Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps

In microelectronic packaging technology for three-dimensional integrated circuits (3D ICs), Cu-to-Cu direct bonding appears to be the solution to solve the problems of Joule heating and electromigration (EM) in solder microbumps under 10 <inline-formula><math xmlns="http://www.w3.org/1...

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Autores principales:	Kai-Cheng Shie, Po-Ning Hsu, Yu-Jin Li, K. N. Tu, Chih Chen
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	electromigration Cu–Cu direct bonding three-dimensional integrated circuits (3D ICs) Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85
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spelling	oai:doaj.org-article:001536b276f041919c682d97487e8dc02021-11-11T17:58:20ZEffect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps10.3390/ma142163941996-1944https://doaj.org/article/001536b276f041919c682d97487e8dc02021-10-01T00:00:00Zhttps://www.mdpi.com/1996-1944/14/21/6394https://doaj.org/toc/1996-1944In microelectronic packaging technology for three-dimensional integrated circuits (3D ICs), Cu-to-Cu direct bonding appears to be the solution to solve the problems of Joule heating and electromigration (EM) in solder microbumps under 10 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mrow><mi mathvariant="sans-serif">μ</mi><mi mathvariant="normal">m</mi></mrow></mrow></semantics></math></inline-formula> in diameter. However, EM will occur in Cu–Cu bumps when the current density is over <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mn>6</mn></msup><mo> </mo><mi mathvariant="normal">A</mi><mo>/</mo><msup><mrow><mi>cm</mi></mrow><mn>2</mn></msup></mrow></semantics></math></inline-formula>. The surface, grain boundary, and the interface between the Cu and TiW adhesion layer are the three major diffusion paths in EM tests, and which one may lead to early failure is of interest. This study showed that bonding strength affects the outcome. First, if the bonding strength is not strong enough to sustain the thermal mismatch of materials during EM tests, the bonding interface will fracture and lead to an open circuit of early failure. Second, if the bonding strength can sustain the bonding structure, voids will form at the passivation contact area between the Cu–Cu bump and redistribution layer (RDL) due to current crowding. When the void grows along the passivation interface and separates the Cu–Cu bump and RDL, an open circuit can occur, especially when the current density and temperature are severe. Third, under excellent bonding, when the voids at the contact area between the Cu–Cu bump and RDL do not merge together, the EM lifetime can be more than 5000 h.Kai-Cheng ShiePo-Ning HsuYu-Jin LiK. N. TuChih ChenMDPI AGarticleelectromigrationCu–Cu direct bondingthree-dimensional integrated circuits (3D ICs)TechnologyTElectrical engineering. Electronics. Nuclear engineeringTK1-9971Engineering (General). Civil engineering (General)TA1-2040MicroscopyQH201-278.5Descriptive and experimental mechanicsQC120-168.85ENMaterials, Vol 14, Iss 6394, p 6394 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	electromigration Cu–Cu direct bonding three-dimensional integrated circuits (3D ICs) Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85
spellingShingle	electromigration Cu–Cu direct bonding three-dimensional integrated circuits (3D ICs) Technology T Electrical engineering. Electronics. Nuclear engineering TK1-9971 Engineering (General). Civil engineering (General) TA1-2040 Microscopy QH201-278.5 Descriptive and experimental mechanics QC120-168.85 Kai-Cheng Shie Po-Ning Hsu Yu-Jin Li K. N. Tu Chih Chen Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
description	In microelectronic packaging technology for three-dimensional integrated circuits (3D ICs), Cu-to-Cu direct bonding appears to be the solution to solve the problems of Joule heating and electromigration (EM) in solder microbumps under 10 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mrow><mi mathvariant="sans-serif">μ</mi><mi mathvariant="normal">m</mi></mrow></mrow></semantics></math></inline-formula> in diameter. However, EM will occur in Cu–Cu bumps when the current density is over <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mn>6</mn></msup><mo> </mo><mi mathvariant="normal">A</mi><mo>/</mo><msup><mrow><mi>cm</mi></mrow><mn>2</mn></msup></mrow></semantics></math></inline-formula>. The surface, grain boundary, and the interface between the Cu and TiW adhesion layer are the three major diffusion paths in EM tests, and which one may lead to early failure is of interest. This study showed that bonding strength affects the outcome. First, if the bonding strength is not strong enough to sustain the thermal mismatch of materials during EM tests, the bonding interface will fracture and lead to an open circuit of early failure. Second, if the bonding strength can sustain the bonding structure, voids will form at the passivation contact area between the Cu–Cu bump and redistribution layer (RDL) due to current crowding. When the void grows along the passivation interface and separates the Cu–Cu bump and RDL, an open circuit can occur, especially when the current density and temperature are severe. Third, under excellent bonding, when the voids at the contact area between the Cu–Cu bump and RDL do not merge together, the EM lifetime can be more than 5000 h.
format	article
author	Kai-Cheng Shie Po-Ning Hsu Yu-Jin Li K. N. Tu Chih Chen
author_facet	Kai-Cheng Shie Po-Ning Hsu Yu-Jin Li K. N. Tu Chih Chen
author_sort	Kai-Cheng Shie
title	Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
title_short	Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
title_full	Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
title_fullStr	Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
title_full_unstemmed	Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps
title_sort	effect of bonding strength on electromigration failure in cu–cu bumps
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/001536b276f041919c682d97487e8dc0
work_keys_str_mv	AT kaichengshie effectofbondingstrengthonelectromigrationfailureincucubumps AT poninghsu effectofbondingstrengthonelectromigrationfailureincucubumps AT yujinli effectofbondingstrengthonelectromigrationfailureincucubumps AT kntu effectofbondingstrengthonelectromigrationfailureincucubumps AT chihchen effectofbondingstrengthonelectromigrationfailureincucubumps
_version_	1718431921168449536

Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps

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