Ultrashallow doping by excimer laser drive-in of RPCVD surface deposited arsenic monolayers

Abstract

Reduced pressure CVD of arsenic has been investigated as a source of dopants in combination with excimer laser annealing (LA). Energy densities used for LA are above the Si melt limit and abrupt, highly doped, nearly defect-free, ultrashallow junctions have been formed. The junction depth is determined by the melt depth and is independent of the doping level, which is determined by the As deposition. Multiple LA of the surface deposited As layer was performed to yield improved uniformity while multiple cycles of As deposition plus LA have been performed to yield a higher dose and consequently lower sheet resistance, which in the case of three depositions drops to around 80 Qlsq for layers of an estimated depth of less than 20 nm. Near-ideal diode characteristics have been measured.

Low temperature pure boron layer deposition for Si diode and micromachining applications

“…In this way, a highly-doped yet very shallow junction could be achieved. For example, in [62][63][64] a monolayer of CVD arsenic deposited on a p-type substrate was exposed to 308-nm excimer laser annealing with energy densities from 600 to 1200 mJ/cm 2 . The resulting junctions were contacted by Al/Si (1%) sputtering and diode I-V characteristics going from Schottky-like current levels to deep-junction-like levels were obtained as shown in Fig.…”

Advances in ultrashallow doping of silicon

“…Since ELA is used for elimination of implantation-induced defects and dopant activation, the resulting dopant profile is dependent on the ion-implantation parameters. Popadic et al [73]. explored the possibility of fabricating USJs in silicon by combining CVD deposited arsenic monolayer with ELA.…”

Integration of laser-annealed junctions in a low-temperature high-k metal-gate MISFET

“…An effective reflective masking for this laser light is provided by a sputtered layer of Al/1%Si and it is therefore attractive to protect the gate oxide with this metal. Laser action has previously been successfully demonstrated for the annealing of dopants introduced by ion implantation as well as by a CVD source [8,9]. To fully utilize self-alignment, dopants need to be introduced after the gate formation which prohibits the use of a CVD process with the Al gate and low-energy ion-implantation was used instead.…”