XRD and ToF-SIMS study of intermetallic void formation in Cu-Sn micro-connects. (September 2017)

• Record Type: Journal Article
• Authors: Ross, G.; Vuorinen, V.; Krause, M.; Reissaus, S.; Petzold, M.; Paulasto-Kröckel, M.
• Is Part Of: Microelectronics and reliability. Volume 76/77(2017)
• Page Start: 390
• Page End: 394
• Publication Date: 2017-09
• Subjects: Intermetallic voids -- Kirkendall voids -- Reliability -- 3D integration -- X-ray diffraction -- Time-of-flight mass spectroscopy; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2017.07.044
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: An identified reliability challenge of significant importance to Cu–Sn bonding for 3D integration is Cu–Sn intermetallic void formation. Voids, often referred to as Kirkendall voids, form within the inter-diffusional zone between Cu and Sn, more specifically within the intermetallic compound Cu3 Sn. The root-cause(s) of void formation is not well understood, therefore this study is designed to understand under what conditions voids form. The two main hypotheses for the root-causes of void formation are (i) the imbalance of diffusion rates between Cu and Sn during the formation of Cu–Sn intermetallic compounds and the resulting residual stresses and (ii) the co-deposition of impurities during Cu electroplating to void formation. Therefore, an ex- and in-situ x-ray diffraction (XRD) study is used to probe the material state as a function of thermal annealing, and a time-of-flight mass spectroscopy (ToF-SIMS) study is used to detect impurities co-deposited during Cu electroplating and to understand the effects of thermal annealing on the impurities' kinetic behaviour. Highlights: An XRD and ToF-SIM study of Cu-Sn intermetallic compound voids. Limited Cu crystal growth during isothermal annealing in the sample that exhibited dense voiding. Detected electroplated Cu impurities include Cl, S, O and C. Segregation of impurities from the electroplated Cu to the Cu/Cu3 Sn interface and the Cu3 Sn IMC.