Low Thermal Budget Activation of B in Si

Advanced devices may today require implantation and annealing steps after the metallic interconnection realization. Depending on the application, a thin p-doped layer has to be formed after wafer bonding. The issue, in such a case, is to correctly anneal the Boron implanted layer without degrading the buried devices and interconnections which lies at a depth around 3mum below the surface. Here, the authors propose to study different way to anneal this thin p-doped layer. Low energy and low dose implantations are performed without reaching the amorphisation threshold. Long thermal annealing at 400degC (RTP) and UV laser annealing are investigated through sheet resistance, thermal wave, SIMS or TEM. On one hand, a significant activation is obtained with RTP at temperature as low as 400degC and that Boron is activated with a better activation rate with B⁺ than with BF₂ ⁺. On the other hand, a much better activation was achieved with laser annealing as compared to RTP regardless of the implantation conditions