Abstract
In order to provide in situ, real time, non-invasive monitoring of the etching and deposition rates and the passivation levels of semiconductor wafers, during the processing of these materials for chip fabrication, we have developed and tested three techniques, which can be used at any pressure, and at temperatures between 300 and 500°C.
Implementing the “Interferometric Technique”, we have used HeNe laser interferometry to follow the etching of Si, GaAs, and InP by Cl2, Cl, Br2, Br, I2, H, and CH3, at various doping levels and as a function of temperature. The technique involves monitoring the interference between a stationary reflecting surface and the surface being etched. The results have provided new information regarding the effects of doping and the mechanisms of these reactions.
With the “Photoluminescence Technique”, we have monitored the surface passivation on direct bandgap semiconductors by observing the surface-sensitive laser-induced photoluminescence from thin layers of InGaAs and GaAs in situ, during exposure of their surfaces to reactive gaseous species. We have observed the surface passivation to improve by as much as a factor of 6000 following an exposure of a few seconds to atomic hydrogen and atomic sulphur at gas phase atom densities of about 1013 cm−3. XPS spectra of the surfaces after most of these exposures were found to be indistinguishable, showing that conventional techniques for surface analysis cannot reveal the passivation level required for the fabrication of electronic devices.
For indirect band gap materials such as Si, which are non-fluorescent, we have developed an “RF-Probe Technique”, in which the laser-induced carrier concentrations were determined by coupling a resonance circuit to a silicon wafer. The effect of the laser-induced charge-carriers on the resonance-frequency of the circuit was used to monitor the carrier concentration. The technique has been developed specifically to monitor in situ the density of carrier traps near the SiO2/Si interface in “gate” oxides, when they are formed by low temperature plasma oxidation.
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© 1995 Springer Science+Business Media Dordrecht
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Gu, G., Li, H., Cook, J., Ogryzlo, E.A. (1995). In Situ Laser Beam Probes for Semiconductor Processing. In: Misaelides, P. (eds) Application of Particle and Laser Beams in Materials Technology. NATO ASI Series, vol 283. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-8459-3_16
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DOI: https://doi.org/10.1007/978-94-015-8459-3_16
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-4510-2
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