Smart Cut is Soitec's proprietary technology, used to manufacture the company's UNIBOND SOI wafers. Based on two key techniques—ion implantation and wafer bonding—the process begins with two bulk silicon wafers, one of which is reused to create a SOI wafer later on. The UNIBOND wafer is created by growing an oxide layer on one wafer (Wafer A). This oxide layer subsequently forms the bulk-oxide (BOX) layer of the SOI structure (see the figure). Ion implantation of hydrogen ions through the oxide into the underlying silicon forms a damage layer at the end of the ion's range.
Using Van der Waals' forces, Wafer A is bonded to Wafer B. Wafer A is then cut across the damage plane, and a thin layer of silicon is transferred to Wafer B to form the SOI structure. Finally, a CMP polish touch finishes the SOI surface to the original bulk-silicon wafer specification.
Hydrogen ion implantation acts as an atomic scalpel in the Smart Cut process, enabling thin slices of monocrystalline film to be cut from a donor wafer and transferred on top of a receiving wafer. (Its crystalline quality doesn't matter.) The process provides optimal usage of valuable material by placing the amount of materials needed for electronic functionality on top of a very inexpensive support layer. This method is a highly viable option for design and manufacture of sub-0.13-µm devices on 300-mm wafers.