Transparent and electrically conductive GaSb/Si direct wafer bonding at low temperatures by argon-beam surface activation

Highlights

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Direct, argon-beam activated n-GaSb/n-Si wafer bonding established.

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GaSb deoxidation without altering the surface topography.

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Fully bonded wafer pairs with high bonding strengths.

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Optical transparency of the boundary layers.

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Low interface resistivities <5 mΩ cm² by optimization of the process parameters.

Direct wafer bonds of the material system n-GaSb/n-Si have been achieved by means of a low-temperature direct wafer bonding process, enabling an optical transparency of the bonds along with a high electrical conductivity of the boundary layer. In the used technique, the surfaces are activated by sputter-etching with an argon fast-atom-beam (FAB) and bonded in ultra-high vacuum. The bonds were annealed at temperatures between 300 and 400 °C, followed by an optical, mechanical and electrical characterization of the interface. Additionally, the influence of the sputtering on the surface topography of the GaSb was explicitly investigated. Fully bonded wafer pairs with high bonding strengths were found, as no blade could be inserted into the bonds without destroying the samples. The interfacial resistivities of the bonded wafers were significantly reduced by optimizing the process parameters, by which Ohmic interfacial resistivities of less than 5 mΩ cm² were reached reproducibly. These promising results make the monolithic integration of GaSb on Si attractive for various applications.

Keywords:

• Direct wafer bonding;
• Argon-beam surface activation;
• Gallium antimonide;
• Heterojunction;
• Carrier transport
• GaSb

Source: Sciencedirect

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