Excimer laser thermal processing of ultra-shallow junction: laser pulse duration

Abstract According to the International Technology Roadmap for Semiconductors (ITRS), source and drain extensions thickness for 65 nm and below technology nodes MOSFET lead to a major challenge. Rapid thermal processing (RTP) tools reach the limit of their physical abilities in term of temperature cycle and pulsed laser thermal processing (LTP) tool arise as a major potential candidates to solve the fundamental problem of ultra-shallow junction (USJ) activation. LTP experiments have been performed with two different XeCl excimer lasers ( λ =308 nm) with different pulse characteristics (20 and 200 ns). We examine the influence of the pulse duration on LTP of B + (with and without Ge + pre-amorphization) implanted silicon samples on the basis of real-time optical monitoring of the laser induced process, four-point probe resistivity measurements and secondary ion mass spectroscopy (SIMS) depth profiles. Experimental results are compared to model calculations for both laser pulses. The activated dopant dose, junction depth and sheet resistance, as a function of the laser fluence and shot number for both lasers, confirm the relevance and efficiency of laser processing to realize ultra-shallow and highly doped junctions required for the future CMOS generations. Influence of the pulse duration on the USJ formation process is also discussed. In particular, we show the capabilities of the 200 ns pulse to activate B in Si without melting the Si doped layer.