SOI Structures by Ion Implantation and Annealing in a Temperature Gradient

Si-on-insulator (SOI) technology is essential for space and military applications where immunity to ionizing radiation is required. It will also lead to commercial, high speed CMOS circuits. This paper reviews formation of SOI structures by implantation of high doses of oxygen, followed by heat treatments at 1405°C in a lamp furnace. The result is an SiO2 layer, with atomically abrupt interfaces, buried under a film of a device quality single crystalline Si. Since the SOI technology and the 3-D integration place new requirements on control of dopants in the wafers, trapping and drift of arsenic introduced into the SiO2 is also discussed. It is demonstrated that As is immobile in the oxide under isothermal conditions up to the melting temperature of silicon. When a temperature gradient is applied, the arsenic is swept toward the heat source until it reaches the SiO2/Si interface and is released into Si. The difference between dopant transport with and without temperature gradients adds flexibility to processing of multilayer structures.