Structure of vapor-phase deposited Al-Ge thin films and Al-Ge intermediate layer bonding of Al-based microchannel structures

Abstract

Al-based high-aspect-ratio microscale structures (HARMS) are basic building blocks for all-Al microdevices. Bonding of Al-based HARMS is essential for device assembly. In this paper, bonding of Al-based HARMS to flat Al plates using Al-Ge thin film intermediate layers is investigated. The structure of sputter codeposited Al-Ge thin films was studied by high-resolution transmission electron microscopy as a function of the average film composition. The structure of the interface region between Al-based HARMS bonded to flat Al plates is studied by combining focused ion beam sectioning and scanning electron microscopy. An extended bonding interface region, ∼100 μm in width, is observed and suggested to result from liquidus/solidus reactions as well as diffusion of Ge in solid Al at the bonding temperature of 500 °C. The extended interface region is suggested to be beneficial to Al-Al bonding via Al-Ge intermediate layers.

Fabrication of copper-based microchannel devices and analysis of their flow and heat transfer characteristics

“…Microchannels created in Al and Cu plates by compression molding were bonded through solid-state bonding techniques to Al and Cu plates, respectively, to form all-Al and all-Cu, enclosed, microchannel devices [13][14][15]. Examination of bonding mechanisms was accomplished through focused ion beam sectioning and scanning electron microscopy [16].…”

Experimental investigation of Cu-based, double-layered, microchannel heat exchangers

“…As an alternative, technologies for fabricating microchannel arrays on sheet metals and bonding metallic, open microchannel arrays into fully enclosed MHEs have been developed [8][9][10][11]. Cu-and Al-based MHEs were built, and their liquid flow characteristics and heat transfer performances were measured [12][13][14][15].…”

Low-temperature Al–Ge bonding for 3D integration

“…6 The greatest challenge to achieve monolithic 3DICs is obtaining single-crystal, device-quality semiconductor material on upper circuit layers without damaging circuits below (about 400 C temperature limit). 13 Al-Ge eutectic bonding has been effectively used to package and hermetically seal fabricated MEMS devices, [14][15][16] relying on the eutectic liquid alloy to form strong and void-free bonds between surfaces much rougher than what is achievable with fusion or thermo-compressive bonding. 7,8 Instead, we pursued an alternative approach of attaching high-quality crystal islands to serve as the semiconducting material for upper layer device fabrication of a monolithic 3DIC.…”

“…7,8 Instead, we pursued an alternative approach of attaching high-quality crystal islands to serve as the semiconducting material for upper layer device fabrication of a monolithic 3DIC. However, the methods so far reported [14][15][16] are not suitable for 3DICs, due to either excessive bonding temperature or pressure, or unreasonably thick bonding layers for the purposes of device level vertical interconnection. 13 Al-Ge eutectic bonding has been effectively used to package and hermetically seal fabricated MEMS devices, [14][15][16] relying on the eutectic liquid alloy to form strong and void-free bonds between surfaces much rougher than what is achievable with fusion or thermo-compressive bonding.…”