Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic Materials XIX: Poster Session
Sponsored by: TMS Functional Materials Division, TMS: Alloy Phases Committee
Program Organizers: Hiroshi Nishikawa, Osaka University; Shi-Kang Lin, National Cheng Kung University; Chao-Hong Wang, National Chung Cheng University; Chih-Ming Chen, National Chung Hsing University; Jaeho Lee, Hongik University; Zhi-Quan Liu, Shenzhen Institutes of Advanced Technology; Ming-Tzer Lin, National Chung Hsing University; Dajian Li, Karlsruhe Institute of Technology; Yu Zhong, Worcester Polytechnic Institute; Yee-wen Yen, National Taiwan University of Science and Technology; Song-Mao Liang, Clausthal University of Technology; A.S.Md Abdul Haseeb, Bangladesh University of Engineering and Technology (BUET); Ligang Zhang, Central South University; Sehoon Yoo, Korea Institute of Industrial Technology
Monday 5:30 PM
February 24, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr
Session Chair: Hiroshi Nishikawa, Osaka University; Shih-Kang Lin, National Cheng Kung University
D-10: A Switching Model of Phase-change Memory by Combining Electrothermal and Phase-field Models: Hwanwook Lee1; Minkyu Shin1; Yongwoo Kwon1; 1Hongik University
Phase-change memory (PCM) utilizes a reversible transformation between amorphous and crystalline phases in GeSbTe, a chalcogenide material. Insulating amorphous phase and conducting crystalline phase represent binary data of zero and one. Switching operations between zero and one are electrically done. Melt-quench is done by a short high power pulse while crystallization is done by a long moderate power pulse. The switching operations involve electrostatics, Joule heating, heat transfer, and phase transformation effects altogether. In this presentation, we will demonstrate our PCM device model that integrates electrothermal equations to simulation temperature distribution and phase-field equations to simulate phase distribution. Some simulation results on memory and synapse devices will be also shown.
D-11: CALPHAD-assisted Analyses of BOF Slag Recovery: Han-Yu Wang1; Wan-Yu Huang1; Yung-Chang Liu2; Kuan-Ju Lin2; Shih-kang Lin1; 1National Cheng Kung University; 2China Steel Corporation
Basic-oxygen furnace (BOF) slag is a byproduct during the steelmaking process, composed of high free-CaO (unreacted CaO), FeO, and P2O5 contents. BOF slag is a wasted and has been used as aggregates for road and hydraulic construction. However, free-CaO hydrolyzes with water and causes expansion and metal leaching issues. A new approach for recycling BOF slag is to apply it on construction as BF slag cement. It involves materials modification with multicomponent complex reactions at high temperatures. In this study, we employ CALPHAD modeling to design a modification and reduction processes to increase BOF slag valorization. We optimize the reaction path of BOF slag which satisfied all the criteria for low melting temperature, no solid phase precipitation and low energy consumption in order to lower the CaO, FeO, and P2O5 contents during an entire process. Reaction path in multicomponent system is thoroughly investigated and an optimized reaction path is proposed.
D-12: Comparison of Oxide Reduction Temperature between Highly <111>-Oriented Nanotwinned Cu and Regular Cu Films: Wei-You Hsu1; Cheng-Syuan Wu1; Chi-Shen Lee1; Chih Chen1; 1National Chiao Tung University
Low temperature Cu-Cu direct bonding was successfully achieved in 2014 using highly <111>-oriented Cu. [1] Because Cu (111) planes have the highest diffusivity and low oxidation rates, so two highly <111>-oriented Cu films can be bonded at low temperature of 150°C and low pressure of 1 MPa. Using forming gas in Cu-Cu bonding process can efficiently decrease the oxygen content in the interface. [2] In this study, we use temperature-programmed reduction (H2-TPR) to reduce the oxide of highly <111>-oriented nanotwinned Cu (nt-Cu). Using thermal conductivity detector (TCD) to detect the consumption of hydrogen and then knowing the reduction temperature of nt-Cu under the reducing atmosphere (5%H2+95%Ar) is about 215°C. In contrast, the reduction temperature of regular Cu under the same condition is about 290°C.
D-13: Effects of Current Stressing on Mechanical Property and Microstructure of an Fe-Ni Alloy at Ambient Temperature: Jun-Jia Huang1; Kwang-Lung Lin1; 1National Cheng Kung University
Electromigration is a phenomenal process that can induce recrystallization without traditional deformation. Previous studies found that electric current can induce non-deformation electro-recrystallization and cause electro-refining on bonding wire and solder materials. The study investigated the electro-recrystallization behavior of an Fe-Ni alloy (Invar 36, Fe-36%Ni gamma phase solid solution). Typical recrystallization temperature needs to be higher than 0.4 times of melting point temperature, and common manufacturing processes for Invar 36 using temperature even up to 830℃ to cause recrystallization and homogenization. The present study adopted 7000~8000 A/cm^2 electric current and various stressing cycles to investigate the effects of electrical current on Vickers microhardness and microstructure of Invar 36 strips. The process was conducted at ambient condition well below 0.4 times of the alloy melting point. Microhardness of the annealed alloys vary between 150~170 HV depending on stressing conditions. The microstructures were analyzed by XRD, SEM/EBSD, and TEM.
D-14: Effects of Plating Current Density on the Microstructure of Cu Pillars and Its Solderability: Pei-Tzu Lee1; Ying-Syuan Wu2; Cheng-Yu Lee2; Wei-Ling Chou2; Hung-Cheng Liu3; Cheng-En Ho2; 1National Taiwan University; 2Yuan Ze University; 3Kinsus Interconnect Technology Corporation
In this study, effects of plating current density (j) on the Cu pillar microstructure and its solderability were investigated. Analyses of transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) showed that the Cu grain size and the crystallographic orientation strongly depended on j. Two intermetallic compound (IMC) species (η-Cu6Sn5 and Cu3Sn) accompanying with the material defects (e.g., nanovoids) formed at the solder/Cu pillar interface after reflow, particularly for the high j case (10 ASD). Upon high-speed ball shear testing, the shear force of Cu pillar bumps significantly decreased with increasing j due to the presence of numerous nanovoids at the interface. The information of the present study advances our understanding of the j effects on the electrochemical metal deposition, and will be helpful in development of the high-speed Cu electrodeposition and Cu pillar bump technologies.
D-15: Effects of Surface Finish on the Interfacial Cu6Sn5 Morphology and Mechanical Characteristics in Solder Joints: Wei-Ling Chou1; Shu-Ping Yang1; Cheng-Yu Lee1; Tsai-Tung Kuo2; Cheng-En Ho1; 1Yuan Ze University; 2Taiwan Uyemura Limited Company
Phase formation and transformation in the metallurgical reactions between an 96.5Sn-3Ag-0.5Cu (wt.%) alloy and Cu pads with different surface finishes were systematically investigated. The surface finishes included organic solderability preservative (OSP), immersion Ag, immersion Sn, Au/Pd (EPIG), and Au/Pd/Au (IGEPIG). Cu6Sn5 and Cu3Sn were the predominant intermetallic compound (IMC) species nucleated at the joint interface after reflow(s). Interestingly, the growth morphology of Cu6Sn5 strongly depended on the surface finish type, dominating the mechanical characteristics of the joint interface. Finally, finite element analysis via ANSYS software was conducted to rationalize this interesting finding. Details will be presented in this study.
D-16: From Electric Current-induced Lattice Strain to Electromigration Occurrence: An In-situ Study: Kuan-Hsueh Lin1; Yu-chen Liu1; Shih-kang Lin1; Ching-Shun Ku2; Shang-Jui Chiu2; 1National Cheng Kung University; 2National Synchrotron Radiation Research Center
In 1976, Blech proposed the “critical product”, which is the product of current density and length, to be the criteria for the occurrence of electromigration (EM). EM causes atomic diffusion in metal strip and leads to device failure. The back stress model well explained this effect for strips up to 150 microns. However, we found in this study that it failed to predict EM occurrence in strips 5000 long or longer. The correlation between the lattice strain and electromigration (EM) occurrence and the mechanism governing will be elucidated in this poster. Al strips with different lengths ranging from microns to centimeters were stressed by electric current with in situ synchrotron X-ray diffraction characterization. The results showed that over certain critical lattice strain, hillocks formation on all Al strips in spite of lengths was observed under scanning electron microscopy. Further first principles calculations were conducted to explain this critical lattice strain.
D-17: Interfacial Reaction of Au-xAg/Al Couples: Chiao-Yi Yang1; Kuo-Jung Chen1; Hsien-Ming Hsiao2; Yee-Wen Yen3; 1Department of Materials Science and Engineering, National Taiwan University of Science and Technology; 2Institute of Nuclear Energy Research; 3National Taiwan University of Science and Technology
The Au/Al structure in the wire bonding technology is the most widely used and mature connection circuit in electronic assembly. In this study, various Au-xAg/Al couples were prepared and aged at 450°C. The results indicated that the AuAl2, Au2Al, and Au4Al phases were formed at the Au-25 wt.%Ag/Al interface. When the Ag content in the Au was increased to 30, 40, 50 and 75 wt.%., the Ag2Al, AuAl2, and Au4Al phases were formed at the interface. The total intermetallic compounds (IMCs) thickness was increased when the Ag content was increased. Meanwhile, when the Ag content was increased, the IMCs formation at the interface was changed from the Au-Al system to the Au-Ag and Au-Al systems.
D-18: Interfacial Reactions in the Au/Sn-xZn/Cu Sandwich Couples: Yi-Show Lin1; Yi-Pin Wu1; Yee-Wen Yen1; 1National Taiwan University of Science and Technology
The Sn-xZn alloys (1.0 mm thickness) were reacted with Cu substrate at 270°C for 1 h then clamped together over an Au foil to form the Au/Sn-xZn/Cu sandwich couples. Au-Sn intermetallic compounds (IMCs) were formed at the Sn-1Zn/Au interface for 160°C and 20-h aging. The Cu6Sn5 phase was observed which revealed that Cu atoms rapidly diffused through the Sn-1Zn solder. Au-Sn, Au-Zn IMCs, and an Au-Sn-Zn ternary metastable phase were formed at the Sn-xZn/Au interface (x=5 and 9 wt.%). Only Au-Zn IMCs were formed when Zn contents were more than 20 wt.%. On Cu side, the (Cu, Zn)6Sn5, (Cu, Sn)Zn phases at the Sn-1Zn/Cu interface, the Cu5Zn8 phase at the Sn-5Zn/Cu interface and the (Cu, Sn)5Zn8, (Cu, Sn)Zn5 phases at the Sn-xZn/Cu interfaces (x=9, 20 and 40 wt.%) were observed. The results indicated that IMC formation in the Au side strongly depended on the Zn concentration in the Sn-xZn alloys.
D-19: Interfacial Reactions in the Cu/Sn/Ni Sandwich Couples: Cheng-Han Lee1; Shih-Jung Chai1; Yee-Wen Yen1; 1National Taiwan University of Science and Technology
A soldering technique is commonly used to connect chip and chip in 3D IC packaging. Three different couples: Cu/Sn(5 m)/Ni, Cu/Sn(10 m)/Ni and Cu/Sn(15 m)/Ni were prepare to investigated interfacial reactions in the Cu/Sn/Ni sandwich couples . All couples were reflowed at 250oC for 1, 3 and 5 min then aged at 180oC up to 300 h. The results show that the complete Sn layer consumption time was increased with the increase of the Sn layer thickness for the same reflowing condition. The Cu6Sn5 phase was gradually transferred to the Cu3Sn phase, and Ni3Sn4 phase was disappeared when the aging time was increased. Meanwhile, the Cu3Sn thickness was increased with the increase of aged time and no Ni atom was observed in Cu3Sn phase for 300-h aging. The (Cu, Ni)6Sn5 phase acted the diffusion barrier to prevent Ni atom diffusion toward the Cu side.
D-20: Interfacial Reactions in the Sn/Au-xCu Couples: Po-Cheng Kuo1; Chia-Yi Yeh1; Hsien-Ming Hsiao2; Yee-Wen Yen3; 1Department of Materials Science and Engineering, National Taiwan University of Science and Technology; 2Institute of Nuclear Energy Research; 3National Taiwan University of Science and Technology
The solid/solid interfacial reactions of Sn/Au-xCu (x=15, 40, 60, 80 wt.%) couples at 150, 180 and 200˚C for 5 to 600 h were investigated in this study. The results indicated that (Au, Cu)Sn4, (Au, Cu)Sn, (Cu, Au)6Sn5 phases and Au-Cu-Sn ternary phase-B phase were formed in Sn/Au-15Cu system. The (Au, Cu)Sn, (Cu, Au)6Sn5, B phase and (Cu, Au)6Sn5, (Cu, Au)3Sn, B phase were formed in the Sn/Au-40Cu and Sn/Au-60Cu couples, respectively. The (Cu, Au)6Sn5, (Cu, Au)3Sn and B phase were observed in the Sn/Au-80Cu couple. Increasing the Cu content in Au-Cu alloys, reaction time and temperature, the formation of intermetallic compounds (IMCs) was gradually changed from Au-Sn system to Cu-Sn system. Meanwhile, the total IMC thickness was increased with the increase of reaction time and temperature. The IMC thickness was proportional to the square root of reaction time and IMC growth mechanism was diffusion controlled in the Sn/Au-xCu couples.
D-21: Interfacial Reactions of Ag-Au-xPd Alloys Wire Bonding with Al: Chiao-Yi Yang1; Kuo-Jung Chen1; Wallace Chuang2; Eckart Schellkes2; Yee-Wen Yen1; 1National Taiwan University of Science and Technology; 2Robert Bosch Taiwan Co. Ltd. Automotive Electronics Division
Recently, the wire bonding technology is the most widely used to connect chip and pad in the electronic packaging. Au-Ag alloys have good thermal and electrical conductivity and great ductility. They are suitable to replace the pure Au wire for the cost reduction. The interfacial reactions of several Au-Ag wires reacted with the Al pad at 150°C for various time, decapsulation and corrosion test were investigated in this study. The Au4Al phase was formed at the Au/Al interface. The Ag2Al phase was formed at Ag (coated Au)/Al, Ag (coated Pd)/Al, Au-95 wt.%Ag/Al and Ag/Al interface for 2000-h aging. When the aging time was increased to 3000 h, the Ag3Al phase was formed. For decapsulation, 95 vol.% HNO3 solution was a good solution to dissolve the mold compound. The result showed that the corrosion resistance order was Au > Ag (coated Au) > Ag (coated Pd) > Au-95 wt.%Ag.
D-22: Mechanisms of Abnormal Grain Growth of Al Bonding Wires under Annealing Process: Jen-Hsuan Tsai1; Fan-Yi Ouyang1; 1National Tsing Hua University
Wire bonding technology has been utilized in semiconductor industry for electrical connections. Al wire bonding considered as a potential material due to low cost, good conductivity, softness and the ability to be bonded at room temperature. This study investigated the grain growth of Al wire at different annealing temperatures. The Al bonding wires with diameter of 50 μm were carried out in baker at 200°C, 250°C and 300°C for 12 h, 24 h and 48 h, respectively, and the corresponding evolution of grain orientation of Al bonding wires was analyzed using electron back scatter diffraction. Initially, the grains of as-received Al wires were slender grains which is caused by the drawing process during fabrication of the wires. After annealing treatment, considerable grain growth and bamboo structure were observed in Al wires. The mechanism of abnormal grain growth of Al wires will be discussed.