Au-In bonding below the eutectic temperature

Lee, C.C.; Wang, C.Y.; Matijasevic, G.

doi:10.1109/33.232058

Cited by 119 publications

(46 citation statements)

References 22 publications

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“…The temperature was raised to 250 • C over the course of approximately 10 minutes, while pressure was applied to various parts of the wafer stack. The wafers are then cooled to room temperature over the course of [154,155]. Because the melting points of the resulting eutectic alloys are greater than 450 • C (see Fig.…”

Section: In-au Reactive Bondingmentioning

confidence: 99%

Terahertz quantum-cascade lasers

2007

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The development of the terahertz frequency range (1-10 THz, λ ≈ 30-300 µm) has long been impeded by the relative dearth of compact, coherent radiation sources of reasonable power. This thesis details the development of quantum cascade lasers (QCLs) that operate in the terahertz with photon energies below the semiconductor Reststrahlen band. Photons are emitted via electronic intersubband transitions that take place entirely within the conduction band, where the wavelength is chosen by engineering the well and barrier widths in multiple-quantum-well heterostructures. Fabrication of such long wavelength lasers has traditionally been challenging, since it is difficult to obtain a population inversion between such closely spaced energy levels (hω ≈ 4-40 meV), and because traditional dielectric waveguides become extremely lossy due to free carrier absorption.This thesis reports the development of terahertz QCLs in which the lower radiative state is depopulated via resonant longitudinal-optical phonon scattering. This mechanism is efficient and temperature insensitive, and provides protection from thermal backfilling due to the large energy separation (∼36 meV) between the lower radiative state and the injector. Both properties are important in allowing higher temperature operation at longer wavelengths. Lasers using a surface plasmon based waveguide grown on a semi-insulating (SI) GaAs substrate were demonstrated at 3.4 THz (λ ≈ 88 µm) in pulsed mode up to 87 K, with peak collected powers of 14 mW at 5 K, and 4 mW at 77 K.Additionally, the first terahertz QCLs have been demonstrated that use metalmetal waveguides, where the mode is confined between metal layers placed immediately above and below the active region. These devices have confinement factors close to unity, and are expected to be advantageous over SI-surface-plasmon waveguides, especially at long wavelengths. Such a waveguide was used to obtain lasing at 3.8 THz (λ ≈ 79 µm) in pulsed mode up to a record high temperature of 137 K, whereas similar devices fabricated in SI-surface-plasmon waveguides had lower maximum lasing temperatures (∼92 K) due to the higher losses and lower confinement factors.This thesis describes the theory, design, fabrication, and testing of terahertz quantum cascade laser devices. A summary of theory relevant to design is presented, 3 including intersubband radiative transitions and gain, intersubband scattering, and coherent resonant tunneling transport using a tight-binding density matrix model. Analysis of the effects of the complex heterostructure phonon spectra on terahertz QCL design are considered. Calculations of the properties of various terahertz waveguides are presented and compared with experimental results. Various fabrication methods have been developed, including a robust metallic wafer bonding technique used to fabricate metal-metal waveguides. A wide variety of quantum cascade structures, both lasing and non-lasing, have been experimentally characterized, which yield valuable information about the transport ...

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Section: In-au Reactive Bondingmentioning

confidence: 99%

Terahertz quantum-cascade lasers

2007

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“…Several bonding techniques are available and we highlight eutectic and direct bonding as the most suitable methods due to their low outgassing and high hermeticity, with anodic bonding as a suitable alternative if the oxygen released during bonding can be pumped away. Lowering the temperatures of these bonding techniques should be investigated as they can reduce the outgassing limitations by two or three orders of magnitude 171,174,175,181,[243][244][245][246][247][248] .…”

Section: E Vacuum Discussionmentioning

confidence: 99%

“…Moreover, thin films, such as gold on silicon, can diffuse at moderate temperatures if additional barrier layers are not used 170 . In these situations one must use lower temperature degassing, such as UV desorption or plasma cleaning, and also develop lower temperature bonding methods 171,174,175,181,[243][244][245][246][247][248] .…”

Section: Discussionmentioning

confidence: 99%

Contributed Review: The feasibility of a fully miniaturized magneto-optical trap for portable ultracold quantum technology

Rushton

Aldous

Himsworth

2014

Review of Scientific Instruments

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Experiments using laser cooled atoms and ions show real promise for practical applications in quantumenhanced metrology, timing, navigation, and sensing as well as exotic roles in quantum computing, networking and simulation. The heart of many of these experiments has been translated to microfabricated platforms known as atom chips whose construction readily lend themselves to integration with larger systems and future mass production. To truly make the jump from laboratory demonstrations to practical, rugged devices, the complex surrounding infrastructure (including vacuum systems, optics, and lasers) also needs to be miniaturized and integrated. In this paper we explore the feasibility of applying this approach to the Magneto-Optical Trap; incorporating the vacuum system, atom source and optical geometry into a permanently sealed microlitre system capable of maintaining 10 −10 mbar for more than 1000 days of operation with passive pumping alone. We demonstrate such an engineering challenge is achievable using recent advances in semiconductor microfabrication techniques and materials.PACS numbers: 07.07.Df, 37.10.Gh, 07.30.Kf, I. ULTRACOLD QUANTUM TECHNOLOGYSince the first demonstrations of atoms and ions at sub-millikelvin temperatures in the mid-1980s, the field of atomic physics has been revolutionized by laser cooling and trapping as it provides researchers with a method to probe some of the purest and sensitive quantum systems available. This field is still highly productive and recently has put significant emphasis on the practical applications of this technology beyond the laboratory 1,2 . It was evident very early on that ultracold matter would be an indispensable tool in precise timing applications and a recent demonstration 3 has shown extremely low instabilities at the 10 −18 level. The wavelike nature of atoms as they are cooled to lower temperatures can be used to form atomic interferometers that outperform optical counterparts in measurements of accelerated reference frames 4-7 , which are important for inertial guidance systems, but can also provide sensitive measurements of mass, charge and magnetic fields [8][9][10][11] . Greater sensitivity beyond the classical limit is possible via squeezed 12 and entangled states 13-15 , which are also fundamental attributes for quantum computing 16,17 , and long distance quantum networking 18 . Ultracold matter has been used in the emerging field of quantum simulation 19 and is an indispensable tool in determining fundamental constants 20 , testing general relativity 21 and defining measurement standards 22 . Many researchers and industries believe such tools will be a major part of the 'second quantum revolution' in which the more 'exotic' properties of quantum physics are applied for practical applications 23,24 .The field of ultracold matter has reached a matua) m.d.himsworth@soton.ac.uk rity in both experimental methods and theoretical understanding allowing experiments to begin leaving the laboratory 25-27 . These systems are bespoke, rarely take up a ...

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“…We have developed fluxless bonding processes involving In with In-Ag, In-Au, and In-Sn systems. [2][3][4][5] In these fluxless processes, a thin outer Ag or Au capping layer is used in solder manufacturing to prevent indium oxidation. The multilayer solder structures can then be fabricated using vacuum deposition techniques or electroplating processes.…”

Section: Introductionmentioning

confidence: 99%

Intermetallic Reaction of Indium and Silver in an Electroplating Process

Wang

Kim

Lee

2009

Journal of Elec Materi

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The reaction of indium (In) and silver (Ag) during the electroplating process of indium over a thick silver layer was investigated. It was found that the plated In atoms react with Ag to form AgIn 2 intermetallic compounds at room temperature. Indium is commonly used in the electronics industry to bond delicate devices due to its low yield strength and low melting temperature. In this study, copper (Cu) substrates were electroplated with a 60-lm-thick Ag layer, followed by electroplating an In layer with a thickness of 5 lm or 10 lm, at room temperature. To investigate the chemical reaction between In and Ag, the microstructure and composition on the surface and the cross section of samples were observed by scanning electron microscopy (SEM) with energydispersive x-ray spectroscopy (EDX). The x-ray diffraction method (XRD) was also employed for phase identification. It was clear that indium atoms reacted with underlying Ag to form AgIn 2 during the plating process. After the sample was stored at room temperature in air for 1 day, AgIn 2 grew to 5 lm in thickness. With longer storage time, AgIn 2 continued to grow until all indium atoms were consumed. The indium layer, thus, disappeared and could barely be detected by XRD.

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Au-In bonding below the eutectic temperature

Cited by 119 publications

References 22 publications

Terahertz quantum-cascade lasers

Terahertz quantum-cascade lasers

Contributed Review: The feasibility of a fully miniaturized magneto-optical trap for portable ultracold quantum technology

Intermetallic Reaction of Indium and Silver in an Electroplating Process

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