correlation while no such correlation is observed in capped vias. This clearly suggests the significance of mass transport along grain boundaries, which as a main extrusion mechanism, is effectively controlled by the cap layer.
3:20 PM Break
3:40 PM
Reducing Interfacial Voids in Cu/In/Cu Microbump with In-Sn-Cu Solder Alloy: Rui Wen Song1; Jenq Gong Duh1; 1National Tsing Hua University
3D-IC is an ongoing trend and challenge in electronic packaging industry, and the microbump reliability has been attracting lots of interests. To overcome the reliability or manufacturing challenges, such as warpage and low thermal budget, low melting point solder alloys are increasingly studied. Although Indium-rich solder has a beneficial low melting point of 156°C, the formation of interfacial voids after bonding has raised concerns for reliability. By introducing Cu and Sn, the solder remained low melting points and the interfacial voids were significantly reduced. The melting point of Cu-Sn-In alloys were measured by DSC to ensure that there is no additional phase transformation at higher temperature. In addition, the interfacial IMCs phases were characterized by EPMA and XRD. Moreover, the grain structure was also altered by adjusting Cu and Sn compositions, and thus better mechanical reliability could be expected.
4:00 PM
Investigation to Micro Friction Stir Spot Welding Al and Cu Sheets to Foils for Automotive Lithium-ion Battery Cells Assembly: Harry Chang1; Jason Silberman1; Danny Ventura1; Kylie Dodge1; David Yan1; 1San Jose State University
Electric vehicle battery packs consist of a large number of battery cells which must be assembled together with robust mechanical and electrical joints. One of the challenges in battery manufacturing is to join highly conductive and dissimilar multilayer materials such as Al and Cu sheets to foils with 100% reliability. Micro friction stir spot welding (MFSSW) is a spot-like joining process utilizing a non-consumable tool to generate frictional heat and join multilayer materials under the solid-state condition. This present work investigates the capability of MFSSW thirty aluminum foils sandwiched between aluminum and copper sheets. The joint strength and electrical conductivity in relation to MFSSW force/torque and temperature are characterized and presented.
4:20 PM
Thermal Management through Networks of Highly Purified Boron Nitride Nanotubes: Mahmoud Amin1; David Kranbuehl1; Hannes Schniepp1; 1The College of William & Mary
Advanced materials with high thermal conductivity while electrically insulating are needed for thermal management in high-power microelectronics. Boron nitride nanotubes (BNNTs) feature outstanding performance in both respects, thus being highly promising for such applications. We developed a technique to produce highly purified BNNTs in a scalable manner to further enhance their performance. We further developed spectroscopic methods to detect BNNT purity. Rather than simply embedding BNNTs into a matrix material, we are working with 3-dimensional networks of strongly connected tubes for enhanced thermal transport. Compared to composites made of disconnected tubes of the same volume concentration, this approach leads to enhanced thermal and mechanical properties. Based on the network topology we have detected directional thermal conductivity, which has great potential for advanced thermal applications.
4:40 PM
Effect of Sn3.0 Ag 0.5Cu and Sn58Bi Solder Alloys on Through Silicon Via under Thermal Conditions: Jiaojiao Wang1; Limin Ma1; Fu Guo1; Yishu Wang1; Jianyu Feng1; 1Beijing University of Technology
Through Silicon Via (TSV) is considered as a novel and significant three-dimensional packaging technology as result of its high degree of technical freedom. The coefficients of thermal expansion (CTE) mismatch among various materials in TSVs, therefore the negative reliability problems under thermal conditions can’t be overlooked. In this paper, TSVs were experienced thermal cycling between -55℃～125℃ and thermal aging between 80℃～120℃. The samples exhibited deformation and failure such as bulging and cracking. The results of Raman spectrums showed that tensile stress of the top of TSVs filled with Sn3.0 Ag 0.5Cu and Sn58Bi solders was proportional to the peak temperature of thermal loads. The failure behaviors of the solder such as swelling and cracking were relevant to the tensile stress. Meanwhile, EBSD analysis showed that the grain size of TSVs increased with the increase of peak temperature, and the grain orientation was related to the thermal stress.