Micromolding of NiFe and Ni Thick Films for 3D Integration of MEMS

Cortés, M.; Moulin, Johan; Couty, Magdalèna; Peng, Tao; Garel, Olivier; Dinh, Thi Hong Nhung; Zhu, Yunhui; Souadda, Malika; Woytasik, Marion; Lefeuvre, Élie

doi:10.1149/2.006402jes

Cited by 9 publications

(8 citation statements)

References 18 publications

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“…Theoretical background.-The anomalous codeposition phenomenon known as a ,,volcano" type curve-with a maximum in Fecontent in NiFe as a function of the applied potential or current densitywas observed in the literature for the thin NiFe films [32][33][34] and NiFe nanowires. 20 The observed results were explained through the limited mass transport of Fe +2 ions after the peak.…”

Section: Resultsmentioning

confidence: 99%

Anomalous Codeposition offccNiFe Nanowires with 5–55% Fe and Their Morphology, Crystal Structure and Magnetic Properties

Dragos

Chiriac

Lupu

et al. 2015

J. Electrochem. Soc.

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The electrodeposition of NiFe nanowires-with the length ∼3.0 μm and diameter 200 nm-using the porous anodized aluminum oxide (AAO) templates on the sputtered Au-back electrode (300 nm) using sulfate/chloride electrolyte solution and potential pulsed deposition. The electrode area of Au-AAO template, determined by the reversible one-electron transfer oxidation of K 4 Fe(CN) 6 , used as a probe in CV, was found to be ∼2.4 times larger than Au-thin film electrode. The anomalous codeposition phenomenon known as a ,,volcano" type curve-with a maximum in Fe-content in NiFe as a function of the applied potential-was observed in the literature. The observed results were explained through the limited mass transport of Fe +2 ions after the peak. This explanation is partially correct, but not complete. The electrodeposition of NiFe nanowire in this work resulted in a similar "volcano" type curve. The alternative explanation of anomalous codeposition-through the surface concentration of H + dependent adsorption/desorption of FeOH + and NiOH + electroactive species-was proposed. The electrodeposition of NiFe nanowire arrays using a designed pulse potential method produced fcc NiFe nanowires with 5-55% Fe with controlled composition, length, and uniformity.The distinct decrease of parallel coercivity of NiFe nanowire arrays having the same length was observed with increase of Fe-content in NiFe, which also correlates with the increase of their magnetic saturation. 12 The studies on magnetic properties of NiFe nanowire arrays were intensified during last 15 years. [13][14][15][16][17][18][19][20] The electrodeposition of NiFe alloys exhibits a phenomenon known as an anomalous codeposition, which is characterized by the anomaly that less noble metal, i.e. Fe, deposits preferentially. 21 The extent of anomalous codeposition can be evaluated by the "selectivity ratio" (SR), which is defined as an atomic ratio of Fe/Ni in the deposit to the molar ratio of Fe +2 /Ni +2 in the electrolyte. 22 The SR is dependent on solution condition (pH, presence of organic additives, concentration of electrolytes, temperature, etc), method of electrodeposition (constant current density, controlled potential, pulsed current or potential), and the thickness of deposit. The value of SR ranges from 1.0 (for non-anomalous codeposition) to 15 (for anomalous codeposition). The variation of composition of NiFe films affects the following properties of deposit: (i) stress, 23 (ii) magnetostriction, 24 (iii) crystal structure, 25 and (iv) grain size. 26 Thereby, the resulting changes profoundly influence the magnetic behavior of electrodeposited NiFe alloys, which was demonstrated recently. 27The present work describes the method of electrodeposition of NiFe nanowires into anodized aluminum oxide (AAO) templates with the controlled elemental composition using designed potential pulse electrodeposition. We report here a new explanation for the observed anomalous codeposition of NiFe in nanowires, through the surface concentration of H + dependent adsorption/...

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Section: Resultsmentioning

confidence: 99%

Anomalous Codeposition offccNiFe Nanowires with 5–55% Fe and Their Morphology, Crystal Structure and Magnetic Properties

Dragos

Chiriac

Lupu

et al. 2015

J. Electrochem. Soc.

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“…The electrodeposition and micromolding process of copper and Ni-Fe have been previously detailed. 17 In the present work, DC electrodeposition with a current density of −20 mA/cm 2 has been used for Cu, and pulsed positive/negative electrodeposition with cathodic and anodic current densities (resp. pulse times) of −10 mA/cm 2 and 22.5 mA/cm 2 (resp.…”

Section: Methodsmentioning

confidence: 99%

Shape Anisotropy in Magneto-Impedance NiFe-Based Microsensors

Cortés

Peng

Woytasik

et al. 2015

J. Electrochem. Soc.

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The magneto-impedance response of narrow multilayered NiFe/Cu/NiFe structures realized by micromolding has been characterized as a function of both the excitation frequency and the magnetic field. It has been found that intrinsic magnetic properties do not depend on the ferromagnetic geometry, but properties linked to the applied magnetic field, i.e. anisotropy field and magneto-impedance value do. The results are consistent with numerical simulations and show that the anisotropy field varies with the ferromagnetic film thickness. The highest magneto-impedance variation and anisotropy field, 170% and 4200 A/m were found for the narrowest and thickest structure. Magneto-impedance effect is based on the impedance variations of a ferromagnetic material due to changes of the skin depth while supplying the material with an AC current and applying an external magnetic field. The skin depth itself varies with the transverse (in case of a film) or circular (in case of a wire) magnetic permeability, thus to the external applied magnetic field:where f is the excitation current frequency going through the material, σ the electrical conductivity and μ t or μ c the magnetic permeability. The impedance depends on the skin effect and the highest variations are obtained for frequencies where the skin depth approximately matches the wire radius or the film half thickness. Values of several hundreds of % have been reported with microwires of amorphous Fe-based alloys, 1,2 thanks to the particular configuration of magnetic domains in rapidly quenched wires. Indeed, the rapid cooling of the material leads to a longitudinal magnetization in the core and a circular magnetization in the shell. The permeability is thus particularly sensitive with the external applied field. Such high magneto-impedance variations together with the use of soft materials lead to high sensitivities to the external magnetic field. Thus, that presents potential applications to small magnetic field measurement or magnetic nanoparticles detection. 3Thin film technology has also been investigated in order to benefit from the ability of collective fabrication process. However, the use of flat configurations and the contact with the substrate can create pinning sites for magnetic domains displacement or can induce stress which hardens the material and lowers the magneto-impedance properties. However large variations have been obtained by using a multilayered structure.4 This structure involves a conductive track between two ferromagnetic layers. Fe-based amorphous or nanocrystalline ferromagnetic materials, 5-10 particularly NiFe, 4,11-14 have been studied leading to magneto-impedance up to 400% at excitation frequencies in a range of several tens to several hundreds of MHz. However, these high frequencies, linked to under-μm thicknesses, make difficult the integration of an associated electronics. In order to decrease the excitation frequency, thick film technology has been investigated. In this way, electrodeposition of NiFe and Cu thin films has been used for ...

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“…C v,0 can be estimated from both mechanical and electrical results with (21) or from electrical results only with (23). Comparing C v,0 obtained from these two equations show the good consistency of the mechanical and electrical characteristics.…”

Section: Electrical Resultsmentioning

confidence: 85%

“…From the estimated gap, it becomes possible to compute C v,0 based on (6). C v,0 was also estimated from (23).…”

Section: Electrical Resultsmentioning

confidence: 99%

“…Ti appears as a promising candidate, because it has already been widely used in the industry of implantable devices for its resistance to body fluid corrosion and biocompatibility [18][19][20][21]. The use of micromachining techniques such as photolithography, Ni micromolding and titanium reactive ion-etching to obtain a membrane from a monolithical Ti material [22][23][24][25][26] insure a reliable mechanical transducer. The use of grade 1 Ti wafers inherently enables biocompatibility of the transducer.and its future integration in the biocompatible package.…”

Section: Introductionmentioning

confidence: 99%

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A grade 1 titanium capacitive microsensor for continuous pressure monitoring of intracorporal pressures

Becan¹,

Philippe²,

Phung³

et al. 2021

J. Micromech. Microeng.

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Long-term implantable pressure monitoring is a key clinical parameter bringing a lot to clinicians by helping them treating many chronical diseases (e.g. glaucoma, hydrocephalus or heart failure). However for decades and up to now, most of the implantable sensors exhibited poor technological and clinical success due to the long-term biocompatibility constraints of the transducing part. The prime novelty of this paper is to propose a functional implantable MEMS pressure sensor with a bulk-micromachined titanium (Ti) transducer. Thanks to its small size, the active part of the sensor is thought versatile enough to be integrated in an active implantable device for measuring various intracorporal pressures. The transducer is made out of grade 1 Ti, which is one of the metalic materials of choice to insure long-term biocompatibility and has been proved to be a reliable material in the implantable industry. The uniqueness of the proposed sensor comes from its micromachining. The transducer, including a bulk titanium membrane, has been obtained through subtractive machining techniques benefiting from the extensive research experience on silicon MEMS. This Ti-based technology avoids the use of additionnal costly, complex and bulky encapsulation step to get a biocompatible device, thus enabling higher miniaturization level of implantable devices and lower rate of long term drift risks thanks to its monolithic architecture. The presented Ti MEMS sensor exhibits 1 fF mmHg−1 sensitivity within a clinically relevant pressure range of 0–300 mmHg, which is compatible with off the shelf low-power readout electronics.

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Micromolding of NiFe and Ni Thick Films for 3D Integration of MEMS

Cited by 9 publications

References 18 publications

Anomalous Codeposition offccNiFe Nanowires with 5–55% Fe and Their Morphology, Crystal Structure and Magnetic Properties

Anomalous Codeposition offccNiFe Nanowires with 5–55% Fe and Their Morphology, Crystal Structure and Magnetic Properties

Shape Anisotropy in Magneto-Impedance NiFe-Based Microsensors

A grade 1 titanium capacitive microsensor for continuous pressure monitoring of intracorporal pressures

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