Kinetics of phosphorus proximity rapid thermal diffusion using spin-on dopant source for shallow junctions fabrication

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Abstract
Proximity rapid thermal diffusion (RTD) has been investigated using phosphorus spin‐on dopants (SOD) as a function of SOD thickness, baking and diffusion temperatures, separation distance between wafers, and ambient. Experimental results, based on sheet resistance measurements, dopant distributions obtained by secondary ion mass spectroscopy, and electron microprobe analyses indicate fast phosphorus out‐diffusion from the dopant source. Simplified modelling of phosphorus diffusion within the SOD and evaporation confirms its fast transport and limited evaporation. An analysis of the process kinetics suggest that at high RTD temperatures doping of the processed wafer is controlled by gas phase transport. At low diffusion temperature surface reactions control the process.