Ultra-Shallow Junction Formation by a Non-Melting Process; Double-Pulsed Green Laser Annealing
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A21.7.1
Ultra-Shallow Junction Formation by a Non-Melting Process; Double-Pulsed Green Laser Annealing Toshio Kudo, Susumu Sakuragi and Kazunori Yamazaki Research & Development Center, Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka-shi, Kanagawa-ken 237-8555, JAPAN ABSTRACT In order to investigate the possibility of nanosecond activation in the non-melting state, we adopted the method of double-pulsed green laser annealing (DPSS), controlling effectively the combined pulse width with two pulsed lasers (pulse duration: ~100ns, frequency: 1kHz). We investigated the formation of ultra-shallow junctions (USJ) less than 10nm in spite of the deep penetration depth of the green wavelength in crystalline Si (~1000nm). In order to limit the depth of B implant, a Ge pre-amorphization implant was performed at an energy of 3keV to a dose of 3E+14/cm2. After the pre-amorphization implant, a B implant was performed at 0.2kev and doses of 5E+14/cm2 and 1E+15/cm2. The implanted B dopants remain within the preamorphized Si layer. The double-pulsed laser irradiation was performed with a homogenized line beam of 0.1mm x 17mm, scanning a sample stage at a constant velocity of 10mm/s, that is, at an overlap ratio of 90%. The non-melting state was found to be in the pulse energy density range of E ≤ 780mJ/cm2 at a delay time of 300ns. Overcoming the issues of the short annealing time (< 1µs) and the deep penetration depth (~1000nm), we succeeded in the ultra-shallow junction formation beyond the 45nm CMOS node: maximum junction depth of 6nm, minimum sheet resistance of 0.65kohm/sq at a B dose of 1E+15/cm2, an abruptness of 1.4nm/dec. INTRODUCTION MOS annealing technology for the 45nm node of International Technology Roadmap for Semiconductors (ITRS) is at a critical point; it is urgent that current spike rapid thermal annealing (RTA) systems should be replaced with a new annealing system. Solid phase epitaxial regrowth (SPER) [1], flash lamp annealing (FLA) [2], laser spike annealing (LSA) [3], and laser thermal process (LTP) [3] are considered as major candidates for the new annealing technology [3]. The laser annealing technologies, LSA and LTP exceed SPER and FLA in lower sheet resistance, shallower junction depth and the more abruptness. LSA activates dopants at time scales over microseconds at temperatures just below silicon’s melting point to achieve full activation [4]. Meanwhile, LTP activates dopants at nanosecond time scales at temperatures above the melting point. However, the LTP process in the liquid-phase state is not suitable for mass production because of device pattern distortion. Therefore, the non-melting laser annealing activated in the solid-phase state could be a promising candidate in the anneal technologies beyond the technical 45nm node. We approach the ultra-shallow junction formation beyond the 45nm technology node using the non-melting activation process of nanosecond time scales by combining double-pulsed green lasers (diode pumped solid state, or DPSS) with overlap irradiation of a line-beam [5
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