Experiment and Modelisation Results on Laser Thermal Processing for Ultra-Shallow Junction Formation: Influence of Laser Pulse Duration

Abstract

AbstractAccording to the International Technology Roadmap for Semiconductors (ITRS), the doping technology requirements for the MOSFET source and drain regions of the future CMOS generations lead to a major challenge. A critical point of this evolution is the formation of ultra-shallow junctions(USJ) for which present technologies, based on ion implantation and rapid thermal annealing, will hardly meet the ITRS specifications. Laser Thermal Processing (LTP) has been shown to be a potential candidate to solve this fundamental problem. In the present paper, LTP experiments have been performed with two XeCl excimer lasers (λ= 308 nm) with different pulse characteristics. The first laser (Lambda Physik, Compex 102) delivers 200 mJ laser pulses with a duration of ∼25 ns. The second laser is an industrial tool (SOPRA, VEL 15) that delivers 16 J laser pulses with a duration of ∼200 ns and allows to anneal a few cm die in a single laser shot. Here we examine the influence of the pulse duration on LTP of B+ (with and without Ge+ pre-amorphization) and BF2 implanted silicon samples on the basis of real-time optical monitoring of the laser induced melting/recrystallisation process, four-point probe resistivity measurements, secondary ion mass spectrometry (SIMS) depth profiles. Experimental results are compared to finite element modelisation (FIDAP Fluent Software) that takes into account 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 efficiency of laser processing to realize ultra-shallow and highly doped junctions as required by the future CMOS generations. Influence of the pulse duration on the USJ formation process is also discussed.