Water management in direct bonding

Published : 27 February 2019

Direct bonding is now used in many applications. Very recently, at CEA Grenoble, it has been shown that water can soak in a non-annealed direct bonding interface as well as to be removed from it. As water is one of the main parameter in hydrophilic direct bonding, controlling and accurately understand this phenomenon is very important for all hydrophilic direct bonding and not only for the Silicon/Silicon bonding.

This study aim will be to study in detail the water management inside a direct bonding interface following different ways:

A first part of the study will be to find a way to isolate the bonding interface. It is mandatory for all the accurate characterization of the direct bonding in order to have stable samples. It is also very interesting for many applications for which the edges are important and would like to get rid of this phenomenon.

A second part of the study will be to continue the characterization of the water low dynamic at an annealed direct bonding interface. It will be also interesting to evaluate this flow during the annealing. The in or out dynamic will be evaluate regarding the bonding energy reached by the interface at the different annealing temperature.

A last part of the study will be to evaluate accurately the water amount at the hydrophilic direct bonding interface of “stable” samples. Varying this water quantity, a link will be done with the direct bonding energy and the possible defectivity which could appear under certain conditions. For this study, wafer with cavities will also be used in order to have acces to the water cinetic movement inside the bonding interface itself. Different bonding atmospheres and conditions will be used to analyse the water and/or the gaz direct bonding by-product production and movement.

The student will be formed to all the needed technology used in direct bonding (chemistry, CMP, bonding, thermal annealing…) as well as all its usual characterization techniques (Infrared spectroscopy, acoustic microscopy, anhydrous bonding energy, XRR…)

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