Optimization of a BEOL aluminum deposition process enabling wafer level Al-Al thermo-compression bonding

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Schulze, Sebastian and Wietstruck, Matthias and Fraschke, Mirko and Kerepesi, Peter and Kurz, Helmut and Rebhan, Bernhard and Kaynak, Mehmet (2019) Optimization of a BEOL aluminum deposition process enabling wafer level Al-Al thermo-compression bonding. In: IEEE 69th Electronic Components and Technology Conference (ECTC), Las Vegas, NV, USA

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Abstract

The main challenges for Al-Al wafer bonding are the fast oxidation and the high roughness of the Al surface. This paper describes an optimized Al sputter-deposition process reducing the surface roughness to values below 2 nm. Based on this, a wafer level Al-Al thermo-compression bonding process is presented, where a surface treatment and the subsequent bonding are both performed in a high vacuum cluster. The patterned wafers were bonded with temperatures between 300 and 500 °C for 1 h using a bonding force of 60 kN. Scanning acoustic microscopy and transmission electron microscopy studies revealed a reliable bonding, an accurate alignment and a high uniformity for 200 mm wafers. The electrical characterization of contact chains with Al bonding pad sizes of 20×20 μm2 showed resistances lower than 50 mΩ per contact, which might indicate areas of oxide-free bonding.
Item Type: Papers in Conference Proceedings
Uncontrolled Keywords: Al surface roughness; Al-Al thermocompression bonding; Aluminum; Wafer level bonding
Divisions: Faculty of Engineering and Natural Sciences > Academic programs > Electronics
Faculty of Engineering and Natural Sciences
Depositing User: Mehmet Kaynak
Date Deposited: 26 Jul 2023 16:12
Last Modified: 26 Jul 2023 16:12
URI: https://research.sabanciuniv.edu/id/eprint/46309

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