► Assembling materials or components for innovative applications. ► Low temperature (<500
°C) direct bonding processes. ► Review of key surface preparation parameters. ► Improvement shown through ...various processes as CMP or surface activation by plasma. ► Applications to bare or patterned surfaces for bonded heterostructure fabrication.
Low temperature direct bonding has been used extensively for assembling materials or components in the microelectronics and microsystem industries. We review here some key features of this technique both from the experimental and practical point of views. We give also some indications on the physical and chemical mechanisms involved in this attractive process, to better identify the important parameters impacting the quality and reliability of the technique. We describe mechanisms and report results on Si and SiO
2 bonding processes. Emphasis is put on improvements that allow obtaining strong and high quality bonding in low temperature process. We demonstrate that direct bonding can be applied as well to metal bonding, mainly to obtain conductive bonding, provided an efficient process can be used for surface preparation, e.g. CMP smoothing. More generally we show that direct bonding is well suited for many heterostructures via low temperature process for instance.
The Smart Cut™ process technology was originally developed to manufacture silicon on insulator wafers (SOI). The process is based on ion implantation (hydrogen, helium, argon, etc.) and wafer bonding ...and allows single crystal layers transferred onto substrates. This generic process is suited for creating advanced or composite engineered wafers, combining different thin layer materials on a given substrate in order to address requirements of many diverse applications. This article is first focused on hydrogen ion implantation impacts and on mechanisms enabling splitting for silicon layer transfer. Using transmission electron microscopy, infrared spectroscopy and X-ray diffraction, the formation and evolution of extended defects formed in Si has been studied, from the as-implanted state to the splitting. Mechanism for platelet growth by Ostwald ripening, diffusion of atomic hydrogen to molecular hydrogen in the microcavities and mechanic effects (stress, gas pressure) leading to microcavity expansion, microcrack propagation and splitting are detailed in the specific case of thermal annealing. Splitting kinetics and mechanisms are deduced. Then window on other natures of implanted ions is opened and described for co-implantation for instance. Advantages of such as (H, He) co-implantation are highlighted as it allows high crystal quality of transferred layer and fast splitting kinetics. Finally, diverse applications are described to illustrate the versatility of the Smart Cut™ process with other materials than silicon.
Water Stress Corrosion in Bonded Structures Fournel, F.; Martin-Cocher, C.; Radisson, D. ...
ECS journal of solid state science and technology,
01/2015, Volume:
4, Issue:
5
Journal Article
Peer reviewed
Open access
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.
Dynamics of a bonding front RIEUTORD, F; BATAILLOU, B; MORICEAU, H
Physical review letters,
06/2005, Volume:
94, Issue:
23
Journal Article
Peer reviewed
A description of the bonding front propagation between two adhesive plates is proposed. The model relates the velocity of a bonding front to the adhesion energy, with application to wafer direct ...bonding. Its derivation is based on a competition between the bonding energy and the viscous drag of the air flow in the gap between the two wafers. The model describes well the experimental data, including the wafer deformation profile during bonding or the dependence of the velocity on the gas viscosity, pressure, and wafer thickness.
Water management on semiconductor surfaces Le Tiec, Y.; Ventosa, C.; Rochat, N. ...
Microelectronic engineering,
12/2011, Volume:
88, Issue:
12
Journal Article, Conference Proceeding
Peer reviewed
The wafer direct bonding technique is very sensitive to water adsorbed on surfaces just before bonding; hence it is a useful way to characterize the impact of the trapped water and subsequently the ...wafer drying efficiency. We have focused this work on the water behavior at the bonding interface depending on the nature of the surface but also depending on the thermal treatment. Then we described the drying impact on surfaces after innovative solvent exposure, in a liquid or in a vapor phase, compared with standard isopropyl alcohol drying. We report characterization results from different techniques investigating both native and thermal oxides. We also characterized innovative solvent drying, especially in a vapor phase.
The Smart-Cutregistered trademark process, based on ion implantation (hydrogen, helium) and wafer bonding, appears more and more as a generic process. The first part of the paper is dedicated to the ...specific case of thermally-induced splitting. Cavity growth by the Ostwald ripening mechanism and crack propagation are responsible for thermally-induced splitting. In this case, the splitting kinetics are controlled by hydrogen diffusion. In the second part, the latest results concerning new structures are presented.
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