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Laser Writing of High Purity Gold Lines

Published online by Cambridge University Press:  21 February 2011

M. Jubber
Affiliation:
Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
J.I.B. Wilson
Affiliation:
Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
J.L. Davidson
Affiliation:
Departments of Physics and Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
P. John
Affiliation:
Departments of Physics and Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
P.G. Roberts
Affiliation:
Departments of Physics and Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, Scotland
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Abstract

Gold tracks have been deposited on thermally oxidised and single crystal silicon, gold and nichrome coated silicon wafers by pyrolytic decomposition of gaseous alkyl (triethyl phosphine) gold(I) complexes using focussed 514 nm radiation from an argon ion laser. The precursors, RAu(I)Et3P, R = CH3, C2H5 are low melting point crystalline solids with relatively high vapour pressures (∼5 mtorr). They are representative of a class of compounds being evaluated for laser deposition of gold. Differential scanning calorimetry, DSC, shows that the thermal decomposition of MeAu(I)Et3P in the solid state is a two-stage process. The decomposition temperature is 63 ± 1°C. Tracks were deposited at laser scan speeds up to 35 μm s−1 with a beam diameter (1/e2) at the focus of ∼12 μm. SIMS, EDX and laser ionisation microprobe analysis, LIMA, were used to determine the chemical composition of the tracks. The purity of >98% is consistent with the measured resistivities (4.2 μΩ cm) at room temperature compared to bulk gold (∼2 μΩ cm). These resistivities were achieved without post deposition annealing. Stylus profilimetry and SEM data showed the lines produced from MeAu(I)Et3P have a virtually rectangular cross-section. Together with the absence of the ubiquitous λ-ripples, this feature suggests that deposition is more rapid on the gold surface than on the SiO2 substrate. Laser power thresholds are lower for silicon substrates coated with thin (5 - 10°A) films of gold or nichrome.

Type
Research Article
Copyright
Copyright © Materials Research Society 1990

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References

REFERENCES

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