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Book ChapterDOI

All‐Copper Interconnects for High‐Temperature Applications

29 Mar 2019-pp 293-312
About: The article was published on 2019-03-29. It has received 1 citations till now. The article focuses on the topics: Thermocompression bonding & Copper.
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Journal ArticleDOI
TL;DR: In this paper , the authors used computational modeling to provide a detailed insight into the structures and formation energies of primary vacancy clusters, mechanisms and barriers for their migration in bulk copper, and how these properties are affected at simple grain boundaries.
Abstract: Voids in face-centered cubic (fcc) metals are commonly assumed to form via the aggregation of vacancies; however, the mechanisms of vacancy clustering and diffusion are not fully understood. In this study, we use computational modeling to provide a detailed insight into the structures and formation energies of primary vacancy clusters, mechanisms and barriers for their migration in bulk copper, and how these properties are affected at simple grain boundaries. The calculations were carried out using embedded atom method (EAM) potentials and density functional theory (DFT) and employed the site-occupation disorder code (SOD), the activation relaxation technique nouveau (ARTn) and the knowledge led master code (KLMC). We investigate stable structures and migration paths and barriers for clusters of up to six vacancies. The migration of vacancy clusters occurs via hops of individual constituent vacancies with di-vacancies having a significantly smaller migration barrier than mono-vacancies and other clusters. This barrier is further reduced when di-vacancies interact with grain boundaries. This interaction leads to the formation of self-interstitial atoms and introduces significant changes into the boundary structure. Tetra-, penta-, and hexa-vacancy clusters exhibit increasingly complex migration paths and higher barriers than smaller clusters. Finally, a direct comparison with the DFT results shows that EAM can accurately describe the vacancy-induced relaxation effects in the Cu bulk and in grain boundaries. Significant discrepancies between the two methods were found in structures with a higher number of low-coordinated atoms, such as penta-vacancies and di-vacancy absortion by grain boundary. These results will be useful for modeling the mechanisms of diffusion of complex defect structures and provide further insights into the structural evolution of metal films under thermal and mechanical stress.
References
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Journal ArticleDOI
TL;DR: In this article, the structural phases and the growth of self-assembled monolayers (SAMs) are reviewed from a surface science perspective, with emphasis on simple model systems, and a summary of the techniques used for the study of SAMs is given.

2,374 citations

Journal ArticleDOI
TL;DR: This literature work seeks to review the numerous research attempts thus far for high temperature die attach materials on wide band gap materials of silicon carbide, gallium nitride and diamond, document their successes, concerns and application possibilities, all of which are essential for highTemperature reliability.
Abstract: The need for high power density and high temperature capabilities in today's electronic devices continues to grow. More robust devices with reliable and stable functioning capabilities are needed, for example in aerospace and automotive industries as well as sensor technology. These devices need to perform under extreme temperature conditions, and not show any deterioration in terms of switching speeds, junction temperatures, and power density, and so on. While the bulk of research is performed to source and manufacture these high temperature devices, the device interconnect technology remains under high focus for packaging. The die attach material has to withstand high temperatures generated during device functioning and also cope with external conditions which will directly determine how well the device performs in the field. This literature work seeks to review the numerous research attempts thus far for high temperature die attach materials on wide band gap materials of silicon carbide, gallium nitride and diamond, document their successes, concerns and application possibilities, all of which are essential for high temperature reliability.

405 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the hopping self diffusion coefficient of an adatom on the (1, 0, 0) surface of nine FCC metals using Monte Carlo variational transition state theory and the Lennard-Jones (L-J) interactions.

288 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a review of high-temperature power devices with a focus on the die attach materials operating at temperatures higher than 623 K (350 K).
Abstract: Recently, high-temperature power devices have become a popular discussion topic because of their various potential applications in the automotive, down-hole oil and gas industries for well logging, aircraft, space exploration, nuclear environments, and radars. Devices for these applications are fabricated on silicon carbide-based semiconductor material. For these devices to perform effectively, an appropriate die attach material with specific requirements must be selected and employed correctly. This article presents a review of this topic, with a focus on the die attach materials operating at temperatures higher than 623 K (350 °C). Future challenges and prospects related to high-temperature die attach materials also are proposed at the end of this article.

284 citations

Journal ArticleDOI
TL;DR: A low energy Ar ion beam of 40-100 eV was used to activate the Cu surface prior to bonding in this paper, which enables successful Cu-Cu direct bonding under an ultrahigh vacuum condition.
Abstract: Thin copper (Cu) films of 80 nm thickness deposited on a diffusion barrier layered 8 in. silicon wafers were directly bonded at room temperature using the surface activated bonding method. A low energy Ar ion beam of 40–100 eV was used to activate the Cu surface prior to bonding. Contacting two surface-activated wafers enables successful Cu–Cu direct bonding. The bonding process was carried out under an ultrahigh vacuum condition. No thermal annealing was required to increase the bonding strength since the bonded interface was strong enough at room temperature. The chemical constitution of the Cu surface was examined by Auger electron spectroscope. It was observed that carbon-based contaminations and native oxides on copper surface were effectively removed by Ar ion beam irradiation for 60 s without any wet cleaning processes. An atomic force microscope study shows that the Ar ion beam process causes no surface roughness degradation. Tensile test results show that high bonding strength equivalent to bulk ...

269 citations