- Joshi, S.M. and Gosele, U.M. and Tan, T.Y., Gold diffusion in silicon during gettering by an aluminum layer,
Semiconductor Process and Device Performance Modelling. Symposium
pp. 117 - 22 .
(last updated on 2007/04/10)
Previous modeling of Al gettering of Au in Si indicated that, for an Al gettering layer placed on one surface of a Si wafer, Au is gettered from both wafer surface regions to progressively greater depths with time. This is because, in Si, Au is a substitutional-interstitial (Aus-Aui) species with its diffusion governed by the kick-out mechanism which is mediated by Si self-interstitials (I). During gettering by the Al-Si liquid at one wafer surface, Au, atoms change over to Aui atoms to rapidly migrate out of Si into the liquid. The changeover process consumes I. At the two wafer surface regions, the consumed I are quickly replenished, while in the wafer interior an I undersaturation develops which hinders the Aus-Aui changeover and hence the gettering process. Experimental evidence which confirms these predictions have been obtained. Au was indiffused into a FZ Si wafer at 950°C for 16 hr. After removing the Au source and etching, samples from the indiffused wafer were annealed at 1000°C without or with an Al layer on one surface. For samples without Al, there is no change in the net Au content, while the U-shaped indiffused profile becomes flatter. For samples with an Al layer, both wafer surface region Au concentrations were significantly decreased in 30 minutes, while the wafer interior Au concentrations decreased only after annealing for longer times. The model predictions, the experimental results, and the implications for Si self-diffusion parameters are discussed
aluminium;annealing;diffusion;elemental semiconductors;etching;getters;gold;impurity distribution;interstitials;semiconductor process modelling;silicon;