- Mme Marie-France BEAUFORT, CNRS-Institut Pprime (Poitiers), Rapportrice
- M. Daniel ALQUIER, CNRS-GREMAN (Tours), Rapporteur
- M. Alain CLAVERIE, CNRS-CEMES (Toulouse), Directeur de thèse
- M. Frédéric MAZEN, CEA-LETI (Grenoble), Directeur de thèse, invité
- M. Jérémie GRISOLIA, CNRS-LPCNO (Toulouse), Examinateur
The development of the advanced microelectronics requires the manufacturing of SOI (Silicon-On-Insulator) wafers with a very thin top Si layer (around 10 nm) and drastic uniformity specification (<+/- 0,5 nm on 300 mm wafers). An interesting way to raise this challenge would be to integrate, in the Smart CutTM technology, modified donors substrates in order to “force” hydrogen to precipitate, during the annealing, in a plane parallel and close to the surface.
In this work, we study the potential benefits of the incorporation of thin buried layers of boron doped silicon (Si:B) or SiGe alloy in the donor substrate. We show that Si:B is particularly interesting : fracture is obtained for a lower implanted hydrogen dose and for a lower thermal budget than when using a SiGe buried layer. Moreover, the layer roughness after transfer is obviously lower than that obtained with the reference process. We have shown, using TEM and SIMS, that the mechanisms leading to hydrogen trapping are different in these two types of buried layers. Then, we have studied the hydrogen redistribution after implantation and annealing (by SIMS) and the platelets evolution (by TEM) during isothermal annealing in the Si/Si:B/Si structure. During annealing, the platelets formed outside of the Si:B buried layer dissolved in favor of the ones, larger, formed in the doped layer, which grow and finally form microcracks. This growth results in the transfer of implanted hydrogen towards the trapping layer. Nevertheless, this diffusion is slow and all implanted hydrogen is not finally « pumped » by the trapping layer. A simple numerical model makes it possible to understand then to reproduce qualitatively the redistribution phenomenon observed by SIMS.
This work shows that the incorporation of Si:B buried layer in the donor substrate is a very promising technique for the manufacturing of ultrathin SOI. This process was optimized in an industrial environment and transferred films with a post fracture roughness a decade lower compared to the reference process were obtained.