@misc{oai:uec.repo.nii.ac.jp:00001207,
 author = {横川, 慎二 and Yokogawa, Shinji},
 month = {2016-09-16},
 note = {2007, The interconnect technology in large-scale integration (LSI) is one of the importanttechnologies that determine the performance, characteristics, and components per chipof LSI.The most important characteristic of the “Planer patent” of Robert Noyce et al.,which addresses one of the fundamental concepts of integrated circuits, is theinterconnect technology, which involves printing and connecting semiconductor deviceson a substrate. This technology is cheap and suitable for mass production, and hencethe integration degree has evolved explosively with advancement in the processtechnology. Today, LSI has been developed to ultra large scale integration (ULSI),which involves device components that exceed hundreds of millions. Every device isconnected by interconnects, which are spread around in all directions. Multi-levelinterconnects are required for these circuit integrations. As of 2007, the multi-levelstructures have exceeded ten layers. Moreover, the interconnect dimension has beenreduced to 100 nm or less due to the evolution in the process technology. Along withthe augmentation of the integration degree, the interconnect technology continues tosignificantly contribute toward the quality and reliability of LSI.Electromigration was considered to be a significant issue with regard to thereliability of interconnects from that sudden rise period. Because Si substrates with large heat capacities are used, the nature of radiation of the interconnects that arecovered by SiO2 with high thermal conductivity is outstanding as compared to that ofthe electric wire usually used. Therefore, this phenomenon allows large currentdensities and can contribute toward improvement in the speed of integrated circuitfunctions. However, this significantly high current density induces electromigration,which is the factor that affects the reliability of LSI interconnects.In order to control the electromigration over a product life cycle period,countermeasures must be adopted in all the phases of LSI product development, that is,action plans are required to maintain a sufficiently low probability of failure in eachphase of product development, planning, design, prototype, manufacture, and testing inorder to achieve high reliability. For this purpose, it is important to understand thefailure mechanisms correctly, and this becomes an important key for establishing aphysical and statistical model for reliability prediction. In particular, ensuringreliability is one of the important measures of success in the development of anext-generation LSI process technology.In this thesis, the reliability focused on electromigration and fundamentaltechnology of highly reliable, narrow damascene Cu interconnects are discussed. Thelifetime characteristics and failure mechanisms are clarified based on a reliability test.Moreover, the fundamental physical characteristics are investigated, and a methodologyto realize highly reliable interconnects is proposed. Based on this investigation, theadvanced process technologies were developed and a comparison between them wasperformed. The failure mechanisms of Cu interconnect, which are clarified in thisstudy, will contribute toward the development of ULSI process technologies in thefuture. Moreover, the approach adopted in this study will also be effective in thedevelopment of integrated circuits in next-generation nano-devices.This thesis comprises eight chapters.Chapter 1, “Introduction,” surveys the role and importance of the interconnecttechnology for achieving advanced LSI. Moreover, the modeling phase from a failurephysics model to a LSI lifetime prediction model is indicated, and the organic link andnecessity for each phase are discussed. Based on these relationships, the purpose ofthis thesis is proposed.In Chapter 2, “Reliability of narrow Cu interconnect and Failure Mechanism,” theelectromigration characteristics that are investigated by the conventional lifetime testare discussed. In particular, based on the comparison with aluminum interconnectsthat were widely adopted before Cu interconnect, the electromigration characteristicsand key points required to improve Cu reliability are proposed.In Chapter 3, “Void nucleation and growth,” the characteristics of theelectromigration-induced void nucleation and growth are discussed based on Blech’sbasic electromigration model. The coefficient of diffusion and driving force in Blech’smodel are investigated experimentally, and the Cu diffusion mechanism is discussed.In the study of the diffusion coefficient, the dominant diffusion mechanism isinvestigated experimentally by using the activation energy and crystal structure.Moreover, the atomic driving forces of Cu, electron wind force, and stress-inducedbackflow, are discussed in detail along with the electromigration threshold currentdensity-length product.In Chapter 4, “Dimension dependence on electromigration of Cu interconnect,” thevoid nucleation and growth are investigated with regard to line-width dependence, andthe effects of miniaturization based on Blech’s model are discussed. The contributionsof the diffusion path of Cu are discussed according to the line-width dependence.The current waveform, which flows into the interconnect in actual LSI operations,is a pulse current and not a direct-current electricity that is widely used for reliabilitytests. Hence, in Chapter 5, “Void nucleation and growth behavior under pulsecurrent,” the void nucleation and growth under pulse current are investigated, and the effect of the electromigration phenomenon on actual LSI operations is discussed.In Chapter 6, “Electromigration lifetime distribution and failure mode,” thepurpose, function, and superiority of the new proposed test structure are shown in orderto study the correlation between the failure mode and lifetime distribution. This teststructure enables the investigation of the electromigration failure modes of very lowcumulative failure probability physically and statistically by using the opticalbeam-induced resistance change (OBIRCH) method. The relationship between theelectromigration lifetime distribution and the results of the physical analysis arediscussed.In Chapter 7, “Advanced interconnect technology to improve electromigration,”the challenges involved in achieving performance and reliability are described based onthe development of interconnect technologies for 45 nm and beyond generation, and thenovel resistivity measurement technique for the efficient development is proposed. Byusing this technique, a comparison of the several advanced process technologies isperformed, and the efficiency of the technique is discussed. Moreover, the reliabilityimprovement efficiency of the impurity doping to Cu is investigated based on thephysical mechanism; further, the directionality and guidelines are proposed for thedevelopments of interconnect technology for 32 nm node and beyond.In Chapter 8, “Conclusion,” the conclusion of this thesis is summarized along withthe challenges involved in the development of a reliable LSI system in the future.},
 title = {LSI微細Cu配線におけるエレクトロマイグレーション信頼性に関する研究},
 year = {},
 yomi = {ヨコガワ, シンジ}
}