High-Aspect-Ratio Through Silicon Vias for High-Frequency Application Fabricated by Magnetic Assembly of Gold-Coated Nickel Wires

Bleiker, Simon J.; Fischer, Andreas; Shah, Umer; Somjit, Nutapong; Haraldsson, Tommy; Roxhed, Niclas; Oberhammer, J.; Stemme, Göran; Niklaus, Frank

doi:10.1109/tcpmt.2014.2369236

Cited by 37 publications

(21 citation statements)

References 24 publications

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“…The etching step removes burr defects created by the dicing saw at the ends of the rods during cutting. Figure 10 summarizes the steps involved in the TSV manufacturing by magnetic assembly [22,23]. A 300 µm thick double-sidedpolished p-type silicon wafer with (100) crystal orientation was thermally oxidized.…”

Section: Invar Tsv Fabrication and Characterizationmentioning

confidence: 99%

“…Invar is a Ni-Fe alloy containing 36% of nickel, featuring an extremely low CTE that is well matched to the CTE of silicon. Invar is a ferromagnetic material that is commercially available in wire form; thus, it is compatible with magnetic assembly, a lowcost fabrication technique for realizing very high aspect-ratio TSVs with inherently void-free metal cores [22,23].…”

Section: Introductionmentioning

confidence: 99%

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Through Silicon Vias With Invar Metal Conductor for High-Temperature Applications

Asiatici

Laakso

Fischer

et al. 2017

J. Microelectromech. Syst.

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Abstract-Through silicon vias (TSVs) are key enablers of 3D integration technologies which, by vertically stacking and interconnecting multiple chips, achieve higher performances, lower power and a smaller footprint. Copper is the most commonly used conductor to fill TSVs; however, copper has a high thermal expansion mismatch in relation to the silicon substrate. This mismatch results in a large accumulation of thermomechanical stress when TSVs are exposed to high temperatures and/or temperature cycles, potentially resulting in device failure.In this paper, we demonstrate 300 µm long, 7:1 aspect ratio TSVs with Invar as a conductive material. The entire TSV structure can withstand at least 100 thermal cycles from -50• C to 190• C and at least one hour at 365 • C, limited by the experimental setup. This is possible thanks to matching coefficients of thermal expansion (CTE) of the Invar via conductor and of silicon substrate. This results in thermomechanical stresses that are one order of magnitude smaller compared to copper TSV structures with identical geometries, according to finite element modelling. Our TSV structures are thus a promising approach enabling 2.5D and 3D integration platforms for high-temperature and harsh-environment applications.

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Section: Invar Tsv Fabrication and Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Through Silicon Vias With Invar Metal Conductor for High-Temperature Applications

Asiatici

Laakso

Fischer

et al. 2017

J. Microelectromech. Syst.

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“…This approach exhibits no limitation on the substrate size or the positioning of the TSV structures on the wafer. As shown in [13], the magnetic assembly is also insensitive to different TSV structure designs, making it possible to assemble many different TSV structures with different numbers of vias and even varying via densities side-by-side.…”

Section: Parallelized Magnetic Assemblymentioning

confidence: 99%

“…Fischer et al [12,13] have proposed an alternative method of TSV fabrication by magnetic assembly of prefabricated nickel wires. By utilizing pre-fabricated solid nickel wires, this method offers inherently void-free TSV conductors.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the magnetic assembly method enables fabrication of TSVs with very high-aspect ratios of more than 24 and lengths of over 450 μm. However, the magnetic assembly approach demonstrated in [12,13] is based on a sequential process resulting in limited overall throughput. Only a small number of TSVs could be assembled simultaneously and the assembled area of TSV structures typically was in the order of less than 1 cm 2 .…”

Section: Introductionmentioning

confidence: 99%

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High-speed metal-filling of through-silicon vias (TSVs) by parallelized magnetic assembly of micro-wires

Bleiker

Fischer

Niklaus

2016

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS)

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This work reports a parallelized magnetic assembly method for scalable and cost-effective through-silicon via (TSV) fabrication. Our fabrication approach achieves high throughput by utilizing multiple magnets below the substrate to assemble TSV structures on many dies in parallel. Experimental results show simultaneous filling of four arrays of TSVs on a single substrate, with 100 via-holes each, in less than 20 seconds. We demonstrate that increasing the degree of parallelization by employing more assembly magnets below the substrate has no negative effect on the TSV filling speed or yield, thus enabling scaled-up TSV fabrication on full wafer-level. This method shows potential for industrial application with an estimated throughput of more than 70 wafers per hour in one single fabrication module. Such a TSV fabrication process could offer shorter processing times as well as higher obtainable aspect ratios compared to conventional TSV filling methods.

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A Magnetically Assembled High‐Aspect‐Ratio Needle Electrode for Recording Neuronal Activity

Yasui

Yamagiwa

Sawahata

et al. 2019

Adv Healthcare Materials

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Microelectrodes, which penetrate the brain tissue and are located near neurons, enable the electrical recording of neuronal signals at a high spatiotemporal resolution. Such high spatiotemporal signal quality of the neuronal activity is necessary to understand neuronal networks and the working of brain. [1] Owing to the small size and high density of neurons in tissues, needle-like microelectrode devices are commonly used in neuronal recordings; such devices have made significant contributions in the fields of neuroscience and brain-machine interfaces. [2][3][4][5][6][7] To further develop such microelectrode devices, a microelectrode should i) have a fine needle diameter (<30 µm) to reduce damage to tissues. Several groups have demonstrated chronic recordings using >30 µm diameter wire-electrodes (e.g., four-month recordings of 50 µm diameter wires using rats [8] and five-year recordings of 30-50 µm diameter wire arrays using monkeys [9] ). Further requirements for a microelectrode device include ii) a long needle (e.g., ≈1 mm for rodents [10,11] and ≈2 mm for macaque cortices [12] ) and iii) multiple electrodes with a high density to achieve high spatial recordings (<100 µm in pitch).To meet these requirements, we proposed an assembly technique for vertical microwires on a substrate using the magnetic force. Figure 1a1-a4 shows the principle of the proposed assembly. A magnetic wire is placed on a substrate that comprises a through hole [ Figure 1a1]. The wire is then magnetized by applying a magnetic force [ Figure 1a2]. The wire is magnetized as an n-pole; one end is repelled from the substrate and the other is attracted to the substrate [ Figure 1a3]. After sliding the magnet under the through hole, the wire falls into the through hole [ Figure 1a4]. This principle enables the magnetic assembly of microelectrodes for neuronal recording. Characteristics of both a fine electrode diameter and a long electrode are achieved by using microscale diameter wires and a photo lithographybased etching process. In addition, these wires are assembled into through holes in the platform of the device substrate, allowing an electrical connection from the back side of the substrate [ Figure 1b1]. [13,14] In this study, we report this magnetic assembly using a nickel (Ni) wire as the electrode and a silicon (Si) substrate as the device's platform. We used Ni wires with a 25 µm diameter Microelectrode devices, which enable the detection of neuronal signals in brain tissues, have made significant contributions in the field of neuroscience and the brain-machine interfaces. To further develop such microelectrode devices, the following requirements must be met: i) a fine needle's diameter (<30 µm) to reduce damage to tissues; ii) a long needle (e.g., ≈1 mm for rodents and ≈2 mm for macaques); and iii) multiple electrodes to achieve high spatial recording (<100 µm in pitch). In order to meet these requirements, this study herein reports an assembly technique for high-aspect-ratio microneedles, which employs a magnet. The assembly is...

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High-Aspect-Ratio Through Silicon Vias for High-Frequency Application Fabricated by Magnetic Assembly of Gold-Coated Nickel Wires

Cited by 37 publications

References 24 publications

Through Silicon Vias With Invar Metal Conductor for High-Temperature Applications

Through Silicon Vias With Invar Metal Conductor for High-Temperature Applications

High-speed metal-filling of through-silicon vias (TSVs) by parallelized magnetic assembly of micro-wires

A Magnetically Assembled High‐Aspect‐Ratio Needle Electrode for Recording Neuronal Activity

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