Physical mechanisms of transient enhanced dopant diffusion in ion-implanted silicon (original) (raw)
Related papers
Atomic scale models of ion implantation and dopant diffusion in silicon
Thin Solid Films, 2000
We review our recent work on an atomistic approach to the development of predictive process simulation tools. First-principles methods, molecular dynamics simulations, and experimental results are used to construct a database of defect and dopant energetics in Si. This is used as input for kinetic Monte Carlo simulations. C and B trapping of the Si self-interstitial is shown to help explain the enormous disparity in its measured diffusivity. Excellent agreement is found between experiments and simulations of transient enhanced diffusion following 20±80 keV B implants into Si, and with those of 50 keV Si implants into complex B-doped structures. Our simulations predict novel behavior of the time evolution of the electrically active B fraction during annealing.
Applied Physics Letters, 1996
A new atomistic approach to Si device process simulation is presented. It is based on a Monte Carlo diffusion code coupled to a binary collision program. Besides diffusion, the simulation includes recombination of vacancies and interstitials, clustering and re-emission from the clusters, and trapping of interstitials. We discuss the simulation of a typical room-temperature implant at 40 keV, 5ϫ10 13 cm Ϫ2 Si into ͑001͒Si, followed by a high temperature ͑815°C͒ anneal. The damage evolves into an excess of interstitials in the form of extended defects and with a total number close to the implanted dose. This result explains the success of the ''ϩ1'' model, used to simulate transient diffusion of dopants after ion implantation. It is also in agreement with recent transmission electron microscopy observations of the number of interstitials stored in ͑311͒ defects.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2001
We discuss atomistic simulations of ion implantation and annealing of Si over a wide range of ion dose and substrate temperatures. The DADOS Monte Carlo model has been extended to include the formation of amorphous regions, and this allows simulations of dopant diusion at high doses. As the dose of ions increases, the amorphous regions formed by cascades eventually overlap, and a continuous amorphous layer is formed. In that case, most of the excess interstitials generated by the implantation are swept to the surface as the amorphous layer regrows, and do not diuse in the crystalline region. This process reduces the amount of transient enhanced diusion (TED) during annealing. This model also reproduces the dynamic annealing during high temperature implants. In this case, the local amorphous regions regrow as the implant proceeds, without the formation of a continuous amorphous layer. For suciently high temperatures, each cascade is annealed out independently; interstitials and vacancies can escape from the cascade and thus increase dopant diusion. Ó
Atomistic modeling of dopant implantation, diffusion, and activation
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2006
Atomistic kinetic Monte Carlo simulations have been performed to illustrate the correlation between the Si interstitial defects generated by ion implantation, and B diffusion and activation in Si. The amount of residual damage is not very affected by moderate dynamic anneal during subamorphizing implants. However, dynamic anneal even at room temperature significantly influences the residual damage in amorphizing implants. The efficiency of the surface as a sink for point defects affects the evolution of Si interstitial defects. They set the Si interstitial supersaturation that is responsible for transient enhanced diffusion of B and also control the formation and dissolution of B-Si interstitial clusters.
Defects evolution and dopant activation anomalies in ion implanted silicon
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006
The interactions between the defects and the implanted dopants are at the origin of the diffusion and activation anomalies that are among the major obstacles to the realisation of ultra-shallow junctions satisfying the ITRS requirements.
Defect engineering via ion implantation to control B diffusion in Si
Materials Science and Engineering: B, 2009
The processes which are currently studied in the fabrication of B-doped ultra shallow junctions (USJ) usually involve a preamorphization step to reduce B channelling effect during implantation and to improve B electrical activation. At this stage a high amount of Si interstitial atoms (Is), which dramatically increases the B diffusivity, is introduced. The introduction of voids in Si is a promising tool to control B transient enhanced diffusion (TED), because of their ability to capture Is. In this work the efficiency of a cavity band to reduce B TED is checked in silicon interstitial supersaturation conditions, obtained by high dose Si implantation. He is implanted either at 10 keV or at 50 keV with a fluence of 5×10 16 cm -2 . Conventional techniques to introduce and activate the B (conventional ion implantation and rapid thermal annealing (RTA)) are applied in order to have a better control of the technological process to focus on the benefit of the cavity layer.
Nucleation, growth and dissolution of extended defects in implanted Si: impact on dopant diffusion
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999
Transient Enhanced Diusion (TED) of boron in silicon is driven by the large supersaturations of self-interstitial silicon atoms left after implantation which also often lead to the nucleation and subsequent growth, upon annealing, of extended defects. In this paper we review selected experimental results and concepts concerning boron diusion and/or defect behavior which have recently emerged with the ion implantation community and brie¯y indicate how they are, or will be, currently used to improve``predictive simulations'' softwares aimed at predicting TED. In a ®rst part, we focuss our attention on TED and on the formation of defects in the case of``direct'' implantation of boron in silicon. In a second part, we review our current knowledge of the defects and of the diusion behavior of boron when annealing preamorphised Si. In a last part, we try to compare these two cases and to ®nd out what are the reasons for some similarities and many dierences in defect types and thermal evolution depending on whether boron is implanted in crystalline or amorphous silicon. While rising many more questions, we propose a``thermodynamical'' vision of the nucleation and growth of clusters and extended defects and stress the interactions between these defects and the free Si self-interstitial atoms which surround them and are the source for TED in all cases. A pragmatic approach to the simulation of TED for various experimental conditions is proposed. Ó 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 -5 8 3 X ( 9 8 ) 0 0 6 1 7 -X
Transient enhanced diffusion of dopant in preamorphised Si: the role of EOR defects
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995
Transient enhanced diffusion of boron is observed during annealing of preamorphised Si wafers. This anomalous diffusion is seen to originate from the interaction between EOR defects and dopant. Dopant trapping also occurs on the dislocation loops. Upon annealing, these defects grow in size and reduce their density through the emission and capture of Si interstitial atoms and this phenomenon can be described within the framework of the theory of Ostwald ripening. The boron diffusivity enhancement that is experimentally noticed takes its origin in the large supersaturation of Si interstitials in the defect-rich region and to the strong coupling between boron atoms and these Si interstitials. Both phenomena are transient and quantitative informations allowing this diffusion to be simulated can be extracted from TEM images of the time evolution of the dislocation loops upon annealing.
First-principles-based predictive simulations of B diffusion and activation in ion implanted Si
2000
We present a kinetic Monte Carlo model for boron diffusion, clustering and activation in i o n implanted silicon. The input to the model is based on a combination o f experimental data and ab i n i t i o calculations. The model shows that boron diffusion and activation are low while vacancy clusters are present in the system. As the vacancy clusters dissociate, boron becomes substitutional and the active fraction increases rapidly. At the same time, the total boron diffusion length also increases rapidly while interstitial clusters ripen. The final burst of boron diffusion occurs a s the large interstitial clusters d i s s o l v e , but most of the transient diffusion of the implanted boron has already taken place by this time. We show that these results are in excellent agreement with experimental data on annealed dopant profiles and dopant activation as a function of annealing time.