Impurity gettering in silicon using cavities formed by helium im

Details Impurity gettering in silicon using cavities formed by helium im Impurity gettering in silicon using cavities formed by helium im

1993-12-01

1998-11-24

Chaudhari, Chandra

Fishing, trapping, and vermin destroying

437 24, 148DIG24, H01L 21306

Patent

active

058405909

ABSTRACT:
Impurity gettering in silicon wafers is achieved by a new process consisting of helium ion implantation followed by annealing. This treatment creates cavities whose internal surfaces are highly chemically reactive due to the presence of numerous silicon dangling bonds. For two representative transition-metal impurities, copper and nickel, the binding energies at cavities were demonstrated to be larger than the binding energies in precipitates of metal silicide, which constitutes the basis of most current impurity gettering. As a result the residual concentration of such impurities after cavity gettering is smaller by several orders of magnitude than after precipitation gettering. Additionally, cavity gettering is effective regardless of the starting impurity concentration in the wafer, whereas precipitation gettering ceases when the impurity concentration reaches a characteristic solubility determined by the equilibrium phase diagram of the silicon-metal system. The strong cavity gettering was shown to induce dissolution of metal-silicide particles from the opposite side of a wafer.

REFERENCES:
patent: 3874936 (1975-04-01), d'Hervilly et al.
patent: 4069068 (1978-01-01), Beyer et al.
patent: 4956693 (1990-09-01), Sawahata et al.

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