Study of millisecond laser annealing on recrystallization, activation, and mobility of laser annealed SOI doped via arsenic ion implantation

Abstract

Millisecond anneal techniques have been demonstrated to achieve fully recrystallized, highly activated, shallow, and abrupt junctions in silicon with both p- and n-type dopants due to the technique's fast time scale and high temperature. To understand and model the effects of millisecond laser annealing, knowledge of the true thermal profile experienced by the active semiconductor region must be known. This work simulates the impacts of a scanning laser in a series of shallow implants, and compares those results to experimental results. Arsenic ion (As+) implant energies of 10, 19, and 25 keV at doses of 1.5 × 1015 and 3 × 1015 cm−2 into a silicon-on-insulator substrate are studied to achieve different doping levels and amorphization depths. The recrystallization, activation, and mobility of the laser annealed, ion implanted experimental cells are then analyzed. For each experiment, Sentaurus technology computer aided design is used to create a calibrated 2D laser model to approximate the thermal budget of the lasing recipes (850–1250 °C) then using that output as an input into lattice kinetic Monte Carlo (LKMC) to simulate the solid phase epitaxial regrowth (SPER) during anneal of the various implant conditions. Sheet resistance and Hall effect measurements were used to correlate dopant activation and mobility with the regrowth process during laser anneal, showing the onset of high conductivity associated with completion of SPER in the films. The LKMC model shows an excellent agreement with cross section transmission electron microscopy, correlating the increase of conductivity with completion of crystal regrowth, increased activation, and crystal quality at various temperatures. Shallow, lower dose implants are capable of single crystal regrowth, producing high levels of activation >1 × 1020 cm−2 and nominal mobilities for highly arsenic-doped silicon. However, higher energy implants that fully amorphize the film regrow polycrystalline silicon with low mobilities even at very high temperatures (1250 °C), unsuitable for source–drain formation in logic devices.

Comprehensive Analysis of Phosphorus-Doped Silicon Annealed by Continuous-Wave Laser Beam at High Scan Speed

“…Although various studies have been carried out on P-doped Si to achieve a low sheet resistance by ion implantation and postannealing [6][7][8], the traditional method causes diffusion of dopants into the substrate, which weakens the electrical properties of Si [9][10][11]. Considering these problems, laser annealing is being investigated as an alternative to anneal P-doped Si with higher temperatures and simultaneously reduce the diffusion with a shorter annealing time [12][13][14]. The demand for high-performance devices and novel materials is driving the expansion of laser-based applications.…”

Study of recrystallization and activation processes in thin and highly doped silicon-on-insulator layers by nanosecond laser thermal annealing

“…In contrast, fewer studies exist for laser annealing. For instance, Michalak et al [18] considered the case of millisecond laser anneals in sub-melt regime, while Chang et al [19] investigated the activation of phosphorus in thick SOI layers (200 nm) by applying a complex sequence of furnace, RTA and nanosecond LTA.…”