Anne-Marie Charvet

Overview of recent direct wafer bonding advances and applications

Direct wafer bonding processes are being increasingly used to achieve innovative stacking structures. Many of them have already been implemented in industrial applications. This article looks at direct bonding mechanisms, processes developed recently and trends. Homogeneous and heterogeneous bonded structures have been successfully achieved with various materials. Active, insulating or conductive materials have been widely investigated. This article gives an overview of Si and SiO2 direct wafer bonding processes and mechanisms, silicon-on-insulator type bonding, diverse material stacking and the transfer of devices. Direct bonding clearly enables the emergence and development of new applications, such as for microelectronics, microtechnologies, sensors, MEMs, optical devices, biotechnologies and 3D integration.

Rough Surface Adhesion Mechanisms for Wafer Bonding.

Wafer bonding can be viewed as an example of rough surface adhesion. We show that formalisms developed to describe rough surface adhesion can be rescaled to nanometer range and applied to silicon wafer bonding, with results that fit well with experimental observations.

Direct wafer bonding for nanostructure preparations

Direct Wafer Bonding has been widely developed and is very attractive for a lot of applications. Using original techniques based on direct bonding enable to carry out specific engineered substrates. Various illustrations are given among which twisted Si-Si bonded substrates, where buried dislocation networks play a key role in the subsequent elaboration of nanostructures.

Silicon Technologies for Nanoscale Device Packaging

We present our recent developments on silicon technologies dedicated to the packaging of nano-objects/nano-devices. These technologies aim at both protecting and electrically connecting a nanoscale device positioned on a perfect Si(001)-(2 × 1):H surface smoothed thanks to a 950 °C thermal treatment. The nano-device is connected to nanopads implanted on the silicon surface. Each nanopad is linked to a nanovia which is locally achieved by etching and filling processes operated in a FIB (Focused Ion Beam) equipment. Impacts of the FIB process on via morphology and properties are depicted. Nanopads are fabricated through the local implantation of arsenic, and the effect of the surface smoothing thermal treatment on the dopants diffusion length is estimated by simulation and then experimentally explored. Key process steps such as the etching of a deep cavity and the surface protection with a temporary cap are also described, and a first assembly consisting in a substrate equipped with nanopads and directly bonded with a cap substrate is presented.