Mechanism Investigations and Control of Phonon-Excitation Anneal Process for Ultra-Shallow Junction Formation

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Formation of ultra-shallow junctions (10-30 nm) is required for fabrication of CMOS devices in next-generation ULSIs. State-of-the-art technologies for the dopant activation are based on thermal processes such as rapid thermal annealing (RTA) and laser thermal annealing with surface melting, which are constrained by the thermal budget to cause unwanted transient diffusion of the dopants into deeper region and/or in lateral direction. This research has been carried out to investigate the non-equilibrium (non-thermal) anneal processes of the implanted dopants in the shallow region by directly exciting phonons and/or interatomic bonding states as one of the effective low-temperature formation technology of the ultra-shallow junctions. Major results are summarized as follows. 1) Pomp-probe reflectivity measurements showed that the ultra-short pulse laser irradiation induced phonon vibrations followed by relaxation of the optically excited carriers, in which the phonon vibration was enhanced nonlinearly with laser intensities. 2) Cross-sectional high-resolution TEM observations confirmed successful re-crystallization of the implanted layer by the ultra-short pulse laser irradiation. 3) Sheet resistance of the implanted layer was controlled by the laser irradiation conditions, in which the sheet resistance was confirmed to show close correlation with the atomic-scale nanostructure. 4) Feasibility of the sheet resistance as low as 400 ohms/sq. was demonstrated for the 0.5-keV B implanted samples. 5) As one of the effective surface excitation processes to control defects after the laser irradiation, plasma technologies were developed for generation and control of the large-area non-equilibrium plasmas, in which feasibility of the 300-mm wafer processes was demonstrated.