The History, Physics, and Applications of the Smart-Cut® Process

Abstract

In a silicon-on-insulator (SOI) structure, a thin layer of monocrystalline silicon rests on a dielectric layer—generally amorphous—itself on a silicon wafer. Because such a structure cannot be achieved by conventional methods, different ways had to be imagined to facilitate its construction.The basic physics phenomenon that led the author to invent the process generally known under the name of Smart-Cut® is blistering. Blistering (Figure 1), in addition to flaking and exfoliation, is a visible macroscopic effect that has been known for a long time and is induced by high-dose implantations of inert gas or hydrogen ions in materials. These macroscopic effects result from the cooperative result of the microscopic effects induced in depth by penetration of particles. The microscopic effects of hydrogen or rare-gas implantation such as creation of microcavities, microblisters, or microbubbles (close to the penetration depth Rp corresponding to the maximum concentration) have been known for a long time. These microcavities enhance propagation of intercavity fractures where their density (depending on statistical fluctuations) reaches a percolation threshold. This leads to formation of a local cluster where all the microcavities are joined by a fractured zone, resulting in a blister at the surface. The driving force of this mechanism is the gas pressure in the microcavities and the stresses in the layer.