Ultra-Shallow Junction Formation by a Non-Melting Process; Double-Pulsed Green Laser Annealing

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 pre-amorphized Si layer. The double-pulsed laser irradiation was performed with a homogenized line beam of 0.1mm × 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.