Impurity gettering in silicon using cavities formed by helium implantation and annealing

Patent · Thu Jan 01 04:00:00 EST 1998

OSTI ID:871993

Bishop, Dawn M ^[1]; Follstaedt, David M ^[1]

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1. Albuquerque, NM

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.

• Research Organization: AT & T CORP
• DOE Contract Number: AC04-76DP00789
• Assignee: Sandia Corporation (Albuquerque, NM)
• Patent Number(s): US 5840590
• OSTI ID: 871993
• Country of Publication: United States
• Language: English

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/438/148/
achieved
additionally
annealing
basis
binding
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bonds
cavities
cavities formed
cavity
ceases
characteristic
chemically
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chemically reactive
concentration
consisting
constitutes
copper
creates
current
dangling
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diagram
dissolution
due
effective
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gettering
helium
highly
implantation
impurities
impurity
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impurity gettering
induce
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larger
magnitude
metal
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metal-silicide
nickel
numerous
opposite
particles
phase
phase diagram
precipitates
precipitation
presence
process
process consisting
reaches
reactive
regardless
representative
residual
result
shown
silicide
silicon
silicon wafer
silicon wafers
silicon-metal
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starting
strong
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