Water Stress Corrosion in Bonded Structures

Abstract

Direct bonding is now a well-known technique to join two flat surfaces without any additional material. This technique is used in many applications and especially in SOI (Silicon-On-Insulator) elaboration or in some backside imager manufacturing processes which are now almost in mass production. Direct bonding mechanism study is then very important in order to clearly understand this bonding behavior. Especially in the case of silicon or silicon dioxide hydrophilic surface, the role of water is essential. Water could lead to lots of different reactions at the bonding interface and especially the water stress corrosion could play an important role in the direct bonding mechanism.

Direct Homo/Heterogeneous Bonding of Silicon and Glass Using Vacuum Ultraviolet Irradiation in Air

“…• C. This result showed well agreement with the bonding model for the water stress corrosion proposed by Fournel et al 21 It is also worth noting that the interfacial water might soften these nanometersized apexes and help them to deform even further. Consequently, smoother interfacial layers were formed across the bonding interfaces (Fig.…”

Influence of water diffusion in deposited silicon oxides on direct bonding of hydrophilic surfaces

“…As direct bonding operates through surface asperities deformation, specific mechanical properties of such contact asperities can lead to a stronger bonding by increasing bonding area (Fournel 2015, Rieutord 2006Ventosa 2008;Ventosa 2009). As the mechanical properties of silicon oxide material are greatly influenced by internal water concentration, aging and water diffusion on asperity have a real impact in term of direct bonding energy.…”

“…Stresses evolutions and water penetration are characterized and a correlation is made between the kinetics of both stress variations and water diffusion through the oxide thin films. Impacts of room temperature (RT) storage prior to bonding and thermal treatments applied for strengthening the bonding is shown.As direct bonding operates through surface asperities deformation, specific mechanical properties of such contact asperities can lead to a stronger bonding by increasing bonding area (Fournel 2015, Rieutord 2006Ventosa 2008;Ventosa 2009). As the mechanical properties of silicon oxide material are greatly influenced by internal water concentration, aging and water diffusion on asperity have a real impact in term of direct bonding energy.…”

Combined Surface-Activated Bonding Technique for Low-Temperature Hydrophilic Wafer Bonding with Interfacial Water Management

“…In case of SiO 2 -SiO 2 bonding, water remains at the bonding interface even after a 400-600 °C annealing, generating water-filled voids. [3] The remaining water may also prevent bonding gap closure at a low temperature and weaken the bonding interface due to the water stress corrosion effect. Therefore, interfacial water management is a critical issue to improve the bonding quality in low-temperature hydrophilic wafer bonding.…”

“…A main challenge of this task is that it is difficult to remove the trapped water by either prebonding or postbonding annealing. [3] [4] Wafer bonding in vacuum is a promising approach to minimize the trapped water, which easily desorbs from the wafer surfaces exposed to vacuum. However, performing wafer bonding in vacuum conditions does not simply improve the hydrophilic bonding quality.…”