Ultra-shallow Junction Formed by Plasma Doping and Laser Annealing
We investigated ultra-shallow junction prepared by plasma doping (PLAD) and laser annealing (LA). Although PLAD is promising doping technology for the sub-45nm technology node due to the high dose rate at low energy, it has problems which is related with hydrogen or fluorine. The implanted hydrogen generally increases damage in the Si substrate. The fluorine also retards dopant activation and increases dopant deactivation during post-annealing step. Conventional one step annealing processes such as rapid thermal annealing (RTA) or excimer laser annealing (LA) are not effective method for high dopant activation. To minimize the effect of hydrogen or fluorine, we propose additional pre-annealing followed by conventional laser annealing. By employing low temperature pre-annealing, we can improve electrical characteristics such as low sheet resistance, high activation rates, shallow junction depth and reduced dopant deactivation. The improvement can be explained by reduced defect density and out-diffusion of fluorine or hydrogen which in turn enhances dopant activation during ELA
Annealing of ultrashallow p+/n junction by 248 nm excimer laser and rapid thermal processing with different preamorphization depths
Ultrashallow p+/n junctions formed by B+-ion implantation and annealed by spike rapid thermal annealing (RTA) or laser annealing were studied. The effect of the preamorphizing depth on the redistribution of boron atoms after annealing has also been investigated. Our results show that for ultrashallow junctions formed by ultra-low-energy ion implantation and spike RTA, the depth of the preamorphizing implant has very little impact on the junction depth. By optimizing the laser fluence and preamorphization depth, a highly activated, ultrashallow, and abrupt junction can be obtained using a 248 nm excimer laser. The secondary-ion-mass spectrometry results clearly indicate that a step-like profile with a junction depth of 370 A (for a B+ implant at 1 keV) can be formed with a single-pulse laser irradiation at 0.5 J/cm2.
p–n junctions formed by BF2 ion implantation and laser annealing
Abstract p–n junctions formed by BF 2 ion implantation and pulse laser annealing were studied. Boron atoms implanted were sufficiently activated without being subject to diffusion during laser annealing by optimizing the irradiation energy. In the diffusion-free annealing condition, p–n junctions were formed using various values of implantation energy with the same dose. The leakage current increased with implantation energy. The crystallinity of the junctions was investigated using cross sectional transmission electron microscopy. It was found that all defects originated from the interface between the amorphous layer formed by ion implantation and the underlying crystal silicon substrate. In addition the relation between the defect depth and the leakage current was investigated.