13 September 1996 Reflow of Al-Cu by low-temperature germane reactions
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Abstract
This paper describes a low temperature reflow of Al-Cu using GeH4 reactions. The Al-alloy reflow occurs due to formation of low melting point eutectic with Germanium. This technique results in a low cost process for filling high aspect ratio vias/lines with Al-based alloys with improved damascene capability. This is achieved at temperatures below 400 degree(s)C by reacting Germane (GeH4) with Al-Cu alloys deposited by conventional techniques which result in voids, gaps and poor filling. Using such a process it is demonstrated that high aspect ratio vias with large undercuts can also be filled without voids. The low temperature provides capability to form multilevel homogeneous Al-alloy via/line structure without degrading the resistance of underlying interconnects. The reliability data shows that Al-Cu-Ge via/interconnect structure deposited by this method is at least `1.5X' better electromigration life time (t50) to that of hot sputtered Al-Cu (deposited at 535 degree(s)C) and almost `2X' to that of conventionally used CVD W stud/Al-Cu interconnect structure. The improvement in the reliability may be attributed to filling without voids high aspect ratio sub- half micron vias with low resistivity metal such as Al-Cu-Ge at temperatures well below 400 degree(s)C. Since this technique does not rely on the wetting layer or diffusion barrier a lower sheet resistance of Al-Cu-Ge line is achieved compared to high temperature reflow processes. Also the reaction between Al and GeH4 takes place uniformly resulting in reproducible contact resistance. Most importantly it is possible to achieve `high open-short yields' of comb- serpentine structures, and via chains of difficult to polish materials like Al-Cu using `damascene' process.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
R. V. Joshi, "Reflow of Al-Cu by low-temperature germane reactions", Proc. SPIE 2875, Microelectronic Device and Multilevel Interconnection Technology II, (13 September 1996); doi: 10.1117/12.250872; https://doi.org/10.1117/12.250872
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