Silicon On Insulator - Manufacture of SOI Wafers

Manufacture of SOI Wafers

SiO₂-based SOI wafers can be produced by several methods:

• SIMOX - Separation by IMplantation of OXygen – uses an oxygen ion beam implantation process followed by high temperature annealing to create a buried SiO₂ layer.

• Wafer bonding – the insulating layer is formed by directly bonding oxidized silicon with a second substrate. The majority of the second substrate is subsequently removed, the remnants forming the topmost Si layer.
  • One prominent example of a wafer bonding process is the Smart Cut method developed by the French firm Soitec which uses ion implantation followed by controlled exfoliation to determine the thickness of the uppermost silicon layer.
  • NanoCleave is a technology developed by Silicon Genesis Corporation that separates the silicon via stress at the interface of silicon and silicon-germanium alloy.
  • ELTRAN is a technology developed by Canon which is based on porous silicon and water cut.
• Seed methods - wherein the topmost Si layer is grown directly on the insulator. Seed methods require some sort of template for homoepitaxy, which may be achieved by chemical treatment of the insulator, an appropriately oriented crystalline insulator, or vias through the insulator from the underlying substrate.

An exhaustive review of these various manufacturing processes may be found in reference