Ultra-shallow junctions and the effect of ramp-up rate during spike anneals in lamp-based and hot-walled RTP systems

Ultra-shallow p-type junction formation has been investigated using 1050°C spike anneals in lamp-based and hot-walled rapid thermal processing (RTP) systems. A spike anneal may be characterized by a fast ramp-up to temperature with only a fraction of a second soak-time at temperature. The effects of the ramp-up rate during a spike anneal on junction depth and sheet resistance were measured for rates of 40, 70 and 155°C/s in a lamp-based RTP, and for 50 and 85°C/s in a hot-walled RTP. B⁺ implants of 0.5-, 2- and 5-keV at doses of 2×10¹⁴ and 2×10¹⁵ cm^-2 were annealed. A significant reduction in junction depth was observed at the highest ramp-up rate for the shallower 0.5 keV B implants, while only a marginal improvement was observed for 2- and 5-keV implants. It is concluded that high ramp-up rates can achieve the desired ultra-shallow junctions with low sheet resistance but only when used with spike anneals and the lowest energy implants