Shallow-junction formation on silicon by rapid thermal diffusion of impurities from a spin-on source

Rapid thermal diffusion (RTD) of P and/or B into silicon wafer from spin-on sources using tungsten halogen lamps was successfully used to fabricate very shallow n⁺-p and/or p⁺-n junctions. RTD was performed in the temperature range of 600-1080°C for 5-60 s, and the heating rates were varied in the range 10-83°C/s. Effects of the two-step RTD, high temperature for several seconds, and subsequent low temperature for 60 s, were also examined. The RTD of P was carried out from P-doped oxide films and that of B was carried out from polymeric boron-doped films. Using RTD one can obtain a very shallow junction, thinner than 20 nm in depth. The impurity diffusion by RTD is similar to conventional furnace processing. However, the RTD of P and/for B was enhanced with the heating rate, especially at 83°C/s. This was assumed to be caused by the stress field induced in the heating stage. The junction depth, I-V characteristics, spectral response, and cell parameters of fabricated photodiodes are presented